From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5935545349A; Fri, 7 Aug 2026 21:38:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786138722; cv=none; b=grsk49V4sAu03D56dDcuCNtLQIgqQHAQGz8ofJ5rbrox+0Ee8e3YJYZSRF5rJPWEKnNpvBzalmbcc58S0v8VC8kJQ+IYn+z5XCWctx7hIoGeIj2pDO472tKPnkgBMvh+icpmFjSvTC8UTQwW4hltI08Glnrju5n0LyCimHlTg8A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786138722; c=relaxed/simple; bh=IW9cNFoRiuJy4YzMq2KgLK/cOVTbSvW08rirZRcR+dw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W5x9GKW+6qNVZcy8dW+jdlxIOTZFjSejNXG9e4H46pDer9ZYOWXIi4SgR0lwRygjfPJ+ZfLH+VyJbbho4QBfCxuHyB0rHXFTOdF7jgZy2xS1Jxut+Df35Ab+T/BexGe08+2UyFxElxNHxXV/W/mXxYHR+HJp2TgNB25Z9AszmVo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JsefgDlh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JsefgDlh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC1911F00A3F; Fri, 7 Aug 2026 21:38:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786138721; bh=Ew7p+eDY/IuJsUiGQLZRB/XNmXqA8BRiHUnlU+zcnAg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JsefgDlhYp6NMA/Wqa/iIjgTslALBSqUH40792URkWhc9qpUFc8ndOQL9Ddx6Df+b UstyBEwtlPxmZmRcLf0he4zHfNXKNgm7cmSZoD3O0HVnQDaAIqNeM9sTILCA6oUBZT P7aK9E8sP0bDwy4I3897aybkGSo7V0tIg4ETx4aOzwaoXKWHLjxgEkRkGnRkLms4Rq WpjLssSq36UrEoGsO/T92B67cWu1ZBrDHc22zUpHwGHsJaKe63zW6FYVMJndbvXYAE NwmeiOzeFctMf0pD1g949WCuIybV3+U8T2By++97rELXGmv3ltzDmjQEclDI2N7mgi ci/hxTZuRRdqw== From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Peter Zijlstra , Joe Lawrence , Miroslav Benes , Petr Mladek , Song Liu Subject: [PATCH v3 5/9] objtool/klp: Fix cross-module klp relocation section naming Date: Fri, 7 Aug 2026 14:37:50 -0700 Message-ID: X-Mailer: git-send-email 2.54.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: live-patching@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A klp relocation section is .klp.rela.., where objname is the object being patched. klp-build wrongly derives objname from where the referenced symbol lives, not where it's referenced. For a cross-module reference like patched can_isotp code calling can.ko's can_rx_unregister(), that gives .klp.rela.can..text rather than .klp.rela.can_isotp..text. Unless the patch happens to patch can.ko as well, the relocation never gets applied and the call goes off into the weeds. Name the intermediate section __klp_relocs. so post-link can read the patched object's name from there. Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files") Reported-by: Joe Lawrence Link: https://lore.kernel.org/20260720145658.1103243-2-joe.lawrence@redhat.com Acked-by: Song Liu Signed-off-by: Josh Poimboeuf --- tools/objtool/include/objtool/klp.h | 10 ++++-- tools/objtool/klp-diff.c | 17 +++++++-- tools/objtool/klp-post-link.c | 53 +++++++++++++++++------------ 3 files changed, 52 insertions(+), 28 deletions(-) diff --git a/tools/objtool/include/objtool/klp.h b/tools/objtool/include/objtool/klp.h index 0118c2c170c3f..646d8e1f12eff 100644 --- a/tools/objtool/include/objtool/klp.h +++ b/tools/objtool/include/objtool/klp.h @@ -14,11 +14,15 @@ #define KLP_FUNCS_SEC ".init.klp_funcs" /* - * __klp_relocs is an intermediate section which are created by klp diff and - * converted into KLP symbols/relas by "objtool klp post-link". This is needed - * to work around the linker, which doesn't preserve SHN_LIVEPATCH or + * __klp_relocs. are intermediate sections which are created by klp + * diff and converted into KLP symbols/relas by "objtool klp post-link". This + * is needed to work around the linker, which doesn't preserve SHN_LIVEPATCH or * SHF_RELA_LIVEPATCH, nor does it support having two RELA sections for a * single PROGBITS section. + * + * "objname" is the name of the object being patched ("vmlinux" or a module + * name). post-link uses it to name the resulting + * .klp.rela.objname.section_name sections. */ #define KLP_RELOCS_SEC "__klp_relocs" #define KLP_STRINGS_SEC ".rodata.klp.str1.1" diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c index 3923fabc13331..e2c6c69dbb4f0 100644 --- a/tools/objtool/klp-diff.c +++ b/tools/objtool/klp-diff.c @@ -1380,8 +1380,8 @@ static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc, } /* - * Create