From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Fredrik Strupe <fredrik@strupe.net>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PING] [PATCH v2] arm: ptrace: Fix mask for thumb breakpoint hook
Date: Mon, 18 May 2020 15:18:59 +0100 [thread overview]
Message-ID: <20200518141858.GV1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <d7381f90-f597-2a9c-4387-5714b41e02e6@strupe.net>
On Mon, May 18, 2020 at 03:12:06PM +0200, Fredrik Strupe wrote:
> call_undef_hook() in traps.c applies the same instr_mask for both 16-bit
> and 32-bit thumb instructions. If instr_mask then is only 16 bits wide
> (0xffff as opposed to 0xffffffff), the first half-word of 32-bit thumb
> instructions will be masked out. This makes the function match 32-bit
> thumb instructions where the second half-word is equal to instr_val,
> regardless of the first half-word.
>
> The result in this case is that all undefined 32-bit thumb instructions
> with the second half-word equal to de01 (udf #1) work as breakpoints
> and will raise a SIGTRAP instead of a SIGILL, instead of just the one
> intended 16-bit instruction. An example of such an instruction is
> eaa0b650, which is unallocated according to Arm ARM and should raise a
> SIGILL, but instead raises a SIGTRAP.
How can 0xeaa0b650 match 0xde01 when masked with 0xffff ?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
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WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Fredrik Strupe <fredrik@strupe.net>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PING] [PATCH v2] arm: ptrace: Fix mask for thumb breakpoint hook
Date: Mon, 18 May 2020 15:18:59 +0100 [thread overview]
Message-ID: <20200518141858.GV1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <d7381f90-f597-2a9c-4387-5714b41e02e6@strupe.net>
On Mon, May 18, 2020 at 03:12:06PM +0200, Fredrik Strupe wrote:
> call_undef_hook() in traps.c applies the same instr_mask for both 16-bit
> and 32-bit thumb instructions. If instr_mask then is only 16 bits wide
> (0xffff as opposed to 0xffffffff), the first half-word of 32-bit thumb
> instructions will be masked out. This makes the function match 32-bit
> thumb instructions where the second half-word is equal to instr_val,
> regardless of the first half-word.
>
> The result in this case is that all undefined 32-bit thumb instructions
> with the second half-word equal to de01 (udf #1) work as breakpoints
> and will raise a SIGTRAP instead of a SIGILL, instead of just the one
> intended 16-bit instruction. An example of such an instruction is
> eaa0b650, which is unallocated according to Arm ARM and should raise a
> SIGILL, but instead raises a SIGTRAP.
How can 0xeaa0b650 match 0xde01 when masked with 0xffff ?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
next prev parent reply other threads:[~2020-05-18 14:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 17:38 [PATCH v2] arm: ptrace: Fix mask for thumb breakpoint hook Fredrik Strupe
2020-04-13 17:38 ` Fredrik Strupe
2020-05-18 13:12 ` [PING] " Fredrik Strupe
2020-05-18 13:12 ` Fredrik Strupe
2020-05-18 14:18 ` Russell King - ARM Linux admin [this message]
2020-05-18 14:18 ` Russell King - ARM Linux admin
2020-05-18 15:02 ` Fredrik Strupe
2020-05-18 15:02 ` Fredrik Strupe
2020-05-18 16:39 ` Russell King - ARM Linux admin
2020-05-18 16:39 ` Russell King - ARM Linux admin
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