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) <peterz@infradead.org>
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index bc6723a..26d11d8 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -529,8 +529,9 @@
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 @@
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 aa9c64d..7324e77 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -64,9 +64,10 @@
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 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);
