[PATCH v2 08/10] objtool: Add abstraction for computation of symbols offsets

Julien Thierry
2020-03-27T15:29:23Z

From: Raphael Gault <raphael.gault@arm.com>

The jump destination and relocation offset used previously are only
reliable on x86_64 architecture. We abstract these computations by calling
arch-dependent implementations.

Signed-off-by: Raphael Gault <raphael.gault@arm.com>
[J.T. Remove superfluous comment, replace other addend offsets
with arch_dest_rela_offset]
Signed-off-by: Julien Thierry <jthierry@redhat.com>
---
tools/objtool/arch.h | 6 ++++++
tools/objtool/arch/x86/decode.c | 11 +++++++++++
tools/objtool/check.c | 18 ++++++++++--------
3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index ced3765c4f44..a9a50a25ca66 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -66,6 +66,8 @@ struct stack_op {
struct op_src src;
};

+struct instruction;
+
void arch_initial_func_cfi_state(struct cfi_state *state);

int arch_decode_instruction(struct elf *elf, struct section *sec,
@@ -75,4 +77,8 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,

bool arch_callee_saved_reg(unsigned char reg);

+unsigned long arch_jump_destination(struct instruction *insn);
+
+unsigned long arch_dest_rela_offset(int addend);
+
#endif /* _ARCH_H */
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index a62e032863a8..7ce8650cf085 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -11,6 +11,7 @@
#include "../../../arch/x86/lib/inat.c"
#include "../../../arch/x86/lib/insn.c"

+#include "../../check.h"
#include "../../elf.h"
#include "../../arch.h"
#include "../../warn.h"
@@ -66,6 +67,16 @@ bool arch_callee_saved_reg(unsigned char reg)
}
}

+unsigned long arch_dest_rela_offset(int addend)
+{
+ return addend + 4;
+}
+
+unsigned long arch_jump_destination(struct instruction *insn)
+{
+ return insn->offset + insn->len + insn->immediate;
+}
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, enum insn_type *type,
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fb1ddde66b48..dbfd1f5d06f7 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -577,13 +577,14 @@ static int add_jump_destinations(struct objtool_file *file)
insn->offset, insn->len);
if (!rela) {
dest_sec = insn->sec;
- dest_off = insn->offset + insn->len + insn->immediate;
+ dest_off = arch_jump_destination(insn);
} else if (rela->sym->type == STT_SECTION) {
dest_sec = rela->sym->sec;
- dest_off = rela->addend + 4;
+ dest_off = arch_dest_rela_offset(rela->addend);
} else if (rela->sym->sec->idx) {
dest_sec = rela->sym->sec;
- dest_off = rela->sym->sym.st_value + rela->addend + 4;
+ dest_off = rela->sym->sym.st_value +
+ arch_dest_rela_offset(rela->addend);
} else if (strstr(rela->sym->name, "_indirect_thunk_")) {
/*
* Retpoline jumps are really dynamic jumps in
@@ -673,7 +674,7 @@ static int add_call_destinations(struct objtool_file *file)
rela = find_rela_by_dest_range(file->elf, insn->sec,
insn->offset, insn->len);
if (!rela) {
- dest_off = insn->offset + insn->len + insn->immediate;
+ dest_off = arch_jump_destination(insn);
insn->call_dest = find_func_by_offset(insn->sec, dest_off);
if (!insn->call_dest)
insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
@@ -696,13 +697,14 @@ static int add_call_destinations(struct objtool_file *file)
}

} else if (rela->sym->type == STT_SECTION) {
+ dest_off = arch_dest_rela_offset(rela->addend);
insn->call_dest = find_func_by_offset(rela->sym->sec,
- rela->addend+4);
+ dest_off);
if (!insn->call_dest) {
- WARN_FUNC("can't find call dest symbol at %s+0x%x",
+ WARN_FUNC("can't find call dest symbol at %s+0x%lx",
insn->sec, insn->offset,
rela->sym->sec->name,
- rela->addend + 4);
+ dest_off);
return -1;
}
} else
@@ -814,7 +816,7 @@ static int handle_group_alt(struct objtool_file *file,
if (!insn->immediate)
continue;

- dest_off = insn->offset + insn->len + insn->immediate;
+ dest_off = arch_jump_destination(insn);
if (dest_off == special_alt->new_off + special_alt->new_len) {
if (!fake_jump) {
WARN("%s: alternative jump to end of section",
--
2.21.1