From: Kristen Carlson Accardi <kristen@linux.intel.com> To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org Cc: rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Kristen Carlson Accardi <kristen@linux.intel.com> Subject: [RFC PATCH 02/11] x86: tools/relocs: Support >64K section headers Date: Wed, 5 Feb 2020 14:39:41 -0800 [thread overview] Message-ID: <20200205223950.1212394-3-kristen@linux.intel.com> (raw) In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com> While it is already supported to find the total number of section headers if we exceed 64K sections, we need to support the extended symbol table to get section header indexes for symbols when there are > 64K sections. Parse the elf file to read the extended symbol table info, and then replace all direct references to st_shndx with calls to sym_index(), which will determine whether we can read the value directly or whether we need to pull it out of the extended table. Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> --- arch/x86/tools/relocs.c | 104 ++++++++++++++++++++++++++++++---------- 1 file changed, 78 insertions(+), 26 deletions(-) diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index ce7188cbdae5..a00dc133f109 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -14,6 +14,10 @@ static Elf_Ehdr ehdr; static unsigned long shnum; static unsigned int shstrndx; +static unsigned int shsymtabndx; +static unsigned int shxsymtabndx; + +static int sym_index(Elf_Sym *sym); struct relocs { uint32_t *offset; @@ -32,6 +36,7 @@ struct section { Elf_Shdr shdr; struct section *link; Elf_Sym *symtab; + Elf32_Word *xsymtab; Elf_Rel *reltab; char *strtab; }; @@ -265,7 +270,7 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym) name = sym_strtab + sym->st_name; } else { - name = sec_name(sym->st_shndx); + name = sec_name(sym_index(sym)); } return name; } @@ -335,6 +340,23 @@ static uint64_t elf64_to_cpu(uint64_t val) #define elf_xword_to_cpu(x) elf32_to_cpu(x) #endif +static int sym_index(Elf_Sym *sym) +{ + Elf_Sym *symtab = secs[shsymtabndx].symtab; + Elf32_Word *xsymtab = secs[shxsymtabndx].xsymtab; + unsigned long offset; + int index; + + if (sym->st_shndx != SHN_XINDEX) + return sym->st_shndx; + + /* calculate offset of sym from head of table. */ + offset = (unsigned long) sym - (unsigned long) symtab; + index = offset/sizeof(*sym); + + return elf32_to_cpu(xsymtab[index]); +} + static void read_ehdr(FILE *fp) { if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) { @@ -468,31 +490,60 @@ static void read_strtabs(FILE *fp) static void read_symtabs(FILE *fp) { int i,j; + for (i = 0; i < shnum; i++) { struct section *sec = &secs[i]; - if (sec->shdr.sh_type != SHT_SYMTAB) { + int num_syms; + + switch (sec->shdr.sh_type) { + case SHT_SYMTAB_SHNDX: + sec->xsymtab = malloc(sec->shdr.sh_size); + if (!sec->xsymtab) { + die("malloc of %d bytes for xsymtab 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->xsymtab, 1, sec->shdr.sh_size, fp) + != sec->shdr.sh_size) { + die("Cannot read extended symbol table: %s\n", + strerror(errno)); + } + shxsymtabndx = i; + continue; + + case SHT_SYMTAB: + num_syms = sec->shdr.sh_size/sizeof(Elf_Sym); + + sec->symtab = malloc(sec->shdr.sh_size); + if (!sec->symtab) { + die("malloc of %d bytes for symtab 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->symtab, 1, sec->shdr.sh_size, fp) + != sec->shdr.sh_size) { + die("Cannot read symbol table: %s\n", + strerror(errno)); + } + for (j = 0; j < num_syms; j++) { + Elf_Sym *sym = &sec->symtab[j]; + + sym->st_name = elf_word_to_cpu(sym->st_name); + sym->st_value = elf_addr_to_cpu(sym->st_value); + sym->st_size = elf_xword_to_cpu(sym->st_size); + sym->st_shndx = elf_half_to_cpu(sym->st_shndx); + } + shsymtabndx = i; + continue; + + default: continue; - } - sec->symtab = malloc(sec->shdr.sh_size); - if (!sec->symtab) { - die("malloc of %d bytes for symtab 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->symtab, 1, sec->shdr.sh_size, fp) - != sec->shdr.sh_size) { - die("Cannot read symbol table: %s\n", - strerror(errno)); - } - for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Sym); j++) { - Elf_Sym *sym = &sec->symtab[j]; - sym->st_name = elf_word_to_cpu(sym->st_name); - sym->st_value = elf_addr_to_cpu(sym->st_value); - sym->st_size = elf_xword_to_cpu(sym->st_size); - sym->st_shndx = elf_half_to_cpu(sym->st_shndx); } } } @@ -759,13 +810,14 @@ static void percpu_init(void) */ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname) { - return (sym->st_shndx == per_cpu_shndx) && + int shndx = sym_index(sym); + + return (shndx == per_cpu_shndx) && strcmp(symname, "__init_begin") && strcmp(symname, "__per_cpu_load") && strncmp(symname, "init_per_cpu_", 13); } - static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { @@ -1088,7 +1140,7 @@ static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, sec_name(sec->shdr.sh_info), rel_type(ELF_R_TYPE(rel->r_info)), symname, - sec_name(sym->st_shndx)); + sec_name(sym_index(sym))); return 0; } -- 2.24.1
