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

From: "Björn Töpel" <bjorn@kernel.org>
To: yunhui cui <cuiyunhui@bytedance.com>
Cc: paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, guoren@kernel.org, bjorn@rivosinc.com,
	conor.dooley@microchip.com, jszhang@kernel.org,
	andy.chiu@sifive.com, dave.hansen@linux.intel.com,
	elver@google.com, glider@google.com, cyphar@cyphar.com,
	kirill.shutemov@linux.intel.com, keescook@chromium.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [External] Re: [PATCH v5] riscv: add userland instruction dump to RISC-V splats
Date: Fri, 08 Sep 2023 20:00:55 +0200	[thread overview]
Message-ID: <87r0n8pmso.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <CAEEQ3wnDAJOMo2SZAB23aZgOhBKPmZegC9E048YJaFhiXEkA-A@mail.gmail.com>

yunhui cui <cuiyunhui@bytedance.com> writes:

> Hi Björn，
>
> On Fri, Sep 8, 2023 at 2:45 AM Björn Töpel <bjorn@kernel.org> wrote:
>>
>> Yunhui Cui <cuiyunhui@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@bytedance.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));
>>
>> Hmm, I think you missed the actual problem in [1]. I'm still getting:
>>
>>   |   CHECK   arch/riscv/kernel/traps.c
>>   | arch/riscv/kernel/traps.c:46:44: warning: incorrect type in argument 2 (different address spaces)
>>   | arch/riscv/kernel/traps.c:46:44:    expected void const [noderef] __user *src
>>   | arch/riscv/kernel/traps.c:46:44:    got unsigned short const [usertype] *insns
>>
>
> How did the warnings above come about? I don't have one locally. What
> is your risc-v gcc version?

It's from the "sparse" tool. Pass "C=1" to make. Unfortunately RV sparse
needs to be built manually: https://github.com/ConchuOD/sparse

 | make ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu- C=1 W=1 arch/riscv/kernel/traps.o

Thanks!
Björn

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