Hi, Ding
Thank you for the fix.
On Thu, Dec 1, 2022 at 8:00 PM <crash-utility-request@xxxxxxxxxx> wrote:
> Date: Thu, 1 Dec 2022 15:01:45 +0800
> From: Ding Hui <dinghui@xxxxxxxxxxxxxx>
> To: crash-utility@xxxxxxxxxx
> Cc: Ding Hui <dinghui@xxxxxxxxxxxxxx>
> Subject: [PATCH] arm64: fix backtraces of KASAN kernel
> dumpfile truncated
> Message-ID: <20221201070145.10830-1-dinghui@xxxxxxxxxxxxxx>
> Content-Type: text/plain; charset="US-ASCII"; x-default=true
>
> We met "bt" cmd on KASAN kernel vmcore display truncated backtraces
> like this:
>
> crash> bt
> PID: 4131 TASK: ffff8001521df000 CPU: 3 COMMAND: "bash"
> #0 [ffff2000224b0cb0] machine_kexec_prepare at ffff2000200bff4c
>
Can you help explain how to reproduce this issue? Or what's the
critical configuration of the kernel? Can this issue be always
reproduced?
I tried to reproduce it on the latest kernel(commit bce9332220bd )
with the CONFIG_KASAN*=y, but can not reproduce this error.
crash> bt
PID: 23838 TASK: ffff3d83abe61300 CPU: 2 COMMAND: "bash"
#0 [ffff800010587650] machine_kexec at ffffbb61b39bd460
#1 [ffff8000105876a0] __crash_kexec at ffffbb61b3b8e2fc
#2 [ffff8000105878c0] panic at ffffbb61b4b6c158
#3 [ffff8000105879f0] sysrq_handle_crash at ffffbb61b43b1144
#4 [ffff800010587a00] __handle_sysrq at ffffbb61b43b1ddc
#5 [ffff800010587a80] write_sysrq_trigger at ffffbb61b43b26e0
#6 [ffff800010587ab0] proc_reg_write at ffffbb61b3f9c4ac
#7 [ffff800010587af0] vfs_write at ffffbb61b3ebeaf4
#8 [ffff800010587c30] ksys_write at ffffbb61b3ebf054
#9 [ffff800010587cd0] __arm64_sys_write at ffffbb61b3ebf144
#10 [ffff800010587df0] invoke_syscall.constprop.0 at ffffbb61b39afc88
#11 [ffff800010587e30] el0_svc_common.constprop.0 at ffffbb61b39afeac
#12 [ffff800010587e60] do_el0_svc at ffffbb61b39aff08
#13 [ffff800010587e80] el0_svc at ffffbb61b4b8defc
#14 [ffff800010587ea0] el0t_64_sync_handler at ffffbb61b4b8e274
#15 [ffff800010587fe0] el0t_64_sync at ffffbb61b39915bc
PC: 0000ffffa42a4880 LR: 0000ffffa424321c SP: 0000ffffe889dd60
X29: 0000ffffe889dd60 X28: 0000000000000000 X27: 0000aaaad1c10000
X26: 0000aaaad1c73018 X25: 0000aaaad1cb89bc X24: 0000000000000002
X23: 0000aaaadd9ce140 X22: 0000ffffa43e77e0 X21: 0000ffffa436a5c0
X20: 0000aaaadd9ce140 X19: 0000000000000001 X18: 0000000000000000
X17: 0000ffffa423ff50 X16: 0000ffffa4244600 X15: 0000ffffa4311350
X14: 0000000000000000 X13: 0000000000000000 X12: 0000000000000000
X11: 0000000000000020 X10: 0000000000000063 X9: 0000aaaadd9dc2c0
X8: 0000000000000040 X7: 00000000ffffffff X6: 0000000000000063
X5: 0000aaaadd9ce141 X4: 0000aaaadd9dc2c1 X3: 0000ffffa43e7020
X2: 0000000000000002 X1: 0000aaaadd9ce140 X0: 0000000000000001
ORIG_X0: 0000000000000001 SYSCALLNO: 40 PSTATE: 20000000
crash>
Thanks.
