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Subject: Re: [PATCH V2] riscv: compat: Using seperated vdso_maps for
 compat_vdso_info
From:   Jessica Clarke <jrtc27@jrtc27.com>
In-Reply-To: <20220526003339.2948309-1-guoren@kernel.org>
Date:   Thu, 26 May 2022 02:00:49 +0100
Cc:     palmer@rivosinc.com, arnd@arndb.de, linux@roeck-us.net,
        palmer@dabbelt.com, heiko@sntech.de,
        linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, Guo Ren <guoren@linux.alibaba.com>
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Message-Id: <EC36D0A9-AE06-4C05-A31B-CC348881937D@jrtc27.com>
References: <20220526003339.2948309-1-guoren@kernel.org>
To:     guoren@kernel.org
Precedence: bulk

On 26 May 2022, at 01:33, guoren@kernel.org wrote:
>=20
> From: Guo Ren <guoren@linux.alibaba.com>
>=20
> This is a fixup for vdso implementation which caused musl to
> fail.
>=20
> [   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
>=20
> The last __vdso_init(&compat_vdso_info) replaces the data in normal
> vdso_info. This is an obvious bug.
>=20
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Tested-by: Guenter Roeck <linux@roeck-us.net>
> Tested-by: Heiko St=C3=BCbner <heiko@sntech.de>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> ---
> Changes in V2:
> - Add Tested-by
> - Rename vvar & vdso in /proc/<pid>/maps.

Why? No other architecture renames it to that, and various pieces of
software look for the magic [vdso] name, including GDB and LLDB, though
by my count there are 57 source packages in Debian that contain the
string literal "[vdso]" (including quotes), including Firefox,
Android's ART, lvm2 and elfutils.

Jess

> ---
> arch/riscv/kernel/vdso.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>=20
> diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
> index 50fe4c877603..957f164c9778 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 =3D {
> };
>=20
> #ifdef CONFIG_COMPAT
> +static struct vm_special_mapping rv_compat_vdso_maps[] =
__ro_after_init =3D {
> +	[RV_VDSO_MAP_VVAR] =3D {
> +		.name   =3D "[compat vvar]",
> +		.fault =3D vvar_fault,
> +	},
> +	[RV_VDSO_MAP_VDSO] =3D {
> +		.name   =3D "[compat vdso]",
> +		.mremap =3D vdso_mremap,
> +	},
> +};
> +
> static struct __vdso_info compat_vdso_info __ro_after_init =3D {
> 	.name =3D "compat_vdso",
> 	.vdso_code_start =3D compat_vdso_start,
> 	.vdso_code_end =3D compat_vdso_end,
> -	.dm =3D &rv_vdso_maps[RV_VDSO_MAP_VVAR],
> -	.cm =3D &rv_vdso_maps[RV_VDSO_MAP_VDSO],
> +	.dm =3D &rv_compat_vdso_maps[RV_VDSO_MAP_VVAR],
> +	.cm =3D &rv_compat_vdso_maps[RV_VDSO_MAP_VDSO],
> };
> #endif
>=20
> --=20
> 2.36.1
>=20
>=20
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