From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x226yvSgKZRbZRu6RqV53xHN/gs67+gEY9i9OZtlscoaNn/SOML+9OLSY6iDbv2AgOKzILfIA ARC-Seal: i=1; a=rsa-sha256; t=1516721578; cv=none; d=google.com; s=arc-20160816; b=MfuexC4wjQSxDyeQqBt4/OpOoZVxkmxePsPwMaD5RhH5XxGApGkkxcObyUx7qeGlzs MpqwMQiXFt55xl3jzFg6QdXc8/5coxeWwu+e3ix6qZxt4Cd2wRskL7a0txZC6BGgpLQ1 nnYb9M8Q325oJYpX1yzOYj9AFEuwpWWJI6Ftrm0Y9Kh7vgJD9t/tP6o5pZoPHAyo35Ee K7udU0aLOCE3dAl4ozecyaADOMniRscXQIhRQBP6SLye9SBLHX0r+2fBhqXtf75bDpmd PBbtJBc6+VNyTokk02nu9t9vYE/p58JzYqR9dTbkretlKyKdRwWpNeXRGiMKJm+V+07O QyVg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-disposition:mime-version:references:subject:cc:to:from:date :user-agent:message-id:dkim-signature:arc-authentication-results; bh=ta//I8MFhNVWQ+bMDNQNfhuyMS6pgPL5+B6f0ZVVN+Y=; b=f9Set4VapSWHSIj4pgiKXfGM4S1wQngDATkNlSbPVvoF2dK4/Yjn0CkW8rjd0gGvVw aO3qBub+EDJ5ddIOhVzuWZ5TMysL0ks7PLcFZC/6jaaGY6B3UKxBPP8a/MLkBgG2LYM9 S/I2OdCypYoHPIIIKnt4Z96P/YE0G+NGnBA3KZ5Z2HQWZeBBL4JvvW9Kz/sIVGs2L7S6 zY2L9zjsaqHOczREaLASpaLNpoxdERDjJyNoquNvrBvF6xMG+7hjLXTVdaBMrD8s7E97 uKLihHA31/mtaw72kqQ6jPACfyCffXItdwVyMUc18WaY2cbg4Rgx9HcKi89JlIaoitEy 2zQw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=UApvpPB9; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 65.50.211.133 as permitted sender) smtp.mailfrom=peterz@infradead.org Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=UApvpPB9; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 65.50.211.133 as permitted sender) smtp.mailfrom=peterz@infradead.org Message-Id: <20180123152638.102799023@infradead.org> User-Agent: quilt/0.63-1 Date: Tue, 23 Jan 2018 16:25:41 +0100 From: Peter Zijlstra To: David Woodhouse , Thomas Gleixner , Josh Poimboeuf Cc: linux-kernel@vger.kernel.org, Dave Hansen , Ashok Raj , Tim Chen , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , Arjan Van De Ven , Dan Williams , Paolo Bonzini , Jun Nakajima , Asit Mallick , Jason Baron , Peter Zijlstra Subject: [PATCH 02/24] objtool: Add retpoline validation References: <20180123152539.374360046@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-objtool-indirect.patch X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590397846371595223?= X-GMAIL-MSGID: =?utf-8?q?1590397846371595223?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: David requested a objtool validation pass for RETPOLINE enabled builds, where it validates no unannotated indirect jumps or calls are left. Add an additional .discard.retpoline_safe section to allow annotating the few indirect sites that are required and safe. Requested-by: David Woodhouse Signed-off-by: Peter Zijlstra (Intel) --- scripts/Makefile.build | 4 + tools/objtool/builtin-check.c | 3 - tools/objtool/builtin.h | 2 tools/objtool/check.c | 87 ++++++++++++++++++++++++++++++++++++++++-- tools/objtool/check.h | 1 5 files changed, 92 insertions(+), 5 deletions(-) --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -269,6 +269,10 @@ objtool_args += --no-unreachable else objtool_args += $(call cc-ifversion, -lt, 0405, --no-unreachable) endif +ifdef CONFIG_RETPOLINE + objtool_args += --retpoline +endif + ifdef CONFIG_MODVERSIONS objtool_o = $(@D)/.tmp_$(@F) --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -29,7 +29,7 @@ #include "builtin.h" #include "check.h" -bool no_fp, no_unreachable; +bool no_fp, no_unreachable, retpoline; static const char * const check_usage[] = { "objtool check [] file.o", @@ -39,6 +39,7 @@ static const char * const check_usage[] const struct option check_options[] = { OPT_BOOLEAN('f', "no-fp", &no_fp, "Skip frame pointer validation"), OPT_BOOLEAN('u', "no-unreachable", &no_unreachable, "Skip 'unreachable