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>
This commit is contained in:
Andy Lutomirski
H. Peter Anvin
parent
c9712944b2
commit
59e97e4d6f
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@ -17,8 +17,8 @@
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.macro altinstruction_entry orig alt feature orig_len alt_len
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.align 8
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.quad \orig
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.quad \alt
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.long \orig - .
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.long \alt - .
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.word \feature
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.byte \orig_len
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.byte \alt_len
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@ -43,8 +43,8 @@
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#endif
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struct alt_instr {
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u8 *instr; /* original instruction */
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u8 *replacement;
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s32 instr_offset; /* original instruction */
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s32 repl_offset; /* offset to replacement instruction */
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u16 cpuid; /* cpuid bit set for replacement */
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u8 instrlen; /* length of original instruction */
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u8 replacementlen; /* length of new instruction, <= instrlen */
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@ -84,8 +84,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
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"661:\n\t" oldinstr "\n662:\n" \
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".section .altinstructions,\"a\"\n" \
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_ASM_ALIGN "\n" \
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_ASM_PTR "661b\n" /* label */ \
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_ASM_PTR "663f\n" /* new instruction */ \
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" .long 661b - .\n" /* label */ \
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" .long 663f - .\n" /* new instruction */ \
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" .word " __stringify(feature) "\n" /* feature bit */ \
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" .byte 662b-661b\n" /* sourcelen */ \
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" .byte 664f-663f\n" /* replacementlen */ \
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@ -331,8 +331,8 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
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"2:\n"
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".section .altinstructions,\"a\"\n"
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_ASM_ALIGN "\n"
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_ASM_PTR "1b\n"
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_ASM_PTR "0\n" /* no replacement */
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" .long 1b - .\n"
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" .long 0\n" /* no replacement */
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" .word %P0\n" /* feature bit */
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" .byte 2b - 1b\n" /* source len */
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" .byte 0\n" /* replacement len */
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@ -349,8 +349,8 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
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"2:\n"
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".section .altinstructions,\"a\"\n"
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_ASM_ALIGN "\n"
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_ASM_PTR "1b\n"
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_ASM_PTR "3f\n"
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" .long 1b - .\n"
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" .long 3f - .\n"
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" .word %P1\n" /* feature bit */
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" .byte 2b - 1b\n" /* source len */
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" .byte 4f - 3f\n" /* replacement len */
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@ -263,6 +263,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
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struct alt_instr *end)
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{
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struct alt_instr *a;
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u8 *instr, *replacement;
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u8 insnbuf[MAX_PATCH_LEN];
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DPRINTK("%s: alt table %p -> %p\n", __func__, start, end);
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@ -276,25 +277,29 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
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* order.
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*/
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for (a = start; a < end; a++) {
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u8 *instr = a->instr;
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instr = (u8 *)&a->instr_offset + a->instr_offset;
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replacement = (u8 *)&a->repl_offset + a->repl_offset;
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BUG_ON(a->replacementlen > a->instrlen);
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BUG_ON(a->instrlen > sizeof(insnbuf));
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BUG_ON(a->cpuid >= NCAPINTS*32);
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if (!boot_cpu_has(a->cpuid))
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continue;
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memcpy(insnbuf, replacement, a->replacementlen);
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/* 0xe8 is a relative jump; fix the offset. */
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if (*insnbuf == 0xe8 && a->replacementlen == 5)
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*(s32 *)(insnbuf + 1) += replacement - instr;
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add_nops(insnbuf + a->replacementlen,
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a->instrlen - a->replacementlen);
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#ifdef CONFIG_X86_64
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/* vsyscall code is not mapped yet. resolve it manually. */
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if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
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instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
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DPRINTK("%s: vsyscall fixup: %p => %p\n",
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__func__, a->instr, instr);
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}
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#endif
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memcpy(insnbuf, a->replacement, a->replacementlen);
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if (*insnbuf == 0xe8 && a->replacementlen == 5)
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*(s32 *)(insnbuf + 1) += a->replacement - a->instr;
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add_nops(insnbuf + a->replacementlen,
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a->instrlen - a->replacementlen);
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text_poke_early(instr, insnbuf, a->instrlen);
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}
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}
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@ -2,6 +2,7 @@
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#include <linux/linkage.h>
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#include <asm/dwarf2.h>
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#include <asm/alternative-asm.h>
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ALIGN
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copy_page_c:
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@ -110,10 +111,6 @@ ENDPROC(copy_page)
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2:
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.previous
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.section .altinstructions,"a"
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.align 8
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.quad copy_page
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.quad 1b
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.word X86_FEATURE_REP_GOOD
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.byte .Lcopy_page_end - copy_page
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.byte 2b - 1b
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altinstruction_entry copy_page, 1b, X86_FEATURE_REP_GOOD, \
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.Lcopy_page_end-copy_page, 2b-1b
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.previous
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@ -9,6 +9,7 @@
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#include <linux/linkage.h>
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#include <asm/dwarf2.h>
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#include <asm/cpufeature.h>
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#include <asm/alternative-asm.h>
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#undef memmove
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@ -214,11 +215,9 @@ ENTRY(memmove)
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.previous
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.section .altinstructions,"a"
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.align 8
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.quad .Lmemmove_begin_forward
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.quad .Lmemmove_begin_forward_efs
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.word X86_FEATURE_ERMS
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.byte .Lmemmove_end_forward-.Lmemmove_begin_forward
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.byte .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs
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altinstruction_entry .Lmemmove_begin_forward, \
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.Lmemmove_begin_forward_efs,X86_FEATURE_ERMS, \
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.Lmemmove_end_forward-.Lmemmove_begin_forward, \
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.Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs
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.previous
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ENDPROC(memmove)
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