diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2021-05-06 21:34:05 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-05-12 14:54:56 +0200 |
| commit | ab3257042c26d0cd44793c741e2f89bf38b21fe8 (patch) | |
| tree | 1b20008657d1d7ee5681252672e9b7a5cab58431 | |
| parent | e2d9494beff21a26438eb611c260b8a6c2dc4dbf (diff) | |
jump_label, x86: Allow short NOPs
Now that objtool is able to rewrite jump_label instructions, have the
compiler emit a JMP, such that it can decide on the optimal encoding,
and set jump_entry::key bit1 to indicate that objtool should rewrite
the instruction to a matching NOP.
For x86_64-allyesconfig this gives:
jl\ NOP JMP
short: 22997 124
long: 30874 90
IOW, we save (22997+124) * 3 bytes of kernel text in hotpaths.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210506194158.216763632@infradead.org
| -rw-r--r-- | arch/x86/include/asm/jump_label.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index ef819e33cfc1..0449b125d27f 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -20,6 +20,22 @@ _ASM_PTR "%c0 + %c1 - .\n\t" \ ".popsection \n\t" +#ifdef CONFIG_STACK_VALIDATION + +static __always_inline bool arch_static_branch(struct static_key *key, bool branch) +{ + asm_volatile_goto("1:" + "jmp %l[l_yes] # objtool NOPs this \n\t" + JUMP_TABLE_ENTRY + : : "i" (key), "i" (2 | branch) : : l_yes); + + return false; +l_yes: + return true; +} + +#else + static __always_inline bool arch_static_branch(struct static_key * const key, const bool branch) { asm_volatile_goto("1:" @@ -32,6 +48,8 @@ l_yes: return true; } +#endif /* STACK_VALIDATION */ + static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch) { asm_volatile_goto("1:" |