From: Tong Tiangen <tongtiangen@huawei.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Robin Murphy <robin.murphy@arm.com>,
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>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>, <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
<linuxppc-dev@lists.ozlabs.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
Xie XiuQi <xiexiuqi@huawei.com>, Guohanjun <guohanjun@huawei.com>
Subject: Re: [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO
Date: Sat, 18 Jun 2022 16:42:06 +0800 [thread overview]
Message-ID: <0da734f3-5743-3df3-3f90-d92e5bd585ce@huawei.com> (raw)
In-Reply-To: <4371a7c9-8766-9fee-2558-e6f43f06ad19@huawei.com>
在 2022/6/18 11:26, Tong Tiangen 写道:
>
>
> 在 2022/6/17 16:24, Mark Rutland 写道:
>> On Sat, May 28, 2022 at 06:50:50AM +0000, Tong Tiangen wrote:
>>> Currnetly, the extable type used by __arch_copy_from/to_user() is
>>> EX_TYPE_FIXUP. In fact, It is more clearly to use meaningful
>>> EX_TYPE_UACCESS_*.
>>>
>>> Suggested-by: Mark Rutland <mark.rutland@arm.com>
>>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
>>> ---
>>> arch/arm64/include/asm/asm-extable.h | 8 ++++++++
>>> arch/arm64/include/asm/asm-uaccess.h | 12 ++++++------
>>> 2 files changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/arm64/include/asm/asm-extable.h
>>> b/arch/arm64/include/asm/asm-extable.h
>>> index 56ebe183e78b..9c94ac1f082c 100644
>>> --- a/arch/arm64/include/asm/asm-extable.h
>>> +++ b/arch/arm64/include/asm/asm-extable.h
>>> @@ -28,6 +28,14 @@
>>> __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0)
>>> .endm
>>> +/*
>>> + * Create an exception table entry for uaccess `insn`, which will
>>> branch to `fixup`
>>> + * when an unhandled fault is taken.
>>> + * ex->data = ~0 means both reg_err and reg_zero is set to wzr(x31).
>>> + */
>>> + .macro _asm_extable_uaccess, insn, fixup
>>> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_ERR_ZERO, ~0)
>>> + .endm
>>
>> I'm not too keen on using `~0` here, since that also sets other bits
>> in the
>> data field, and its somewhat opaque.
>>
>> How painful is it to generate the data fields as with the C version of
>> this
>> macro, so that we can pass in wzr explciitly for the two sub-fields?
>>
>> Other than that, this looks good to me.
>>
>> Thanks,
>> Mark.
>
> ok, will fix next version.
>
> Thanks,
> Tong.
I tried to using data filelds as with C version, but here assembly code
we can not using operator such as << and |, if we use lsl and orr
instructions, the gpr will be occupied.
So how about using 0x3ff directly here? it means err register and zero
register both set to x31.
Thanks,
Tong.
>
>>
>>> /*
>>> * Create an exception table entry for `insn` if `fixup` is
>>> provided. Otherwise
>>> * do nothing.
>>> diff --git a/arch/arm64/include/asm/asm-uaccess.h
>>> b/arch/arm64/include/asm/asm-uaccess.h
>>> index 0557af834e03..75b211c98dea 100644
>>> --- a/arch/arm64/include/asm/asm-uaccess.h
>>> +++ b/arch/arm64/include/asm/asm-uaccess.h
>>> @@ -61,7 +61,7 @@ alternative_else_nop_endif
>>> #define USER(l, x...) \
>>> 9999: x; \
>>> - _asm_extable 9999b, l
>>> + _asm_extable_uaccess 9999b, l
>>> /*
>>> * Generate the assembly for LDTR/STTR with exception table entries.
>>> @@ -73,8 +73,8 @@ alternative_else_nop_endif
>>> 8889: ldtr \reg2, [\addr, #8];
>>> add \addr, \addr, \post_inc;
>>> - _asm_extable 8888b,\l;
>>> - _asm_extable 8889b,\l;
>>> + _asm_extable_uaccess 8888b, \l;
>>> + _asm_extable_uaccess 8889b, \l;
>>> .endm
>>> .macro user_stp l, reg1, reg2, addr, post_inc
>>> @@ -82,14 +82,14 @@ alternative_else_nop_endif
>>> 8889: sttr \reg2, [\addr, #8];
>>> add \addr, \addr, \post_inc;
>>> - _asm_extable 8888b,\l;
>>> - _asm_extable 8889b,\l;
>>> + _asm_extable_uaccess 8888b,\l;
>>> + _asm_extable_uaccess 8889b,\l;
>>> .endm
>>> .macro user_ldst l, inst, reg, addr, post_inc
>>> 8888: \inst \reg, [\addr];
>>> add \addr, \addr, \post_inc;
>>> - _asm_extable 8888b,\l;
>>> + _asm_extable_uaccess 8888b, \l;
>>> .endm
>>> #endif
>>> --
>>> 2.25.1
>>>
>> .
>
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next prev parent reply other threads:[~2022-06-18 8:43 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-28 6:50 [PATCH -next v5 0/8]arm64: add machine check safe support Tong Tiangen
2022-05-28 6:50 ` [PATCH -next v5 1/8] arm64: extable: add new extable type EX_TYPE_KACCESS_ERR_ZERO support Tong Tiangen
2022-06-17 8:23 ` Mark Rutland
2022-06-18 2:44 ` Tong Tiangen
2022-05-28 6:50 ` [PATCH -next v5 2/8] arm64: extable: make uaaccess helper use extable type EX_TYPE_UACCESS_ERR_ZERO Tong Tiangen
2022-06-17 8:24 ` Mark Rutland
2022-06-18 3:26 ` Tong Tiangen
2022-06-18 8:42 ` Tong Tiangen [this message]
2022-06-18 12:40 ` Mark Rutland
2022-06-20 2:59 ` Tong Tiangen
2022-06-20 9:10 ` Mark Rutland
2022-06-20 13:32 ` Tong Tiangen
2022-06-20 14:13 ` Tong Tiangen
2022-06-20 14:26 ` Mark Rutland
2022-05-28 6:50 ` [PATCH -next v5 3/8] arm64: extable: move _cond_extable to _cond_uaccess_extable Tong Tiangen
2022-06-17 8:31 ` Mark Rutland
2022-05-28 6:50 ` [PATCH -next v5 4/8] arm64: extable: cleanup redundant extable type EX_TYPE_FIXUP Tong Tiangen
2022-06-17 8:43 ` Mark Rutland
2022-05-28 6:50 ` [PATCH -next v5 5/8] Add generic fallback version of copy_mc_to_user() Tong Tiangen
2022-05-28 6:50 ` [PATCH -next v5 6/8] arm64: add support for machine check error safe Tong Tiangen
2022-06-17 8:55 ` Mark Rutland
2022-06-18 9:18 ` Tong Tiangen
2022-06-18 12:52 ` Mark Rutland
2022-06-20 1:53 ` Tong Tiangen
2022-05-28 6:50 ` [PATCH -next v5 7/8] arm64: add uaccess to machine check safe Tong Tiangen
2022-06-17 9:06 ` Mark Rutland
2022-06-18 9:27 ` Tong Tiangen
2022-06-18 11:35 ` Mark Rutland
2022-06-20 2:04 ` Tong Tiangen
2022-05-28 6:50 ` [PATCH -next v5 8/8] arm64: add cow " Tong Tiangen
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