On Tue, 2019-06-18 at 14:32 +0100, Dave Martin wrote: > On Tue, Jun 18, 2019 at 02:55:12PM +0200, Peter Zijlstra wrote: > > On Tue, Jun 18, 2019 at 02:47:00PM +0200, Florian Weimer wrote: > > > * Peter Zijlstra: > > > > > > > I'm not sure I read Thomas' comment like that. In my reading keeping the > > > > PT_NOTE fallback is exactly one of those 'fly workarounds'. By not > > > > supporting PT_NOTE only the 'fine' people already shit^Hpping this out > > > > of tree are affected, and we don't have to care about them at all. > > > > > > Just to be clear here: There was an ABI document that required PT_NOTE > > > parsing. > > > > URGH. > > > > > The Linux kernel does *not* define the x86-64 ABI, it only > > > implements it. The authoritative source should be the ABI document. > > > > > > In this particularly case, so far anyone implementing this ABI extension > > > tried to provide value by changing it, sometimes successfully. Which > > > makes me wonder why we even bother to mainatain ABI documentation. The > > > kernel is just very late to the party. > > > > How can the kernel be late to the party if all of this is spinning > > wheels without kernel support? > > PT_GNU_PROPERTY is mentioned and allocated a p_type value in hjl's > spec [1], but otherwise seems underspecified. > > In particular, it's not clear whether a PT_GNU_PROPERTY phdr _must_ be > emitted for NT_GNU_PROPERTY_TYPE_0. While it seems a no-brainer to emit > it, RHEL's linker already doesn't IIUC, and there are binaries in the > wild. > > Maybe this phdr type is a late addition -- I haven't attempted to dig > through the history. > > > For arm64 we don't have this out-of-tree legacy to support, so we can > avoid exhausitvely searching for the note: no PT_GNU_PROPERTY -> > no note. > > So, can we do the same for x86, forcing RHEL to carry some code out of > tree to support their legacy binaries? Or do we accept that there is > already a de facto ABI and try to be compatible with it? > > > From my side, I want to avoid duplication between x86 and arm64, and > keep unneeded complexity out of the ELF loader where possible. Hi Florian, The kernel looks at only ld-linux. Other applications are loaded by ld-linux. So the issues are limited to three versions of ld-linux's. Can we somehow update those?? Thanks, Yu-cheng
