Re: [PATCH] riscv: compat: Using seperated vdso_maps for compat_vdso_info

[Heiko Stübner]

Am Mittwoch, 25. Mai 2022, 18:04:04 CEST schrieb guoren@xxxxxxxxxx:
> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: Heiko Stübner <heiko@xxxxxxxxx>

on palmer's for-next branch and a Debian riscv64 rootfs:

- WITHOUT this patch I end up with:
[    3.142030] Unable to handle kernel paging request at virtual address ff60007265776f78
[    3.144398] Oops [#1]
[    3.144882] Modules linked in:
[    3.145620] CPU: 1 PID: 1 Comm: init Not tainted 5.18.0-rc1-00049-g8810d7feee5a #225
[    3.146698] Hardware name: riscv-virtio,qemu (DT)
[    3.147441] epc : special_mapping_fault+0x4c/0x8e
[    3.148352]  ra : __do_fault+0x28/0x11c
[    3.149005] epc : ffffffff8011ce3e ra : ffffffff80113216 sp : ff2000000060bd20
[    3.149851]  gp : ffffffff810de540 tp : ff600000012a8000 t0 : ffffffff80008af0
[    3.150651]  t1 : ffffffff80c001e0 t2 : ffffffff80c00260 s0 : ff2000000060bd30
[    3.151434]  s1 : ff2000000060bd78 a0 : ff600000013165f0 a1 : ff60000001dbc450
[    3.152734]  a2 : ff2000000060bd78 a3 : 00fffffffffff000 a4 : ff6000003f0337c8
[    3.153821]  a5 : ff60007265776f70 a6 : 0000000000000000 a7 : 0000000000000007
[    3.154709]  s2 : ff60000001dbc450 s3 : ff60000001dbc450 s4 : ffffffff810ddd69
[    3.155557]  s5 : ff60000001dbc450 s6 : 0000000000000254 s7 : 000000000000000c
[    3.156369]  s8 : 000000000000000f s9 : 000000000000000d s10: ff60000001cf8080
[    3.157242]  s11: 000000000000000d t3 : 00ffffff8232d000 t4 : 000000006ffffdff
[    3.158094]  t5 : 000000006ffffe35 t6 : 000000000000000a
[    3.158742] status: 0000000200000120 badaddr: ff60007265776f78 cause: 000000000000000d
[    3.160000] [<ffffffff80113216>] __do_fault+0x28/0x11c
[    3.160881] [<ffffffff80116f3e>] __handle_mm_fault+0x6ec/0x9c8
[    3.161619] [<ffffffff8011729c>] handle_mm_fault+0x82/0x136
[    3.162308] [<ffffffff80008c10>] do_page_fault+0x120/0x31c
[    3.163006] [<ffffffff800032dc>] ret_from_exception+0x0/0xc
[    3.164607] ---[ end trace 0000000000000000 ]---
-> a different error


- WITH this patch applied on top, the error above goes away and the
  qemu-system can boot normally.

So, while my error is different and I don't think there is any musl in
my rootfs, this patch definitly fixes the issue for me, so

Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>


> ---
>  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
>  
>