Lianbo
> After digging the root cause, it turns out that arm64_in_kdump_text()
> found wrong bt->bptr at "machine_kexec" branch.
>
> Disassemble machine_kexec() of KASAN vmlinux (gcc 7.3.0):
>
> crash> dis -x machine_kexec
> 0xffff2000200bff50 <machine_kexec>: stp x29, x30, [sp,#-208]!
> 0xffff2000200bff54 <machine_kexec+0x4>: mov x29, sp
> 0xffff2000200bff58 <machine_kexec+0x8>: stp x19, x20, [sp,#16]
> 0xffff2000200bff5c <machine_kexec+0xc>: str x24, [sp,#56]
> 0xffff2000200bff60 <machine_kexec+0x10>: str x26, [sp,#72]
> 0xffff2000200bff64 <machine_kexec+0x14>: mov x2, #0x8ab3
> 0xffff2000200bff68 <machine_kexec+0x18>: add x1, x29, #0x70
> 0xffff2000200bff6c <machine_kexec+0x1c>: lsr x1, x1, #3
> 0xffff2000200bff70 <machine_kexec+0x20>: movk x2, #0x41b5, lsl #16
> 0xffff2000200bff74 <machine_kexec+0x24>: mov x19, #0x200000000000
> 0xffff2000200bff78 <machine_kexec+0x28>: adrp x3, 0xffff2000224b0000
> 0xffff2000200bff7c <machine_kexec+0x2c>: movk x19, #0xdfff, lsl #48
> 0xffff2000200bff80 <machine_kexec+0x30>: add x3, x3, #0xcb0
> 0xffff2000200bff84 <machine_kexec+0x34>: add x4, x1, x19
> 0xffff2000200bff88 <machine_kexec+0x38>: stp x2, x3, [x29,#112]
> 0xffff2000200bff8c <machine_kexec+0x3c>: adrp x2, 0xffff2000200bf000 <swsusp_arch_resume+0x1e8>
> 0xffff2000200bff90 <machine_kexec+0x40>: add x2, x2, #0xf50
> 0xffff2000200bff94 <machine_kexec+0x44>: str x2, [x29,#128]
> 0xffff2000200bff98 <machine_kexec+0x48>: mov w2, #0xf1f1f1f1
> 0xffff2000200bff9c <machine_kexec+0x4c>: str w2, [x1,x19]
> 0xffff2000200bffa0 <machine_kexec+0x50>: mov w2, #0xf200
> 0xffff2000200bffa4 <machine_kexec+0x54>: mov w1, #0xf3f3f3f3
> 0xffff2000200bffa8 <machine_kexec+0x58>: movk w2, #0xf2f2, lsl #16
> 0xffff2000200bffac <machine_kexec+0x5c>: stp w2, w1, [x4,#4]
>
> We notice that:
> 1. machine_kexec() start address is 0xffff2000200bff50
> 2. the instruction at machine_kexec+0x44 store the same value
> 0xffff2000200bff50 (comes from 0xffff2000200bf000 + 0xf50)
> into stack postion [x29,#128].
>
> When arm64_in_kdump_text() search LR from stack, it met
> 0xffff2000200bff50 firstly, so got wrong bt->bptr.
>
> We know that the real LR is always great than the start address
> of a function, so let's fix it by change the search conditon to
> (*ptr > xxx_start) && (*ptr < xxx_end).
