From patchwork Tue Jul 18 22:33:29 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 9850097 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 816C260392 for ; Tue, 18 Jul 2017 22:37:43 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6CA52285CB for ; Tue, 18 Jul 2017 22:37:43 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5F752285D8; Tue, 18 Jul 2017 22:37:43 +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=-4.1 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, RCVD_IN_DNSWL_MED, T_DKIM_INVALID 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 346CA285CB for ; Tue, 18 Jul 2017 22:37:42 +0000 (UTC) Received: (qmail 28210 invoked by uid 550); 18 Jul 2017 22:34:52 -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 28119 invoked from network); 18 Jul 2017 22:34:50 -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=6oBzPTRkz1qHsUv5KB+I7sdLRyDZ0uCvABUl6O61uyU=; b=ekFTUklEwC/6OjHuTsTdsj5SJhehMB6Z/Fxu/oyutS288s+iolZ8VTzKQ2t8CwxWGh XwCzvKk+Z61Wvfab4RjV5Nh07/IYgDXFL7naEgMX41aC4fJEuj8eRq5rn36vFLiYMfuK loROCcxC0GPupsOdA12wZdmueJIdpJTFQUpAVQthbOshbN2Hv7/jiUl5rhJ3QIwFEzS6 EtLdfs7HZfn3HcxCYun+6BnS1SrlZimTqIAnHSlh0H3bvTdqxo9OP2tl8vgcrxDr5sZY MAuhhRuaDOeguh6iN55OYH6BN+tQPbXx9f5Wi6P0emsSfQlVs2k/q35CJC5w+mIOwRll XUYg== 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=6oBzPTRkz1qHsUv5KB+I7sdLRyDZ0uCvABUl6O61uyU=; b=piUGlBvfy0BEOKOweR4U4noo0zZ99idyIUOidT9AMex9KcUhYu5mvqMJAHn+FxnroK OcSEaMgoHjAVNnIA5saMJeFymwCsETu5M0uDf918RtY6qqgvqaxMbUlpAdKvmHoNQ4nA tO3m7kUXCWtL+KxbAx6zHveztDt61O+FkQG/uQU4lsYg4PkS/Fe2/L5uUZjnt9ANuZ2l Ik3lal/el5gtLY8b989NcNfWJyhON341JLlnf2c097zELNhNmnI9HjGrRqFS9CMIUTuN LO5+3dNoxEGqKFqVD61NXVGfKJ/Tr1YC67XBPGtzCSeMxq1VOnjGyVfXv2KovEn1RrJ8 pKSw== X-Gm-Message-State: AIVw1100QB6kWw4gIDWluCMVQJiVTTFRJL4Kzu3Dmg+feNDegyqenHEX FnFL0lJQzSLb51vR X-Received: by 10.99.175.12 with SMTP id w12mr3959124pge.250.1500417277912; Tue, 18 Jul 2017 15:34:37 -0700 (PDT) From: Thomas Garnier To: Herbert Xu , "David S . Miller" , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Peter Zijlstra , Josh Poimboeuf , Thomas Garnier , Arnd Bergmann , Matthias Kaehlcke , Boris Ostrovsky , Juergen Gross , Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Joerg Roedel , Andy Lutomirski , Borislav Petkov , "Kirill A . Shutemov" , Brian Gerst , Borislav Petkov , Christian Borntraeger , "Rafael J . Wysocki" , Len Brown , Pavel Machek , Tejun Heo , Christoph Lameter , Kees Cook , Paul Gortmaker , Chris Metcalf , "Paul E . McKenney" , Andrew Morton , Christopher Li , Dou Liyang , Masahiro Yamada , Daniel Borkmann , Markus Trippelsdorf , Peter Foley , Steven Rostedt , Tim Chen , Ard Biesheuvel , Catalin Marinas , Matthew Wilcox , Michal Hocko , Rob Landley , Jiri Kosina , "H . J . Lu" , Paul Bolle , Baoquan He , Daniel Micay Cc: x86@kernel.org, linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-pm@vger.kernel.org, linux-arch@vger.kernel.org, linux-sparse@vger.kernel.org, kernel-hardening@lists.openwall.com Date: Tue, 18 Jul 2017 15:33:29 -0700 Message-Id: <20170718223333.110371-19-thgarnie@google.com> X-Mailer: git-send-email 2.13.2.932.g7449e964c-goog In-Reply-To: <20170718223333.110371-1-thgarnie@google.com> References: <20170718223333.110371-1-thgarnie@google.com> Subject: [kernel-hardening] [RFC 18/22] x86/relocs: Handle DYN relocations for PIE support X-Virus-Scanned: ClamAV using ClamSMTP Change the relocation tool to correctly handle DYN/PIE kernel where the relocation table does not reference symbols and percpu support is not needed. Also add support for R_X86_64_RELATIVE relocations that can be handled like a 64-bit relocation due to the usage of -Bsymbolic. Position Independent Executable (PIE) support will allow to extended the KASLR randomization range below the -2G memory limit. Signed-off-by: Thomas Garnier --- arch/x86/tools/relocs.c | 74 +++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 65 insertions(+), 9 deletions(-) diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index 73eb7fd4aec4..70f523dd68ff 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -642,6 +642,13 @@ static void add_reloc(struct relocs *r, uint32_t offset) r->offset[r->count++] = offset; } +/* Relocation found in a DYN binary, support only for 64-bit PIE */ +static int is_dyn_reloc(struct section *sec) +{ + return ELF_BITS == 64 && ehdr.e_type == ET_DYN && + sec->shdr.sh_info == SHT_NULL; +} + static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, Elf_Sym *sym, const char *symname)) { @@ -652,6 +659,7 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, Elf_Sym *sh_symtab; struct section *sec_applies, *sec_symtab; int j; + int dyn_reloc = 0; struct section *sec = &secs[i]; if (sec->shdr.sh_type != SHT_REL_TYPE) { @@ -660,14 +668,20 @@ static void walk_relocs(int (*process)(struct section *sec, Elf_Rel *rel, sec_symtab = sec->link; sec_applies = &secs[sec->shdr.sh_info]; if (!(sec_applies->shdr.sh_flags & SHF_ALLOC)) { - continue; + if (!is_dyn_reloc(sec_applies)) + continue; + dyn_reloc = 1; } sh_symtab = sec_symtab->symtab; sym_strtab = sec_symtab->link->strtab; for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Rel); j++) { Elf_Rel *rel = &sec->reltab[j]; - Elf_Sym *sym = &sh_symtab[ELF_R_SYM(rel->r_info)]; - const char *symname = sym_name(sym_strtab, sym); + Elf_Sym *sym = NULL; + const char *symname = NULL; + if (!dyn_reloc) { + sym = &sh_symtab[ELF_R_SYM(rel->r_info)]; + symname = sym_name(sym_strtab, sym); + } process(sec, rel, sym, symname); } @@ -746,16 +760,21 @@ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname) strncmp(symname, "init_per_cpu_", 13); } - static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { unsigned r_type = ELF64_R_TYPE(rel->r_info); ElfW(Addr) offset = rel->r_offset; - int shn_abs = (sym->st_shndx == SHN_ABS) && !is_reloc(S_REL, symname); + int shn_abs = 0; + int dyn_reloc = is_dyn_reloc(sec); - if (sym->st_shndx == SHN_UNDEF) - return 0; + if (!dyn_reloc) { + shn_abs = (sym->st_shndx == SHN_ABS) && + !is_reloc(S_REL, symname); + + if (sym->st_shndx == SHN_UNDEF) + return 0; + } /* * Adjust the offset if this reloc applies to the percpu section. @@ -769,6 +788,9 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, break; case R_X86_64_PC32: + if (dyn_reloc) + die("PC32 reloc in PIE DYN binary"); + /* * PC relative relocations don't need to be adjusted unless * referencing a percpu symbol. @@ -783,7 +805,7 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, /* * References to the percpu area don't need to be adjusted. */ - if (is_percpu_sym(sym, symname)) + if (!dyn_reloc && is_percpu_sym(sym, symname)) break; if (shn_abs) { @@ -814,6 +836,14 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, add_reloc(&relocs32, offset); break; + case R_X86_64_RELATIVE: + /* + * -Bsymbolic means we don't need the addend and we can reuse + * the original relocs64. + */ + add_reloc(&relocs64, offset); + break; + default: die("Unsupported relocation type: %s (%d)\n", rel_type(r_type), r_type); @@ -1044,6 +1074,21 @@ static void emit_relocs(int as_text, int use_real_mode) } } +/* Print a different header based on the type of relocation */ +static void print_reloc_header(struct section *sec) { + static int header_printed = 0; + int header_type = is_dyn_reloc(sec) ? 2 : 1; + + if (header_printed == header_type) + return; + header_printed = header_type; + + if (header_type == 2) + printf("reloc type\toffset\tvalue\n"); + else + printf("reloc section\treloc type\tsymbol\tsymbol section\n"); +} + /* * As an aid to debugging problems with different linkers * print summary information about the relocs. @@ -1053,6 +1098,18 @@ static void emit_relocs(int as_text, int use_real_mode) static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { + + print_reloc_header(sec); + +#if ELF_BITS == 64 + if (is_dyn_reloc(sec)) { + printf("%s\t0x%lx\t0x%lx\n", + rel_type(ELF_R_TYPE(rel->r_info)), + rel->r_offset, + rel->r_addend); + return 0; + } +#endif printf("%s\t%s\t%s\t%s\n", sec_name(sec->shdr.sh_info), rel_type(ELF_R_TYPE(rel->r_info)), @@ -1063,7 +1120,6 @@ static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, static void print_reloc_info(void) { - printf("reloc section\treloc type\tsymbol\tsymbol section\n"); walk_relocs(do_reloc_info); }