From 59e97e4d6fbcd5b74a94cb48bcbfc6f8478a5e93 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Wed, 13 Jul 2011 09:24:10 -0400 Subject: [PATCH] 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 Link: http://lkml.kernel.org/r/ff64a6b9a1a3860ca4a7b8b6dc7b4754f9491cd7.1310563276.git.luto@mit.edu Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/alternative-asm.h | 4 ++-- arch/x86/include/asm/alternative.h | 8 ++++---- arch/x86/include/asm/cpufeature.h | 8 ++++---- arch/x86/kernel/alternative.c | 21 +++++++++++++-------- arch/x86/lib/copy_page_64.S | 9 +++------ arch/x86/lib/memmove_64.S | 11 +++++------ 6 files changed, 31 insertions(+), 30 deletions(-) diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h index 94d420b360d..4554cc6fb96 100644 --- a/arch/x86/include/asm/alternative-asm.h +++ b/arch/x86/include/asm/alternative-asm.h @@ -17,8 +17,8 @@ .macro altinstruction_entry orig alt feature orig_len alt_len .align 8 - .quad \orig - .quad \alt + .long \orig - . + .long \alt - . .word \feature .byte \orig_len .byte \alt_len diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h index bf535f947e8..23fb6d79f20 100644 --- a/arch/x86/include/asm/alternative.h +++ b/arch/x86/include/asm/alternative.h @@ -43,8 +43,8 @@ #endif struct alt_instr { - u8 *instr; /* original instruction */ - u8 *replacement; + s32 instr_offset; /* original instruction */ + s32 repl_offset; /* offset to replacement instruction */ u16 cpuid; /* cpuid bit set for replacement */ u8 instrlen; /* length of original instruction */ u8 replacementlen; /* length of new instruction, <= instrlen */ @@ -84,8 +84,8 @@ static inline int alternatives_text_reserved(void *start, void *end) "661:\n\t" oldinstr "\n662:\n" \ ".section .altinstructions,\"a\"\n" \ _ASM_ALIGN "\n" \ - _ASM_PTR "661b\n" /* label */ \ - _ASM_PTR "663f\n" /* new instruction */ \ + " .long 661b - .\n" /* label */ \ + " .long 663f - .\n" /* new instruction */ \ " .word " __stringify(feature) "\n" /* feature bit */ \ " .byte 662b-661b\n" /* sourcelen */ \ " .byte 664f-663f\n" /* replacementlen */ \ diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 71cc3800712..9929b35929f 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -331,8 +331,8 @@ static __always_inline __pure bool __static_cpu_has(u16 bit) "2:\n" ".section .altinstructions,\"a\"\n" _ASM_ALIGN "\n" - _ASM_PTR "1b\n" - _ASM_PTR "0\n" /* no replacement */ + " .long 1b - .\n" + " .long 0\n" /* no replacement */ " .word %P0\n" /* feature bit */ " .byte 2b - 1b\n" /* source len */ " .byte 0\n" /* replacement len */ @@ -349,8 +349,8 @@ static __always_inline __pure bool __static_cpu_has(u16 bit) "2:\n" ".section .altinstructions,\"a\"\n" _ASM_ALIGN "\n" - _ASM_PTR "1b\n" - _ASM_PTR "3f\n" + " .long 1b - .\n" + " .long 3f - .\n" " .word %P1\n" /* feature bit */ " .byte 2b - 1b\n" /* source len */ " .byte 4f - 3f\n" /* replacement len */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index a81f2d52f86..ddb207bb5f9 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); } } diff --git a/arch/x86/lib/copy_page_64.S b/arch/x86/lib/copy_page_64.S index 6fec2d1cebe..01c805ba535 100644 --- a/arch/x86/lib/copy_page_64.S +++ b/arch/x86/lib/copy_page_64.S @@ -2,6 +2,7 @@ #include #include +#include ALIGN copy_page_c: @@ -110,10 +111,6 @@ ENDPROC(copy_page) 2: .previous .section .altinstructions,"a" - .align 8 - .quad copy_page - .quad 1b - .word X86_FEATURE_REP_GOOD - .byte .Lcopy_page_end - copy_page - .byte 2b - 1b + altinstruction_entry copy_page, 1b, X86_FEATURE_REP_GOOD, \ + .Lcopy_page_end-copy_page, 2b-1b .previous diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S index d0ec9c2936d..ee164610ec4 100644 --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -9,6 +9,7 @@ #include #include #include +#include #undef memmove @@ -214,11 +215,9 @@ ENTRY(memmove) .previous .section .altinstructions,"a" - .align 8 - .quad .Lmemmove_begin_forward - .quad .Lmemmove_begin_forward_efs - .word X86_FEATURE_ERMS - .byte .Lmemmove_end_forward-.Lmemmove_begin_forward - .byte .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs + altinstruction_entry .Lmemmove_begin_forward, \ + .Lmemmove_begin_forward_efs,X86_FEATURE_ERMS, \ + .Lmemmove_end_forward-.Lmemmove_begin_forward, \ + .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs .previous ENDPROC(memmove) -- 2.41.0