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| author | Andy Lutomirski <luto@mit.edu> | 2011-07-13 15:24:10 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2011-07-13 20:22:56 +0200 |
| commit | 59e97e4d6fbcd5b74a94cb48bcbfc6f8478a5e93 (patch) | |
| tree | 015fd8e63e1fcd8fdf7a066bd2e09a5636a14449 /arch/x86/kernel/alternative.c | |
| parent | x86-64: Improve vsyscall emulation CS and RIP handling (diff) | |
| download | linux-59e97e4d6fbcd5b74a94cb48bcbfc6f8478a5e93.tar.xz linux-59e97e4d6fbcd5b74a94cb48bcbfc6f8478a5e93.zip | |
x86: Make alternative instruction pointers relative
This save a few bytes on x86-64 and means that future patches can
apply alternatives to unrelocated code.
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/ff64a6b9a1a3860ca4a7b8b6dc7b4754f9491cd7.1310563276.git.luto@mit.edu
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/alternative.c')
| -rw-r--r-- | arch/x86/kernel/alternative.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index a81f2d52f869..ddb207bb5f91 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -263,6 +263,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start, struct alt_instr *end) { struct alt_instr *a; + u8 *instr, *replacement; u8 insnbuf[MAX_PATCH_LEN]; DPRINTK("%s: alt table %p -> %p\n", __func__, start, end); @@ -276,25 +277,29 @@ void __init_or_module apply_alternatives(struct alt_instr *start, * order. */ for (a = start; a < end; a++) { - u8 *instr = a->instr; + instr = (u8 *)&a->instr_offset + a->instr_offset; + replacement = (u8 *)&a->repl_offset + a->repl_offset; BUG_ON(a->replacementlen > a->instrlen); BUG_ON(a->instrlen > sizeof(insnbuf)); BUG_ON(a->cpuid >= NCAPINTS*32); if (!boot_cpu_has(a->cpuid)) continue; + + memcpy(insnbuf, replacement, a->replacementlen); + + /* 0xe8 is a relative jump; fix the offset. */ + if (*insnbuf == 0xe8 && a->replacementlen == 5) + *(s32 *)(insnbuf + 1) += replacement - instr; + + add_nops(insnbuf + a->replacementlen, + a->instrlen - a->replacementlen); + #ifdef CONFIG_X86_64 /* vsyscall code is not mapped yet. resolve it manually. */ if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) { instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0)); - DPRINTK("%s: vsyscall fixup: %p => %p\n", - __func__, a->instr, instr); } #endif - memcpy(insnbuf, a->replacement, a->replacementlen); - if (*insnbuf == 0xe8 && a->replacementlen == 5) - *(s32 *)(insnbuf + 1) += a->replacement - a->instr; - add_nops(insnbuf + a->replacementlen, - a->instrlen - a->replacementlen); text_poke_early(instr, insnbuf, a->instrlen); } } |