[Crash-utility] [PATCH V2 2/2] RISCV64: Fix 'bt' output when no ra on the stack top
Same as the Linux commit f766f77a74f5 ("riscv/stacktrace: Fix
stack output without ra on the stack top").
When a function doesn't have a callee, then it will not
push ra into the stack, such as lkdtm functions, so
correct the FP of the second frame and use pt_regs to get
the right PC of the second frame.
TEST:
Before this patch, the `bt -f` outputs only the first frame with
the wrong PC and FP of next frame:
```
crash> bt -f
PID: 1 TASK: ff600000000e0000 CPU: 1 COMMAND: "sh"
#0 [ff20000000013cf0] lkdtm_EXCEPTION at ffffffff805303c0
[PC: ffffffff805303c0 RA: ff20000000013d10 SP: ff20000000013cf0 SIZE: 16] <- wrong
next PC
ff20000000013cf0: 0000000000000001 ff20000000013d10 <- next FP
ff20000000013d00: ff20000000013d40
crash>
```
After this patch, the `bt` outputs the full frames:
```
crash> bt
PID: 1 TASK: ff600000000e0000 CPU: 1 COMMAND: "sh"
#0 [ff20000000013cf0] lkdtm_EXCEPTION at ffffffff805303c0
#1 [ff20000000013d00] lkdtm_do_action at ffffffff8052fe36
#2 [ff20000000013d10] direct_entry at ffffffff80530018
#3 [ff20000000013d40] full_proxy_write at ffffffff80305044
#4 [ff20000000013d80] vfs_write at ffffffff801b68b4
#5 [ff20000000013e30] ksys_write at ffffffff801b6c4a
#6 [ff20000000013e80] __riscv_sys_write at ffffffff801b6cc4
#7 [ff20000000013e90] do_trap_ecall_u at ffffffff80836798
crash>
```
Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com>
Signed-off-by: Song Shuai <songshuaishuai(a)tinylab.org>
---
riscv64.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/riscv64.c b/riscv64.c
index 0aaa14b..872be59 100644
--- a/riscv64.c
+++ b/riscv64.c
@@ -747,11 +747,14 @@ riscv64_back_trace_cmd(struct bt_info *bt)
{
struct riscv64_unwind_frame current, previous;
struct stackframe curr_frame;
+ struct riscv64_register * regs;
int level = 0;
if (bt->flags & BT_REGS_NOT_FOUND)
return;
+ regs = (struct riscv64_register *) bt->machdep;
+
current.pc = bt->instptr;
current.sp = bt->stkptr;
current.fp = bt->frameptr;
@@ -788,8 +791,16 @@ riscv64_back_trace_cmd(struct bt_info *bt)
sizeof(curr_frame), "get stack frame", RETURN_ON_ERROR))
return;
- previous.pc = curr_frame.ra;
- previous.fp = curr_frame.fp;
+ /* correct PC and FP of the second frame when the first frame has no callee */
+
+ if (regs && (regs->regs[RISCV64_REGS_EPC] == current.pc) &&
curr_frame.fp & 0x7){
+ previous.pc = regs->regs[RISCV64_REGS_RA];
+ previous.fp = curr_frame.ra;
+ } else {
+ previous.pc = curr_frame.ra;
+ previous.fp = curr_frame.fp;
+ }
+
previous.sp = current.fp;
riscv64_dump_backtrace_entry(bt, symbol, ¤t, &previous, level++);
--
2.20.1