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When all CPUs in the system implement the SSBS extension, the SSBS field
in PSTATE is the definitive indication of the mitigation state. Further,
when the CPUs implement the SSBS manipulation instructions (advertised
to userspace via an HWCAP), EL0 can toggle the SSBS field directly and
so we cannot rely on any shadow state such as TIF_SSBD at all.
Avoid forcing the SSBS field in context-switch on such a system, and
simply rely on the PSTATE register instead.
Cc: <stable@vger.kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Srinivas Ramana <sramana@codeaurora.org>
Fixes: cbdf8a189a66 ("arm64: Force SSBS on context switch")
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
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Use shared sysctl variables for zero and one constants, as in
commit eec4844fae7c ("proc/sysctl: add shared variables for range check")
Fixes: 63f0c6037965 ("arm64: Introduce prctl() options to control the tagged user addresses ABI")
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Will Deacon <will@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Will Deacon:
"The changes are a real mixed bag this time around.
The only scary looking one from the diffstat is the uapi change to
asm-generic/mman-common.h, but this has been acked by Arnd and is
actually just adding a pair of comments in an attempt to prevent
allocation of some PROT values which tend to get used for
arch-specific purposes. We'll be using them for Branch Target
Identification (a CFI-like hardening feature), which is currently
under review on the mailing list.
New architecture features:
- Support for Armv8.5 E0PD, which benefits KASLR in the same way as
KPTI but without the overhead. This allows KPTI to be disabled on
CPUs that are not affected by Meltdown, even is KASLR is enabled.
- Initial support for the Armv8.5 RNG instructions, which claim to
provide access to a high bandwidth, cryptographically secure
hardware random number generator. As well as exposing these to
userspace, we also use them as part of the KASLR seed and to seed
the crng once all CPUs have come online.
- Advertise a bunch of new instructions to userspace, including
support for Data Gathering Hint, Matrix Multiply and 16-bit
floating point.
Kexec:
- Cleanups in preparation for relocating with the MMU enabled
- Support for loading crash dump kernels with kexec_file_load()
Perf and PMU drivers:
- Cleanups and non-critical fixes for a couple of system PMU drivers
FPU-less (aka broken) CPU support:
- Considerable fixes to support CPUs without the FP/SIMD extensions,
including their presence in heterogeneous systems. Good luck
finding a 64-bit userspace that handles this.
Modern assembly function annotations:
- Start migrating our use of ENTRY() and ENDPROC() over to the
new-fangled SYM_{CODE,FUNC}_{START,END} macros, which are intended
to aid debuggers
Kbuild:
- Cleanup detection of LSE support in the assembler by introducing
'as-instr'
- Remove compressed Image files when building clean targets
IP checksumming:
- Implement optimised IPv4 checksumming routine when hardware offload
is not in use. An IPv6 version is in the works, pending testing.
Hardware errata:
- Work around Cortex-A55 erratum #1530923
Shadow call stack:
- Work around some issues with Clang's integrated assembler not
liking our perfectly reasonable assembly code
- Avoid allocating the X18 register, so that it can be used to hold
the shadow call stack pointer in future
ACPI:
- Fix ID count checking in IORT code. This may regress broken
firmware that happened to work with the old implementation, in
which case we'll have to revert it and try something else
- Fix DAIF corruption on return from GHES handler with pseudo-NMIs
Miscellaneous:
- Whitelist some CPUs that are unaffected by Spectre-v2
- Reduce frequency of ASID rollover when KPTI is compiled in but
inactive
- Reserve a couple of arch-specific PROT flags that are already used
by Sparc and PowerPC and are planned for later use with BTI on
arm64
- Preparatory cleanup of our entry assembly code in preparation for
moving more of it into C later on
- Refactoring and cleanup"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (73 commits)
arm64: acpi: fix DAIF manipulation with pNMI
arm64: kconfig: Fix alignment of E0PD help text
arm64: Use v8.5-RNG entropy for KASLR seed
arm64: Implement archrandom.h for ARMv8.5-RNG
arm64: kbuild: remove compressed images on 'make ARCH=arm64 (dist)clean'
arm64: entry: Avoid empty alternatives entries
arm64: Kconfig: select HAVE_FUTEX_CMPXCHG
arm64: csum: Fix pathological zero-length calls
arm64: entry: cleanup sp_el0 manipulation
arm64: entry: cleanup el0 svc handler naming
arm64: entry: mark all entry code as notrace
arm64: assembler: remove smp_dmb macro
arm64: assembler: remove inherit_daif macro
ACPI/IORT: Fix 'Number of IDs' handling in iort_id_map()
mm: Reserve asm-generic prot flags 0x10 and 0x20 for arch use
arm64: Use macros instead of hard-coded constants for MAIR_EL1
arm64: Add KRYO{3,4}XX CPU cores to spectre-v2 safe list
arm64: kernel: avoid x18 in __cpu_soft_restart
arm64: kvm: stop treating register x18 as caller save
arm64/lib: copy_page: avoid x18 register in assembler code
...
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We finalize the system wide capabilities after the SMP CPUs
are booted by the kernel. This is used as a marker for deciding
various checks in the kernel. e.g, sanity check the hotplugged
CPUs for missing mandatory features.
However there is no explicit helper available for this in the
kernel. There is sys_caps_initialised, which is not exposed.
The other closest one we have is the jump_label arm64_const_caps_ready
which denotes that the capabilities are set and the capability checks
could use the individual jump_labels for fast path. This is
performed before setting the ELF Hwcaps, which must be checked
against the new CPUs. We also perform some of the other initialization
e.g, SVE setup, which is important for the use of FP/SIMD
where SVE is supported. Normally userspace doesn't get to run
before we finish this. However the in-kernel users may
potentially start using the neon mode. So, we need to
reject uses of neon mode before we are set. Instead of defining
a new marker for the completion of SVE setup, we could simply
reuse the arm64_const_caps_ready and enable it once we have
finished all the setup. Also we could expose this to the
various users as "system_capabilities_finalized()" to make
it more meaningful than "const_caps_ready".
