[Crash-utility] Problem in bt for ARM64
Dave Anderson
anderson at redhat.com
Fri Oct 13 18:47:03 UTC 2017
Hi Takahiro,
Welcome back! It's great to get you back in the fold again...
I just ran a quick test of your patch on a set of sample dumpfiles,
and only found one issue. It was on a 4.2 QEMU dump where all of the
active tasks were running in user-space, and all of their "bt" commands
fail immediately with a "zero-size" allocation message. As it turns out,
that was due to this GETBUF() call in arm64_in_kdump_text_on_irq_stack():
static int
arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
{
int cpu;
ulong stackbase;
char *stackbuf;
ulong *ptr, *start, *base;
struct machine_specific *ms;
if ((machdep->flags & (IRQ_STACKS|KDUMP_ENABLED)) != (IRQ_STACKS|KDUMP_ENABLED))
return FALSE;
ms = machdep->machspec;
cpu = bt->tc->processor;
stackbase = ms->irq_stacks[cpu];
stackbuf = GETBUF(ms->irq_stack_size); <===
...
ms->irq_stack_size is zero because that kernel version does not have IRQ stacks.
As it turns out, the problem is that your reworked arm64_irq_stack_init() is setting
the IRQ_STACKS flag unconditionally at the bottom of the function. Moving the
flag setting up into the two if-else segments fixes it.
I'll check out the patches in detail next week, but this looks good.
Thanks,
Dave
----- Original Message -----
> Dave,
>
> On Fri, Sep 22, 2017 at 03:06:00PM -0400, Dave Anderson wrote:
> >
> > Jan,
> >
> > I went back to creating a machdep->machspec->user_eframe_offset value
> > to be able to account for both the 4.7 and the upcoming 4.14 pt_regs
> > changes:
> >
> > https://github.com/crash-utility/crash/commit/c975008e61121ef8785622c3bc26964da8fe0deb
> >
> > Again, though, note that "bt" does not work with 4.14.
>
> Even with your latest changes in 7.2.0, "bt" still has some issues:
> a.register dump at exception frame doesn't have correct values
> (due to added stackframe[] in pt_regs)
> b. tracing irq stack to process stack fails
> (due to irq-stack implementation changes and VMAP_STACK)
> c."bt -o" seems to have been broken for a while
>
> Attached is my tentative patch, which hopefully addresses (a) and (b).
> While it is still far from perfect, it may help give you a heads-up.
>
> Thanks,
> -Takahiro AKASHI
>
> ===8<===
> >From 156ec115b2a436a0738908153d676f8eeed84cb1 Mon Sep 17 00:00:00 2001
> From: AKASHI Takahiro <takahiro.akashi at linaro.org>
> Date: Thu, 12 Oct 2017 10:46:34 +0900
> Subject: [PATCH] arm64: backtrace for v4.14
>
> ---
> arm64.c | 172
> ++++++++++++++++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 136 insertions(+), 36 deletions(-)
>
> diff --git a/arm64.c b/arm64.c
> index 20c5d34..22c8556 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -72,6 +72,7 @@ static void arm64_cmd_mach(void);
> static void arm64_display_machine_stats(void);
> static int arm64_get_smp_cpus(void);
> static void arm64_clear_machdep_cache(void);
> +static int arm64_on_process_stack(struct bt_info *, ulong);
> static int arm64_in_alternate_stack(int, ulong);
> static int arm64_on_irq_stack(int, ulong);
> static void arm64_set_irq_stack(struct bt_info *);
> @@ -1336,29 +1337,60 @@ arm64_irq_stack_init(void)
> req = &request;
> struct machine_specific *ms = machdep->machspec;
>
> - if (!symbol_exists("irq_stack") ||
> - !(sp = per_cpu_symbol_search("irq_stack")) ||
> - !get_symbol_type("irq_stack", NULL, req) ||
> - (req->typecode != TYPE_CODE_ARRAY) ||
> - (req->target_typecode != TYPE_CODE_INT))
> - return;
> + if (!(ms->irq_stacks = (ulong *)malloc((size_t)(kt->cpus
> + * sizeof(ulong)))))
> + error(FATAL, "cannot malloc irq_stack addresses\n");
>
> - if (CRASHDEBUG(1)) {
> - fprintf(fp, "irq_stack: \n");
> - fprintf(fp, " type: %s\n",
> - (req->typecode == TYPE_CODE_ARRAY) ? "TYPE_CODE_ARRAY" : "other");
> - fprintf(fp, " target_typecode: %s\n",
> - req->target_typecode == TYPE_CODE_INT ? "TYPE_CODE_INT" : "other");
> - fprintf(fp, " target_length: %ld\n", req->target_length);
> - fprintf(fp, " length: %ld\n", req->length);
> - }
> + if (symbol_exists("irq_stack") &&
> + (sp = per_cpu_symbol_search("irq_stack")) &&
> + get_symbol_type("irq_stack", NULL, req)) {
> + /* before v4.14 or CONFIG_VMAP_STACK disabled */
> + if (CRASHDEBUG(1)) {
> + fprintf(fp, "irq_stack: \n");
> + fprintf(fp, " type: %s\n",
> + (req->typecode == TYPE_CODE_ARRAY) ?
> + "TYPE_CODE_ARRAY" : "other");
> + fprintf(fp, " target_typecode: %s\n",
> + req->target_typecode == TYPE_CODE_INT ?
> + "TYPE_CODE_INT" : "other");
> + fprintf(fp, " target_length: %ld\n",
> + req->target_length);
> + fprintf(fp, " length: %ld\n", req->length);
> + }
>
> - ms->irq_stack_size = req->length;
> - if (!(ms->irq_stacks = (ulong *)malloc((size_t)(kt->cpus *
> sizeof(ulong)))))
> - error(FATAL, "cannot malloc irq_stack addresses\n");
> + ms->irq_stack_size = req->length;
> +
> + for (i = 0; i < kt->cpus; i++)
> + ms->irq_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
> + } else if (symbol_exists("irq_stack_ptr") &&
> + (sp = per_cpu_symbol_search("irq_stack_ptr")) &&
> + get_symbol_type("irq_stack_ptr", NULL, req)) {
> + /* v4.14 and later with CONFIG_VMAP_STACK enabled */
> + if (CRASHDEBUG(1)) {
> + fprintf(fp, "irq_stack_ptr: \n");
> + fprintf(fp, " type: %x, %s\n",
> + (int)req->typecode,
> + (req->typecode == TYPE_CODE_PTR) ?
> + "TYPE_CODE_PTR" : "other");
> + fprintf(fp, " target_typecode: %x, %s\n",
> + (int)req->target_typecode,
> + req->target_typecode == TYPE_CODE_INT ?
> + "TYPE_CODE_INT" : "other");
> + fprintf(fp, " target_length: %ld\n",
> + req->target_length);
> + fprintf(fp, " length: %ld\n", req->length);
> + }
> +
> + ms->irq_stack_size = 16384;
> +
> + for (i = 0; i < kt->cpus; i++) {
> + ulong p;
>
> - for (i = 0; i < kt->cpus; i++)
> - ms->irq_stacks[i] = kt->__per_cpu_offset[i] + sp->value;
> + p = kt->__per_cpu_offset[i] + sp->value;
> + readmem(p, KVADDR, &(ms->irq_stacks[i]), sizeof(ulong),
> + "IRQ stack pointer", RETURN_ON_ERROR);
> + }
> + }
>
> machdep->flags |= IRQ_STACKS;
> }
> @@ -1750,11 +1782,20 @@ arm64_display_full_frame(struct bt_info *bt, ulong
> sp)
> if (bt->frameptr == sp)
> return;
>
> - if (!INSTACK(sp, bt) || !INSTACK(bt->frameptr, bt)) {
> - if (sp == 0)
> - sp = bt->stacktop - USER_EFRAME_OFFSET;
> - else
> - return;
> + if (INSTACK(bt->frameptr, bt)) {
> + if (INSTACK(sp, bt)) {
> + /* normal case */;
> + } else {
> + if (sp == 0)
> + /* interrupt in user mode */
> + sp = bt->stacktop - USER_EFRAME_OFFSET;
> + else
> + /* interrupt in kernel mode */
> + sp = bt->stacktop;
> + }
> + } else {
> + error(WARNING, "full display ?\n");
> + return;
> }
>
> words = (sp - bt->frameptr) / sizeof(ulong);
> @@ -1873,6 +1914,25 @@ arm64_unwind_frame(struct bt_info *bt, struct
> arm64_stackframe *frame)
> * orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr); (pt_regs pointer on
> process stack)
> */
> if (machdep->flags & IRQ_STACKS) {
> + if (machdep->flags & UNW_4_14) {
> + if ((bt->flags & BT_IRQSTACK) &&
> + !arm64_on_irq_stack(bt->tc->processor, frame->fp)) {
> + if (arm64_on_process_stack(bt, frame->fp)) {
> + arm64_set_process_stack(bt);
> +
> + frame->sp = frame->fp - SIZE(pt_regs) + 16;
> + /* for switch_stack */
> + /* fp still points to irq stack */
> + bt->bptr = fp;
> + /* for display_full_frame */
> + /* sp points to process stack */
> + bt->frameptr = frame->sp;
> + } else {
> + /* irq -> user */
> + return FALSE;
> + }
> + }
> + } else { /* !UNW_4_14 */
> ms = machdep->machspec;
> irq_stack_ptr = ms->irq_stacks[bt->tc->processor] + ms->irq_stack_size -
> 16;
>
> @@ -1896,6 +1956,7 @@ arm64_unwind_frame(struct bt_info *bt, struct
> arm64_stackframe *frame)
> return FALSE;
> }
> }
> + } /* UNW_4_14 */
> }
>
> return TRUE;
> @@ -2086,10 +2147,17 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct
> arm64_stackframe *frame,
