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| author | Peter Zijlstra <peterz@infradead.org> | 2021-05-06 21:34:01 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-05-12 14:54:55 +0200 |
| commit | e7bf1ba97afdde75b0ef43e4bdb718bf843613f1 (patch) | |
| tree | 090e3ff09488c36c2becee9bc596f92d752ef6be | |
| parent | 5af0ea293d78c8b8f0b87ae2b13f7ac584057bc3 (diff) | |
| download | lwn-e7bf1ba97afdde75b0ef43e4bdb718bf843613f1.tar.gz lwn-e7bf1ba97afdde75b0ef43e4bdb718bf843613f1.zip | |
jump_label, x86: Emit short JMP
Now that we can patch short JMP/NOP, allow the compiler/assembler to
emit short JMP instructions.
There is no way to have the assembler emit short NOPs based on the
potential displacement, so leave those long for now.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210506194157.967034497@infradead.org
| -rw-r--r-- | arch/x86/include/asm/jump_label.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/jump_label.c | 8 |
2 files changed, 8 insertions, 3 deletions
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index d85802a00629..ef819e33cfc1 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -35,8 +35,7 @@ l_yes: static __always_inline bool arch_static_branch_jump(struct static_key * const key, const bool branch) { asm_volatile_goto("1:" - ".byte 0xe9 \n\t" - ".long %l[l_yes] - (. + 4) \n\t" + "jmp %l[l_yes]\n\t" JUMP_TABLE_ENTRY : : "i" (key), "i" (branch) : : l_yes); diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index 190d810fa435..a762dc1c615e 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -15,12 +15,18 @@ #include <asm/kprobes.h> #include <asm/alternative.h> #include <asm/text-patching.h> +#include <asm/insn.h> #define JUMP_LABEL_NOP_SIZE JMP32_INSN_SIZE int arch_jump_entry_size(struct jump_entry *entry) { - return JMP32_INSN_SIZE; + struct insn insn = {}; + + insn_decode_kernel(&insn, (void *)jump_entry_code(entry)); + BUG_ON(insn.length != 2 && insn.length != 5); + + return insn.length; } struct jump_label_patch { |