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[Qemu-devel] Strange behaviour with MSR?
From: |
François |
Subject: |
[Qemu-devel] Strange behaviour with MSR? |
Date: |
Mon, 07 Jul 2014 14:10:53 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 |
Hello,
I'm not sure I'm on the right list to post, sorry about that, but I
tried on IRC and got no answer.
I'm working on a low level piece of system, which has to change PSR
values on ARM.
I use qemu-system-arm v 2.0.0, with the command : qemu-system-arm
-nographic -s -S -m 1024 -M vexpress-a9 -kernel ./bootstrap
My issue is the following: Just before the MSR call, I have an LR value.
When executing MSR, the LR value gets nulled.
After a second iteration, MSR does *not* set this value to 0.
I really don't see wether it can come from qemu, if I'm writting this
message, I think it does not come from my code, since the reset caused
by the lr = 0 restarts the system, and thus, re initilizes the context
with the same values and same call graph.
Here is a gdb trace from the issue :
(gdb) target remote 127.0.0.1:1234
Remote debugging using 127.0.0.1:1234
0x60000000 in ?? ()
(gdb) b *0x61005814
Breakpoint 1 at 0x61005814
(gdb) c
Continuing.
Breakpoint 1, 0x61005814 in ?? ()
(gdb) x /i $pc
=> 0x61005814: msr CPSR_fsxc, r3
(gdb) info reg
r0 0xe1a010b2 -509603662
r1 0x0 0
r2 0x2822001 42082305
r3 0xe1a010b2 -509603662
r4 0x0 0
r5 0x6100ec04 1627450372
r6 0x0 0
r7 0x0 0
r8 0x0 0
r9 0x0 0
r10 0x0 0
r11 0x60340be4 1614023652
r12 0x0 0
sp 0x60340bc0 0x60340bc0
lr 0x610057cc 1627412428
pc 0x61005814 0x61005814
cpsr 0x80000013 -2147483629
(gdb) si
0x61005818 in ?? ()
(gdb) info reg
r0 0xe1a010b2 -509603662
r1 0x0 0
r2 0x2822001 42082305
r3 0xe1a010b2 -509603662
r4 0x0 0
r5 0x6100ec04 1627450372
r6 0x0 0
r7 0x0 0
r8 0x0 0
r9 0x0 0
r10 0x0 0
r11 0x60340be4 1614023652
r12 0x0 0
sp 0x0 0x0
lr 0x0 0
pc 0x61005818 0x61005818
cpsr 0xe0000092 -536870766
Thanks in advance for any piece of advice :)
--
François
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