objtool: Add --backtrace support
For when you want to know the path that reached your fail state:
$ ./objtool check --no-fp --backtrace arch/x86/lib/usercopy_64.o
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x3: UACCESS disable without MEMOPs: __clear_user()
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x3a: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x2e: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x18: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x5: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x0: <=== (func)
0000000000000000 <__clear_user>:
0: e8 00 00 00 00 callq 5 <__clear_user+0x5>
1: R_X86_64_PLT32 __fentry__-0x4
5: 90 nop
6: 90 nop
7: 90 nop
8: 48 89 f0 mov %rsi,%rax
b: 48 c1 ee 03 shr $0x3,%rsi
f: 83 e0 07 and $0x7,%eax
12: 48 89 f1 mov %rsi,%rcx
15: 48 85 c9 test %rcx,%rcx
18: 74 0f je 29 <__clear_user+0x29>
1a: 48 c7 07 00 00 00 00 movq $0x0,(%rdi)
21: 48 83 c7 08 add $0x8,%rdi
25: ff c9 dec %ecx
27: 75 f1 jne 1a <__clear_user+0x1a>
29: 48 89 c1 mov %rax,%rcx
2c: 85 c9 test %ecx,%ecx
2e: 74 0a je 3a <__clear_user+0x3a>
30: c6 07 00 movb $0x0,(%rdi)
33: 48 ff c7 inc %rdi
36: ff c9 dec %ecx
38: 75 f6 jne 30 <__clear_user+0x30>
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 48 89 c8 mov %rcx,%rax
40: c3 retq
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8d8191f2..ccc66af 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1885,8 +1885,11 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
if (!insn->ignore_alts) {
list_for_each_entry(alt, &insn->alts, list) {
ret = validate_branch(file, alt->insn, state);
- if (ret)
- return 1;
+ if (ret) {
+ if (backtrace)
+ BT_FUNC("(alt)", insn);
+ return ret;
+ }
}
}
@@ -1933,8 +1936,11 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
insn->jump_dest->func->pfunc == func)) {
ret = validate_branch(file, insn->jump_dest,
state);
- if (ret)
- return 1;
+ if (ret) {
+ if (backtrace)
+ BT_FUNC("(branch)", insn);
+ return ret;
+ }
} else if (func && has_modified_stack_frame(&state)) {
WARN_FUNC("sibling call from callable instruction with modified stack frame",
@@ -2005,6 +2011,8 @@ static int validate_unwind_hints(struct objtool_file *file)
for_each_insn(file, insn) {
if (insn->hint && !insn->visited) {
ret = validate_branch(file, insn, state);
+ if (ret && backtrace)
+ BT_FUNC("<=== (hint)", insn);
warnings += ret;
}
}
@@ -2133,6 +2141,8 @@ static int validate_functions(struct objtool_file *file)
continue;
ret = validate_branch(file, insn, state);
+ if (ret && backtrace)
+ BT_FUNC("<=== (func)", insn);
warnings += ret;
}
}
