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
On Tue, Jun 3, 2025 at 1:18 PM <devel-requ...@lists.crash-utility.osci.io>
wrote:
> Date: Tue, 3 Jun 2025 17:11:38 +1200
> From: Tao Liu <l...@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.makha...@broadcom.com>
> Message-ID: <20250603051138.59896-6-l...@redhat.com>
> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>
> Co-developed-by: Alexey Makhalov <alexey.makha...@broadcom.com>
> Co-developed-by: Tao Liu <l...@redhat.com>
> Signed-off-by: Tao Liu <l...@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
>
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