diff options
| author | Jani Nikula <jani.nikula@intel.com> | 2021-03-11 08:19:46 +0200 |
|---|---|---|
| committer | Jani Nikula <jani.nikula@intel.com> | 2021-03-11 08:52:53 +0200 |
| commit | 35bb28ece90dfb7f72b77ba529f25f79323d9581 (patch) | |
| tree | 4ae931a45b83b5701214952066bb6fa6d839d7ff /arch/x86/kernel/static_call.c | |
| parent | aaca50ef45ed247d98a66c0a754d1be93ff35dde (diff) | |
| parent | a38fd8748464831584a19438cbb3082b5a2dab15 (diff) | |
Merge drm/drm-next into drm-intel-next
Sync up with upstream.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Diffstat (limited to 'arch/x86/kernel/static_call.c')
| -rw-r--r-- | arch/x86/kernel/static_call.c | 17 |
1 files changed, 15 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; } |