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
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This is required for clone3 which passes the TLS value through a
struct rather than a register.
Signed-off-by: Amanieu d'Antras <amanieu@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: <stable@vger.kernel.org> # 5.3.x
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200102172413.654385-3-amanieu@gmail.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
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Preempting from IRQ-return means that the task has its PSTATE saved
on the stack, which will get restored when the task is resumed and does
the actual IRQ return.
However, enabling some CPU features requires modifying the PSTATE. This
means that, if a task was scheduled out during an IRQ-return before all
CPU features are enabled, the task might restore a PSTATE that does not
include the feature enablement changes once scheduled back in.
* Task 1:
PAN == 0 ---| |---------------
| |<- return from IRQ, PSTATE.PAN = 0
| <- IRQ |
+--------+ <- preempt() +--
^
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reschedule Task 1, PSTATE.PAN == 1
* Init:
--------------------+------------------------
^
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enable_cpu_features
set PSTATE.PAN on all CPUs
Worse than this, since PSTATE is untouched when task switching is done,
a task missing the new bits in PSTATE might affect another task, if both
do direct calls to schedule() (outside of IRQ/exception contexts).
Fix this by preventing preemption on IRQ-return until features are
enabled on all CPUs.
This way the only PSTATE values that are saved on the stack are from
synchronous exceptions. These are expected to be fatal this early, the
exception is BRK for WARN_ON(), but as this uses do_debug_exception()
which keeps IRQs masked, it shouldn't call schedule().
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
[james: Replaced a really cool hack, with an even simpler static key in C.
expanded commit message with Julien's cover-letter ascii art]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
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The system which has SVE feature crashed because of
the memory pointed by task->thread.sve_state was destroyed
by someone.
That is because sve_state is freed while the forking the
child process. The child process has the pointer of sve_state
which is same as the parent's because the child's task_struct
is copied from the parent's one. If the copy_process()
fails as an error on somewhere, for example, copy_creds(),
then the sve_state is freed even if the parent is alive.
The flow is as follows.
copy_process
p = dup_task_struct
=> arch_dup_task_struct
*dst = *src; // copy the entire region.
:
retval = copy_creds
if (retval < 0)
goto bad_fork_free;
:
bad_fork_free:
...
delayed_free_task(p);
=> free_task
=> arch_release_task_struct
=> fpsimd_release_task
=> __sve_free
=> kfree(task->thread.sve_state);
// free the parent's sve_state
Move child's sve_state = NULL and clearing TIF_SVE flag
to arch_dup_task_struct() so that the child doesn't free the
parent's one.
There is no need to wait until copy_process() to clear TIF_SVE for
dst, because the thread flags for dst are initialized already by
copying the src task_struct.
This change simplifies the code, so get rid of comments that are no
longer needed.
As a note, arm64 used to have thread_info on the stack. So it
would not be possible to clear TIF_SVE until the stack is initialized.
From commit c02433dd6de3 ("arm64: split thread_info from task stack"),
the thread_info is part of the task, so it should be valid to modify
the flag from arch_dup_task_struct().
Cc: stable@vger.kernel.org # 4.15.x-
Fixes: bc0ee4760364 ("arm64/sve: Core task context handling")
Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reported-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Suggested-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Tested-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
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This commits selects ARCH_HAS_ELF_RANDOMIZE when an arch uses the generic
topdown mmap layout functions so that this security feature is on by
default.
Note that this commit also removes the possibility for arm64 to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.
Link: http://lkml.kernel.org/r/20190730055113.23635-6-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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opt-in
First rename the sysctl control to abi.tagged_addr_disabled and make it
default off (zero). When abi.tagged_addr_disabled == 1, only block the
enabling of the TBI ABI via prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE).
Getting the status of the ABI or disabling it is still allowed.
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
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It is not desirable to relax the ABI to allow tagged user addresses into
the kernel indiscriminately. This patch introduces a prctl() interface
for enabling or disabling the tagged ABI with a global sysctl control
for preventing applications from enabling the relaxed ABI (meant for
testing user-space prctl() return error checking without reconfiguring
the kernel). The ABI properties are inherited by threads of the same
application and fork()'ed children but cleared on execve(). A Kconfig
option allows the overall disabling of the relaxed ABI.
The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle
MTE-specific settings like imprecise vs precise exceptions.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
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On a CPU that doesn't support SSBS, PSTATE[12] is RES0. In a system
where only some of the CPUs implement SSBS, we end-up losing track of
the SSBS bit across task migration.
To address this issue, let's force the SSBS bit on context switch.
Fixes: 8f04e8e6e29c ("arm64: ssbd: Add support for PSTATE.SSBS rather than trapping to EL3")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
[will: inverted logic and added comments]
Signed-off-by: Will Deacon <will@kernel.org>
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Some common code is required by each stacktrace user to initialise
struct stackframe before the first call to unwind_frame().
In preparation for adding to the common code, this patch factors it
out into a separate function start_backtrace(), and modifies the
stacktrace callers appropriately.
No functional change.
