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| author | Peter Zijlstra <peterz@infradead.org> | 2023-08-02 12:55:46 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-09-12 17:50:53 +0200 |
| commit | 25e73b7e3f72a25aa30cbb2eecb49036e0acf066 (patch) | |
| tree | ec51d86d83644e810a6ea761725bd6c344654dca | |
| parent | 5290e88ba2c742ca77c5f5b690e5af549cfd8591 (diff) | |
| download | linux-25e73b7e3f72a25aa30cbb2eecb49036e0acf066.tar.gz | |
x86/ibt: Suppress spurious ENDBR
It was reported that under certain circumstances GCC emits ENDBR
instructions for _THIS_IP_ usage. Specifically, when it appears at the
start of a basic block -- but not elsewhere.
Since _THIS_IP_ is never used for control flow, these ENDBR
instructions are completely superfluous. Override the _THIS_IP_
definition for x86_64 to avoid this.
Less ENDBR instructions is better.
Fixes: 156ff4a544ae ("x86/ibt: Base IBT bits")
Reported-by: David Kaplan <David.Kaplan@amd.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230802110323.016197440@infradead.org
| -rw-r--r-- | arch/x86/include/asm/linkage.h | 8 | ||||
| -rw-r--r-- | include/linux/instruction_pointer.h | 5 |
2 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h index 97a3de7892d3ff..5ff49fd67732e9 100644 --- a/arch/x86/include/asm/linkage.h +++ b/arch/x86/include/asm/linkage.h @@ -8,6 +8,14 @@ #undef notrace #define notrace __attribute__((no_instrument_function)) +#ifdef CONFIG_64BIT +/* + * The generic version tends to create spurious ENDBR instructions under + * certain conditions. + */ +#define _THIS_IP_ ({ unsigned long __here; asm ("lea 0(%%rip), %0" : "=r" (__here)); __here; }) +#endif + #ifdef CONFIG_X86_32 #define asmlinkage CPP_ASMLINKAGE __attribute__((regparm(0))) #endif /* CONFIG_X86_32 */ diff --git a/include/linux/instruction_pointer.h b/include/linux/instruction_pointer.h index cda1f706eaeb11..aa0b3ffea93536 100644 --- a/include/linux/instruction_pointer.h +++ b/include/linux/instruction_pointer.h @@ -2,7 +2,12 @@ #ifndef _LINUX_INSTRUCTION_POINTER_H #define _LINUX_INSTRUCTION_POINTER_H +#include <asm/linkage.h> + #define _RET_IP_ (unsigned long)__builtin_return_address(0) + +#ifndef _THIS_IP_ #define _THIS_IP_ ({ __label__ __here; __here: (unsigned long)&&__here; }) +#endif #endif /* _LINUX_INSTRUCTION_POINTER_H */ |