On 24.11.22 09:51, Hou Wenlong wrote:
Similar to the alternative patching, use relative reference for original instruction rather than absolute one, which saves 8 bytes for one entry on x86_64. And it could generate R_X86_64_PC32 relocation instead of
8 bytes saved? I think those are 4 bytes only.
R_X86_64_64 relocation, which also reduces relocation metadata on relocatable builds. Signed-off-by: Hou Wenlong <[email protected]> --- arch/x86/include/asm/paravirt.h | 6 +++--- arch/x86/include/asm/paravirt_types.h | 4 ++-- arch/x86/kernel/alternative.c | 8 +++++--- 3 files changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 2851bc2339d5..2cbe9b64e103 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -735,13 +735,13 @@ extern void default_banner(void);#else /* __ASSEMBLY__ */ -#define _PVSITE(ptype, ops, word, algn) \+#define _PVSITE(ptype, ops, algn) \
Would you please drop the algn parameter, too? It isn't needed anymore as the alignment can be hard coded to be 4 now. This would need to be adjusted in the _paravirt_alt() macro, too.
771:; \ ops; \ 772:; \ .pushsection .parainstructions,"a"; \ .align algn; \ - word 771b; \ + .long 771b-.; \ .byte ptype; \ .byte 772b-771b; \ _ASM_ALIGN; \ @@ -752,7 +752,7 @@ extern void default_banner(void); #ifdef CONFIG_PARAVIRT_XXL#define PARA_PATCH(off) ((off) / 8)-#define PARA_SITE(ptype, ops) _PVSITE(ptype, ops, .quad, 8) +#define PARA_SITE(ptype, ops) _PVSITE(ptype, ops, 8) #define PARA_INDIRECT(addr) *addr(%rip)#ifdef CONFIG_DEBUG_ENTRYdiff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 8c1da419260f..19f709cf7df9 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -5,7 +5,7 @@ #ifndef __ASSEMBLY__ /* These all sit in the .parainstructions section to tell us what to patch. */ struct paravirt_patch_site { - u8 *instr; /* original instructions */ + s32 instr_offset; /* original instructions */ u8 type; /* type of this instruction */ u8 len; /* length of original instruction */ }; @@ -274,7 +274,7 @@ extern struct paravirt_patch_template pv_ops; "771:\n\t" insn_string "\n" "772:\n" \ ".pushsection .parainstructions,\"a\"\n" \ _ASM_ALIGN "\n" \ - _ASM_PTR " 771b\n" \ + " .long 771b-.\n" \ " .byte " type "\n" \ " .byte 772b-771b\n" \ _ASM_ALIGN "\n" \ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 111b809f0ac2..6eea563a098d 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1232,20 +1232,22 @@ void __init_or_module apply_paravirt(struct paravirt_patch_site *start, { struct paravirt_patch_site *p; char insn_buff[MAX_PATCH_LEN]; + u8 *instr;for (p = start; p < end; p++) {unsigned int used;+ instr = (u8 *)&p->instr_offset + p->instr_offset;BUG_ON(p->len > MAX_PATCH_LEN); /* prep the buffer with the original instructions */ - memcpy(insn_buff, p->instr, p->len); - used = paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->len); + memcpy(insn_buff, instr, p->len); + used = paravirt_patch(p->type, insn_buff, (unsigned long)instr, p->len);BUG_ON(used > p->len); /* Pad the rest with nops */add_nops(insn_buff + used, p->len - used); - text_poke_early(p->instr, insn_buff, p->len); + text_poke_early(instr, insn_buff, p->len); } } extern struct paravirt_patch_site __start_parainstructions[],
Juergen
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