Signed-off-by: Dave Martin <dave.martin@arm.com>
[Mark: drop tsk argument, update more callsites]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Catalin Marinas:
- arm64 support for syscall emulation via PTRACE_SYSEMU{,_SINGLESTEP}
- Wire up VM_FLUSH_RESET_PERMS for arm64, allowing the core code to
manage the permissions of executable vmalloc regions more strictly
- Slight performance improvement by keeping softirqs enabled while
touching the FPSIMD/SVE state (kernel_neon_begin/end)
- Expose a couple of ARMv8.5 features to user (HWCAP): CondM (new
XAFLAG and AXFLAG instructions for floating point comparison flags
manipulation) and FRINT (rounding floating point numbers to integers)
- Re-instate ARM64_PSEUDO_NMI support which was previously marked as
BROKEN due to some bugs (now fixed)
- Improve parking of stopped CPUs and implement an arm64-specific
panic_smp_self_stop() to avoid warning on not being able to stop
secondary CPUs during panic
- perf: enable the ARM Statistical Profiling Extensions (SPE) on ACPI
platforms
- perf: DDR performance monitor support for iMX8QXP
- cache_line_size() can now be set from DT or ACPI/PPTT if provided to
cope with a system cache info not exposed via the CPUID registers
- Avoid warning on hardware cache line size greater than
ARCH_DMA_MINALIGN if the system is fully coherent
- arm64 do_page_fault() and hugetlb cleanups
- Refactor set_pte_at() to avoid redundant READ_ONCE(*ptep)
- Ignore ACPI 5.1 FADTs reported as 5.0 (infer from the
'arm_boot_flags' introduced in 5.1)
- CONFIG_RANDOMIZE_BASE now enabled in defconfig
- Allow the selection of ARM64_MODULE_PLTS, currently only done via
RANDOMIZE_BASE (and an erratum workaround), allowing modules to spill
over into the vmalloc area
- Make ZONE_DMA32 configurable
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (54 commits)
perf: arm_spe: Enable ACPI/Platform automatic module loading
arm_pmu: acpi: spe: Add initial MADT/SPE probing
ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens
ACPI/PPTT: Modify node flag detection to find last IDENTICAL
x86/entry: Simplify _TIF_SYSCALL_EMU handling
arm64: rename dump_instr as dump_kernel_instr
arm64/mm: Drop [PTE|PMD]_TYPE_FAULT
arm64: Implement panic_smp_self_stop()
arm64: Improve parking of stopped CPUs
arm64: Expose FRINT capabilities to userspace
arm64: Expose ARMv8.5 CondM capability to userspace
arm64: defconfig: enable CONFIG_RANDOMIZE_BASE
arm64: ARM64_MODULES_PLTS must depend on MODULES
arm64: bpf: do not allocate executable memory
arm64/kprobes: set VM_FLUSH_RESET_PERMS on kprobe instruction pages
arm64/mm: wire up CONFIG_ARCH_HAS_SET_DIRECT_MAP
arm64: module: create module allocations without exec permissions
arm64: Allow user selection of ARM64_MODULE_PLTS
acpi/arm64: ignore 5.1 FADTs that are reported as 5.0
arm64: Allow selecting Pseudo-NMI again
...
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When using IRQ priority masking to disable interrupts, in order to deal
with the PSR.I state, local_irq_save() would convert the I bit into a
PMR value (GIC_PRIO_IRQOFF). This resulted in local_irq_restore()
potentially modifying the value of PMR in undesired location due to the
state of PSR.I upon flag saving [1].
In an attempt to solve this issue in a less hackish manner, introduce
a bit (GIC_PRIO_IGNORE_PMR) for the PMR values that can represent
whether PSR.I is being used to disable interrupts, in which case it
takes precedence of the status of interrupt masking via PMR.
GIC_PRIO_PSR_I_SET is chosen such that (<pmr_value> |
GIC_PRIO_PSR_I_SET) does not mask more interrupts than <pmr_value> as
some sections (e.g. arch_cpu_idle(), interrupt acknowledge path)
requires PMR not to mask interrupts that could be signaled to the
CPU when using only PSR.I.
[1] https://www.spinics.net/lists/arm-kernel/msg716956.html
Fixes: 4a503217ce37 ("arm64: irqflags: Use ICC_PMR_EL1 for interrupt masking")
Cc: <stable@vger.kernel.org> # 5.1.x-
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Wei Li <liwei391@huawei.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Pouloze <suzuki.poulose@arm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation this program is
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details you should have received a copy of the gnu general
public license along with this program if not see http www gnu org
licenses
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 503 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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CPU does not received signals for interrupts with a priority masked by
ICC_PMR_EL1. This means the CPU might not come back from a WFI
instruction.
Make sure ICC_PMR_EL1 does not mask interrupts when doing a WFI.
Since the logic of cpu_do_idle is becoming a bit more complex than just
two instructions, lets turn it from ASM to C.
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Suggested-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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In order to replace PSR.I interrupt disabling/enabling with ICC_PMR_EL1
interrupt masking, ICC_PMR_EL1 needs to be saved/restored when
taking/returning from an exception. This mimics the way hardware saves
and restores PSR.I bit in spsr_el1 for exceptions and ERET.
Add PMR to the registers to save in the pt_regs struct upon kernel entry,
and restore it before ERET. Also, initialize it to a sane value when
creating new tasks.
Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
- Rework of the kprobe/uprobe and synthetic events to consolidate all
the dynamic event code. This will make changes in the future easier.
- Partial rewrite of the function graph tracing infrastructure. This
will allow for multiple users of hooking onto functions to get the
callback (return) of the function. This is the ground work for having
kprobes and function graph tracer using one code base.
- Clean up of the histogram code that will facilitate adding more
features to the histograms in the future.
- Addition of str_has_prefix() and a few use cases. There currently is
a similar function strstart() that is used in a few places, but only
returns a bool and not a length. These instances will be removed in
the future to use str_has_prefix() instead.
- A few other various clean ups as well.