>
> Signed-off-by: Ding Hui <dinghui@xxxxxxxxxxxxxx>
> ---
> arm64.c | 18 +++++++++---------
> 1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/arm64.c b/arm64.c
> index c3e26a3..7e8a7db 100644
> --- a/arm64.c
> +++ b/arm64.c
> @@ -3479,7 +3479,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
> ms = machdep->machspec;
> for (ptr = start - 8; ptr >= base; ptr--) {
> if (bt->flags & BT_OPT_BACK_TRACE) {
> - if ((*ptr >= ms->crash_kexec_start) &&
> + if ((*ptr > ms->crash_kexec_start) &&
> (*ptr < ms->crash_kexec_end) &&
> INSTACK(*(ptr - 1), bt)) {
> bt->bptr = ((ulong)(ptr - 1) - (ulong)base)
> @@ -3488,7 +3488,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
> fprintf(fp, "%lx: %lx (crash_kexec)\n", bt->bptr, *ptr);
> return TRUE;
> }
> - if ((*ptr >= ms->crash_save_cpu_start) &&
> + if ((*ptr > ms->crash_save_cpu_start) &&
> (*ptr < ms->crash_save_cpu_end) &&
> INSTACK(*(ptr - 1), bt)) {
> bt->bptr = ((ulong)(ptr - 1) - (ulong)base)
> @@ -3498,14 +3498,14 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
> return TRUE;
> }
> } else {
> - if ((*ptr >= ms->machine_kexec_start) && (*ptr < ms->machine_kexec_end)) {
> + if ((*ptr > ms->machine_kexec_start) && (*ptr < ms->machine_kexec_end)) {
> bt->bptr = ((ulong)ptr - (ulong)base)
> + task_to_stackbase(bt->tc->task);
> if (CRASHDEBUG(1))
> fprintf(fp, "%lx: %lx (machine_kexec)\n", bt->bptr, *ptr);
> return TRUE;
> }
> - if ((*ptr >= ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
> + if ((*ptr > ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
> /*
> * Stash the first crash_kexec frame in case the machine_kexec
> * frame is not found.
> @@ -3519,7 +3519,7 @@ arm64_in_kdump_text(struct bt_info *bt, struct arm64_stackframe *frame)
> }
> continue;
> }
> - if ((*ptr >= ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
> + if ((*ptr > ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
> bt->bptr = ((ulong)ptr - (ulong)base)
> + task_to_stackbase(bt->tc->task);
> if (CRASHDEBUG(1))
> @@ -3566,7 +3566,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
>
> for (ptr = start - 8; ptr >= base; ptr--) {
> if (bt->flags & BT_OPT_BACK_TRACE) {
> - if ((*ptr >= ms->crash_kexec_start) &&
> + if ((*ptr > ms->crash_kexec_start) &&
> (*ptr < ms->crash_kexec_end) &&
> INSTACK(*(ptr - 1), bt)) {
> bt->bptr = ((ulong)(ptr - 1) - (ulong)base) + stackbase;
> @@ -3576,7 +3576,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
> FREEBUF(stackbuf);
> return TRUE;
> }
> - if ((*ptr >= ms->crash_save_cpu_start) &&
> + if ((*ptr > ms->crash_save_cpu_start) &&
> (*ptr < ms->crash_save_cpu_end) &&
> INSTACK(*(ptr - 1), bt)) {
> bt->bptr = ((ulong)(ptr - 1) - (ulong)base) + stackbase;
> @@ -3587,7 +3587,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
> return TRUE;
> }
> } else {
> - if ((*ptr >= ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
> + if ((*ptr > ms->crash_kexec_start) && (*ptr < ms->crash_kexec_end)) {
> bt->bptr = ((ulong)ptr - (ulong)base) + stackbase;
> if (CRASHDEBUG(1))
> fprintf(fp, "%lx: %lx (crash_kexec on IRQ stack)\n",
> @@ -3595,7 +3595,7 @@ arm64_in_kdump_text_on_irq_stack(struct bt_info *bt)
> FREEBUF(stackbuf);
> return TRUE;
> }
> - if ((*ptr >= ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
> + if ((*ptr > ms->crash_save_cpu_start) && (*ptr < ms->crash_save_cpu_end)) {
> bt->bptr = ((ulong)ptr - (ulong)base) + stackbase;
> if (CRASHDEBUG(1))
> fprintf(fp, "%lx: %lx (crash_save_cpu on IRQ stack)\n",
> --
> 2.17.1
--
Crash-utility mailing list
Crash-utility@xxxxxxxxxx
https://listman.redhat.com/mailman/listinfo/crash-utility
Contribution Guidelines: https://github.com/crash-utility/crash/wiki
