* Permission of overlapping segments
@ 2007-08-09 18:20 Udo A. Steinberg
2007-08-10 7:06 ` Alan Modra
0 siblings, 1 reply; 2+ messages in thread
From: Udo A. Steinberg @ 2007-08-09 18:20 UTC (permalink / raw)
To: binutils
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Hi all,
In the following example I've put .text and .rodata in the first program
header and .data and .bss in the second. Unless I'm page-aligning the
.data section, linking results in two segments that overlap page 0x400000
with different/conflicting permissions as follows:
Program Header:
LOAD off 0x00000000 vaddr 0x00400000 paddr 0x00400000 align 2**12
filesz 0x00000595 memsz 0x00000595 flags r-x
LOAD off 0x00000598 vaddr 0x00400598 paddr 0x00400598 align 2**12
filesz 0x00000008 memsz 0x00001000 flags rw-
What should an ELF loader do here - merge permissions such that 0x400000
is rwx or is such a segment layout illegal?
Cheers,
- Udo
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Permission of overlapping segments
2007-08-09 18:20 Permission of overlapping segments Udo A. Steinberg
@ 2007-08-10 7:06 ` Alan Modra
0 siblings, 0 replies; 2+ messages in thread
From: Alan Modra @ 2007-08-10 7:06 UTC (permalink / raw)
To: Udo A. Steinberg; +Cc: binutils
On Thu, Aug 09, 2007 at 08:20:29PM +0200, Udo A. Steinberg wrote:
> LOAD off 0x00000000 vaddr 0x00400000 paddr 0x00400000 align 2**12
> filesz 0x00000595 memsz 0x00000595 flags r-x
> LOAD off 0x00000598 vaddr 0x00400598 paddr 0x00400598 align 2**12
> filesz 0x00000008 memsz 0x00001000 flags rw-
>
> What should an ELF loader do here - merge permissions such that 0x400000
> is rwx or is such a segment layout illegal?
You're asking for trouble. The loader may refuse to load this file,
or it may mmap the pages occupied by the second PT_LOAD segment on top
of the first.
--
Alan Modra
Australia Development Lab, IBM
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2007-08-09 18:20 Permission of overlapping segments Udo A. Steinberg
2007-08-10 7:06 ` Alan Modra
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