gdb/2541: ARM single step problem with instruction 0xa5ffffeb

gdb/2541: ARM single step problem with instruction 0xa5ffffeb

[julien.lincy]

>Number:         2541
>Category:       gdb
>Synopsis:       ARM single step problem with instruction 0xa5ffffeb
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          support
>Submitter-Id:   net
>Arrival-Date:   Wed Oct 22 11:48:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     J. Lincy
>Release:        GDB 6.8
>Organization:
>Environment:
ARM 1136 Linux 2.6.21 (EABI)
>Description:
I have a problem single stepping with a simple C program on ARM, with the instruction 0xa5ffffeb.

8538:       a5ffffeb        ldrgeb  pc, [pc, #4075]!        ; 952b <__clz_tab+0x6b>

GDB stops with the error "Invalid update to pc in instruction".

The C program i'm trying to test is attached.
The ARM I use is an ARM v1136 (a bit specific...).

I compiled GDB  with the following options 

./configure --enable-debug --build=i686-pc-linux-gnu --host=i686-pc-linux-gnu --target=i686-pc-linux-gnu --prefix=/home/lincyj/gdb-6.8/build --disable-werror --disable-sim 

And gdbserver with the following options:

../gdb/gdbserver/configure --host=armeb-none-linux-gnueabi --target=armeb-none-linux-gnueabi --prefix=/home/lincyj/gdb-6.8/gdb-6.8/gdbserver_build

>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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pending/2542: Re: ARM single step problem with instruction 0xa5ffffeb

[Daniel Jacobowitz]

>Number:         2542
>Category:       pending
>Synopsis:       Re: ARM single step problem with instruction 0xa5ffffeb
>Confidential:   yes
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   unknown
>Arrival-Date:   Wed Oct 22 13:08:01 UTC 2008
>Closed-Date:
>Last-Modified:
>Originator:     
>Release:        
>Organization:
>Environment:
>Description:
 On Wed, Oct 22, 2008 at 11:41:01AM -0000, julien.lincy@thomson.net wrote:
 > >Description:
 > I have a problem single stepping with a simple C program on ARM, with the instruction 0xa5ffffeb.
 > 
 > 8538:       a5ffffeb        ldrgeb  pc, [pc, #4075]!        ; 952b <__clz_tab+0x6b>
 > 
 > GDB stops with the error "Invalid update to pc in instruction".
 > 
 > The C program i'm trying to test is attached.
 > The ARM I use is an ARM v1136 (a bit specific...).
 
 I think there's something wrong with your environment.  That's not a
 valid instruction; PC is always aligned, so pc+4075 is unaligned.
 The middle of __clz_tab doesn't have function pointers in it.  And you
 can't do PC-relative loads with writeback.
 
 GDB is right to complain about that instruction.
 
 -- 
 Daniel Jacobowitz
 CodeSourcery
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: