From patchwork Tue May 29 22:15:18 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 10437315 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 23826601C7 for ; Tue, 29 May 2018 22:21:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0AD942891B for ; Tue, 29 May 2018 22:21:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F2EAE2892B; Tue, 29 May 2018 22:21:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id BD2E02891B for ; Tue, 29 May 2018 22:21:34 +0000 (UTC) Received: (qmail 19611 invoked by uid 550); 29 May 2018 22:17:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 19464 invoked from network); 29 May 2018 22:17:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=P5KjS1vgVS34pLzcmc7il5aUG62D0LdZZkGAf+CycAE=; b=egS94V0TQFTWzzB07h3TBPwmvzvktPHKxTVLe1jZMSsCFJrykIqXMX7BRawyMnhf8T nuChUrISmruPzDHQEzPTpK2DIx3UytkWeJbrea2M6MNeE6SsJ9j35mPcYk8q1Y0fvXmd Iipja3EmAAiPVvY2G+OImjNLqXbOFg82z3dyInlxIgO5dc9yYbu7Yh6gucJFDqkKnZw8 bskJFHLg4drvFChtm531q+U1azuvRHJo0xgIxtrNgxU1WraSUQrO0cBYRMTSubrZHInc 3M03c/OssrPwZ0YO/ldo9rrMIot5XjLAvGGxCC3W62iaHI3P1MqhfbVelnRu0Xv+46Sj xOlA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=P5KjS1vgVS34pLzcmc7il5aUG62D0LdZZkGAf+CycAE=; b=cnTFSEsuGW49+PflSXL4ndTVcY24Q2rPG4gDrC6sKS+5ui9b/YBcX7sLGr2AMEs3QO Y4jZ1vola74LTZgIs3o8C93folKJ6YPNW0oBGqso+Cpg+kMxsgyaFtw5k2ia0NrX9UJG B4qUAxRuGh2pyDaSO/e58malRWRfJYgahOF5iR0SvQXbNlvpCoM21Q9an98P7SvgOzi8 kFyeXk3ghJU9TeoBZ2RzBFyHPPM/DkGTUGbocxAF1O/wlEEjRj732/truLcLTUpWKyJf vTigm7xkSgyxrTjPBbyOfF41DccCCJi3r/gGtPFJJ4P5silRO2hozF80oyyqtlhi13b8 quDQ== X-Gm-Message-State: ALKqPwetiRNAvHDH81t5bKs57BJa2vR+gooHfw9ycz8qbuUcdYdswfxY LAgf6PgLMQf8jFnGKVCiDvGGIYLsby4= X-Google-Smtp-Source: ADUXVKJgsqoiS/zTXIGlihFcjtbsZZP97+BDlq/rxbhwQQMr81VJm7f5J3GVHJF1IHwIMvLnUpA9ew== X-Received: by 2002:a62:89db:: with SMTP id n88-v6mr206034pfk.11.1527632255915; Tue, 29 May 2018 15:17:35 -0700 (PDT) From: Thomas Garnier To: kernel-hardening@lists.openwall.com Cc: Thomas Garnier , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Kate Stewart , Philippe Ombredanne , "H.J. Lu" , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: [PATCH v4 17/27] x86/relocs: Handle PIE relocations Date: Tue, 29 May 2018 15:15:18 -0700 Message-Id: <20180529221625.33541-18-thgarnie@google.com> X-Mailer: git-send-email 2.17.0.921.gf22659ad46-goog In-Reply-To: <20180529221625.33541-1-thgarnie@google.com> References: <20180529221625.33541-1-thgarnie@google.com> X-Virus-Scanned: ClamAV using ClamSMTP Change the relocation tool to correctly handle relocations generated by -fPIE option: - Add relocation for each entry of the .got section given the linker does not generate R_X86_64_GLOB_DAT on a simple link. - Ignore R_X86_64_GOTPCREL. Signed-off-by: Thomas Garnier --- arch/x86/tools/relocs.c | 93 ++++++++++++++++++++++++++++++++++++++++- 1 file changed, 92 insertions(+), 1 deletion(-) diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index 220e97841e49..a35cc337f883 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -32,6 +32,7 @@ struct section { Elf_Sym *symtab; Elf_Rel *reltab; char *strtab; + Elf_Addr *got; }; static struct section *secs; @@ -293,6 +294,35 @@ static Elf_Sym *sym_lookup(const char *symname) return 0; } +static Elf_Sym *sym_lookup_addr(Elf_Addr addr, const char **name) +{ + int i; + for (i = 0; i < ehdr.e_shnum; i++) { + struct section *sec = &secs[i]; + long nsyms; + Elf_Sym *symtab; + Elf_Sym *sym; + + if (sec->shdr.sh_type != SHT_SYMTAB) + continue; + + nsyms = sec->shdr.sh_size/sizeof(Elf_Sym); + symtab = sec->symtab; + + for (sym = symtab; --nsyms >= 0; sym++) { + if (sym->st_value == addr) { + if (name) { + *name = sym_name(sec->link->strtab, + sym); + } + return sym; + } + } + } + return 0; +} + + #if BYTE_ORDER == LITTLE_ENDIAN #define le16_to_cpu(val) (val) #define le32_to_cpu(val) (val) @@ -513,6 +543,33 @@ static void read_relocs(FILE *fp) } } +static void read_got(FILE *fp) +{ + int i; + for (i = 0; i < ehdr.e_shnum; i++) { + struct section *sec = &secs[i]; + sec->got = NULL; + if (sec->shdr.sh_type != SHT_PROGBITS || + strcmp(sec_name(i), ".got")) { + continue; + } + sec->got = malloc(sec->shdr.sh_size); + if (!sec->got) { + die("malloc of %d bytes for got failed\n", + sec->shdr.sh_size); + } + if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + sec->shdr.sh_offset, strerror(errno)); + } + if (fread(sec->got, 1, sec->shdr.sh_size, fp) + != sec->shdr.sh_size) { + die("Cannot read got: %s\n", + strerror(errno)); + } + } +} + static void print_absolute_symbols(void) { @@ -643,6 +700,32 @@ static void add_reloc(struct relocs *r, uint32_t offset) r->offset[r->count++] = offset; } +/* + * The linker does not generate relocations for the GOT for the kernel. + * If a GOT is found, simulate the relocations that should have been included. + */ +static void walk_got_table(int (*process)(struct section *sec, Elf_Rel *rel, + Elf_Sym *sym, const char *symname), + struct section *sec) +{ + int i; + Elf_Addr entry; + Elf_Sym *sym; + const char *symname; + Elf_Rel rel; + + for (i = 0; i < sec->shdr.sh_size/sizeof(Elf_Addr); i++) { + entry = sec->got[i]; + sym = sym_lookup_addr(entry, &symname); + if (!sym) + die("Could not found got symbol for entry %d\n", i); + rel.r_offset = sec->shdr.sh_addr + i * sizeof(Elf_Addr); + rel.r_info = ELF_BITS == 64 ? R_X86_64_GLOB_DAT + : R_386_GLOB_DAT; + process(sec, &rel, sym, symname); + } +} + static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, Elf_Sym *sym, const char *symname)) { @@ -656,6 +739,8 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, struct section *sec = &secs[i]; if (sec->shdr.sh_type != SHT_REL_TYPE) { + if (sec->got) + walk_got_table(process, sec); continue; } sec_symtab = sec->link; @@ -765,6 +850,7 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, offset += per_cpu_load_addr; switch (r_type) { + case R_X86_64_GOTPCREL: case R_X86_64_NONE: /* NONE can be ignored. */ break; @@ -809,7 +895,7 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, * the relocations are processed. * Make sure that the offset will fit. */ - if ((int32_t)offset != (int64_t)offset) + if (r_type != R_X86_64_64 && (int32_t)offset != (int64_t)offset) die("Relocation offset doesn't fit in 32 bits\n"); if (r_type == R_X86_64_64) @@ -818,6 +904,10 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, add_reloc(&relocs32, offset); break; + case R_X86_64_GLOB_DAT: + add_reloc(&relocs64, offset); + break; + default: die("Unsupported relocation type: %s (%d)\n", rel_type(r_type), r_type); @@ -1087,6 +1177,7 @@ void process(FILE *fp, int use_real_mode, int as_text, read_strtabs(fp); read_symtabs(fp); read_relocs(fp); + read_got(fp); if (ELF_BITS == 64) percpu_init(); if (show_absolute_syms) {