From nobody Mon Feb 9 20:36:57 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 88F40EB64DC for ; Tue, 11 Jul 2023 16:09:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232570AbjGKQJ2 (ORCPT ); Tue, 11 Jul 2023 12:09:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43812 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233278AbjGKQJX (ORCPT ); Tue, 11 Jul 2023 12:09:23 -0400 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B51B51734 for ; Tue, 11 Jul 2023 09:09:15 -0700 (PDT) Received: from localhost (mailhub3.si.c-s.fr [192.168.12.233]) by localhost (Postfix) with ESMTP id 4R0m5M42ymz9sFJ; Tue, 11 Jul 2023 18:08:55 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ku5ZcE946RLp; Tue, 11 Jul 2023 18:08:55 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4R0m5C4qSYz9sFL; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id A020E8B77B; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id ReZQums-OiIn; Tue, 11 Jul 2023 18:08:47 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.233.184]) by messagerie.si.c-s.fr (Postfix) with ESMTP id D64B08B77C; Tue, 11 Jul 2023 18:08:46 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (localhost [127.0.0.1]) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.16.1) with ESMTPS id 36BG8kDX3696848 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 11 Jul 2023 18:08:46 +0200 Received: (from chleroy@localhost) by PO20335.IDSI0.si.c-s.fr (8.17.1/8.17.1/Submit) id 36BG8kSu3696847; Tue, 11 Jul 2023 18:08:46 +0200 X-Authentication-Warning: PO20335.IDSI0.si.c-s.fr: chleroy set sender to christophe.leroy@csgroup.eu using -f From: Christophe Leroy To: Michael Ellerman , Nicholas Piggin , Josh Poimboeuf , Peter Zijlstra , Sathvika Vasireddy , Naveen N Rao Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v4 12/15] objtool: Add support for more complex UACCESS control Date: Tue, 11 Jul 2023 18:08:38 +0200 Message-ID: <2c8974e5ae927507afcdc99aed5206440b35d961.1689091394.git.christophe.leroy@csgroup.eu> X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1689091706; l=3403; i=christophe.leroy@csgroup.eu; s=20211009; h=from:subject:message-id; bh=f+XU9TWm8xqu2MpxnXa2i+rCa6BF3wyA38g4Qi0L0pQ=; b=pNyE4XFPJPUI8gtHGox2oFfg4xB+zq2Qr29SEbM/VBKtFmeyXXaOKDSv1fmdc9XeS8X+qRbWv Nh+anOkCenRBbSLGrvfExRKSrlvh+uCi0OVceywsSAYPa/MfD5j23t4 X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" On x86, UACCESS is controlled by two instructions: STAC and CLAC. STAC instruction enables UACCESS while CLAC disables UACCESS. This is simple enough for objtool to locate UACCESS enable and disable. But on powerpc it is a bit more complex, the same instruction is used for enabling and disabling UACCESS, and the same instruction can be used for many other things. It would be too complex to use exclusively instruction decoding. To help objtool, mark such instruction into .discard.uaccess_begin and .discard.uaccess_end sections, on the same principle as for reachable/unreachable instructions. And add ASM_UACCESS_BEGIN and ASM_UACCESS_END macros to be used in inline assembly code to annotate UACCESS enable and UACCESS disable instructions. Signed-off-by: Christophe Leroy --- include/linux/objtool.h | 14 ++++++++++++++ tools/objtool/check.c | 33 +++++++++++++++++++++++++++++++++ 2 files changed, 47 insertions(+) diff --git a/include/linux/objtool.h b/include/linux/objtool.h index 03f82c2c2ebf..d8fde4158a40 100644 --- a/include/linux/objtool.h +++ b/include/linux/objtool.h @@ -57,6 +57,18 @@ ".long 998b - .\n\t" \ ".popsection\n\t" =20 +#define ASM_UACCESS_BEGIN \ + "998:\n\t" \ + ".pushsection .discard.uaccess_begin\n\t" \ + ".long 998b - .\n\t" \ + ".popsection\n\t" + +#define ASM_UACCESS_END \ + "998:\n\t" \ + ".pushsection .discard.uaccess_end\n\t" \ + ".long 998b - .\n\t" \ + ".popsection\n\t" + #else /* __ASSEMBLY__ */ =20 /* @@ -156,6 +168,8 @@ #define STACK_FRAME_NON_STANDARD_FP(func) #define ANNOTATE_NOENDBR #define ASM_REACHABLE +#define ASM_UACCESS_BEGIN +#define ASM_UACCESS_END #else #define ANNOTATE_INTRA_FUNCTION_CALL .macro UNWIND_HINT type:req sp_reg=3D0 sp_offset=3D0 signal=3D0 diff --git a/tools/objtool/check.c b/tools/objtool/check.c index d2a0dfec5909..5af6c6c3fbed 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1052,6 +1052,38 @@ static void add_ignores(struct objtool_file *file) } } =20 +static void __add_uaccess(struct objtool_file *file, const char *name, + int type, const char *action) +{ + struct section *rsec; + struct reloc *reloc; + struct instruction *insn; + + rsec =3D find_section_by_name(file->elf, name); + if (!rsec) + return; + + for_each_reloc(rsec, reloc) { + if (reloc->sym->type !=3D STT_SECTION) { + WARN("unexpected relocation symbol type in %s: ", rsec->name); + continue; + } + insn =3D find_insn(file, reloc->sym->sec, reloc_addend(reloc)); + if (!insn) { + WARN("can't find UACCESS %s insn at %s+0x%" PRIx64, + action, reloc->sym->sec->name, reloc_addend(reloc)); + continue; + } + insn->type =3D type; + } +} + +static void add_uaccess(struct objtool_file *file) +{ + __add_uaccess(file, ".rela.discard.uaccess_begin", INSN_STAC, "enable"); + __add_uaccess(file, ".rela.discard.uaccess_end", INSN_CLAC, "disable"); +} + /* * This is a whitelist of functions that is allowed to be called with AC s= et. * The list is meant to be minimal and only contains compiler instrumentat= ion @@ -2597,6 +2629,7 @@ static int decode_sections(struct objtool_file *file) return ret; =20 add_ignores(file); + add_uaccess(file); add_uaccess_safe(file); =20 ret =3D add_ignore_alternatives(file); --=20 2.41.0