The following commit has been merged into the x86/core branch of tip: Commit-ID: 99c95c5d4f1027130d555fdb27b576520894827d Gitweb: https://git.kernel.org/tip/99c95c5d4f1027130d555fdb27b576520894827d Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 08 Mar 2022 16:30:37 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 15 Mar 2022 10:32:40 +01:00 x86/alternative: Simplify int3_selftest_ip Similar to ibt_selftest_ip, apply the same pattern. Suggested-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220308154318.700456643@xxxxxxxxxxxxx --- arch/x86/kernel/alternative.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index b4470ea..14d1003 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -719,7 +719,7 @@ asm ( " .popsection\n" ); -extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */ +extern void int3_selftest_ip(void); /* defined in asm below */ static int __init int3_exception_notify(struct notifier_block *self, unsigned long val, void *data) @@ -733,14 +733,15 @@ int3_exception_notify(struct notifier_block *self, unsigned long val, void *data if (val != DIE_INT3) return NOTIFY_DONE; - if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip) + if (regs->ip - INT3_INSN_SIZE != (unsigned long)&int3_selftest_ip) return NOTIFY_DONE; int3_emulate_call(regs, (unsigned long)&int3_magic); return NOTIFY_STOP; } -static void __init int3_selftest(void) +/* Must be noinline to ensure uniqueness of int3_selftest_ip. */ +static noinline void __init int3_selftest(void) { static __initdata struct notifier_block int3_exception_nb = { .notifier_call = int3_exception_notify, @@ -753,18 +754,10 @@ static void __init int3_selftest(void) /* * Basically: int3_magic(&val); but really complicated :-) * - * Stick the address of the INT3 instruction into int3_selftest_ip, - * then trigger the INT3, padded with NOPs to match a CALL instruction - * length. + * INT3 padded with NOP to CALL_INSN_SIZE. The int3_exception_nb + * notifier above will emulate CALL for us. */ - asm volatile ("1: int3; nop; nop; nop; nop\n\t" - ".pushsection .init.data,\"aw\"\n\t" - ".align " __ASM_SEL(4, 8) "\n\t" - ".type int3_selftest_ip, @object\n\t" - ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t" - "int3_selftest_ip:\n\t" - __ASM_SEL(.long, .quad) " 1b\n\t" - ".popsection\n\t" + asm volatile ("int3_selftest_ip: int3; nop; nop; nop; nop\n\t" : ASM_CALL_CONSTRAINT : __ASM_SEL_RAW(a, D) (&val) : "memory");
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