For ppc64 machine, I noticed that the gdb bt may not work as expected, for example:
crash> set 2
PID: 2
COMMAND: "kthreadd"
TASK: c000000004797f80 [THREAD_INFO: c000000004797f80]
CPU: 0
STATE: TASK_INTERRUPTIBLE
crash> bt
PID: 2 TASK: c000000004797f80 CPU: 0 COMMAND: "kthreadd"
#0 [c00000000484fbc0] _end at c00000000484fd70 (unreliable)
#1 [c00000000484fd70] __switch_to at c00000000001fabc
#2 [c00000000484fdd0] __schedule at c0000000011ca9dc
#3 [c00000000484feb0] schedule at c0000000011caeb0
#4 [c00000000484ff20] kthreadd at c0000000001af6c4
#5 [c00000000484ffe0] start_kernel_thread at c00000000000ded8
crash> gdb bt
#0 0xc00000000484fd70 in ?? ()
gdb: gdb request failed: bt
crash>
crash> sys|grep RELEASE
RELEASE: 6.12.0
Is that expected behavior?(I do not remember if I mentioned the similar issue in the previous patch review.)
I have no more comments for other changes, just three issues(see another two comments).
Thanks
Lianbo
Date: Tue, 3 Jun 2025 17:11:38 +1200
From: Tao Liu <ltao@redhat.com>
Subject: [Crash-utility] [PATCH v3 5/5] ppc64: Add gdb multi-stack
unwind support
To: devel@lists.crash-utility.osci.io
Cc: Alexey Makhalov <alexey.makhalov@broadcom.com>
Message-ID: <20250603051138.59896-6-ltao@redhat.com>
Content-Type: text/plain; charset="US-ASCII"; x-default=true
Co-developed-by: Alexey Makhalov <alexey.makhalov@broadcom.com>
Co-developed-by: Tao Liu <ltao@redhat.com>
Signed-off-by: Tao Liu <ltao@redhat.com>
---
ppc64.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 64 insertions(+), 6 deletions(-)
diff --git a/ppc64.c b/ppc64.c
index 532eb3f..d1a5067 100644
--- a/ppc64.c
+++ b/ppc64.c
@@ -2053,6 +2053,7 @@ ppc64_back_trace_cmd(struct bt_info *bt)
char buf[BUFSIZE];
struct gnu_request *req;
extern void print_stack_text_syms(struct bt_info *, ulong, ulong);
+ extra_stacks_idx = 0;
bt->flags |= BT_EXCEPTION_FRAME;
@@ -2071,6 +2072,29 @@ ppc64_back_trace_cmd(struct bt_info *bt)
req->pc = bt->instptr;
req->sp = bt->stkptr;
+ if (is_task_active(bt->task)) {
+ if (!extra_stacks_regs[extra_stacks_idx]) {
+ extra_stacks_regs[extra_stacks_idx] =
+ (struct user_regs_bitmap_struct *)
+ malloc(sizeof(struct user_regs_bitmap_struct));
+ }
+ memset(extra_stacks_regs[extra_stacks_idx], 0,
+ sizeof(struct user_regs_bitmap_struct));
+ extra_stacks_regs[extra_stacks_idx]->ur.nip = req->pc;
+ extra_stacks_regs[extra_stacks_idx]->ur.gpr[1] = req->sp;
+ SET_BIT(extra_stacks_regs[extra_stacks_idx]->bitmap,
+ REG_SEQ(ppc64_pt_regs, nip));
+ SET_BIT(extra_stacks_regs[extra_stacks_idx]->bitmap,
+ REG_SEQ(ppc64_pt_regs, gpr[0]) + 1);
+ if (!bt->machdep ||
+ (extra_stacks_regs[extra_stacks_idx]->ur.gpr[1] !=
+ ((struct user_regs_bitmap_struct *)(bt->machdep))->ur.gpr[1] &&
+ extra_stacks_regs[extra_stacks_idx]->ur.nip !=
+ ((struct user_regs_bitmap_struct *)(bt->machdep))->ur.nip)) {