instruction' warnings"), + OPT_BOOLEAN('r', "retpoline", &retpoline, "Validate retpoline assumptions"), OPT_END(), }; --- a/tools/objtool/builtin.h +++ b/tools/objtool/builtin.h @@ -20,7 +20,7 @@ #include extern const struct option check_options[]; -extern bool no_fp, no_unreachable; +extern bool no_fp, no_unreachable, retpoline; extern int cmd_check(int argc, const char **argv); extern int cmd_orc(int argc, const char **argv); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -496,6 +496,7 @@ static int add_jump_destinations(struct * disguise, so convert them accordingly. */ insn->type = INSN_JUMP_DYNAMIC; + insn->retpoline_safe = true; continue; } else { /* sibling call */ @@ -548,13 +549,11 @@ static int add_call_destinations(struct * normal for a function to call within itself. So * disable this warning for now. */ -#if 0 - if (!insn->call_dest) { + if (!retpoline && !insn->call_dest) { WARN_FUNC("can't find call dest symbol at offset 0x%lx", insn->sec, insn->offset, dest_off); return -1; } -#endif } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_symbol_by_offset(rela->sym->sec, rela->addend+4); @@ -1067,6 +1066,54 @@ static int read_unwind_hints(struct objt return 0; } +static int read_retpoline_hints(struct objtool_file *file) +{ + struct section *sec, *relasec; + struct instruction *insn; + struct rela *rela; + int i; + + sec = find_section_by_name(file->elf, ".discard.retpoline_safe"); + if (!sec) + return 0; + + relasec = sec->rela; + if (!relasec) { + WARN("missing .rela.discard.retpoline_safe section"); + return -1; + } + + if (sec->len % sizeof(unsigned long)) { + WARN("retpoline_safe size mismatch: %d %ld", sec->len, sizeof(unsigned long)); + return -1; + } + + for (i = 0; i < sec->len / sizeof(unsigned long); i++) { + rela = find_rela_by_dest(sec, i * sizeof(unsigned long)); + if (!rela) { + WARN("can't find rela for retpoline_safe[%d]", i); + return -1; + } + + insn = find_insn(file, rela->sym->sec, rela->addend); + if (!insn) { + WARN("can't find insn for retpoline_safe[%d]", i); + return -1; + } + + if (insn->type != INSN_JUMP_DYNAMIC && + insn->type != INSN_CALL_DYNAMIC) { + WARN_FUNC("retpoline_safe hint not a indirect jump/call", + insn->sec, insn->offset); + return -1; + } + + insn->retpoline_safe = true; + } + + return 0; +} + static int decode_sections(struct objtool_file *file) { int ret; @@ -1105,6 +1152,10 @@ static int decode_sections(struct objtoo if (ret) return ret; + ret = read_retpoline_hints(file); + if (ret) + return ret; + return 0; } @@ -1848,6 +1899,29 @@ static int validate_unwind_hints(struct return warnings; } +static int validate_retpoline(struct objtool_file *file) +{ + struct instruction *insn; + int warnings = 0; + + for_each_insn(file, insn) { + if (insn->type != INSN_JUMP_DYNAMIC && + insn->type != INSN_CALL_DYNAMIC) + continue; + + if (insn->retpoline_safe) + continue; + + WARN_FUNC("indirect %s found in RETPOLINE build", + insn->sec, insn->offset, + insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); + + warnings++; + } + + return warnings; +} + static bool is_kasan_insn(struct instruction *insn) { return (insn->type == INSN_CALL && @@ -2002,6 +2076,13 @@ int check(const char *_objname, bool orc if (list_empty(&file.insn_list)) goto out; + if (retpoline) { + ret = validate_retpoline(&file); + if (ret < 0) + return ret; + warnings += ret; + } + ret = validate_functions(&file); if (ret < 0) goto out; --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -45,6 +45,7 @@ struct instruction { unsigned char type; unsigned long immediate; bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts; + bool retpoline_safe; struct symbol *call_dest; struct instruction *jump_dest; struct list_head alts;