Re: [PATCH v2 0/8] clean up vdso-layout.lds.S
From: Roland McGrath
Date: Tue Jun 16 2009 - 06:37:28 EST
> Upfront, thank you very much for reviewing the series, Roland!
I'm glad to help.
> And there currently isn't one. But the writability of the vDSO is a bit
> more complicated. True, the VMA is initially mapped read-only, but it is
> possible to make it writable using mprotect().
Except for CONFIG_COMPAT_VDSO on X86_32.
> You may also set an
> INT3-style breakpoint in the vDSO area. So, it's all about policy. If
> there were any demand to make the vDSO writable, it could be done with a
> trivial patch.
There's a big difference between "writable" and "might be written".
> If we do not _WANT_ to make it writable, then we can simply add .data
> and .bss to .broken.
That is the correct thing to do.
> Yes, all .rel* sections should be in .broken, I guess.
You can toss an "void *x = &x;" into the vdso sources to verify that this
setup makes that explode gracefully.
> This was an attempt to discard .note.GNU-stack, which is what the
> default linker script does, but it appears that all .note.GNU-stack
> sections are zero-size, so this change does not make any difference.
Indeed it does not.
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