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![Josh Poimboeuf](/assets/img/avatar_default.png)
Now that objtool knows the states of all registers on the stack for each instruction, it's straightforward to generate debuginfo for an unwinder to use. Instead of generating DWARF, generate a new format called ORC, which is more suitable for an in-kernel unwinder. See Documentation/x86/orc-unwinder.txt for a more detailed description of this new debuginfo format and why it's preferable to DWARF. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/c9b9f01ba6c5ed2bdc9bb0957b78167fdbf9632e.1499786555.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
212 lines
4.2 KiB
C
212 lines
4.2 KiB
C
/*
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* Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <unistd.h>
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#include "orc.h"
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#include "warn.h"
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static const char *reg_name(unsigned int reg)
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{
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switch (reg) {
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case ORC_REG_PREV_SP:
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return "prevsp";
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case ORC_REG_DX:
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return "dx";
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case ORC_REG_DI:
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return "di";
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case ORC_REG_BP:
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return "bp";
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case ORC_REG_SP:
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return "sp";
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case ORC_REG_R10:
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return "r10";
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case ORC_REG_R13:
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return "r13";
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case ORC_REG_BP_INDIRECT:
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return "bp(ind)";
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case ORC_REG_SP_INDIRECT:
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return "sp(ind)";
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default:
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return "?";
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}
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}
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static const char *orc_type_name(unsigned int type)
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{
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switch (type) {
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case ORC_TYPE_CALL:
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return "call";
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case ORC_TYPE_REGS:
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return "regs";
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case ORC_TYPE_REGS_IRET:
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return "iret";
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default:
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return "?";
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}
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}
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static void print_reg(unsigned int reg, int offset)
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{
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if (reg == ORC_REG_BP_INDIRECT)
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printf("(bp%+d)", offset);
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else if (reg == ORC_REG_SP_INDIRECT)
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printf("(sp%+d)", offset);
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else if (reg == ORC_REG_UNDEFINED)
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printf("(und)");
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else
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printf("%s%+d", reg_name(reg), offset);
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}
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int orc_dump(const char *_objname)
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{
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int fd, nr_entries, i, *orc_ip = NULL, orc_size = 0;
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struct orc_entry *orc = NULL;
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char *name;
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unsigned long nr_sections, orc_ip_addr = 0;
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size_t shstrtab_idx;
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Elf *elf;
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Elf_Scn *scn;
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GElf_Shdr sh;
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GElf_Rela rela;
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GElf_Sym sym;
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Elf_Data *data, *symtab = NULL, *rela_orc_ip = NULL;
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objname = _objname;
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elf_version(EV_CURRENT);
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fd = open(objname, O_RDONLY);
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if (fd == -1) {
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perror("open");
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return -1;
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}
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elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
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if (!elf) {
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WARN_ELF("elf_begin");
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return -1;
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}
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if (elf_getshdrnum(elf, &nr_sections)) {
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WARN_ELF("elf_getshdrnum");
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return -1;
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}
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if (elf_getshdrstrndx(elf, &shstrtab_idx)) {
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WARN_ELF("elf_getshdrstrndx");
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return -1;
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}
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for (i = 0; i < nr_sections; i++) {
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scn = elf_getscn(elf, i);
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if (!scn) {
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WARN_ELF("elf_getscn");
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return -1;
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}
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if (!gelf_getshdr(scn, &sh)) {
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WARN_ELF("gelf_getshdr");
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return -1;
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}
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name = elf_strptr(elf, shstrtab_idx, sh.sh_name);
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if (!name) {
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WARN_ELF("elf_strptr");
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return -1;
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}
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data = elf_getdata(scn, NULL);
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if (!data) {
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WARN_ELF("elf_getdata");
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return -1;
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}
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if (!strcmp(name, ".symtab")) {
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symtab = data;
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} else if (!strcmp(name, ".orc_unwind")) {
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orc = data->d_buf;
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orc_size = sh.sh_size;
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} else if (!strcmp(name, ".orc_unwind_ip")) {
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orc_ip = data->d_buf;
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orc_ip_addr = sh.sh_addr;
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} else if (!strcmp(name, ".rela.orc_unwind_ip")) {
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rela_orc_ip = data;
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}
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}
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if (!symtab || !orc || !orc_ip)
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return 0;
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if (orc_size % sizeof(*orc) != 0) {
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WARN("bad .orc_unwind section size");
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return -1;
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}
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nr_entries = orc_size / sizeof(*orc);
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for (i = 0; i < nr_entries; i++) {
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if (rela_orc_ip) {
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if (!gelf_getrela(rela_orc_ip, i, &rela)) {
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WARN_ELF("gelf_getrela");
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return -1;
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}
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if (!gelf_getsym(symtab, GELF_R_SYM(rela.r_info), &sym)) {
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WARN_ELF("gelf_getsym");
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return -1;
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}
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scn = elf_getscn(elf, sym.st_shndx);
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if (!scn) {
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WARN_ELF("elf_getscn");
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return -1;
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}
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if (!gelf_getshdr(scn, &sh)) {
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WARN_ELF("gelf_getshdr");
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return -1;
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}
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name = elf_strptr(elf, shstrtab_idx, sh.sh_name);
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if (!name || !*name) {
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WARN_ELF("elf_strptr");
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return -1;
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}
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printf("%s+%lx:", name, rela.r_addend);
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} else {
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printf("%lx:", orc_ip_addr + (i * sizeof(int)) + orc_ip[i]);
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}
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printf(" sp:");
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print_reg(orc[i].sp_reg, orc[i].sp_offset);
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printf(" bp:");
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print_reg(orc[i].bp_reg, orc[i].bp_offset);
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printf(" type:%s\n", orc_type_name(orc[i].type));
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}
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elf_end(elf);
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close(fd);
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return 0;
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}
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