* tag 'trace-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (57 commits)
tracing: Use the return of str_has_prefix() to remove open coded numbers
tracing: Have the historgram use the result of str_has_prefix() for len of prefix
tracing: Use str_has_prefix() instead of using fixed sizes
tracing: Use str_has_prefix() helper for histogram code
string.h: Add str_has_prefix() helper function
tracing: Make function ‘ftrace_exports’ static
tracing: Simplify printf'ing in seq_print_sym
tracing: Avoid -Wformat-nonliteral warning
tracing: Merge seq_print_sym_short() and seq_print_sym_offset()
tracing: Add hist trigger comments for variable-related fields
tracing: Remove hist trigger synth_var_refs
tracing: Use hist trigger's var_ref array to destroy var_refs
tracing: Remove open-coding of hist trigger var_ref management
tracing: Use var_refs[] for hist trigger reference checking
tracing: Change strlen to sizeof for hist trigger static strings
tracing: Remove unnecessary hist trigger struct field
tracing: Fix ftrace_graph_get_ret_stack() to use task and not current
seq_buf: Use size_t for len in seq_buf_puts()
seq_buf: Make seq_buf_puts() null-terminate the buffer
arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack
...
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The structure of the ret_stack array on the task struct is going to
change, and accessing it directly via the curr_ret_stack index will no
longer give the ret_stack entry that holds the return address. To access
that, architectures must now use ftrace_graph_get_ret_stack() to get the
associated ret_stack that matches the saved return address.
Cc: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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This patch adds basic support for pointer authentication, allowing
userspace to make use of APIAKey, APIBKey, APDAKey, APDBKey, and
APGAKey. The kernel maintains key values for each process (shared by all
threads within), which are initialised to random values at exec() time.
The ID_AA64ISAR1_EL1.{APA,API,GPA,GPI} fields are exposed to userspace,
to describe that pointer authentication instructions are available and
that the kernel is managing the keys. Two new hwcaps are added for the
same reason: PACA (for address authentication) and PACG (for generic
authentication).
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Tested-by: Adam Wallis <awallis@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
[will: Fix sizeof() usage and unroll address key initialisation]
Signed-off-by: Will Deacon <will.deacon@arm.com>
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This enables the use of per-task stack canary values if GCC has
support for emitting the stack canary reference relative to the
value of sp_el0, which holds the task struct pointer in the arm64
kernel.
The $(eval) extends KBUILD_CFLAGS at the moment the make rule is
applied, which means asm-offsets.o (which we rely on for the offset
value) is built without the arguments, and everything built afterwards
has the options set.
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux
Pull stackleak gcc plugin from Kees Cook:
"Please pull this new GCC plugin, stackleak, for v4.20-rc1. This plugin
was ported from grsecurity by Alexander Popov. It provides efficient
stack content poisoning at syscall exit. This creates a defense
against at least two classes of flaws:
- Uninitialized stack usage. (We continue to work on improving the
compiler to do this in other ways: e.g. unconditional zero init was
proposed to GCC and Clang, and more plugin work has started too).
- Stack content exposure. By greatly reducing the lifetime of valid
stack contents, exposures via either direct read bugs or unknown
cache side-channels become much more difficult to exploit. This
complements the existing buddy and heap poisoning options, but
provides the coverage for stacks.
The x86 hooks are included in this series (which have been reviewed by
Ingo, Dave Hansen, and Thomas Gleixner). The arm64 hooks have already
been merged through the arm64 tree (written by Laura Abbott and
reviewed by Mark Rutland and Will Deacon).
With VLAs having been removed this release, there is no need for
alloca() protection, so it has been removed from the plugin"
* tag 'stackleak-v4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
arm64: Drop unneeded stackleak_check_alloca()
stackleak: Allow runtime disabling of kernel stack erasing
doc: self-protection: Add information about STACKLEAK feature
fs/proc: Show STACKLEAK metrics in the /proc file system
lkdtm: Add a test for STACKLEAK
gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack
x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls
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On CPUs with support for PSTATE.SSBS, the kernel can toggle the SSBD
state without needing to call into firmware.
This patch hooks into the existing SSBD infrastructure so that SSBS is
used on CPUs that support it, but it's all made horribly complicated by
the very real possibility of big/little systems that don't uniformly
provide the new capability.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Drop stackleak_check_alloca() for arm64 since the STACKLEAK gcc plugin now
doesn't track stack depth overflow caused by alloca().
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
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This adds support for the STACKLEAK gcc plugin to arm64 by implementing
stackleak_check_alloca(), based heavily on the x86 version, and adding the
two helpers used by the stackleak common code: current_top_of_stack() and
on_thread_stack(). The stack erasure calls are made at syscall returns.
Additionally, this disables the plugin in hypervisor and EFI stub code,
which are out of scope for the protection.
Acked-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Some code cares about the SPSR_ELx format for exceptions taken from
AArch32 to inspect or manipulate the SPSR_ELx value, which is already in
the SPSR_ELx format, and not in the AArch32 PSR format.
To separate these from cases where we care about the AArch32 PSR format,
migrate these cases to use the PSR_AA32_* definitions rather than
COMPAT_PSR_*.
There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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The changes to automatically test for working stack protector compiler
support in the Kconfig files removed the special STACKPROTECTOR_AUTO
option that picked the strongest stack protector that the compiler
supported.
That was all a nice cleanup - it makes no sense to have the AUTO case
now that the Kconfig phase can just determine the compiler support
directly.
HOWEVER.
