From fdabdd0b05e0bdf232340d5da86563ed142a99a7 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 12 Jun 2020 15:43:00 +0200 Subject: objtool: Provide elf_write_{insn,reloc}() 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) --- tools/objtool/elf.c | 40 +++++++++++++++++++++++++++++++++++++++- tools/objtool/elf.h | 7 ++++++- 2 files changed, 45 insertions(+), 2 deletions(-) (limited to 'tools') diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index bc6723a502c3..26d11d821941 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -529,8 +529,9 @@ static int read_relas(struct elf *elf) rela->addend = rela->rela.r_addend; rela->offset = rela->rela.r_offset; symndx = GELF_R_SYM(rela->rela.r_info); - rela->sym = find_symbol_by_index(elf, symndx); rela->sec = sec; + rela->idx = i; + rela->sym = find_symbol_by_index(elf, symndx); if (!rela->sym) { WARN("can't find rela entry symbol %d for %s", symndx, sec->name); @@ -784,6 +785,43 @@ int elf_rebuild_rela_section(struct elf *elf, struct section *sec) 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_rela(struct elf *elf, struct rela *rela) +{ + struct section *sec = rela->sec; + + rela->rela.r_info = GELF_R_INFO(rela->sym->idx, rela->type); + rela->rela.r_addend = rela->addend; + rela->rela.r_offset = rela->offset; + + if (!gelf_update_rela(sec->data, rela->idx, &rela->rela)) { + WARN_ELF("gelf_update_rela"); + return -1; + } + + elf->changed = true; + + return 0; +} + int elf_write(struct elf *elf) { struct section *sec; diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index aa9c64da379f..7324e772583e 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -64,9 +64,10 @@ struct rela { GElf_Rela rela; struct section *sec; struct symbol *sym; - unsigned int type; unsigned long offset; + unsigned int type; int addend; + int idx; bool jump_table_start; }; @@ -119,6 +120,10 @@ struct elf *elf_open_read(const char *name, int flags); struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr); struct section *elf_create_rela_section(struct elf *elf, struct section *base); void elf_add_rela(struct elf *elf, struct rela *rela); +int elf_write_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int len, + const char *insn); +int elf_write_rela(struct elf *elf, struct rela *rela); int elf_write(struct elf *elf); void elf_close(struct elf *elf); -- cgit v1.2.3