From: Yao Qi <yao@codesourcery.com>
To: Richard Earnshaw <Richard.Earnshaw@buzzard.freeserve.co.uk>
Cc: gdb-patches@sourceware.org, julian@codesourcery.com
Subject: Re: [patch] Fix PR tdep/12352: Handle str pc, [Rd, #imm] in displaced stepping
Date: Mon, 24 Jan 2011 13:22:00 -0000 [thread overview]
Message-ID: <4D3D3278.5050602@codesourcery.com> (raw)
In-Reply-To: <4D3AF29E.3020708@buzzard.freeserve.co.uk>
On 01/22/2011 11:07 PM, Richard Earnshaw wrote:
> On 28/12/10 16:41, Yao Qi wrote:
>> When I read arm-tdep.c:copy_ldr_str_ldrb_strb, I feel pretty hard to
>> understand two lines of code,
>>
>> dsc->modinsn[0] = 0xe58ff014; /* str pc, [pc, #20]. */
>> dsc->modinsn[1] = 0xe59f4010; /* ldr r4, [pc, #16]. */
>
> Hmm, looks like a rather convoluted way of moving the PC into R4.
> Julian, I think this patch was yours... can you remember why "MOV R4,
> PC" wasn't sufficient?
>
IIUC, these two instructions together with 'sub r4, r4, pc' are used to
calculate the offset of 'str pc ADDR', which is 8 or
12(implementation-dependent, but consistent for a given device).
AFAIK, 'mov r4, pc' doesn't help.
--
Yao (é½å°§)
next prev parent reply other threads:[~2011-01-24 8:04 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-28 17:24 Yao Qi
2011-01-06 14:03 ` [Ping : patch] " Yao Qi
2011-01-19 16:17 ` [Ping 2: " Yao Qi
2011-01-22 23:44 ` [patch] " Richard Earnshaw
2011-01-24 13:22 ` Yao Qi [this message]
2011-01-31 0:31 ` Yao Qi
2011-01-31 15:56 ` Ulrich Weigand
2011-02-09 6:15 ` Yao Qi
2011-02-09 13:51 ` Ulrich Weigand
2011-02-10 6:19 ` Yao Qi
2011-02-14 14:39 ` Ulrich Weigand
2011-02-15 10:55 ` Yao Qi
2011-02-15 13:36 ` Ulrich Weigand
2011-02-15 15:57 ` Yao Qi
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