It also meant that doing "make oldconfig" would now _disable_ the strong
stackprotector if you had AUTO enabled, because in a legacy config file,
the sane stack protector configuration would look like
CONFIG_HAVE_CC_STACKPROTECTOR=y
# CONFIG_CC_STACKPROTECTOR_NONE is not set
# CONFIG_CC_STACKPROTECTOR_REGULAR is not set
# CONFIG_CC_STACKPROTECTOR_STRONG is not set
CONFIG_CC_STACKPROTECTOR_AUTO=y
and when you ran this through "make oldconfig" with the Kbuild changes,
it would ask you about the regular CONFIG_CC_STACKPROTECTOR (that had
been renamed from CONFIG_CC_STACKPROTECTOR_REGULAR to just
CONFIG_CC_STACKPROTECTOR), but it would think that the STRONG version
used to be disabled (because it was really enabled by AUTO), and would
disable it in the new config, resulting in:
CONFIG_HAVE_CC_STACKPROTECTOR=y
CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
CONFIG_CC_STACKPROTECTOR=y
# CONFIG_CC_STACKPROTECTOR_STRONG is not set
CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
That's dangerously subtle - people could suddenly find themselves with
the weaker stack protector setup without even realizing.
The solution here is to just rename not just the old RECULAR stack
protector option, but also the strong one. This does that by just
removing the CC_ prefix entirely for the user choices, because it really
is not about the compiler support (the compiler support now instead
automatially impacts _visibility_ of the options to users).
This results in "make oldconfig" actually asking the user for their
choice, so that we don't have any silent subtle security model changes.
The end result would generally look like this:
CONFIG_HAVE_CC_STACKPROTECTOR=y
CONFIG_CC_HAS_STACKPROTECTOR_NONE=y
CONFIG_STACKPROTECTOR=y
CONFIG_STACKPROTECTOR_STRONG=y
CONFIG_CC_HAS_SANE_STACKPROTECTOR=y
where the "CC_" versions really are about internal compiler
infrastructure, not the user selections.
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When the hardend usercopy support was added for arm64, it was
concluded that all cases of usercopy into and out of thread_struct
were statically sized and so didn't require explicit whitelisting
of the appropriate fields in thread_struct.
Testing with usercopy hardening enabled has revealed that this is
not the case for certain ptrace regset manipulation calls on arm64.
This occurs because the sizes of usercopies associated with the
regset API are dynamic by construction, and because arm64 does not
always stage such copies via the stack: indeed the regset API is
designed to avoid the need for that by adding some bounds checking.
This is currently believed to affect only the fpsimd and TLS
registers.
Because the whitelisted fields in thread_struct must be contiguous,
this patch groups them together in a nested struct. It is also
necessary to be able to determine the location and size of that
struct, so rather than making the struct anonymous (which would
save on edits elsewhere) or adding an anonymous union containing
named and unnamed instances of the same struct (gross), this patch
gives the struct a name and makes the necessary edits to code that
references it (noisy but simple).
Care is needed to ensure that the new struct does not contain
padding (which the usercopy hardening would fail to protect).
For this reason, the presence of tp2_value is made unconditional,
since a padding field would be needed there in any case. This pads
up to the 16-byte alignment required by struct user_fpsimd_state.
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Mark Rutland <mark.rutland@arm.com>
Fixes: 9e8084d3f761 ("arm64: Implement thread_struct whitelist for hardened usercopy")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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__show_regs pretty prints PC and LR by attempting to map them to kernel
function names to improve the utility of crash reports. Unfortunately,
this mapping is applied even when the pt_regs corresponds to user mode,
resulting in a KASLR oracle.
Avoid this issue by only looking up the function symbols when the register
state indicates that we're actually running at EL1.
Cc: <stable@vger.kernel.org>
Reported-by: NCSC Security <security@ncsc.gov.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk
Pull printk updates from Petr Mladek:
- Add a console_msg_format command line option:
The value "default" keeps the old "[time stamp] text\n" format. The
value "syslog" allows to see the syslog-like "<log
level>[timestamp] text" format.
This feature was requested by people doing regression tests, for
example, 0day robot. They want to have both filtered and full logs
at hands.
- Reduce the risk of softlockup:
Pass the console owner in a busy loop.
This is a new approach to the old problem. It was first proposed by
Steven Rostedt on Kernel Summit 2017. It marks a context in which
the console_lock owner calls console drivers and could not sleep.
On the other side, printk() callers could detect this state and use
a busy wait instead of a simple console_trylock(). Finally, the
console_lock owner checks if there is a busy waiter at the end of
the special context and eventually passes the console_lock to the
waiter.
The hand-off works surprisingly well and helps in many situations.
Well, there is still a possibility of the softlockup, for example,
when the flood of messages stops and the last owner still has too
much to flush.
There is increasing number of people having problems with
printk-related softlockups. We might eventually need to get better
solution. Anyway, this looks like a good start and promising
direction.
- Do not allow to schedule in console_unlock() called from printk():
This reverts an older controversial commit. The reschedule helped
to avoid softlockups. But it also slowed down the console output.
This patch is obsoleted by the new console waiter logic described
above. In fact, the reschedule made the hand-off less effective.
- Deprecate "%pf" and "%pF" format specifier:
It was needed on ia64, ppc64 and parisc64 to dereference function
descriptors and show the real function address. It is done
transparently by "%ps" and "pS" format specifier now.
Sergey Senozhatsky found that all the function descriptors were in
a special elf section and could be easily detected.
- Remove printk_symbol() API:
It has been obsoleted by "%pS" format specifier, and this change
helped to remove few continuous lines and a less intuitive old API.
