diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-entry-64-Remove-the-SYSCALL64-fast-path.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-entry-64-Remove-the-SYSCALL64-fast-path.patch | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-entry-64-Remove-the-SYSCALL64-fast-path.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-entry-64-Remove-the-SYSCALL64-fast-path.patch new file mode 100644 index 00000000..c476da81 --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-entry-64-Remove-the-SYSCALL64-fast-path.patch @@ -0,0 +1,207 @@ +From 18dacfea13d15dbf2fa1037cf76ee463c52af031 Mon Sep 17 00:00:00 2001 +From: Andy Lutomirski <luto@kernel.org> +Date: Sun, 28 Jan 2018 10:38:49 -0800 +Subject: [PATCH 21/42] x86/entry/64: Remove the SYSCALL64 fast path + +(cherry picked from commit 21d375b6b34ff511a507de27bf316b3dde6938d9) + +The SYCALLL64 fast path was a nice, if small, optimization back in the good +old days when syscalls were actually reasonably fast. Now there is PTI to +slow everything down, and indirect branches are verboten, making everything +messier. The retpoline code in the fast path is particularly nasty. + +Just get rid of the fast path. The slow path is barely slower. + +[ tglx: Split out the 'push all extra regs' part ] + +Signed-off-by: Andy Lutomirski <luto@kernel.org> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Acked-by: Ingo Molnar <mingo@kernel.org> +Cc: Borislav Petkov <bp@alien8.de> +Cc: Linus Torvalds <torvalds@linux-foundation.org> +Cc: Kernel Hardening <kernel-hardening@lists.openwall.com> +Link: https://lkml.kernel.org/r/462dff8d4d64dfbfc851fbf3130641809d980ecd.1517164461.git.luto@kernel.org +Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + arch/x86/entry/entry_64.S | 123 +------------------------------------------- + arch/x86/entry/syscall_64.c | 7 +-- + 2 files changed, 3 insertions(+), 127 deletions(-) + +diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S +index e422e15..4360253 100644 +--- a/arch/x86/entry/entry_64.S ++++ b/arch/x86/entry/entry_64.S +@@ -179,94 +179,11 @@ GLOBAL(entry_SYSCALL_64_after_swapgs) + pushq %r11 /* pt_regs->r11 */ + sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */ + +- /* +- * If we need to do entry work or if we guess we'll need to do +- * exit work, go straight to the slow path. +- */ +- movq PER_CPU_VAR(current_task), %r11 +- testl $_TIF_WORK_SYSCALL_ENTRY|_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) +- jnz entry_SYSCALL64_slow_path +- +-entry_SYSCALL_64_fastpath: +- /* +- * Easy case: enable interrupts and issue the syscall. If the syscall +- * needs pt_regs, we'll call a stub that disables interrupts again +- * and jumps to the slow path. +- */ +- TRACE_IRQS_ON +- ENABLE_INTERRUPTS(CLBR_NONE) +-#if __SYSCALL_MASK == ~0 +- cmpq $__NR_syscall_max, %rax +-#else +- andl $__SYSCALL_MASK, %eax +- cmpl $__NR_syscall_max, %eax +-#endif +- ja 1f /* return -ENOSYS (already in pt_regs->ax) */ +- movq %r10, %rcx +- +- /* +- * This call instruction is handled specially in stub_ptregs_64. +- * It might end up jumping to the slow path. If it jumps, RAX +- * and all argument registers are clobbered. +- */ +-#ifdef CONFIG_RETPOLINE +- movq sys_call_table(, %rax, 8), %rax +- call __x86_indirect_thunk_rax +-#else +- call *sys_call_table(, %rax, 8) +-#endif +-.Lentry_SYSCALL_64_after_fastpath_call: +- +- movq %rax, RAX(%rsp) +-1: +- +- /* +- * If we get here, then we know that pt_regs is clean for SYSRET64. +- * If we see that no exit work is required (which we are required +- * to check with IRQs off), then we can go straight to SYSRET64. +- */ +- DISABLE_INTERRUPTS(CLBR_NONE) +- TRACE_IRQS_OFF +- movq PER_CPU_VAR(current_task), %r11 +- testl $_TIF_ALLWORK_MASK, TASK_TI_flags(%r11) +- jnz 1f +- +- LOCKDEP_SYS_EXIT +- TRACE_IRQS_ON /* user mode is traced as IRQs on */ +- movq RIP(%rsp), %rcx +- movq EFLAGS(%rsp), %r11 +- RESTORE_C_REGS_EXCEPT_RCX_R11 +- /* +- * This opens a window where we have a user CR3, but are +- * running in the kernel. This makes using the CS +- * register useless for telling whether or not we need to +- * switch CR3 in NMIs. Normal interrupts are OK because +- * they are off here. +- */ +- SWITCH_USER_CR3 +- movq RSP(%rsp), %rsp +- USERGS_SYSRET64 +- +-1: +- /* +- * The fast path looked good when we started, but something changed +- * along the way and we need to switch to the slow path. Calling +- * raise(3) will trigger this, for example. IRQs are off. +- */ +- TRACE_IRQS_ON +- ENABLE_INTERRUPTS(CLBR_NONE) +- SAVE_EXTRA_REGS +- movq %rsp, %rdi +- call syscall_return_slowpath /* returns with IRQs disabled */ +- jmp return_from_SYSCALL_64 +- +-entry_SYSCALL64_slow_path: + /* IRQs are off. */ + SAVE_EXTRA_REGS + movq %rsp, %rdi + call do_syscall_64 /* returns with IRQs disabled */ + +-return_from_SYSCALL_64: + RESTORE_EXTRA_REGS + TRACE_IRQS_IRETQ /* we're about to change IF */ + +@@ -339,6 +256,7 @@ return_from_SYSCALL_64: + syscall_return_via_sysret: + /* rcx and r11 are already restored (see code above) */ + RESTORE_C_REGS_EXCEPT_RCX_R11 ++ + /* + * This opens a window where we have a user CR3, but are + * running in the kernel. This makes using the CS +@@ -363,45 +281,6 @@ opportunistic_sysret_failed: + jmp restore_c_regs_and_iret + END(entry_SYSCALL_64) + +-ENTRY(stub_ptregs_64) +- /* +- * Syscalls marked as needing ptregs land here. +- * If we are on the fast path, we need to save the extra regs, +- * which we achieve by trying again on the slow path. If we are on +- * the slow path, the extra regs are already saved. +- * +- * RAX stores a pointer to the C function implementing the syscall. +- * IRQs are on. +- */ +- cmpq $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp) +- jne 1f +- +- /* +- * Called from fast path -- disable IRQs again, pop return address +- * and jump to slow path +- */ +- DISABLE_INTERRUPTS(CLBR_NONE) +- TRACE_IRQS_OFF +- popq %rax +- jmp entry_SYSCALL64_slow_path +- +-1: +- JMP_NOSPEC %rax /* Called from C */ +-END(stub_ptregs_64) +- +-.macro ptregs_stub func +-ENTRY(ptregs_\func) +- leaq \func(%rip), %rax +- jmp stub_ptregs_64 +-END(ptregs_\func) +-.endm +- +-/* Instantiate ptregs_stub for each ptregs-using syscall */ +-#define __SYSCALL_64_QUAL_(sym) +-#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_stub sym +-#define __SYSCALL_64(nr, sym, qual) __SYSCALL_64_QUAL_##qual(sym) +-#include <asm/syscalls_64.h> +- + /* + * %rdi: prev task + * %rsi: next task +diff --git a/arch/x86/entry/syscall_64.c b/arch/x86/entry/syscall_64.c +index 9dbc5ab..6705edd 100644 +--- a/arch/x86/entry/syscall_64.c ++++ b/arch/x86/entry/syscall_64.c +@@ -6,14 +6,11 @@ + #include <asm/asm-offsets.h> + #include <asm/syscall.h> + +-#define __SYSCALL_64_QUAL_(sym) sym +-#define __SYSCALL_64_QUAL_ptregs(sym) ptregs_##sym +- +-#define __SYSCALL_64(nr, sym, qual) extern asmlinkage long __SYSCALL_64_QUAL_##qual(sym)(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long); ++#define __SYSCALL_64(nr, sym, qual) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long); + #include <asm/syscalls_64.h> + #undef __SYSCALL_64 + +-#define __SYSCALL_64(nr, sym, qual) [nr] = __SYSCALL_64_QUAL_##qual(sym), ++#define __SYSCALL_64(nr, sym, qual) [nr] = sym, + + extern long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long); + +-- +2.7.4 + |