next prev parent reply other threads:[~2020-02-05 22:40 UTC|newest] Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-05 22:39 [RFC PATCH 00/11] Finer grained kernel address space randomization Kristen Carlson Accardi 2020-02-05 22:39 ` [RFC PATCH 01/11] modpost: Support >64K sections Kristen Carlson Accardi 2020-02-06 12:38 ` Kees Cook 2020-02-05 22:39 ` Kristen Carlson Accardi [this message] 2020-02-06 12:39 ` [RFC PATCH 02/11] x86: tools/relocs: Support >64K section headers Kees Cook 2020-02-05 22:39 ` [RFC PATCH 03/11] x86/boot: Allow a "silent" kaslr random byte fetch Kristen Carlson Accardi 2020-02-06 1:08 ` Andy Lutomirski 2020-02-06 11:48 ` Kees Cook 2020-02-06 16:58 ` Kristen Carlson Accardi 2020-02-05 22:39 ` [RFC PATCH 04/11] x86/boot/KASLR: Introduce PRNG for faster shuffling Kristen Carlson Accardi 2020-02-06 1:11 ` Andy Lutomirski 2020-02-06 15:10 ` Jason A. Donenfeld 2020-02-07 7:23 ` Jean-Philippe Aumasson 2020-02-07 9:05 ` Kees Cook 2020-02-07 16:52 ` Kristen Carlson Accardi 2020-02-05 22:39 ` [RFC PATCH 05/11] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi 2020-02-06 10:30 ` Peter Zijlstra 2020-02-06 11:52 ` Kees Cook 2020-02-25 17:55 ` Arvind Sankar 2020-02-26 19:13 ` Kristen Carlson Accardi 2020-03-24 21:24 ` Kristen Carlson Accardi 2020-03-25 15:34 ` Kees Cook 2020-02-05 22:39 ` [RFC PATCH 06/11] x86: make sure _etext includes function sections Kristen Carlson Accardi 2020-02-06 12:26 ` Kees Cook 2020-02-06 13:15 ` Jann Horn 2020-02-06 16:27 ` David Laight 2020-02-06 14:39 ` Arvind Sankar 2020-02-06 15:29 ` Arvind Sankar 2020-02-06 16:11 ` Andy Lutomirski 2020-02-06 14:57 ` Arvind Sankar 2020-02-06 15:45 ` Arvind Sankar 2020-02-06 19:41 ` Kristen Carlson Accardi 2020-02-06 20:02 ` Andy Lutomirski 2020-02-07 9:24 ` Peter Zijlstra 2020-02-10 1:43 ` Kees Cook 2020-02-10 10:51 ` Peter Zijlstra 2020-02-10 15:54 ` Arjan van de Ven 2020-02-10 16:36 ` Arvind Sankar 2020-02-21 19:50 ` Josh Poimboeuf 2020-02-21 23:05 ` Arvind Sankar 2020-02-05 22:39 ` [RFC PATCH 07/11] x86/tools: Adding relative relocs for randomized functions Kristen Carlson Accardi 2020-02-06 12:37 ` Kees Cook 2020-02-05 22:39 ` [RFC PATCH 08/11] x86: Add support for finer grained KASLR Kristen Carlson Accardi 2020-02-06 1:17 ` Andy Lutomirski 2020-02-06 11:56 ` Kees Cook 2020-02-06 17:36 ` Kristen Carlson Accardi 2020-02-06 10:38 ` Peter Zijlstra 2020-02-06 12:06 ` Kees Cook 2020-02-06 14:52 ` Peter Zijlstra 2020-02-06 17:25 ` Kristen Carlson Accardi 2020-02-06 17:35 ` Peter Zijlstra 2020-02-06 17:43 ` Kristen Carlson Accardi 2020-02-25 17:49 ` Arvind Sankar 2020-02-26 19:26 ` Kristen Carlson Accardi 2020-02-05 22:39 ` [RFC PATCH 09/11] kallsyms: hide layout and expose seed Kristen Carlson Accardi 2020-02-06 12:32 ` Kees Cook 2020-02-06 17:51 ` Kristen Carlson Accardi 2020-02-06 19:27 ` Jann Horn 2020-03-02 19:01 ` Kristen Carlson Accardi 2020-03-02 19:08 ` Kees Cook 2020-03-02 19:19 ` Kristen Carlson Accardi 2020-02-27 2:42 ` Baoquan He 2020-02-27 16:02 ` Kees Cook 2020-02-28 3:36 ` Baoquan He 2020-02-05 22:39 ` [RFC PATCH 10/11] module: Reorder functions Kristen Carlson Accardi 2020-02-06 12:41 ` Kees Cook 2020-02-11 12:39 ` Jessica Yu 2020-02-05 22:39 ` [RFC PATCH 11/11] x86/boot: Move "boot heap" out of .bss Kristen Carlson Accardi 2020-02-06 0:11 ` Arvind Sankar 2020-02-06 0:33 ` Kristen Carlson Accardi 2020-02-06 11:13 ` Kees Cook 2020-02-06 14:25 ` Arvind Sankar 2020-02-06 21:32 ` Kees Cook
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20200205223950.1212394-3-kristen@linux.intel.com \ --to=kristen@linux.intel.com \ --cc=arjan@linux.intel.com \ --cc=bp@alien8.de \ --cc=hpa@zytor.com \ --cc=keescook@chromium.org \ --cc=kernel-hardening@lists.openwall.com \ --cc=linux-kernel@vger.kernel.org \ --cc=mingo@redhat.com \ --cc=rick.p.edgecombe@intel.com \ --cc=tglx@linutronix.de \ --cc=x86@kernel.org \ --subject='Re: [RFC PATCH 02/11] x86: tools/relocs: Support >64K section headers' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).