- Remove redundant memsets:
Sergey removed unnecessary memset when processing printk.devkmsg
command line option.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
printk: drop redundant devkmsg_log_str memsets
printk: Never set console_may_schedule in console_trylock()
printk: Hide console waiter logic into helpers
printk: Add console owner and waiter logic to load balance console writes
kallsyms: remove print_symbol() function
checkpatch: add pF/pf deprecation warning
symbol lookup: introduce dereference_symbol_descriptor()
parisc64: Add .opd based function descriptor dereference
powerpc64: Add .opd based function descriptor dereference
ia64: Add .opd based function descriptor dereference
sections: split dereference_function_descriptor()
openrisc: Fix conflicting types for _exext and _stext
lib: do not use print_symbol()
irq debug: do not use print_symbol()
sysfs: do not use print_symbol()
drivers: do not use print_symbol()
x86: do not use print_symbol()
unicore32: do not use print_symbol()
sh: do not use print_symbol()
mn10300: do not use print_symbol()
...
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print_symbol() is a very old API that has been obsoleted by %pS format
specifier in a normal printk() call.
Replace print_symbol() with a direct printk("%pS") call.
Link: http://lkml.kernel.org/r/20171211125025.2270-3-sergey.senozhatsky@gmail.com
To: Andrew Morton <akpm@linux-foundation.org>
To: Russell King <linux@armlinux.org.uk>
To: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Salter <msalter@redhat.com>
To: Tony Luck <tony.luck@intel.com>
To: David Howells <dhowells@redhat.com>
To: Yoshinori Sato <ysato@users.sourceforge.jp>
To: Guan Xuetao <gxt@mprc.pku.edu.cn>
To: Borislav Petkov <bp@alien8.de>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <vgupta@synopsys.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-am33-list@redhat.com
Cc: linux-sh@vger.kernel.org
Cc: linux-edac@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
[pmladek@suse.com: updated commit message]
Signed-off-by: Petr Mladek <pmladek@suse.com>
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When unmapping the kernel at EL0, we use tpidrro_el0 as a scratch register
during exception entry from native tasks and subsequently zero it in
the kernel_ventry macro. We can therefore avoid zeroing tpidrro_el0
in the context-switch path for native tasks using the entry trampoline.
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Currently, loading of a task's fpsimd state into the CPU registers
is skipped if that task's state is already present in the registers
of that CPU.
However, the code relies on the struct fpsimd_state * (and by
extension struct task_struct *) to unambiguously identify a task.
There is a particular case in which this doesn't work reliably:
when a task exits, its task_struct may be recycled to describe a
new task.
Consider the following scenario:
1) Task P loads its fpsimd state onto cpu C.
per_cpu(fpsimd_last_state, C) := P;
P->thread.fpsimd_state.cpu := C;
2) Task X is scheduled onto C and loads its fpsimd state on C.
per_cpu(fpsimd_last_state, C) := X;
X->thread.fpsimd_state.cpu := C;
3) X exits, causing X's task_struct to be freed.
4) P forks a new child T, which obtains X's recycled task_struct.
T == X.
T->thread.fpsimd_state.cpu == C (inherited from P).
5) T is scheduled on C.
T's fpsimd state is not loaded, because
per_cpu(fpsimd_last_state, C) == T (== X) &&
T->thread.fpsimd_state.cpu == C.
(This is the check performed by fpsimd_thread_switch().)
So, T gets X's registers because the last registers loaded onto C
were those of X, in (2).
This patch fixes the problem by ensuring that the sched-in check
fails in (5): fpsimd_flush_task_state(T) is called when T is
forked, so that T->thread.fpsimd_state.cpu == C cannot be true.
This relies on the fact that T is not schedulable until after
copy_thread() completes.
Once T's fpsimd state has been loaded on some CPU C there may still
be other cpus D for which per_cpu(fpsimd_last_state, D) ==
&X->thread.fpsimd_state. But D is necessarily != C in this case,
and the check in (5) must fail.
An alternative fix would be to do refcounting on task_struct. This
would result in each CPU holding a reference to the last task whose
fpsimd state was loaded there. It's not clear whether this is
preferable, and it involves higher overhead than the fix proposed
in this patch. It would also move all the task_struct freeing
work into the context switch critical section, or otherwise some
deferred cleanup mechanism would need to be introduced, neither of
which seems obviously justified.
Cc: <stable@vger.kernel.org>
Fixes: 005f78cd8849 ("arm64: defer reloading a task's FPSIMD state to userland resume")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[will: word-smithed the comment so it makes more sense]
Signed-off-by: Will Deacon <will.deacon@arm.com>
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This patch adds the core support for switching and managing the SVE
architectural state of user tasks.
Calls to the existing FPSIMD low-level save/restore functions are
factored out as new functions task_fpsimd_{save,load}(), since SVE
now dynamically may or may not need to be handled at these points
depending on the kernel configuration, hardware features discovered
at boot, and the runtime state of the task. To make these
decisions as fast as possible, const cpucaps are used where
feasible, via the system_supports_sve() helper.
The SVE registers are only tracked for threads that have explicitly
used SVE, indicated by the new thread flag TIF_SVE. Otherwise, the
FPSIMD view of the architectural state is stored in
thread.fpsimd_state as usual.
When in use, the SVE registers are not stored directly in
thread_struct due to their potentially large and variable size.
Because the task_struct slab allocator must be configured very
early during kernel boot, it is also tricky to configure it
correctly to match the maximum vector length provided by the
hardware, since this depends on examining secondary CPUs as well as
the primary. Instead, a pointer sve_state in thread_struct points
to a dynamically allocated buffer containing the SVE register data,
and code is added to allocate and free this buffer at appropriate
times.
TIF_SVE is set when taking an SVE access trap from userspace, if
suitable hardware support has been detected. This enables SVE for
the thread: a subsequent return to userspace will disable the trap
accordingly. If such a trap is taken without sufficient system-
wide hardware support, SIGILL is sent to the thread instead as if
an undefined instruction had been executed: this may happen if
userspace tries to use SVE in a system where not all CPUs support
it for example.
