diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2025-06-07 10:06:40 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-11-24 20:23:25 +0100 |
| commit | 860238af7a3348225de228dc0f33a7d631638333 (patch) | |
| tree | d9b6d53173913cb4953fe989bb76afc369ad6a0f | |
| parent | 11bb4944f014d756f35261f5afcb346901ef1efa (diff) | |
x86_64/bug: Inline the UD1
(Ab)use the static_call infrastructure to convert all:
call __WARN_trap
instances into the desired:
ud1 (%edx), %rdi
eliminating the CALL/RET, but more importantly, fixing the
fact that all WARNs will have:
RIP: 0010:__WARN_trap+0
Basically, by making it a static_call trampoline call, objtool will
collect the callsites, and then the inline rewrite will hit the
special case and replace the code with the magic instruction.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251110115758.456717741@infradead.org
| -rw-r--r-- | arch/x86/include/asm/bug.h | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/static_call.c | 13 | ||||
| -rw-r--r-- | arch/x86/kernel/traps.c | 4 |
3 files changed, 19 insertions, 3 deletions
diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index 87199e6633f9..d0a96ff5c02c 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -140,6 +140,9 @@ do { \ #ifdef HAVE_ARCH_BUG_FORMAT_ARGS #ifndef __ASSEMBLY__ +#include <linux/static_call_types.h> +DECLARE_STATIC_CALL(WARN_trap, __WARN_trap); + struct pt_regs; struct sysv_va_list { /* from AMD64 System V ABI */ unsigned int gp_offset; @@ -171,7 +174,7 @@ extern void *__warn_args(struct arch_va_list *args, struct pt_regs *regs); #define __WARN_print_arg(flags, format, arg...) \ do { \ int __flags = (flags) | BUGFLAG_WARNING | BUGFLAG_ARGS ; \ - __WARN_trap(__WARN_bug_entry(__flags, format), ## arg); \ + static_call_mod(WARN_trap)(__WARN_bug_entry(__flags, format), ## arg); \ asm (""); /* inhibit tail-call optimization */ \ } while (0) diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index 378c388d1b31..2892cdb14563 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -26,6 +26,11 @@ static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 }; static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc }; +/* + * ud1 (%edx),%rdi -- see __WARN_trap() / decode_bug() + */ +static const u8 warninsn[] = { 0x67, 0x48, 0x0f, 0xb9, 0x3a }; + static u8 __is_Jcc(u8 *insn) /* Jcc.d32 */ { u8 ret = 0; @@ -69,7 +74,10 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, emulate = code; code = &xor5rax; } - + if (func == &__WARN_trap) { + emulate = code; + code = &warninsn; + } break; case NOP: @@ -128,7 +136,8 @@ static void __static_call_validate(u8 *insn, bool tail, bool tramp) } else { if (opcode == CALL_INSN_OPCODE || !memcmp(insn, x86_nops[5], 5) || - !memcmp(insn, xor5rax, 5)) + !memcmp(insn, xor5rax, 5) || + !memcmp(insn, warninsn, 5)) return; } diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index fbbe3ab145a7..cb324cc1fd99 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -31,6 +31,7 @@ #include <linux/kexec.h> #include <linux/sched.h> #include <linux/sched/task_stack.h> +#include <linux/static_call.h> #include <linux/timer.h> #include <linux/init.h> #include <linux/bug.h> @@ -215,6 +216,9 @@ static inline unsigned long pt_regs_val(struct pt_regs *regs, int nr) } #ifdef HAVE_ARCH_BUG_FORMAT_ARGS +DEFINE_STATIC_CALL(WARN_trap, __WARN_trap); +EXPORT_STATIC_CALL_TRAMP(WARN_trap); + /* * Create a va_list from an exception context. */ |