the __klp_relocs entry. This will be converted to an actual - * KLP rela by "objtool klp post-link". + * Create the __klp_relocs. entry. This will be converted to + * an actual KLP rela by "objtool klp post-link". * * This intermediate step is necessary to prevent corruption by the * linker, which doesn't know how to properly handle two rela sections @@ -1389,7 +1389,18 @@ static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc, */ if (!klp_relocs) { - klp_relocs = elf_create_section(e->out, KLP_RELOCS_SEC, 0, + const char *objname = find_modname(e); + char sec_name[SEC_NAME_LEN]; + + if (!objname) + return -1; + + /* section format: __klp_relocs.objname */ + if (snprintf_check(sec_name, SEC_NAME_LEN, + KLP_RELOCS_SEC ".%s", objname)) + return -1; + + klp_relocs = elf_create_section(e->out, sec_name, 0, 0, SHT_PROGBITS, 8, SHF_ALLOC); if (!klp_relocs) return -1; diff --git a/tools/objtool/klp-post-link.c b/tools/objtool/klp-post-link.c index c013e39957b11..350d20495897b 100644 --- a/tools/objtool/klp-post-link.c +++ b/tools/objtool/klp-post-link.c @@ -19,19 +19,11 @@ #include #include -static int fix_klp_relocs(struct elf *elf) +static int fix_klp_reloc_sec(struct elf *elf, struct section *symtab, + struct section *klp_relocs) { - struct section *symtab, *klp_relocs; - - klp_relocs = find_section_by_name(elf, KLP_RELOCS_SEC); - if (!klp_relocs) - return 0; - - symtab = find_section_by_name(elf, ".symtab"); - if (!symtab) { - ERROR("missing .symtab"); - return -1; - } + /* section format: __klp_relocs.sec_objname */ + const char *sec_objname = klp_relocs->name + strlen(KLP_RELOCS_SEC "."); for (int i = 0; i < sec_size(klp_relocs) / sizeof(struct klp_reloc); i++) { struct klp_reloc *klp_reloc; @@ -39,7 +31,6 @@ static int fix_klp_relocs(struct elf *elf) struct section *sec, *tmp, *klp_rsec; unsigned long offset; struct reloc *reloc; - char sym_modname[64]; char rsec_name[SEC_NAME_LEN]; u64 addend; struct symbol *sym, *klp_sym; @@ -55,7 +46,7 @@ static int fix_klp_relocs(struct elf *elf) reloc = find_reloc_by_dest(elf, klp_relocs, klp_reloc_off + offsetof(struct klp_reloc, offset)); if (!reloc) { - ERROR("malformed " KLP_RELOCS_SEC " section"); + ERROR("malformed %s section", klp_relocs->name); return -1; } @@ -66,17 +57,13 @@ static int fix_klp_relocs(struct elf *elf) reloc = find_reloc_by_dest(elf, klp_relocs, klp_reloc_off + offsetof(struct klp_reloc, sym)); if (!reloc) { - ERROR("malformed " KLP_RELOCS_SEC " section"); + ERROR("malformed %s section", klp_relocs->name); return -1; } klp_sym = reloc->sym; addend = reloc_addend(reloc); - /* symbol format: .klp.sym.modname.sym_name,sympos */ - if (sscanf(klp_sym->name + strlen(KLP_SYM_PREFIX), "%55[^.]", sym_modname) != 1) - ERROR("can't find modname in klp symbol '%s'", klp_sym->name); - /* * Create the KLP rela: */ @@ -84,7 +71,7 @@ static int fix_klp_relocs(struct elf *elf) /* section format: .klp.rela.sec_objname.section_name */ if (snprintf_check(rsec_name, SEC_NAME_LEN, KLP_RELOC_SEC_PREFIX "%s.%s", - sym_modname, sec->name)) + sec_objname, sec->name)) return -1; klp_rsec = find_section_by_name(elf, rsec_name); @@ -134,10 +121,32 @@ static int fix_klp_relocs(struct elf *elf) return 0; } +static int fix_klp_relocs(struct elf *elf) +{ + struct section *symtab, *sec; + + symtab = find_section_by_name(elf, ".symtab"); + if (!symtab) { + ERROR("missing .symtab"); + return -1; + } + + for_each_sec(elf, sec) { + if (strncmp(sec->name, KLP_RELOCS_SEC ".", + strlen(KLP_RELOCS_SEC "."))) + continue; + + if (fix_klp_reloc_sec(elf, symtab, sec)) + return -1; + } + + return 0; +} + /* * This runs on the livepatch module after all other linking has been done. It - * converts the intermediate __klp_relocs section into proper KLP relocs to be - * processed by livepatch. This needs to run last to avoid linker wreckage. + * converts the intermediate __klp_relocs.* sections into proper KLP relocs to + * be processed by livepatch. This needs to run last to avoid linker wreckage. * Linkers don't tend to handle the "two rela sections for a single base * section" case very well, nor do they appreciate SHN_LIVEPATCH. */ -- 2.54.0