[Crash-utility] Re: [PATCH v3 5/5] ppc64: Add gdb multi-stack unwind support

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-request(a)lists.crash-utility.osci.io&gt; wrote: > > Date: Tue, 3 Jun 2025 17:11:38 +1200 > From: Tao Liu <ltao(a)redhat.com&gt; > Subject: [Crash-utility] [PATCH v3 5/5] ppc64: Add gdb multi-stack > unwind support > To: devel(a)lists.crash-utility.osci.io > Cc: Alexey Makhalov <alexey.makhalov(a)broadcom.com&gt; > Message-ID: <20250603051138.59896-6-ltao(a)redhat.com&gt; > Content-Type: text/plain; charset="US-ASCII"; x-default=true > > Co-developed-by: Alexey Makhalov <alexey.makhalov(a)broadcom.com&gt; > Co-developed-by: Tao Liu <ltao(a)redhat.com&gt; > Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; > --- > 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 -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki