linux-kernel - Re: [PATCH] riscv: compat: Using seperated vdso_maps for compat_vdso

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Date:   Wed, 25 May 2022 17:39:39 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     linux@...ck-us.net
CC:     guoren@...nel.org, Arnd Bergmann <arnd@...db.de>, heiko@...ech.de,
        linux-riscv@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org, guoren@...ux.alibaba.com
Subject:     Re: [PATCH] riscv: compat: Using seperated vdso_maps for compat_vdso_info

On Wed, 25 May 2022 15:56:07 PDT (-0700), linux@...ck-us.net wrote:
> On 5/25/22 14:34, Palmer Dabbelt wrote:
>> On Wed, 25 May 2022 14:15:03 PDT (-0700), linux@...ck-us.net wrote:
>>> On 5/25/22 09:04, guoren@...nel.org wrote:
>>>> From: Guo Ren <guoren@...ux.alibaba.com>
>>>>
>>>> This is a fixup for vdso implementation which caused musl to
>>>> fail.
>>>>
>>>> [   11.600082] Run /sbin/init as init process
>>>> [   11.628561] init[1]: unhandled signal 11 code 0x1 at
>>>> 0x0000000000000000 in libc.so[ffffff8ad39000+a4000]
>>>> [   11.629398] CPU: 0 PID: 1 Comm: init Not tainted
>>>> 5.18.0-rc7-next-20220520 #1
>>>> [   11.629462] Hardware name: riscv-virtio,qemu (DT)
>>>> [   11.629546] epc : 00ffffff8ada1100 ra : 00ffffff8ada13c8 sp :
>>>> 00ffffffc58199f0
>>>> [   11.629586]  gp : 00ffffff8ad39000 tp : 00ffffff8ade0998 t0 :
>>>> ffffffffffffffff
>>>> [   11.629598]  t1 : 00ffffffc5819fd0 t2 : 0000000000000000 s0 :
>>>> 00ffffff8ade0cc0
>>>> [   11.629610]  s1 : 00ffffff8ade0cc0 a0 : 0000000000000000 a1 :
>>>> 00ffffffc5819a00
>>>> [   11.629622]  a2 : 0000000000000001 a3 : 000000000000001e a4 :
>>>> 00ffffffc5819b00
>>>> [   11.629634]  a5 : 00ffffffc5819b00 a6 : 0000000000000000 a7 :
>>>> 0000000000000000
>>>> [   11.629645]  s2 : 00ffffff8ade0ac8 s3 : 00ffffff8ade0ec8 s4 :
>>>> 00ffffff8ade0728
>>>> [   11.629656]  s5 : 00ffffff8ade0a90 s6 : 0000000000000000 s7 :
>>>> 00ffffffc5819e40
>>>> [   11.629667]  s8 : 00ffffff8ade0ca0 s9 : 00ffffff8addba50 s10:
>>>> 0000000000000000
>>>> [   11.629678]  s11: 0000000000000000 t3 : 0000000000000002 t4 :
>>>> 0000000000000001
>>>> [   11.629688]  t5 : 0000000000020000 t6 : ffffffffffffffff
>>>> [   11.629699] status: 0000000000004020 badaddr: 0000000000000000
>>>> cause: 000000000000000d
>>>>
>>>> The last __vdso_init(&compat_vdso_info) replaces the data in normal
>>>> vdso_info. This is an obvious bug.
>>>>
>>>> Reported-by: Guenter Roeck <linux@...ck-us.net>
>>>> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
>>>> Signed-off-by: Guo Ren <guoren@...nel.org>
>>>> Cc: Palmer Dabbelt <palmer@...belt.com>
>>>> Cc: Heiko Stübner <heiko@...ech.de>
>>>
>>> Tested-by: Guenter Roeck <linux@...ck-us.net>
>>
>> Sorry I'm a bit buried right now, this is fixing the issue you pointed out earlier?
>>
> Yes.

Awosome, I think that was the only big blocker so far.

I added a musl-based userspace to my test setup, which is rv64-only 
(buildroot doesn't have rv32 musl, I thought upstream had it but maybe 
i'm misremembering).  This patch fixes the bug, so I've added it to 
for-next with

Fixes: 3092eb456375 ("riscv: compat: vdso: Add setup additional pages implementation")

which I think is correct, but LMK if there's an issue.  

Thanks!

(and also sorry I poked Geert instead of you about this one, oops ;))

>
> Thanks,
> Guenter
>
>>>
>>>> ---
>>>>   arch/riscv/kernel/vdso.c | 15 +++++++++++++--
>>>>   1 file changed, 13 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
>>>> index 50fe4c877603..69b05b6c181b 100644
>>>> --- a/arch/riscv/kernel/vdso.c
>>>> +++ b/arch/riscv/kernel/vdso.c
>>>> @@ -206,12 +206,23 @@ static struct __vdso_info vdso_info __ro_after_init = {
>>>>   };
>>>>
>>>>   #ifdef CONFIG_COMPAT
>>>> +static struct vm_special_mapping rv_compat_vdso_maps[] __ro_after_init = {
>>>> +    [RV_VDSO_MAP_VVAR] = {
>>>> +        .name   = "[vvar]",
>>>> +        .fault = vvar_fault,
>>>> +    },
>>>> +    [RV_VDSO_MAP_VDSO] = {
>>>> +        .name   = "[vdso]",
>>>> +        .mremap = vdso_mremap,
>>>> +    },
>>>> +};
>>>> +
>>>>   static struct __vdso_info compat_vdso_info __ro_after_init = {
>>>>       .name = "compat_vdso",
>>>>       .vdso_code_start = compat_vdso_start,
>>>>       .vdso_code_end = compat_vdso_end,
>>>> -    .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
>>>> -    .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
>>>> +    .dm = &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR],
>>>> +    .cm = &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO],
>>>>   };
>>>>   #endif
>>>>