linux-kernel - Re: [PATCH v5] riscv: add userland instruction dump to RISC-V splats

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Message-ID: <CAEEQ3wm6BOMFXr78kb6J5tGXgfNu1fJcvTg=sw4QT2ZeWYQTVQ@mail.gmail.com>
Date:   Thu, 7 Sep 2023 19:43:15 +0800
From:   yunhui cui <cuiyunhui@...edance.com>
To:     paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, guoren@...nel.org, bjorn@...osinc.com,
        conor.dooley@...rochip.com, jszhang@...nel.org,
        andy.chiu@...ive.com, cuiyunhui@...edance.com,
        dave.hansen@...ux.intel.com, elver@...gle.com, glider@...gle.com,
        cyphar@...har.com, kirill.shutemov@...ux.intel.com,
        keescook@...omium.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] riscv: add userland instruction dump to RISC-V splats

Hi Björn,


On Fri, Sep 1, 2023 at 8:30 PM Yunhui Cui <cuiyunhui@...edance.com> wrote:
>
> Add userland instruction dump and rename dump_kernel_instr()
> to dump_instr().
>
> An example:
> [    0.822439] Freeing unused kernel image (initmem) memory: 6916K
> [    0.823817] Run /init as init process
> [    0.839411] init[1]: unhandled signal 4 code 0x1 at 0x000000000005be18 in bb[10000+5fb000]
> [    0.840751] CPU: 0 PID: 1 Comm: init Not tainted 5.14.0-rc4-00049-gbd644290aa72-dirty #187
> [    0.841373] Hardware name:  , BIOS
> [    0.841743] epc : 000000000005be18 ra : 0000000000079e74 sp : 0000003fffcafda0
> [    0.842271]  gp : ffffffff816e9dc8 tp : 0000000000000000 t0 : 0000000000000000
> [    0.842947]  t1 : 0000003fffc9fdf0 t2 : 0000000000000000 s0 : 0000000000000000
> [    0.843434]  s1 : 0000000000000000 a0 : 0000003fffca0190 a1 : 0000003fffcafe18
> [    0.843891]  a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
> [    0.844357]  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
> [    0.844803]  s2 : 0000000000000000 s3 : 0000000000000000 s4 : 0000000000000000
> [    0.845253]  s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
> [    0.845722]  s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000000000000000
> [    0.846180]  s11: 0000000000d144e0 t3 : 0000000000000000 t4 : 0000000000000000
> [    0.846616]  t5 : 0000000000000000 t6 : 0000000000000000
> [    0.847204] status: 0000000200000020 badaddr: 00000000f0028053 cause: 0000000000000002
> [    0.848219] Code: f06f ff5f 3823 fa11 0113 fb01 2e23 0201 0293 0000 (8053) f002
> [    0.851016] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
>
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> ---
>  arch/riscv/kernel/traps.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index f798c853bede..923b49c38985 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -33,7 +33,19 @@ int show_unhandled_signals = 1;
>
>  static DEFINE_SPINLOCK(die_lock);
>
> -static void dump_kernel_instr(const char *loglvl, struct pt_regs *regs)
> +static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
> +{
> +       if (!user_mode(regs))
> +               return get_kernel_nofault(*val, insns);
> +
> +       /* The user space code from other tasks cannot be accessed. */
> +       if (regs != task_pt_regs(current))
> +               return -EPERM;
> +
> +       return copy_from_user_nofault(val, insns, sizeof(*val));
> +}
> +
> +static void dump_instr(const char *loglvl, struct pt_regs *regs)
>  {
>         char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
>         const u16 *insns = (u16 *)instruction_pointer(regs);
> @@ -42,7 +54,7 @@ static void dump_kernel_instr(const char *loglvl, struct pt_regs *regs)
>         int i;
>
>         for (i = -10; i < 2; i++) {
> -               bad = get_kernel_nofault(val, &insns[i]);
> +               bad = copy_code(regs, &val, &insns[i]);
>                 if (!bad) {
>                         p += sprintf(p, i == 0 ? "(%04hx) " : "%04hx ", val);
>                 } else {
> @@ -71,7 +83,7 @@ void die(struct pt_regs *regs, const char *str)
>         print_modules();
>         if (regs) {
>                 show_regs(regs);
> -               dump_kernel_instr(KERN_EMERG, regs);
> +               dump_instr(KERN_EMERG, regs);
>         }
>
>         cause = regs ? regs->cause : -1;
> @@ -104,6 +116,7 @@ void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
>                 print_vma_addr(KERN_CONT " in ", instruction_pointer(regs));
>                 pr_cont("\n");
>                 __show_regs(regs);
> +               dump_instr(KERN_EMERG, regs);
>         }
>
>         force_sig_fault(signo, code, (void __user *)addr);
> --
> 2.20.1
>

This patch has been passed:
https://patchwork.kernel.org/project/linux-riscv/patch/20230901123043.73700-1-cuiyunhui@bytedance.com/

Could you help merge it to linux-next?

Thanks，
Yunhui