The kernel will clear TIF_SVE and disable SVE for the thread
whenever an explicit syscall is made by userspace. For backwards
compatibility reasons and conformance with the spirit of the base
AArch64 procedure call standard, the subset of the SVE register
state that aliases the FPSIMD registers is still preserved across a
syscall even if this happens. The remainder of the SVE register
state logically becomes zero at syscall entry, though the actual
zeroing work is currently deferred until the thread next tries to
use SVE, causing another trap to the kernel. This implementation
is suboptimal: in the future, the fastpath case may be optimised
to zero the registers in-place and leave SVE enabled for the task,
where beneficial.
TIF_SVE is also cleared in the following slowpath cases, which are
taken as reasonable hints that the task may no longer use SVE:
* exec
* fork and clone
Code is added to sync data between thread.fpsimd_state and
thread.sve_state whenever enabling/disabling SVE, in a manner
consistent with the SVE architectural programmer's model.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Alex Bennée <alex.bennee@linaro.org>
[will: added #include to fix allnoconfig build]
[will: use enable_daif in do_sve_acc]
Signed-off-by: Will Deacon <will.deacon@arm.com>
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We can decode the PSTATE easily enough, so pretty-print it in register
dumps.
Tested-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Printing raw pointer values in backtraces has potential security
implications and are of questionable value anyway.
This patch follows x86's lead and removes the "Exception stack:" dump
from kernel backtraces, as well as converting PC/LR values to symbols
such as "sysrq_handle_crash+0x20/0x30".
Tested-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Catalin Marinas:
- VMAP_STACK support, allowing the kernel stacks to be allocated in the
vmalloc space with a guard page for trapping stack overflows. One of
the patches introduces THREAD_ALIGN and changes the generic
alloc_thread_stack_node() to use this instead of THREAD_SIZE (no
functional change for other architectures)
- Contiguous PTE hugetlb support re-enabled (after being reverted a
couple of times). We now have the semantics agreed in the generic mm
layer together with API improvements so that the architecture code
can detect between contiguous and non-contiguous huge PTEs
- Initial support for persistent memory on ARM: DC CVAP instruction
exposed to user space (HWCAP) and the in-kernel pmem API implemented
- raid6 improvements for arm64: faster algorithm for the delta syndrome
and implementation of the recovery routines using Neon
- FP/SIMD refactoring and removal of support for Neon in interrupt
context. This is in preparation for full SVE support
- PTE accessors converted from inline asm to cmpxchg so that we can use
LSE atomics if available (ARMv8.1)
- Perf support for Cortex-A35 and A73
- Non-urgent fixes and cleanups
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (75 commits)
arm64: cleanup {COMPAT_,}SET_PERSONALITY() macro
arm64: introduce separated bits for mm_context_t flags
arm64: hugetlb: Cleanup setup_hugepagesz
arm64: Re-enable support for contiguous hugepages
arm64: hugetlb: Override set_huge_swap_pte_at() to support contiguous hugepages
arm64: hugetlb: Override huge_pte_clear() to support contiguous hugepages
arm64: hugetlb: Handle swap entries in huge_pte_offset() for contiguous hugepages
arm64: hugetlb: Add break-before-make logic for contiguous entries
arm64: hugetlb: Spring clean huge pte accessors
arm64: hugetlb: Introduce pte_pgprot helper
arm64: hugetlb: set_huge_pte_at Add WARN_ON on !pte_present
arm64: kexec: have own crash_smp_send_stop() for crash dump for nonpanic cores
arm64: dma-mapping: Mark atomic_pool as __ro_after_init
arm64: dma-mapping: Do not pass data to gen_pool_set_algo()
arm64: Remove the !CONFIG_ARM64_HW_AFDBM alternative code paths
arm64: Ignore hardware dirty bit updates in ptep_set_wrprotect()
arm64: Move PTE_RDONLY bit handling out of set_pte_at()
kvm: arm64: Convert kvm_set_s2pte_readonly() from inline asm to cmpxchg()
arm64: Convert pte handling from inline asm to using (cmp)xchg
arm64: neon/efi: Make EFI fpsimd save/restore variables static
...
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There is some work that should be done after setting the personality.
Currently it's done in the macro, which is not the best idea.
In this patch new arch_setup_new_exec() routine is introduced, and all
setup code is moved there, as suggested by Catalin:
https://lkml.org/lkml/2017/8/4/494
Cc: Pratyush Anand <panand@redhat.com>
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
[catalin.marinas@arm.com: comments changed or removed]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Implement MEMBARRIER_CMD_PRIVATE_EXPEDITED with IPIs using cpumask built
from all runqueues for which current thread's mm is the same as the
thread calling sys_membarrier. It executes faster than the non-expedited
variant (no blocking). It also works on NOHZ_FULL configurations.
Scheduler-wise, it requires a memory barrier before and after context
switching between processes (which have different mm). The memory
barrier before context switch is already present. For the barrier after
context switch:
* Our TSO archs can do RELEASE without being a full barrier. Look at
x86 spin_unlock() being a regular STORE for example. But for those
archs, all atomics imply smp_mb and all of them have atomic ops in
switch_mm() for mm_cpumask(), and on x86 the CR3 load acts as a full
barrier.
* From all weakly ordered machines, only ARM64 and PPC can do RELEASE,
the rest does indeed do smp_mb(), so there the spin_unlock() is a full
barrier and we're good.
* ARM64 has a very heavy barrier in switch_to(), which suffices.
* PPC just removed its barrier from switch_to(), but appears to be
talking about adding something to switch_mm(). So add a
smp_mb__after_unlock_lock() for now, until this is settled on the PPC
side.
