[OE-core] [PATCH V3] mesa: Disable asm on musl

[Paul Eggleton]

On Wednesday, 3 October 2018 1:44:05 PM NZDT Khem Raj wrote:
> Musl started blocking dlopen of libs with initial-exec references into
> dynamic TLS area, via
> 
> https://github.com/kraj/musl/commit/5c2f46a214fceeee3c3e41700c51415e0a4f1acd
> 
> prior to that commit, musl was loading it and silently letting
> subsequent TLS accesses via the miscompiled code clobber memory that
> didn't belong to them
> 
> This was wrong behavior and it relied on additional space reserved by
> libc in TLS space to adjust fo such broken libs, but it also fails
> with glibc if the reserved space was already used up
> 
> Right fix is that  mesa should be patched to remove all the
> initial-exec hacks and use real TLS, and -mtls-dialect=gnu2 (TLSDESC)
> should be used on archs it's supported on (i386, x86_64, and aarch64)
> to make up for the lost performance, but mesa hardcodes the initial-exec,
> so there must be a reason that probably is better known to mesa devs.
> 
> but we 'fixed' it for musl by adding --disable-glx-tls for mesa in OE,
> which uses pthread_getspecific instead and makes is lot slower.
> 
> this caused additional problems with security flags on, it get textrels
> in .text segment. Therefore this is 'second fix' to get us through this
> warning.
> 
> Cause is some unknown part of mesa's x86 assembly code is broken by
> readonly text segments

That's excellent, thanks!

Cheers,
Paul

-- 

Paul Eggleton
Intel Open Source Technology Centre