The previous implementation to locate the call instruction is
to strstr "call", then check whether the previous char is ' '
or '\t'. The implementation is problematic. For example it
cannot resolve the following disassembly string:
"0xffffffffc0995378 <nfs41_callback_svc+344>:\tcall 0xffffffff8ecfa4c0 <schedule>\n"
strstr will locate the "_call" and char check fails,
as a result, extract_hex fail to get the calling address.
NOTE: the issue is more likely to be reproduced when patch[1] applied.
Because without patch[1], the disassembly string will be as follows,
so the issue is no longer reproducible.
"0xffffffffc0995378:\tcall 0xffffffff8ecfa4c0 <schedule>\n"
Before the patch:
crash> bt 1472
PID: 1472 TASK: ffff8c121fa72f70 CPU: 18 COMMAND: "nfsv4.1-svc"
#0 [ffff8c16231a3db8] __schedule at ffffffff8ecf9ef3
#1 [ffff8c16231a3e40] schedule at ffffffff8ecfa4e9
After the patch:
crash> bt 1472
PID: 1472 TASK: ffff8c121fa72f70 CPU: 18 COMMAND: "nfsv4.1-svc"
#0 [ffff8c16231a3db8] __schedule at ffffffff8ecf9ef3
#1 [ffff8c16231a3e40] schedule at ffffffff8ecfa4e9
#2 [ffff8c16231a3e50] nfs41_callback_svc at ffffffffc099537d [nfsv4]
#3 [ffff8c16231a3ec8] kthread at ffffffff8e6b966f
#4 [ffff8c16231a3f50] ret_from_fork at ffffffff8ed07898
This patch fix the issue by strstr "\tcall" and " call", to
locate the correct call instruction.
[1]: https://www.mail-archive.com/crash-utility@xxxxxxxxxx/msg09490.html
Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---
v1 -> v2: No modification, sent together with patch1
v2 -> v3: Modified the commit log, with failure output of bt cmd
---
x86_64.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/x86_64.c b/x86_64.c
index dfada48..74bd1bb 100644
--- a/x86_64.c
+++ b/x86_64.c
@@ -4432,8 +4432,7 @@ x86_64_function_called_by(ulong rip)
if (gdb_pass_through(buf, pc->tmpfile2, GNU_RETURN_ON_ERROR)) {
rewind(pc->tmpfile2);
while (fgets(buf, BUFSIZE, pc->tmpfile2)) {
- if ((p1 = strstr(buf, "call")) &&
- whitespace(*(p1-1))) {
+ if ((p1 = strstr(buf, " call")) || (p1 = strstr(buf, "\tcall"))) {
if (extract_hex(p1, &value, NULLCHAR, TRUE))
break;
}
--
2.33.1
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