> * We are on process stack. Just add a faked frame
> */
>
> - if (!arm64_on_irq_stack(bt->tc->processor, ext_frame.fp))
> - frame->sp = ext_frame.fp
> - - sizeof(struct arm64_pt_regs);
> - else {
> + if (!arm64_on_irq_stack(bt->tc->processor, ext_frame.fp)) {
> + if (MEMBER_EXISTS("pt_regs", "stackframe")) {
> + frame->sp = ext_frame.fp
> + - sizeof(struct arm64_pt_regs) - 16;
> + frame->fp = ext_frame.fp;
> + } else {
> + frame->sp = ext_frame.fp
> + - sizeof(struct arm64_pt_regs);
> + frame->fp = frame->sp;
> + }
> + } else {
> /*
> * FIXME: very exceptional case
> * We are already back on process stack, but
> @@ -2109,10 +2177,10 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct
> arm64_stackframe *frame,
> * Really ugly
> */
> frame->sp = frame->fp + 0x20;
> + frame->fp = frame->sp;
> fprintf(ofp, " (Next exception frame might be wrong)\n");
> }
>
> - frame->fp = frame->sp;
> } else {
> /* We are on IRQ stack */
>
> @@ -2122,9 +2190,15 @@ arm64_unwind_frame_v2(struct bt_info *bt, struct
> arm64_stackframe *frame,
> if (ext_frame.fp != irq_stack_ptr) {
> /* (2) Just add a faked frame */
>
> - frame->sp = ext_frame.fp
> - - sizeof(struct arm64_pt_regs);
> - frame->fp = frame->sp;
> + if (MEMBER_EXISTS("pt_regs", "stackframe")) {
> + frame->sp = ext_frame.fp
> + - sizeof(struct arm64_pt_regs);
> + frame->fp = ext_frame.fp;
> + } else {
> + frame->sp = ext_frame.fp
> + - sizeof(struct arm64_pt_regs) - 16;
> + frame->fp = frame->sp;
> + }
> } else {
> /*
> * (3)
> @@ -2304,11 +2378,19 @@ arm64_back_trace_cmd(struct bt_info *bt)
> if (arm64_in_exception_text(bt->instptr) && INSTACK(stackframe.fp, bt)) {
> if (!(bt->flags & BT_IRQSTACK) ||
> (((stackframe.sp + SIZE(pt_regs)) < bt->stacktop)))
> - exception_frame = stackframe.fp - SIZE(pt_regs);
> + {
> + if (MEMBER_EXISTS("pt_regs", "stackframe"))
> + /* v4.14 or later */
> + exception_frame = stackframe.fp
> + - SIZE(pt_regs) + 16;
> + else
> + exception_frame = stackframe.fp
> + - SIZE(pt_regs);
> + }
> }
>
> if ((bt->flags & BT_IRQSTACK) &&
> - !arm64_on_irq_stack(bt->tc->processor, stackframe.sp)) {
> + !arm64_on_irq_stack(bt->tc->processor, stackframe.fp)) {
> bt->flags &= ~BT_IRQSTACK;
> if (arm64_switch_stack(bt, &stackframe, ofp) == USER_MODE)
> break;
> @@ -2424,6 +2506,8 @@ user_space:
> * otherwise show an exception frame.
> * Since exception entry code doesn't have a real
> * stackframe, we fake a dummy frame here.
> + * Note: Since we have a real stack frame in pt_regs,
> + * We no longer need a dummy frame on v4.14 or later.
> */
> if (!arm64_in_exp_entry(stackframe.pc))
> continue;
> @@ -2669,7 +2753,9 @@ arm64_switch_stack(struct bt_info *bt, struct
> arm64_stackframe *frame, FILE *ofp
> if (frame->fp == 0)
> return USER_MODE;
>
> - arm64_print_exception_frame(bt, frame->sp, KERNEL_MODE, ofp);
> + if (!(machdep->flags & UNW_4_14))
> + arm64_print_exception_frame(bt, frame->sp, KERNEL_MODE, ofp);
> +
> return KERNEL_MODE;
> }
>
> @@ -3362,6 +3448,20 @@ arm64_clear_machdep_cache(void) {
> return;
> }
>
> +static int
> +arm64_on_process_stack(struct bt_info *bt, ulong stkptr)
> +{
> + ulong stackbase, stacktop;
> +
> + stackbase = GET_STACKBASE(bt->task);
> + stacktop = GET_STACKTOP(bt->task);
> +
> + if ((stkptr >= stackbase) && (stkptr < stacktop))
> + return TRUE;
> +
> + return FALSE;
> +}
> +
> static int
> arm64_on_irq_stack(int cpu, ulong stkptr)
> {
> --
> 2.14.1
>
> --
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