After patch "x86_64: Add gdb multi-stack unwind support" applied, a
warning message is observed for "bt -T" cmd:
crash> bt -T
bt: seek error: kernel virtual address: fffffffffffffffb type:
"gdb_readmem_callback"
[ffffbaebc60d6fa8] srso_return_thunk at ffffffff82246fa5
...
The root cause is, "bt -T" will set BT_TEXT_SYMBOLS_ALL for bt->flags,
and eip is set to be 0 in kernel.c:back_trace(). Later in
x86_64_low_budget_back_trace_cmd(), eip - 5, or 0xfffffffffffffffb is
used for address disassembly by gdb "x/1i 0x%lx". This address is invalid so
the warning message is output.
In fact, multi-stack unwind isn't designed for "bt -T" and eip = 0 case.
To avoid the warning message, let's simply bypass the "bt -T" case for
x86_64. Other archs(arm64/ppc64) aren't affected by the issue because
the gdb "x/1i 0x%lx" are not applied on those archs.
After apply the patch:
crash> bt -T
[ffffbaebc60d6fa8] srso_return_thunk at ffffffff82246fa5
...
Signed-off-by: Tao Liu <l...@redhat.com>
---
x86_64.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/x86_64.c b/x86_64.c
index cfefe3f..d7da536 100644
--- a/x86_64.c
+++ b/x86_64.c
@@ -3636,7 +3636,8 @@ x86_64_low_budget_back_trace_cmd(struct bt_info *bt_in)
level++;
}
- if (is_task_active(bt->task) && bt->flags & BT_DUMPFILE_SEARCH) {
+ if (is_task_active(bt->task) && bt->flags & BT_DUMPFILE_SEARCH &&
+ !(bt->flags & BT_TEXT_SYMBOLS_ALL)) {
if (!extra_stacks_regs[extra_stacks_idx]) {
extra_stacks_regs[extra_stacks_idx] =
(struct user_regs_bitmap_struct *)
--
2.47.0
--
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