linux-kernel - Re: [PATCH v1 2/4] LoongArch: Handle percpu handler address in bt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAAhV-H5pxpEM=efhdF6C0t+p6DGHcr9zQPPDx3X_w_6K18dEGg@mail.gmail.com>
Date: Tue, 20 Jan 2026 20:04:27 +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 v1 2/4] LoongArch: Handle percpu handler address in bt_address()

Hi, Tiezhu,

On Tue, Jan 20, 2026 at 5:23 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 at".
>
> 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" that is
> a very big address.
>
> The root cause is that 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 real address in bt_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 | 12 ++++++++++++
>  2 files changed, 14 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..40f4d6c12cf6 100644
> --- a/arch/loongarch/kernel/unwind_orc.c
> +++ b/arch/loongarch/kernel/unwind_orc.c
> @@ -352,6 +352,18 @@ static inline unsigned long bt_address(unsigned long ra)
>  {
>         extern unsigned long eentry;
>
> +#if defined(CONFIG_NUMA) && !defined(CONFIG_PREEMPT_RT)
> +       for (int cpu = 1; cpu < num_possible_cpus(); cpu++) {
Use nr_cpu_ids instead of num_possible_cpus() can improve performance a little.

> +               int vec_sz = sizeof(exception_handlers);
> +
It is better to add "if (!pcpu_handlers[cpu]) continue" here.


Huacai

> +               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;
>                 unsigned long type = (ra - eentry) / VECSIZE;
> --
> 2.42.0
>