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Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for sh

From: Meador Inge
Subject: Re: [Qemu-devel] [RFC PATCH 1/1] linux-user: Probe the guest base for shared objects when needed
Date: Tue, 12 Jun 2012 13:44:24 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120424 Thunderbird/12.0

On 06/12/2012 09:08 AM, Richard Henderson wrote:

> On 2012-06-07 13:59, Meador Inge wrote:
>>      load_addr = loaddr;
>>      if (ehdr->e_type == ET_DYN) {
>> +        if (loaddr < mmap_min_addr)
>> +            probe_guest_base(image_name, loaddr, hiaddr);
> This doesn't make any sense.  loaddr is almost certainly 0, unless
> you've pre-linked the ld.so image.  But the next statement is letting
> the system pick the address at which the image will be loaded.

It usually is.  I just want guest_base to be computed to something that
will work for cases where a fixed address image is later loaded (at which
point it is too late to compute the guest_base).  Always probing is one way I
found to do that, but as I originally said I don't know this code very well so
maybe that is not a good method.

> I think this is one of those cases where the -B or -R options
> (or QEMU_GUEST_BASE and QEMU_RESERVED_VA env variables) are the best
> way forward for whatever cpu you're emulating.  That or a change to
> the target's default ld script, not to link real executables quite so 
> low in the address space.

Hmmm, OK.  I was really hoping to have something more automatic.  Perhaps
I will have to use the options.

Thanks for the review.

Meador Inge
CodeSourcery / Mentor Embedded

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