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From: Kumar Gala <galak@kernel.crashing.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Subject: Re: issues w/init
Date: Fri, 17 Apr 2009 08:23:17 -0500
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Cc: Scott Wood <scottwood@freescale.com>,
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	Paul Mackerras <paulus@samba.org>
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On Apr 17, 2009, at 5:41 AM, Benjamin Herrenschmidt wrote:

> On Fri, 2009-04-17 at 20:05 +1000, Paul Mackerras wrote:
>> Benjamin Herrenschmidt writes:
>>
>>> I'm pretty sure they are broken already when running off a 64-bit
>>> kernel,
>>
>> Maybe not... for 64-bit kernels we have our definition of
>> elf_read_implies_exec in arch/powerpc/include/asm/elf.h, which IIRC
>> sets the read-implies-exec personality thing on old 32-bit binaries.
>
> Ok, so looking at that more closely, if that had worked, we would
> have had PROT_EXEC, and thus VM_EXEC added to the vma by mmap... which
> apparently didn't occur.
>
> I think what may be happening is that the binary he's running has the
> PT_GNU_STACK but his libc doesn't ... the kernel will set the
> personality flag based on the binary you are trying to run, not any
> library it uses...
>
> Kumar, can you try to instrument that a bit and tell us ? What the
> personality flag gets set to and whether mmap sets PROT_EXEC ?

I can and might have already done this, need to double check.  But  
what I was seeing from elf_map is that we don't get PROT_EXEC set for  
this PHDR, but get VM_MAY_EXEC.  I'm not clear on what VM_MAY_EXEC is  
intended for.

- k