Bug#941559: libxvidcore4: immediately crashes on amd64 since binNMU

[James Cowgill]

Hi,

On 02/10/2019 11:47, Fabian Greffrath wrote:
> Hi James,
> 
> Am 02.10.2019 01:45, schrieb James Cowgill:
>> Indeed readelf contains some non-executable program headers in
>> 2:1.3.5-1+b1 which do not appear in 2:1.3.5-1 in buster. The
>> ".rotext" section sounds suspicious.
> 
> indeed, the check_cpu_feature() function is defined in
> src/utils/x86_asm/cpuid.asm [1] which includes src/nasm.inc, which in
> turn declares a .rotext section [2] for any other output format than
> macho32 and macho64.
> 
> It would probably be the best patch this to simply declare a .text
> section for all output formats. The question remains, however, why this
> is an issue now but not when xvidcore_2:1.3.5-1 was uploaded?

I had a play around and I think this is caused by the "-z separate-code"
option being enabled by default in binutils >= 2.31. With that option
binutils will put "text" and "rodata" into different segments.
Previously it bundled both of those (along with any other read only
data) into a single executable segment.

Second bullet point in the announcement:
https://sourceware.org/ml/binutils/2018-07/msg00213.html

In theory that also means the bug affects buster if the package is ever
rebuilt / updated there.

James

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