Changes since v3:
- Properly document the memory barriers provided by each architecture.
Changes since v2:
- Address comments from Peter Zijlstra,
- Add smp_mb__after_unlock_lock() after finish_lock_switch() in
finish_task_switch() to add the memory barrier we need after storing
to rq->curr. This is much simpler than the previous approach relying
on atomic_dec_and_test() in mmdrop(), which actually added a memory
barrier in the common case of switching between userspace processes.
- Return -EINVAL when MEMBARRIER_CMD_SHARED is used on a nohz_full
kernel, rather than having the whole membarrier system call returning
-ENOSYS. Indeed, CMD_PRIVATE_EXPEDITED is compatible with nohz_full.
Adapt the CMD_QUERY mask accordingly.
Changes since v1:
- move membarrier code under kernel/sched/ because it uses the
scheduler runqueue,
- only add the barrier when we switch from a kernel thread. The case
where we switch from a user-space thread is already handled by
the atomic_dec_and_test() in mmdrop().
- add a comment to mmdrop() documenting the requirement on the implicit
memory barrier.
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: Andrew Hunter <ahh@google.com>
CC: Maged Michael <maged.michael@gmail.com>
CC: gromer@google.com
CC: Avi Kivity <avi@scylladb.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <paulus@samba.org>
CC: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Dave Watson <davejwatson@fb.com>
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The unwind code sets the sp member of struct stackframe to
'frame pointer + 0x10' unconditionally, without regard for whether
doing so produces a legal value. So let's simply remove it now that
we have stopped using it anyway.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
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When reading current's user-writable TLS register (which occurs
when dumping core for native tasks), it is possible that userspace
has modified it since the time the task was last scheduled out.
The new TLS register value is not guaranteed to have been written
immediately back to thread_struct in this case.
As a result, a coredump can capture stale data for this register.
Reading the register for a stopped task via ptrace is unaffected.
For native tasks, this patch explicitly flushes the TPIDR_EL0
register back to thread_struct before dumping when operating on
current, thus ensuring that coredump contents are up to date. For
compat tasks, the TLS register is not user-writable and so cannot
be out of sync, so no flush is required in compat_tls_get().
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Generic code expects show_regs() to dump the stack, but arm64's
show_regs() does not. This makes it hard to debug softlockups and
other issues that result in show_regs() being called.
This patch updates arm64's show_regs() to dump the stack, as common
code expects.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
[will: folded in bug_handler fix from mrutland]
Signed-off-by: Will Deacon <will.deacon@arm.com>
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There are two unnecessary newlines, one is in show_regs, another
is in __show_regs(), drop them.
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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<linux/sched/task_stack.h>
We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task_stack.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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<linux/sched/task.h>
We are going to split <linux/sched/task.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/task.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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<linux/sched/debug.h>
We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/debug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Use linux/size.h to improve code readability.
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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Function graph tracer shows negative time (wrap around) when tracing
__switch_to if the nosleep-time trace option is enabled.
Time compensation for nosleep-time is done by an ftrace probe on
sched_switch. This doesn't work well for the following events (with
letters representing timestamps):
A - sched switch probe called for task T switch out
B - __switch_to calltime is recorded
C - sched_switch probe called for task T switch in
D - __switch_to rettime is recorded
If C - A > D - B, then we end up over compensating for the time spent in
__switch_to giving rise to negative times in the trace output.
On x86, __switch_to is not traced if function graph tracer is enabled.
Do the same for arm64 as well.
Cc: Todd Kjos <tkjos@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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The hypervisor may not have full access to the kernel data structures
and hence cannot safely use cpus_have_cap() helper for checking the
system capability. Add a safe helper for hypervisors to check a constant
system capability, which *doesn't* fall back to checking the bitmap
maintained by the kernel. With this, make the cpus_have_cap() only
check the bitmask and force constant cap checks to use the new API
for quicker checks.
Cc: Robert Ritcher <rritcher@cavium.com>
Cc: Tirumalesh Chalamarla <tchalamarla@cavium.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This patch moves arm64's struct thread_info from the task stack into
task_struct. This protects thread_info from corruption in the case of
stack overflows, and makes its address harder to determine if stack
addresses are leaked, making a number of attacks more difficult. Precise
detection and handling of overflow is left for subsequent patches.
Largely, this involves changing code to store the task_struct in sp_el0,
and acquire the thread_info from the task struct. Core code now
implements current_thread_info(), and as noted in <linux/sched.h> this
relies on offsetof(task_struct, thread_info) == 0, enforced by core
code.
This change means that the 'tsk' register used in entry.S now points to
a task_struct, rather than a thread_info as it used to. To make this
clear, the TI_* field offsets are renamed to TSK_TI_*, with asm-offsets
appropriately updated to account for the structural change.
Userspace clobbers sp_el0, and we can no longer restore this from the
stack. Instead, the current task is cached in a per-cpu variable that we
can safely access from early assembly as interrupts are disabled (and we
are thus not preemptible).
Both secondary entry and idle are updated to stash the sp and task
pointer separately.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: James Morse <james.morse@arm.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Will Deacon
Matteo Croce
Linus Torvalds
Suzuki K Poulose
Amanieu d'Antras
Julien Thierry
Masayoshi Mizuma
Alexandre Ghiti
Catalin Marinas
Marc Zyngier
Dave Martin
Thomas Gleixner
Steven Rostedt (VMware)
Mark Rutland
Ard Biesheuvel
Will Deacon
Alexander Popov
Laura Abbott
Sergey Senozhatsky
Yury Norov
Mathieu Desnoyers
Kefeng Wang
Ingo Molnar
Miles Chen
Joel Fernandes