Commit 5c22c472 authored by Hou Wenlong's avatar Hou Wenlong Committed by Borislav Petkov (AMD)
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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: default avatarHou Wenlong <houwenlong.hwl@antgroup.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/9e6053107fbaabc0d33e5d2865c5af2c67ec9925.1686301237.git.houwenlong.hwl@antgroup.com
parent b85ea95d

arch/x86/include/asm/paravirt.h

+5 −5
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/paravirt_types.h

+4 −4
Original line number Diff line number Diff line
@@ -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. */

arch/x86/kernel/alternative.c

+5 −3
Original line number Diff line number Diff line
@@ -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[],

arch/x86/kernel/callthunks.c

+1 −1
Original line number Diff line number Diff line
@@ -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