From 5c22c4726e4a9c6b2e182c0b21c2d3dd63f608c4 Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Fri, 9 Jun 2023 17:45:31 +0800 Subject: [PATCH] x86/paravirt: Use relative reference for the original instruction offset Similar to the alternative patching, use a relative reference for original instruction offset rather than absolute one, which saves 8 bytes for one PARA_SITE entry on x86_64. As a result, a R_X86_64_PC32 relocation is generated instead of an R_X86_64_64 one, which also reduces relocation metadata on relocatable builds. Hardcode the alignment to 4 now. [ bp: Massage commit message. ] Signed-off-by: Hou Wenlong Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Juergen Gross Link: https://lore.kernel.org/r/9e6053107fbaabc0d33e5d2865c5af2c67ec9925.1686301237.git.houwenlong.hwl@antgroup.com --- arch/x86/include/asm/paravirt.h | 10 +++++----- arch/x86/include/asm/paravirt_types.h | 8 ++++---- arch/x86/kernel/alternative.c | 8 +++++--- arch/x86/kernel/callthunks.c | 2 +- 4 files changed, 15 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 6c8ff12140aea..d9384e9d97f62 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -743,16 +743,16 @@ void native_pv_lock_init(void) __init; #else /* __ASSEMBLY__ */ -#define _PVSITE(ptype, ops, word, algn) \ +#define _PVSITE(ptype, ops) \ 771:; \ ops; \ 772:; \ .pushsection .parainstructions,"a"; \ - .align algn; \ - word 771b; \ + .align 4; \ + .long 771b-.; \ .byte ptype; \ .byte 772b-771b; \ - _ASM_ALIGN; \ + .align 4; \ .popsection @@ -760,7 +760,7 @@ void native_pv_lock_init(void) __init; #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) #define PARA_INDIRECT(addr) *addr(%rip) #ifdef CONFIG_DEBUG_ENTRY diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index 772d03487520e..e1bfb719fca33 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 */ }; @@ -263,11 +263,11 @@ extern struct paravirt_patch_template pv_ops; #define _paravirt_alt(insn_string, type) \ "771:\n\t" insn_string "\n" "772:\n" \ ".pushsection .parainstructions,\"a\"\n" \ - _ASM_ALIGN "\n" \ - _ASM_PTR " 771b\n" \ + " .align 4\n" \ + " .long 771b-.\n" \ " .byte " type "\n" \ " .byte 772b-771b\n" \ - _ASM_ALIGN "\n" \ + " .align 4\n" \ ".popsection\n" /* Generate patchable code, with the default asm parameters. */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 73be3931e4f06..be35c8ccf8267 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1431,20 +1431,22 @@ 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[], diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c index e9ad518a5003c..57e5c2e75c2a7 100644 --- a/arch/x86/kernel/callthunks.c +++ b/arch/x86/kernel/callthunks.c @@ -240,7 +240,7 @@ patch_paravirt_call_sites(struct paravirt_patch_site *start, struct paravirt_patch_site *p; for (p = start; p < end; p++) - patch_call(p->instr, ct); + patch_call((void *)&p->instr_offset + p->instr_offset, ct); } static __init_or_module void