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Re: [Qemu-devel] Re: problems with mmap on qemu-arm
From: |
Riku Voipio |
Subject: |
Re: [Qemu-devel] Re: problems with mmap on qemu-arm |
Date: |
Thu, 18 Jun 2009 21:55:52 +0300 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
On Wed, Jun 17, 2009 at 11:38:32PM +0300, Kai Backman wrote:
> I tracked this down to the code in linux-user/syscall.c. The mmap code
> seems broken, it assumes arg1 is a pointer to an array where the real
> arguments are. Given arg1 = 0 the memory access check fails.
> The code I'm working on will happily take mmap2 instead so I have a
> workaround. Does someone have an opinion on the state of the mmap code?
> �Kai
looking at old_mmap() for arm in kernel, qemu seems to the right thing. Ie
you are probably calling mmap the wrong way, you are supposed to give it a
array.
mmap syscall is depreceated, glibc uses mmap2 since forever.
> On Wed, Jun 17, 2009 at 8:54 PM, Kai Backman <address@hidden> wrote:
>
> I'm running qemu-arm and see the following output from mmap with 'strace
> qemu-arm -strace' (for both host and traget strace output):
> mmap(NULL, 32800, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
> 0) = 0x2ad329b46000
> 4023 mmap(0,131072,7,34,-1,0) = 0xfffffff2
> When my program later tries to read memory at 0xfffffffe it fails with a
> SIGSEGV:
> Program received signal SIGSEGV, Segmentation fault.
> 1: x/i $pc �0xce30: � � ldr � � r1, [r5]
> (gdb) i r
> r5 � � � � � � 0xfffffffe � � � -2
> Why does qemu-arm return such high addresses on a 32 bit platform and
> why is the memory inaccessible? If this doesn't seem like an obvious bug
> in my code, where in the qemu code should I start looking for how mmap
> works?
> �Kai
> --
> Kai Backman, Software Engineer, address@hidden
>
> --
> Kai Backman, Software Engineer, address@hidden
>
> References
>
> Visible links
> 1. mailto:address@hidden
> 2. mailto:address@hidden
> 3. mailto:address@hidden