+ gdb_add_substack (extra_stacks_idx++);
+ }
+ }
+
if (bt->flags &
(BT_TEXT_SYMBOLS|BT_TEXT_SYMBOLS_PRINT|BT_TEXT_SYMBOLS_NOPRINT)) {
if (!INSTACK(req->sp, bt))
@@ -2512,6 +2536,28 @@ ppc64_print_eframe(char *efrm_str, struct ppc64_pt_regs *regs,
fprintf(fp, " %s [%lx] exception frame:\n", efrm_str, regs->trap);
ppc64_print_regs(regs);
ppc64_print_nip_lr(regs, 1);
+
+ if (!((regs->msr >> MSR_PR_LG) & 0x1) &&
+ !(bt->flags & BT_EFRAME_SEARCH)) {
+ if (!extra_stacks_regs[extra_stacks_idx]) {
+ extra_stacks_regs[extra_stacks_idx] =
+ (struct user_regs_bitmap_struct *)
+ malloc(sizeof(struct user_regs_bitmap_struct));
+ }
+ memset(extra_stacks_regs[extra_stacks_idx], 0,
+ sizeof(struct user_regs_bitmap_struct));
+ memcpy(&extra_stacks_regs[extra_stacks_idx]->ur, regs,
+ sizeof(struct ppc64_pt_regs));
+ for (int i = 0; i < sizeof(struct ppc64_pt_regs)/sizeof(ulong); i++)
+ SET_BIT(extra_stacks_regs[extra_stacks_idx]->bitmap, i);
+ if (!bt->machdep ||
+ (extra_stacks_regs[extra_stacks_idx]->ur.gpr[1] !=
+ ((struct user_regs_bitmap_struct *)(bt->machdep))->ur.gpr[1] &&
+ extra_stacks_regs[extra_stacks_idx]->ur.nip !=
+ ((struct user_regs_bitmap_struct *)(bt->machdep))->ur.nip)) {
+ gdb_add_substack (extra_stacks_idx++);
+ }
+ }
}
static int
@@ -2552,6 +2598,12 @@ ppc64_get_current_task_reg(int regno, const char *name, int size,
tc = CURRENT_CONTEXT();
if (!tc)
return FALSE;
+
+ if (sid && sid <= extra_stacks_idx) {
+ ur_bitmap = extra_stacks_regs[sid - 1];
+ goto get_sub;
+ }
+
BZERO(&bt_setup, sizeof(struct bt_info));
clone_bt_info(&bt_setup, &bt_info, tc);
fill_stackbuf(&bt_info);
@@ -2570,39 +2622,45 @@ ppc64_get_current_task_reg(int regno, const char *name, int size,
goto get_all;
}
+get_sub:
switch (regno) {
case PPC64_R0_REGNUM ... PPC64_R31_REGNUM:
if (!NUM_IN_BITMAP(ur_bitmap->bitmap,
REG_SEQ(ppc64_pt_regs, gpr[0]) + regno - PPC64_R0_REGNUM)) {
- FREEBUF(ur_bitmap);
+ if (!sid)
+ FREEBUF(ur_bitmap);
return FALSE;
}
break;
case PPC64_PC_REGNUM:
if (!NUM_IN_BITMAP(ur_bitmap->bitmap,
REG_SEQ(ppc64_pt_regs, nip))) {
- FREEBUF(ur_bitmap);
+ if (!sid)
+ FREEBUF(ur_bitmap);
return FALSE;
}
break;
case PPC64_MSR_REGNUM:
if (!NUM_IN_BITMAP(ur_bitmap->bitmap,
REG_SEQ(ppc64_pt_regs, msr))) {
- FREEBUF(ur_bitmap);
+ if (!sid)
+ FREEBUF(ur_bitmap);
return FALSE;
}
break;
case PPC64_LR_REGNUM:
if (!NUM_IN_BITMAP(ur_bitmap->bitmap,
REG_SEQ(ppc64_pt_regs, link))) {
- FREEBUF(ur_bitmap);
+ if (!sid)
+ FREEBUF(ur_bitmap);
return FALSE;
}
break;
case PPC64_CTR_REGNUM:
if (!NUM_IN_BITMAP(ur_bitmap->bitmap,
REG_SEQ(ppc64_pt_regs, ctr))) {
- FREEBUF(ur_bitmap);
+ if (!sid)
+ FREEBUF(ur_bitmap);
return FALSE;
}
break;
@@ -2645,7 +2703,7 @@ get_all:
ret = TRUE;
break;
}
- if (bt_info.need_free) {
+ if (!sid && bt_info.need_free) {
FREEBUF(ur_bitmap);
bt_info.need_free = FALSE;
}
--
2.47.0