[Cc'ing hppa people for reasons which will become clear] On Tue, Nov 28, 2017 at 08:22:56AM -0500, Jason Duerstock wrote: > Source: glibc > Followup-For: Bug #882874 > > This patch appears to correct the problem. > > -- System Information: > Debian Release: buster/sid > Architecture: ia64 > > Kernel: Linux 3.2.0-4-mckinley (SMP w/2 CPU cores) > Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8) > Shell: /bin/sh linked to /bin/dash
> --- sysdeps/ia64/dl-machine.h > +++ sysdeps/ia64/dl-machine.h > @@ -45,7 +45,8 @@ > } > > #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \ > - __ia64_init_bootstrap_fdesc_table (&bootstrap_map); > + __ia64_init_bootstrap_fdesc_table (&bootstrap_map); \ > + _dl_fptr_init(); > > /* Return nonzero iff ELF header is compatible with the running host. */ > static inline int __attribute__ ((unused)) As discussed on IRC with Jason, here are my findings for what on earth is going on here. This change is required due to the any/local-dlfptr.diff patch in Debian, which modifies elf/dl-fptr.c to introduce a _dl_fptr_init to assign local.root to &local.boot_table, with hppa calling this function early before it might have to process any relocations needing function pointers. Now, ignoring one important fact, this is needed on hppa for a very specific reason: it doesn't have special relative relocation types, instead reusing R_PARISC_DIR32 and others with symbol index 0, and doesn't set DT_RELACOUNT in its dynamic section (I assume because nobody bothered to implement it for bfd), so ld.so cannot perform any early relative relocations, despite having an implementation for elf_machine_rela_relative in sysdeps/hppa/dl-machine.h. This means that, depending on whether any function pointer-needing relocations appear before the R_hppa_DIR32 for local.root, local.root may not have been relocated, and thus cannot be used. Instead, the assignment is done manually in _dl_fptr_init using ELF_MACHINE_LOAD_ADDRESS to do this without needing any dynamic relocations to have been applied. However, hppa, at least currently, has its own sysdeps/hppa/dl-fptr.c, and does not compile elf/dl-fptr.c. This platform-specific dl-fptr.c also has the same workaround in it, so at least in the context of hppa, I don't see why this patch is needed any more (perhaps at one point elf/dl-fptr.c was being used for hppa on Debian, but it isn't now). Now, the only architecture actually using elf/dl-fptr.c currently is ia64. This patch therefore presents a problem, as its ELF_MACHINE_BEFORE_RTLD_RELOC does not call _dl_fptr_init (as pointed out by Jason's patch above). Thus, applying Jason's patch does in fact fix the issue on ia64. However, on ia64, there are specific relative relocations, and DT_RELACOUNT *does* get set to something sensible, so local.root gets relocated early, and this is why upstream glibc has not seen an issue with elf/dl-fptr.c on ia64. Therefore, this patch is *also* not needed on ia64 (albeit for different reasons), and so my suggested fix would be instead to simply drop this local patch, as its sole effect is to break ia64. Thoughts (especially from hppa people)? Regards, James
