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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>
214 lines
4.6 KiB
C
214 lines
4.6 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 <stdlib.h>
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#include <string.h>
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#include "orc.h"
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#include "check.h"
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#include "warn.h"
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int create_orc(struct objtool_file *file)
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{
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struct instruction *insn;
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for_each_insn(file, insn) {
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struct orc_entry *orc = &insn->orc;
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struct cfi_reg *cfa = &insn->state.cfa;
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struct cfi_reg *bp = &insn->state.regs[CFI_BP];
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if (cfa->base == CFI_UNDEFINED) {
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orc->sp_reg = ORC_REG_UNDEFINED;
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continue;
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}
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switch (cfa->base) {
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case CFI_SP:
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orc->sp_reg = ORC_REG_SP;
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break;
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case CFI_SP_INDIRECT:
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orc->sp_reg = ORC_REG_SP_INDIRECT;
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break;
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case CFI_BP:
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orc->sp_reg = ORC_REG_BP;
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break;
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case CFI_BP_INDIRECT:
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orc->sp_reg = ORC_REG_BP_INDIRECT;
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break;
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case CFI_R10:
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orc->sp_reg = ORC_REG_R10;
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break;
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case CFI_R13:
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orc->sp_reg = ORC_REG_R13;
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break;
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case CFI_DI:
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orc->sp_reg = ORC_REG_DI;
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break;
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case CFI_DX:
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orc->sp_reg = ORC_REG_DX;
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break;
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default:
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WARN_FUNC("unknown CFA base reg %d",
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insn->sec, insn->offset, cfa->base);
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return -1;
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}
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switch(bp->base) {
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case CFI_UNDEFINED:
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orc->bp_reg = ORC_REG_UNDEFINED;
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break;
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case CFI_CFA:
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orc->bp_reg = ORC_REG_PREV_SP;
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break;
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case CFI_BP:
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orc->bp_reg = ORC_REG_BP;
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break;
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default:
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WARN_FUNC("unknown BP base reg %d",
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insn->sec, insn->offset, bp->base);
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return -1;
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}
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orc->sp_offset = cfa->offset;
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orc->bp_offset = bp->offset;
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orc->type = insn->state.type;
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}
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return 0;
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}
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static int create_orc_entry(struct section *u_sec, struct section *ip_relasec,
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unsigned int idx, struct section *insn_sec,
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unsigned long insn_off, struct orc_entry *o)
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{
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struct orc_entry *orc;
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struct rela *rela;
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/* populate ORC data */
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orc = (struct orc_entry *)u_sec->data->d_buf + idx;
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memcpy(orc, o, sizeof(*orc));
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/* populate rela for ip */
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rela = malloc(sizeof(*rela));
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if (!rela) {
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perror("malloc");
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return -1;
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}
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memset(rela, 0, sizeof(*rela));
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rela->sym = insn_sec->sym;
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rela->addend = insn_off;
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rela->type = R_X86_64_PC32;
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rela->offset = idx * sizeof(int);
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list_add_tail(&rela->list, &ip_relasec->rela_list);
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hash_add(ip_relasec->rela_hash, &rela->hash, rela->offset);
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return 0;
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}
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int create_orc_sections(struct objtool_file *file)
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{
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struct instruction *insn, *prev_insn;
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struct section *sec, *u_sec, *ip_relasec;
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unsigned int idx;
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struct orc_entry empty = {
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.sp_reg = ORC_REG_UNDEFINED,
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.bp_reg = ORC_REG_UNDEFINED,
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.type = ORC_TYPE_CALL,
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};
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sec = find_section_by_name(file->elf, ".orc_unwind");
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if (sec) {
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WARN("file already has .orc_unwind section, skipping");
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return -1;
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}
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/* count the number of needed orcs */
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idx = 0;
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for_each_sec(file, sec) {
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if (!sec->text)
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continue;
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prev_insn = NULL;
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sec_for_each_insn(file, sec, insn) {
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if (!prev_insn ||
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memcmp(&insn->orc, &prev_insn->orc,
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sizeof(struct orc_entry))) {
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idx++;
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}
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prev_insn = insn;
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}
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/* section terminator */
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if (prev_insn)
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idx++;
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}
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if (!idx)
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return -1;
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/* create .orc_unwind_ip and .rela.orc_unwind_ip sections */
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sec = elf_create_section(file->elf, ".orc_unwind_ip", sizeof(int), idx);
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ip_relasec = elf_create_rela_section(file->elf, sec);
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if (!ip_relasec)
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return -1;
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/* create .orc_unwind section */
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u_sec = elf_create_section(file->elf, ".orc_unwind",
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sizeof(struct orc_entry), idx);
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/* populate sections */
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idx = 0;
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for_each_sec(file, sec) {
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if (!sec->text)
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continue;
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prev_insn = NULL;
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sec_for_each_insn(file, sec, insn) {
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if (!prev_insn || memcmp(&insn->orc, &prev_insn->orc,
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sizeof(struct orc_entry))) {
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if (create_orc_entry(u_sec, ip_relasec, idx,
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insn->sec, insn->offset,
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&insn->orc))
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return -1;
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idx++;
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}
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prev_insn = insn;
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}
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/* section terminator */
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if (prev_insn) {
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if (create_orc_entry(u_sec, ip_relasec, idx,
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prev_insn->sec,
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prev_insn->offset + prev_insn->len,
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&empty))
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return -1;
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idx++;
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}
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}
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if (elf_rebuild_rela_section(ip_relasec))
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return -1;
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return 0;
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}
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