From: Tong Tiangen <tongtiangen@huawei.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Alexander Viro <viro@zeniv.linux.org.uk>, <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [RFC PATCH -next V2 4/7] arm64: add copy_from_user to machine check safe
Date: Thu, 7 Apr 2022 22:28:02 +0800 [thread overview]
Message-ID: <9788a324-05b2-80d7-d062-4bb10cc4d0ee@huawei.com> (raw)
In-Reply-To: <Yk13VJwih44VsCGk@FVFF77S0Q05N>
在 2022/4/6 19:19, Mark Rutland 写道:
> On Wed, Apr 06, 2022 at 09:13:08AM +0000, Tong Tiangen wrote:
>> Add scenarios copy_from_user to machine check safe.
>>
>> The data copied is user data and is machine check safe, so just kill
>> the user process and isolate the error page, not necessary panic.
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
>> ---
>> arch/arm64/include/asm/asm-uaccess.h | 16 ++++++++++++++++
>> arch/arm64/lib/copy_from_user.S | 11 ++++++-----
>> 2 files changed, 22 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
>> index 0557af834e03..f31c8978e1af 100644
>> --- a/arch/arm64/include/asm/asm-uaccess.h
>> +++ b/arch/arm64/include/asm/asm-uaccess.h
>> @@ -92,4 +92,20 @@ alternative_else_nop_endif
>>
>> _asm_extable 8888b,\l;
>> .endm
>> +
>> + .macro user_ldp_mc l, reg1, reg2, addr, post_inc
>> +8888: ldtr \reg1, [\addr];
>> +8889: ldtr \reg2, [\addr, #8];
>> + add \addr, \addr, \post_inc;
>> +
>> + _asm_extable_mc 8888b, \l;
>> + _asm_extable_mc 8889b, \l;
>> + .endm
>> +
>> + .macro user_ldst_mc l, inst, reg, addr, post_inc
>> +8888: \inst \reg, [\addr];
>> + add \addr, \addr, \post_inc;
>> +
>> + _asm_extable_mc 8888b, \l;
>> + .endm
>> #endif
>> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
>> index 34e317907524..d9d7c5291871 100644
>> --- a/arch/arm64/lib/copy_from_user.S
>> +++ b/arch/arm64/lib/copy_from_user.S
>> @@ -21,7 +21,7 @@
>> */
>>
>> .macro ldrb1 reg, ptr, val
>> - user_ldst 9998f, ldtrb, \reg, \ptr, \val
>> + user_ldst_mc 9998f, ldtrb, \reg, \ptr, \val
>> .endm
>>
>> .macro strb1 reg, ptr, val
>> @@ -29,7 +29,7 @@
>> .endm
>>
>> .macro ldrh1 reg, ptr, val
>> - user_ldst 9997f, ldtrh, \reg, \ptr, \val
>> + user_ldst_mc 9997f, ldtrh, \reg, \ptr, \val
>> .endm
>>
>> .macro strh1 reg, ptr, val
>> @@ -37,7 +37,7 @@
>> .endm
>>
>> .macro ldr1 reg, ptr, val
>> - user_ldst 9997f, ldtr, \reg, \ptr, \val
>> + user_ldst_mc 9997f, ldtr, \reg, \ptr, \val
>> .endm
>>
>> .macro str1 reg, ptr, val
>> @@ -45,7 +45,7 @@
>> .endm
>>
>> .macro ldp1 reg1, reg2, ptr, val
>> - user_ldp 9997f, \reg1, \reg2, \ptr, \val
>> + user_ldp_mc 9997f, \reg1, \reg2, \ptr, \val
>> .endm
>>
>> .macro stp1 reg1, reg2, ptr, val
>> @@ -62,7 +62,8 @@ SYM_FUNC_START(__arch_copy_from_user)
>> ret
>>
>> // Exception fixups
>> -9997: cmp dst, dstin
>> +9997: cbz x0, 9998f // Check machine check exception
>> + cmp dst, dstin
>> b.ne 9998f
>
> If you look at the copy template, you'd see that `dstin` *is* x0.
>
> Consier if we took a non-SEA fault. The the fixup handler will overwrite x0,
> it's likely `dst` != `dstin`, and we'll branch to the byte-by-byte copy. Or if
> we're doing something odd and mmap_min_addr is 0, we can do the wrong thing the
> other way around and *not* branch to the byte-by-byte copy when we should.
>
> So this is at best confusing, but likely broken too.
>
> Thanks,
> Mark.
OK, missing that, will be fixed in next verison.
Thanks,
Tong.
>
>> // Before being absolutely sure we couldn't copy anything, try harder
>> USER(9998f, ldtrb tmp1w, [srcin])
>> --
>> 2.18.0.huawei.25
>>
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> .
next prev parent reply other threads:[~2022-04-07 14:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-06 9:13 [RFC PATCH -next V2 0/7]arm64: add machine check safe support Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 1/7] x86: fix copy_mc_to_user compile error Tong Tiangen
2022-04-06 9:22 ` Borislav Petkov
2022-04-06 10:02 ` Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 2/7] arm64: fix page_address return value in copy_highpage Tong Tiangen
2022-04-06 10:22 ` Mark Rutland
2022-04-06 12:47 ` Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 3/7] arm64: add support for machine check error safe Tong Tiangen
2022-04-06 10:58 ` Mark Rutland
2022-04-07 14:26 ` Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 4/7] arm64: add copy_from_user to machine check safe Tong Tiangen
2022-04-06 11:19 ` Mark Rutland
2022-04-07 14:28 ` Tong Tiangen [this message]
2022-04-06 9:13 ` [RFC PATCH -next V2 5/7] arm64: add get_user " Tong Tiangen
2022-04-06 11:22 ` Mark Rutland
2022-04-07 14:38 ` Tong Tiangen
2022-04-08 15:22 ` Mark Rutland
2022-04-09 9:17 ` Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 6/7] arm64: add cow " Tong Tiangen
2022-04-06 9:13 ` [RFC PATCH -next V2 7/7] arm64: add pagecache reading " Tong Tiangen
2022-04-06 11:27 ` Mark Rutland
2022-04-07 14:56 ` Tong Tiangen
2022-04-07 15:53 ` Robin Murphy
2022-04-08 2:43 ` Tong Tiangen
2022-04-08 11:11 ` Robin Murphy
2022-04-09 9:24 ` Tong Tiangen
2022-04-06 10:04 ` [RFC PATCH -next V2 0/7]arm64: add machine check safe support Mark Rutland
2022-04-07 4:21 ` Tong Tiangen
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