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Message-ID: <CAAhV-H7KAcjHdExr-voiB_xJOcTvFD4Hm90YD_=FzV8swOS1Rg@mail.gmail.com>
Date: Wed, 28 Jan 2026 15:35:54 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] LoongArch: Handle percpu handler address for ORC unwinder
Hi, Tiezhu,
On Wed, Jan 21, 2026 at 5:59 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> After commit 4cd641a79e69 ("LoongArch: Remove unnecessary checks for
> ORC unwinder"), the system can not boot normally under some configs,
> there are many error messages "cannot find unwind pc".
Unfortunately, after this series sometimes there are still error
messages, such as:
cannot find unwind pc at ffff80000231fe1c
Obviously, this is no longer related to per-cpu handler, and from the
call stack it seems related to BPF:
[ 75.025389] CPU: 0 UID: 0 PID: 175 Comm: systemd-udevd Not tainted
6.19-rc7+ #721
[ 75.025409] Hardware name: Loongson Loongson-3A6000-7A2000-EVB/EVB,
BIOS Loongson-FwSdk-V5.0.0343-stable2511 01/13/26 20:10:42
[ 75.025422] Stack : 0000000000000000 0000000000000000
9000000000223c20 9000000116460000
[ 75.025455] 900000010009f5e0 900000010009f5e8
0000000000000000 900000010009f728
[ 75.025487] 900000010009f720 900000010009f720
900000010009f490 0000000000000001
[ 75.025519] 0000000000000001 900000010009f5e8
9e6a35e67549a6db 000000fffffffffe
[ 75.025551] 0000010000000000 0000000000000022
0000000fffffffff ffff800000000000
[ 75.025582] 0000800000000000 9000000000000000
00000003f3fe4000 900000010009f9e0
[ 75.025615] 0000000000000000 9000000002fd9000
0000000000000000 9000000002c15220
[ 75.025646] 9000000002ea5820 900000010009f848
90000000040c1320 ffff80000231fe1c
[ 75.025679] 90000000003a8f20 0000000000000000
9000000000223c3c 000055557726cb04
[ 75.025710] 00000000000000b0 0000000000000004
0000000000000000 0000000000071c1d
[ 75.025739] ...
[ 75.025751] Call Trace:
[ 75.025756] [<9000000000223c3c>] show_stack+0x5c/0x190
[ 75.025782] [<9000000001f2cc34>] dump_stack_lvl+0x6c/0x9c
[ 75.025807] [<9000000000236714>] unwind_next_frame+0x764/0xa70
[ 75.025837] [<9000000000231e14>] arch_stack_walk+0xd4/0x1b0
[ 75.025863] [<900000000038aa04>] stack_trace_save+0x54/0x90
[ 75.025892] [<9000000000612f80>] kasan_save_stack+0x30/0x60
[ 75.025914] [<9000000000615a68>] __kasan_record_aux_stack+0x108/0x130
[ 75.025941] [<90000000002b1c40>] task_work_add+0x100/0x300
[ 75.025968] [<90000000002d3cd8>] sched_tick+0x158/0x3e0
[ 75.025987] [<900000000038fa40>] update_process_times+0xf0/0x160
[ 75.026011] [<90000000003a9018>] tick_nohz_handler+0xf8/0x260
[ 75.026038] [<90000000003908dc>] __hrtimer_run_queues+0x20c/0x330
[ 75.026062] [<9000000000392190>] hrtimer_interrupt+0x1a0/0x3f0
[ 75.026086] [<90000000002285ac>] constant_timer_interrupt+0x5c/0x80
[ 75.026110] [<900000000034358c>] __handle_irq_event_percpu+0x6c/0x190
[ 75.026139] [<90000000003436c4>] handle_irq_event_percpu+0x14/0xa0
[ 75.026167] [<900000000034d66c>] handle_percpu_irq+0x8c/0xe0
[ 75.026189] [<9000000000342670>] generic_handle_domain_irq+0x50/0xc0
[ 75.026217] [<9000000000ffaad4>] handle_cpu_irq+0x54/0x90
[ 75.026245] [<9000000001f2d128>] handle_loongarch_irq+0x28/0x40
[ 75.026269] [<9000000001f2d1bc>] do_vint+0x7c/0xf0
[ 75.026289] [<900000000023fa20>] mem_to_shadow+0x0/0x2b0
[ 75.026313] [<9000000000615af4>] kasan_check_range+0x64/0x2c0
[ 75.026336] [<9000000001b2b7a0>] bpf_skb_load_helper_32+0x40/0x220
Huacai
>
> The kernel boots normally with the defconfig, so no problem found out
> at the first time. Here is one way to reproduce:
>
> cd linux
> make mrproper defconfig -j"$(nproc)"
> scripts/config -e KASAN
> make olddefconfig all -j"$(nproc)"
> sudo make modules_install
> sudo make install
> sudo reboot
>
> The address that can not unwind is not a valid kernel address which is
> between "pcpu_handlers[cpu]" and "pcpu_handlers[cpu] + vec_sz" due to
> the code of eentry was copied to the new area of pcpu_handlers[cpu] in
> setup_tlb_handler(), handle this special case to get the valid address
> to unwind normally.
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
> arch/loongarch/include/asm/setup.h | 2 ++
> arch/loongarch/kernel/unwind_orc.c | 15 +++++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
> index 3c2fb16b11b6..79eb63e749f9 100644
> --- a/arch/loongarch/include/asm/setup.h
> +++ b/arch/loongarch/include/asm/setup.h
> @@ -14,6 +14,8 @@
>
> extern unsigned long eentry;
> extern unsigned long tlbrentry;
> +extern unsigned long pcpu_handlers[NR_CPUS];
> +extern long exception_handlers[VECSIZE * 128 / sizeof(long)];
> extern char init_command_line[COMMAND_LINE_SIZE];
> extern void tlb_init(int cpu);
> extern void cpu_cache_init(void);
> diff --git a/arch/loongarch/kernel/unwind_orc.c b/arch/loongarch/kernel/unwind_orc.c
> index d6b3688a1ce9..e0c0dc22eb08 100644
> --- a/arch/loongarch/kernel/unwind_orc.c
> +++ b/arch/loongarch/kernel/unwind_orc.c
> @@ -351,6 +351,21 @@ EXPORT_SYMBOL_GPL(unwind_start);
> static inline unsigned long bt_address(unsigned long ra)
> {
> extern unsigned long eentry;
> +#if defined(CONFIG_NUMA) && !defined(CONFIG_PREEMPT_RT)
> + int cpu;
> + int vec_sz = sizeof(exception_handlers);
> +
> + for_each_possible_cpu(cpu) {
> + if (!pcpu_handlers[cpu])
> + continue;
> +
> + if (ra >= pcpu_handlers[cpu] &&
> + ra < pcpu_handlers[cpu] + vec_sz) {
> + ra = eentry + (ra - pcpu_handlers[cpu]);
> + break;
> + }
> + }
> +#endif
>
> if (ra >= eentry && ra < eentry + EXCCODE_INT_END * VECSIZE) {
> unsigned long func;
> --
> 2.42.0
>
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