From nobody Thu Feb 12 05:00:37 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3F7FC77B61 for ; Fri, 28 Apr 2023 09:53:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345803AbjD1Jxb (ORCPT ); Fri, 28 Apr 2023 05:53:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345869AbjD1JxN (ORCPT ); Fri, 28 Apr 2023 05:53:13 -0400 Received: from out0-208.mail.aliyun.com (out0-208.mail.aliyun.com [140.205.0.208]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 028E42726 for ; Fri, 28 Apr 2023 02:52:48 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R861e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018047187;MF=houwenlong.hwl@antgroup.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---.STFQGHW_1682675543; Received: from localhost(mailfrom:houwenlong.hwl@antgroup.com fp:SMTPD_---.STFQGHW_1682675543) by smtp.aliyun-inc.com; Fri, 28 Apr 2023 17:52:24 +0800 From: "Hou Wenlong" To: linux-kernel@vger.kernel.org Cc: "Thomas Garnier" , "Lai Jiangshan" , "Kees Cook" , "Hou Wenlong" , "Juergen Gross" , "=?UTF-8?B?U3JpdmF0c2EgUy4gQmhhdCAoVk13YXJlKQ==?=" , "Alexey Makhalov" , "VMware PV-Drivers Reviewers" , "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "Dave Hansen" , , "H. Peter Anvin" , "Peter Zijlstra" , "Song Liu" , "Nadav Amit" , "Arnd Bergmann" , Subject: [PATCH RFC 13/43] x86/paravirt: Use relative reference for original instruction Date: Fri, 28 Apr 2023 17:50:53 +0800 Message-Id: X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 R_X86_64_64 relocation, which also reduces relocation metadata on relocatable builds. And the alignment could be hard coded to be 4 now. Signed-off-by: Hou Wenlong Cc: Thomas Garnier Cc: Lai Jiangshan Cc: Kees Cook Reviewed-by: Juergen Gross --- 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/paravir= t.h index b49778664d2b..2350ceb43db0 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -742,16 +742,16 @@ extern void default_banner(void); =20 #else /* __ASSEMBLY__ */ =20 -#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 =20 =20 @@ -759,7 +759,7 @@ extern void default_banner(void); #ifdef CONFIG_PARAVIRT_XXL =20 #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) =20 #ifdef CONFIG_DEBUG_ENTRY diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/p= aravirt_types.h index 4acbcddddc29..982a234f5a06 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 */ }; @@ -270,11 +270,11 @@ 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" =20 /* Generate patchable code, with the default asm parameters. */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index f615e0cb6d93..25c59da6c53b 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1230,20 +1230,22 @@ void __init_or_module apply_paravirt(struct paravir= t_patch_site *start, { struct paravirt_patch_site *p; char insn_buff[MAX_PATCH_LEN]; + u8 *instr; =20 for (p =3D start; p < end; p++) { unsigned int used; =20 + instr =3D (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 =3D paravirt_patch(p->type, insn_buff, (unsigned long)p->instr, p->= len); + memcpy(insn_buff, instr, p->len); + used =3D paravirt_patch(p->type, insn_buff, (unsigned long)instr, p->len= ); =20 BUG_ON(used > p->len); =20 /* 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 ffea98f9064b..f15405acfd42 100644 --- a/arch/x86/kernel/callthunks.c +++ b/arch/x86/kernel/callthunks.c @@ -245,7 +245,7 @@ patch_paravirt_call_sites(struct paravirt_patch_site *s= tart, struct paravirt_patch_site *p; =20 for (p =3D start; p < end; p++) - patch_call(p->instr, ct); + patch_call((void *)&p->instr_offset + p->instr_offset, ct); } =20 static __init_or_module void --=20 2.31.1