From: Catalin Marinas <catalin.marinas@arm.com>
To: Fredrik Strupe <fredrik@strupe.net>
Cc: will.deacon@arm.com, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: Re: [PATCH v2] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend
Date: Wed, 8 Apr 2020 18:17:41 +0100 [thread overview]
Message-ID: <20200408171741.GB2481@gaia> (raw)
In-Reply-To: <ab77076b-774d-9158-bc0c-3cfdd36b6e37@strupe.net>
On Wed, Apr 08, 2020 at 01:29:41PM +0200, Fredrik Strupe wrote:
> For thumb instructions, call_undef_hook() in traps.c first reads a u16,
> and if the u16 indicates a T32 instruction (u16 >= 0xe800), a second
> u16 is read, which then makes up the the lower half-word of a T32
> instruction. For T16 instructions, the second u16 is not read,
> which makes the resulting u32 opcode always have the upper half set to
> 0.
>
> However, having the upper half of instr_mask in the undef_hook set to 0
> masks out the upper half of all thumb instructions - both T16 and T32.
> This results in trapped T32 instructions with the lower half-word equal
> to the T16 encoding of setend (b650) being matched, even though the upper
> half-word is not 0000 and thus indicates a T32 opcode.
>
> An example of such a T32 instruction is eaa0b650, which should raise a
> SIGILL since T32 instructions with an eaa prefix are unallocated as per
> Arm ARM, but instead works as a SETEND because the second half-word is set
> to b650.
>
> This patch fixes the issue by extending instr_mask to include the
> upper u32 half, which will still match T16 instructions where the upper
> half is 0, but not T32 instructions.
>
> Signed-off-by: Fredrik Strupe <fredrik@strupe.net>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Fixes: 2d888f48e056 ("arm64: Emulate SETEND for AArch32 tasks")
Queued for 5.7. Thanks.
--
Catalin
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WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Fredrik Strupe <fredrik@strupe.net>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, will.deacon@arm.com
Subject: Re: [PATCH v2] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend
Date: Wed, 8 Apr 2020 18:17:41 +0100 [thread overview]
Message-ID: <20200408171741.GB2481@gaia> (raw)
In-Reply-To: <ab77076b-774d-9158-bc0c-3cfdd36b6e37@strupe.net>
On Wed, Apr 08, 2020 at 01:29:41PM +0200, Fredrik Strupe wrote:
> For thumb instructions, call_undef_hook() in traps.c first reads a u16,
> and if the u16 indicates a T32 instruction (u16 >= 0xe800), a second
> u16 is read, which then makes up the the lower half-word of a T32
> instruction. For T16 instructions, the second u16 is not read,
> which makes the resulting u32 opcode always have the upper half set to
> 0.
>
> However, having the upper half of instr_mask in the undef_hook set to 0
> masks out the upper half of all thumb instructions - both T16 and T32.
> This results in trapped T32 instructions with the lower half-word equal
> to the T16 encoding of setend (b650) being matched, even though the upper
> half-word is not 0000 and thus indicates a T32 opcode.
>
> An example of such a T32 instruction is eaa0b650, which should raise a
> SIGILL since T32 instructions with an eaa prefix are unallocated as per
> Arm ARM, but instead works as a SETEND because the second half-word is set
> to b650.
>
> This patch fixes the issue by extending instr_mask to include the
> upper u32 half, which will still match T16 instructions where the upper
> half is 0, but not T32 instructions.
>
> Signed-off-by: Fredrik Strupe <fredrik@strupe.net>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Fixes: 2d888f48e056 ("arm64: Emulate SETEND for AArch32 tasks")
Queued for 5.7. Thanks.
--
Catalin
next prev parent reply other threads:[~2020-04-08 17:17 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 14:16 [PATCH] arm64: armv8_deprecated: Fix undef_hook mask for thumb setend Fredrik Strupe
2020-04-06 14:16 ` Fredrik Strupe
2020-04-07 9:27 ` Catalin Marinas
2020-04-07 9:27 ` Catalin Marinas
2020-04-07 10:47 ` Suzuki K Poulose
2020-04-07 10:47 ` Suzuki K Poulose
2020-04-07 11:12 ` Fredrik Strupe
2020-04-07 11:12 ` Fredrik Strupe
2020-04-07 11:18 ` Fredrik Strupe
2020-04-07 11:18 ` Fredrik Strupe
2020-04-08 9:01 ` Catalin Marinas
2020-04-08 9:01 ` Catalin Marinas
2020-04-08 9:58 ` Fredrik Strupe
2020-04-08 9:58 ` Fredrik Strupe
2020-04-08 11:29 ` [PATCH v2] " Fredrik Strupe
2020-04-08 11:29 ` Fredrik Strupe
2020-04-08 11:39 ` Suzuki K Poulose
2020-04-08 11:39 ` Suzuki K Poulose
2020-04-08 17:17 ` Catalin Marinas [this message]
2020-04-08 17:17 ` Catalin Marinas
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