diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0019-x86-retpoline-Simplify-vmexit_fill_RSB.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0019-x86-retpoline-Simplify-vmexit_fill_RSB.patch | 261 |
1 files changed, 261 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0019-x86-retpoline-Simplify-vmexit_fill_RSB.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0019-x86-retpoline-Simplify-vmexit_fill_RSB.patch new file mode 100644 index 00000000..60269d5c --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0019-x86-retpoline-Simplify-vmexit_fill_RSB.patch @@ -0,0 +1,261 @@ +From 53b3bd3747acd3d6633feaa63a998f854d90551c Mon Sep 17 00:00:00 2001 +From: Borislav Petkov <bp@alien8.de> +Date: Sat, 27 Jan 2018 16:24:33 +0000 +Subject: [PATCH 19/42] x86/retpoline: Simplify vmexit_fill_RSB() + +(cherry picked from commit 1dde7415e99933bb7293d6b2843752cbdb43ec11) + +Simplify it to call an asm-function instead of pasting 41 insn bytes at +every call site. Also, add alignment to the macro as suggested here: + + https://support.google.com/faqs/answer/7625886 + +[dwmw2: Clean up comments, let it clobber %ebx and just tell the compiler] + +Signed-off-by: Borislav Petkov <bp@suse.de> +Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Cc: ak@linux.intel.com +Cc: dave.hansen@intel.com +Cc: karahmed@amazon.de +Cc: arjan@linux.intel.com +Cc: torvalds@linux-foundation.org +Cc: peterz@infradead.org +Cc: bp@alien8.de +Cc: pbonzini@redhat.com +Cc: tim.c.chen@linux.intel.com +Cc: gregkh@linux-foundation.org +Link: https://lkml.kernel.org/r/1517070274-12128-3-git-send-email-dwmw@amazon.co.uk +Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + arch/x86/entry/entry_32.S | 3 +- + arch/x86/entry/entry_64.S | 3 +- + arch/x86/include/asm/asm-prototypes.h | 3 ++ + arch/x86/include/asm/nospec-branch.h | 70 ++++------------------------------- + arch/x86/lib/Makefile | 1 + + arch/x86/lib/retpoline.S | 56 ++++++++++++++++++++++++++++ + 6 files changed, 71 insertions(+), 65 deletions(-) + +diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S +index a76dc73..f5434b4 100644 +--- a/arch/x86/entry/entry_32.S ++++ b/arch/x86/entry/entry_32.S +@@ -237,7 +237,8 @@ ENTRY(__switch_to_asm) + * exist, overwrite the RSB with entries which capture + * speculative execution to prevent attack. + */ +- FILL_RETURN_BUFFER %ebx, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW ++ /* Clobbers %ebx */ ++ FILL_RETURN_BUFFER RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW + #endif + + /* restore callee-saved registers */ +diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S +index 16146eb..e422e15 100644 +--- a/arch/x86/entry/entry_64.S ++++ b/arch/x86/entry/entry_64.S +@@ -435,7 +435,8 @@ ENTRY(__switch_to_asm) + * exist, overwrite the RSB with entries which capture + * speculative execution to prevent attack. + */ +- FILL_RETURN_BUFFER %r12, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW ++ /* Clobbers %rbx */ ++ FILL_RETURN_BUFFER RSB_CLEAR_LOOPS, X86_FEATURE_RSB_CTXSW + #endif + + /* restore callee-saved registers */ +diff --git a/arch/x86/include/asm/asm-prototypes.h b/arch/x86/include/asm/asm-prototypes.h +index 5a25ada..1666542 100644 +--- a/arch/x86/include/asm/asm-prototypes.h ++++ b/arch/x86/include/asm/asm-prototypes.h +@@ -37,4 +37,7 @@ INDIRECT_THUNK(dx) + INDIRECT_THUNK(si) + INDIRECT_THUNK(di) + INDIRECT_THUNK(bp) ++asmlinkage void __fill_rsb(void); ++asmlinkage void __clear_rsb(void); ++ + #endif /* CONFIG_RETPOLINE */ +diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h +index 19ecb54..df4ecec 100644 +--- a/arch/x86/include/asm/nospec-branch.h ++++ b/arch/x86/include/asm/nospec-branch.h +@@ -7,50 +7,6 @@ + #include <asm/alternative-asm.h> + #include <asm/cpufeatures.h> + +-/* +- * Fill the CPU return stack buffer. +- * +- * Each entry in the RSB, if used for a speculative 'ret', contains an +- * infinite 'pause; lfence; jmp' loop to capture speculative execution. +- * +- * This is required in various cases for retpoline and IBRS-based +- * mitigations for the Spectre variant 2 vulnerability. Sometimes to +- * eliminate potentially bogus entries from the RSB, and sometimes +- * purely to ensure that it doesn't get empty, which on some CPUs would +- * allow predictions from other (unwanted!) sources to be used. +- * +- * We define a CPP macro such that it can be used from both .S files and +- * inline assembly. It's possible to do a .macro and then include that +- * from C via asm(".include <asm/nospec-branch.h>") but let's not go there. +- */ +- +-#define RSB_CLEAR_LOOPS 32 /* To forcibly overwrite all entries */ +-#define RSB_FILL_LOOPS 16 /* To avoid underflow */ +- +-/* +- * Google experimented with loop-unrolling and this turned out to be +- * the optimal version — two calls, each with their own speculation +- * trap should their return address end up getting used, in a loop. +- */ +-#define __FILL_RETURN_BUFFER(reg, nr, sp) \ +- mov $(nr/2), reg; \ +-771: \ +- call 772f; \ +-773: /* speculation trap */ \ +- pause; \ +- lfence; \ +- jmp 773b; \ +-772: \ +- call 774f; \ +-775: /* speculation trap */ \ +- pause; \ +- lfence; \ +- jmp 775b; \ +-774: \ +- dec reg; \ +- jnz 771b; \ +- add $(BITS_PER_LONG/8) * nr, sp; +- + #ifdef __ASSEMBLY__ + + /* +@@ -121,17 +77,10 @@ + #endif + .endm + +- /* +- * A simpler FILL_RETURN_BUFFER macro. Don't make people use the CPP +- * monstrosity above, manually. +- */ +-.macro FILL_RETURN_BUFFER reg:req nr:req ftr:req ++/* This clobbers the BX register */ ++.macro FILL_RETURN_BUFFER nr:req ftr:req + #ifdef CONFIG_RETPOLINE +- ANNOTATE_NOSPEC_ALTERNATIVE +- ALTERNATIVE "jmp .Lskip_rsb_\@", \ +- __stringify(__FILL_RETURN_BUFFER(\reg,\nr,%_ASM_SP)) \ +- \ftr +-.Lskip_rsb_\@: ++ ALTERNATIVE "", "call __clear_rsb", \ftr + #endif + .endm + +@@ -206,15 +155,10 @@ extern char __indirect_thunk_end[]; + static inline void vmexit_fill_RSB(void) + { + #ifdef CONFIG_RETPOLINE +- unsigned long loops; +- +- asm volatile (ANNOTATE_NOSPEC_ALTERNATIVE +- ALTERNATIVE("jmp 910f", +- __stringify(__FILL_RETURN_BUFFER(%0, RSB_CLEAR_LOOPS, %1)), +- X86_FEATURE_RETPOLINE) +- "910:" +- : "=r" (loops), ASM_CALL_CONSTRAINT +- : : "memory" ); ++ alternative_input("", ++ "call __fill_rsb", ++ X86_FEATURE_RETPOLINE, ++ ASM_NO_INPUT_CLOBBER(_ASM_BX, "memory")); + #endif + } + +diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile +index 6bf1898..4ad7c4d 100644 +--- a/arch/x86/lib/Makefile ++++ b/arch/x86/lib/Makefile +@@ -26,6 +26,7 @@ lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o + lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o + lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o + lib-$(CONFIG_RETPOLINE) += retpoline.o ++OBJECT_FILES_NON_STANDARD_retpoline.o :=y + + obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o + +diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S +index c909961..480edc3 100644 +--- a/arch/x86/lib/retpoline.S ++++ b/arch/x86/lib/retpoline.S +@@ -7,6 +7,7 @@ + #include <asm/alternative-asm.h> + #include <asm/export.h> + #include <asm/nospec-branch.h> ++#include <asm/bitsperlong.h> + + .macro THUNK reg + .section .text.__x86.indirect_thunk +@@ -46,3 +47,58 @@ GENERATE_THUNK(r13) + GENERATE_THUNK(r14) + GENERATE_THUNK(r15) + #endif ++ ++/* ++ * Fill the CPU return stack buffer. ++ * ++ * Each entry in the RSB, if used for a speculative 'ret', contains an ++ * infinite 'pause; lfence; jmp' loop to capture speculative execution. ++ * ++ * This is required in various cases for retpoline and IBRS-based ++ * mitigations for the Spectre variant 2 vulnerability. Sometimes to ++ * eliminate potentially bogus entries from the RSB, and sometimes ++ * purely to ensure that it doesn't get empty, which on some CPUs would ++ * allow predictions from other (unwanted!) sources to be used. ++ * ++ * Google experimented with loop-unrolling and this turned out to be ++ * the optimal version - two calls, each with their own speculation ++ * trap should their return address end up getting used, in a loop. ++ */ ++.macro STUFF_RSB nr:req sp:req ++ mov $(\nr / 2), %_ASM_BX ++ .align 16 ++771: ++ call 772f ++773: /* speculation trap */ ++ pause ++ lfence ++ jmp 773b ++ .align 16 ++772: ++ call 774f ++775: /* speculation trap */ ++ pause ++ lfence ++ jmp 775b ++ .align 16 ++774: ++ dec %_ASM_BX ++ jnz 771b ++ add $((BITS_PER_LONG/8) * \nr), \sp ++.endm ++ ++#define RSB_FILL_LOOPS 16 /* To avoid underflow */ ++ ++ENTRY(__fill_rsb) ++ STUFF_RSB RSB_FILL_LOOPS, %_ASM_SP ++ ret ++END(__fill_rsb) ++EXPORT_SYMBOL_GPL(__fill_rsb) ++ ++#define RSB_CLEAR_LOOPS 32 /* To forcibly overwrite all entries */ ++ ++ENTRY(__clear_rsb) ++ STUFF_RSB RSB_CLEAR_LOOPS, %_ASM_SP ++ ret ++END(__clear_rsb) ++EXPORT_SYMBOL_GPL(__clear_rsb) +-- +2.7.4 + |