From: Peter Zijlstra <peterz@infradead.org> mainline inclusion from mainline-5.12-rc1 commit 3f2a8fc4b15de18644e8a80a09edda168676e22c category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I410UT CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... --------------------------- Provide a stub function that return 0 and wire up the static call site patching to replace the CALL with a single 5 byte instruction that clears %RAX, the return value register. The function can be cast to any function pointer type that has a single %RAX return (including pointers). Also provide a version that returns an int for convenience. We are clearing the entire %RAX register in any case, whether the return value is 32 or 64 bits, since %RAX is always a scratch register anyway. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.org Signed-off-by: Ma Junhai <majunhai2@huawei.com> Reviewed-by: Chen Hui <judy.chenhui@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- arch/x86/kernel/static_call.c | 17 +++++++++++++++-- include/linux/static_call.h | 12 ++++++++++++ kernel/static_call.c | 5 +++++ 3 files changed, 32 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index ca9a380d9c0b..9442c4136c38 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -11,14 +11,26 @@ enum insn_type { RET = 3, /* tramp / site cond-tail-call */ }; +/* + * data16 data16 xorq %rax, %rax - a single 5 byte instruction that clears %rax + * The REX.W cancels the effect of any data16. + */ +static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 }; + static void __ref __static_call_transform(void *insn, enum insn_type type, void *func) { + const void *emulate = NULL; int size = CALL_INSN_SIZE; const void *code; switch (type) { case CALL: code = text_gen_insn(CALL_INSN_OPCODE, insn, func); + if (func == &__static_call_return0) { + emulate = code; + code = &xor5rax; + } + break; case NOP: @@ -41,7 +53,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void if (unlikely(system_state == SYSTEM_BOOTING)) return text_poke_early(insn, code, size); - text_poke_bp(insn, code, size, NULL); + text_poke_bp(insn, code, size, emulate); } static void __static_call_validate(void *insn, bool tail) @@ -54,7 +66,8 @@ static void __static_call_validate(void *insn, bool tail) return; } else { if (opcode == CALL_INSN_OPCODE || - !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5)) + !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5) || + !memcmp(insn, xor5rax, 5)) return; } diff --git a/include/linux/static_call.h b/include/linux/static_call.h index 04e6042d252d..6550902c8b59 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -148,6 +148,8 @@ extern void __static_call_update(struct static_call_key *key, void *tramp, void extern int static_call_mod_init(struct module *mod); extern int static_call_text_reserved(void *start, void *end); +extern long __static_call_return0(void); + #define DEFINE_STATIC_CALL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ @@ -219,6 +221,11 @@ static inline int static_call_text_reserved(void *start, void *end) return 0; } +static inline long __static_call_return0(void) +{ + return 0; +} + #define EXPORT_STATIC_CALL(name) \ EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)) @@ -240,6 +247,11 @@ struct static_call_key { void *func; }; +static inline long __static_call_return0(void) +{ + return 0; +} + #define DEFINE_STATIC_CALL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ diff --git a/kernel/static_call.c b/kernel/static_call.c index f59089a12231..2c5950b0b90e 100644 --- a/kernel/static_call.c +++ b/kernel/static_call.c @@ -496,6 +496,11 @@ int __init static_call_init(void) } early_initcall(static_call_init); +long __static_call_return0(void) +{ + return 0; +} + #ifdef CONFIG_STATIC_CALL_SELFTEST static int func_a(int x) -- 2.20.1