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Date: Sat, 26 Nov 2011 15:31:29 -0800 (PST)
From: Gauresh Rane <gdrane@cs.ucla.edu>
Message-ID: <bb5c2836-6cf7-42c3-8a48-0c50b0923736@mail.cs.ucla.edu>
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Subject: Re: [Qemu-devel] Problem with translating on ARM and Qemu beginner
	question
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>, qemu-devel@nongnu.org

Works Like a charm....The memory at that place was indeed not allocated.
Thanks for your help.

Regards,

Gauresh Rane
Grad Student
CS Department
UCLA

----- Original Message -----
From: "Peter Maydell" <peter.maydell@linaro.org>
To: "Max Filippov" <jcmvbkbc@gmail.com>
Cc: "Gauresh Rane" <gdrane@cs.ucla.edu>, qemu-devel@nongnu.org
Sent: Friday, November 25, 2011 7:40:52 AM
Subject: Re: [Qemu-devel] Problem with translating on ARM and Qemu beginner=
 question

On 25 November 2011 15:35, Max Filippov <jcmvbkbc@gmail.com> wrote:
>> Breakpoint 7, cpu_arm_exec (env=3D0x102033200) at ~/qemu-0.15.0/cpu-exec=
.c:557
>> 557 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 next_tb =3D tcg_qemu_tb_exec(env, tc_ptr);
>> (gdb) p/x env->regs
>> $13 =3D {0x4002c00c, 0x20, 0x4, 0x0, 0x0, 0x0, 0x40000, 0x0, 0x0, 0x0, 0=
x0, 0x0, 0x30, 0x10007fa8, 0x560d, 0x560c}
>> (gdb) s
>> 558 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 if ((next_tb & 3) =3D=3D 2) {
>> (gdb) p/x env->regs
>> $14 =3D {0x10048000, 0x20, 0x4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, =
0x0, 0x30, 0x10007fb8, 0x560d, 0x0}
>>
>> How to check access to unallocated memory? It's not seg faulting.
>
> 290 0000042c <_init>:
> 291 =C2=A042c: =C2=A0 b5f8 =C2=A0 =C2=A0 =C2=A0 =C2=A0push =C2=A0 =C2=A0{=
r3, r4, r5, r6, r7, lr}
>
> set breakpoint here and see with x/6wx $sp whether saved register values =
are good.

To clarify this a bit: that means "set a breakpoint in an ARM gdb attached
to qemu's gdb-stub interface". That gdb will see the view of the guest
CPU, whereas connecting an x86 gdb directly to qemu you're looking at
qemu's internal data structures, which can be more confusing.

-- PMM