This provides infrastructure to rewrite instructions; this is immediately useful for helping out with KCOV-vs-noinstr, but will also come in handy for a bunch of variable sized jump-label patches that are still on ice.
Signed-off-by: Peter Zijlstra (Intel) <[email protected]> --- tools/objtool/elf.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++- tools/objtool/elf.h | 7 ++++++- 2 files changed, 55 insertions(+), 2 deletions(-) --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -114,6 +114,53 @@ static int symbol_to_offset(struct rb_no return 0; } +int elf_write_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int len, + const char *insn) +{ + Elf_Data *data = sec->data; + + if (data->d_type != ELF_T_BYTE || data->d_off) { + WARN("write to unexpected data for section: %s", sec->name); + return -1; + } + + memcpy(data->d_buf + offset, insn, len); + elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY); + + elf->changed = true; + + return 0; +} + +int elf_write_reloc(struct elf *elf, struct reloc *reloc) +{ + struct section *sec = reloc->sec; + + if (sec->sh.sh_type == SHT_REL) { + reloc->rel.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); + reloc->rel.r_offset = reloc->offset; + + if (!gelf_update_rel(sec->data, reloc->idx, &reloc->rel)) { + WARN_ELF("gelf_update_rel"); + return -1; + } + } else { + reloc->rela.r_info = GELF_R_INFO(reloc->sym->idx, reloc->type); + reloc->rela.r_addend = reloc->addend; + reloc->rela.r_offset = reloc->offset; + + if (!gelf_update_rela(sec->data, reloc->idx, &reloc->rela)) { + WARN_ELF("gelf_update_rela"); + return -1; + } + } + + elf->changed = true; + + return 0; +} + static int symbol_by_offset(const void *key, const struct rb_node *node) { const struct symbol *s = rb_entry(node, struct symbol, node); @@ -563,8 +610,9 @@ static int read_relocs(struct elf *elf) break; default: return -1; } - reloc->sym = find_symbol_by_index(elf, symndx); reloc->sec = sec; + reloc->idx = i; + reloc->sym = find_symbol_by_index(elf, symndx); if (!reloc->sym) { WARN("can't find reloc entry symbol %d for %s", symndx, sec->name); --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -67,9 +67,10 @@ struct reloc { }; struct section *sec; struct symbol *sym; - unsigned int type; unsigned long offset; + unsigned int type; int addend; + int idx; bool jump_table_start; }; @@ -122,6 +123,10 @@ struct elf *elf_open_read(const char *na struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr); struct section *elf_create_reloc_section(struct elf *elf, struct section *base, int reltype); void elf_add_reloc(struct elf *elf, struct reloc *reloc); +int elf_write_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int len, + const char *insn); +int elf_write_reloc(struct elf *elf, struct reloc *reloc); int elf_write(struct elf *elf); void elf_close(struct elf *elf);
