[External] Re: [PATCH v4] riscv: add userland instruction dump to RISC-V splats

[yunhui cui]

Hi Björn,

On Fri, Sep 1, 2023 at 5:06 PM Björn Töpel <bjorn at kernel.org> wrote:
>
> yunhui cui <cuiyunhui at bytedance.com> writes:
>
> > Hi Björn，
> >
> > On Fri, Aug 18, 2023 at 9:33 PM Björn Töpel <bjorn at kernel.org> wrote:
> >>
> >> Yunhui Cui <cuiyunhui at bytedance.com> writes:
> >>
> >> > 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 at bytedance.com>
> >>
> >> Nice!
> >>
> >> Reviewed-by: Björn Töpel <bjorn at rivosinc.com>
> >
> > When can this patch be applied to the linux-next branch?
>
> It looks like you're getting a sparse warning on the patch [1], and
> that's probably why it hasn't been considered. You need something like:
>
> --
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 69b5d18b5ae9..c5364131b8bd 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -34,7 +34,7 @@ int show_unhandled_signals = 1;
>  static DEFINE_SPINLOCK(die_lock);
>
>  #define get_user_nofault(val, ptr) ({                          \
> -       const typeof(val) *__gk_ptr = (ptr);                    \
> +       const typeof(val) __user *__gk_ptr = (__force const typeof(val) __user *)(ptr); \
>         copy_from_user_nofault(&(val), __gk_ptr, sizeof(val));\
>  })
> --
>
> IDK, maybe it worth removing the define all together, and just open code
> it.
>
> When you're submitting patches, it's a good thing to track patchwork for
> warnings/errors.
>
>
> Björn
>
> [1] https://patchwork.kernel.org/project/linux-riscv/patch/20230818121504.60492-1-cuiyunhui@bytedance.com/

Okay, I might as well remove the macro, after all, the definition is only here.
I'll update it v5 like:
+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));
+}

Thanks,
Yunhui