Message ID | 20161029134801.15082-1-slyich@gmail.com |
---|---|
State | New |
Headers | show |
On Okt 29 2016, slyich@gmail.com wrote: > commit 96e1bff2513873062233a13c7fd1eea57bb8db24 > Author: Roland McGrath <roland@gnu.org> > Date: Wed Jul 17 18:00:33 1996 +0000 ??? This commit touches csu/initfini.c only. Andreas.
On Sat, 29 Oct 2016 17:37:08 +0200 Andreas Schwab <schwab@linux-m68k.org> wrote: > On Okt 29 2016, slyich@gmail.com wrote: > > > commit 96e1bff2513873062233a13c7fd1eea57bb8db24 > > Author: Roland McGrath <roland@gnu.org> > > Date: Wed Jul 17 18:00:33 1996 +0000 > > ??? This commit touches csu/initfini.c only. > > Andreas. I was looking at this tree: Commit https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=96e1bff2513873062233a13c7fd1eea57bb8db24 among other thing shows disappearance of 'case R_68K_NONE': -static inline void -elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc) -{ - Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset); - switch (ELF32_R_TYPE (reloc->r_info)) - { - case R_68K_NONE: - break; - case R_68K_JMP_SLOT: - *reloc_addr += map->l_addr; - break; - default: - assert (! "unexpected PLT reloc type"); - break; - } -} +static inline void +elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc) +{ + Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset); + switch (ELF32_R_TYPE (reloc->r_info)) + { + case R_68K_JMP_SLOT: + *reloc_addr += map->l_addr; + break; + default: + assert (! "unexpected PLT reloc type"); + break; + } +}
On Okt 29 2016, Sergei Trofimovich <slyich@gmail.com> wrote: > Commit https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=96e1bff2513873062233a13c7fd1eea57bb8db24 > among other thing shows disappearance of 'case R_68K_NONE': The old history is mostly broken, you need to look at <http://repo.or.cz/w/glibc/history.git>. Andreas.
On Sat, 29 Oct 2016 19:11:13 +0200 Andreas Schwab <schwab@linux-m68k.org> wrote: > On Okt 29 2016, Sergei Trofimovich <slyich@gmail.com> wrote: > > > Commit https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=96e1bff2513873062233a13c7fd1eea57bb8db24 > > among other thing shows disappearance of 'case R_68K_NONE': > > The old history is mostly broken, you need to look at > <http://repo.or.cz/w/glibc/history.git>. Same removal: http://repo.or.cz/glibc/history.git/commitdiff/60f0b5f25d09c1ee464141ee41995d9a31a604b7 binutils accidentally generates R_68K_NONE relocations around here https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=bfd/elf32-m68k.c;h=7c2e0fcca3bfb35d71dc1431c69958c84f04de7b;hb=690035b1471a58db62ec27d739f124f0f58f6af2#l3356 [bfd fails to properly estimate final relocation section size and pads with zeros] 3356 /* Allocate memory for the section contents. */ 3357 /* FIXME: This should be a call to bfd_alloc not bfd_zalloc. 3358 Unused entries should be reclaimed before the section's contents 3359 are written out, but at the moment this does not happen. Thus in 3360 order to prevent writing out garbage, we initialise the section's 3361 contents to zero. */ 3362 s->contents = (bfd_byte *) bfd_zalloc (dynobj, s->size); Curious can add "memset(s->contents, '\xFF', s->size);" to make sure it still happens. And indeed m68k-linux-gcc generates R_68K_NONE relocations even for minimal programs: $ echo 'int main(){}' > a.c $ m68k-unknown-linux-gnu-gcc a.c -o a $ readelf -a a | grep -C4 NONE 0x00000000 (NULL) 0x0 Relocation section '.rela.dyn' at offset 0x238 contains 3 entries: Offset Info Type Sym.Value Sym. Name + Addend 00000000 00000000 R_68K_NONE 0 00000000 00000000 R_68K_NONE 0 80004014 00000114 R_68K_GLOB_DAT 00000000 __gmon_start__ + 0 In general relocations happen to be non-lazy. I guess to trigger lazy case we need to build shared library with complex library structure. At least GHC does that. Is there a reason to allow R_68K_NONE for non-lazy relocations in elf_machine_rela() + case R_68K_NONE: /* Alright, Wilbur. */ + break; but forbid R_68K_NONE for lazy relocations in elf_machine_lazy_rel() assuming mechanism to leak R_68K_NONE to both relocation types is the same? Thanks!
On Okt 30 2016, Sergei Trofimovich <slyich@gmail.com> wrote: > Is there a reason to allow R_68K_NONE for non-lazy relocations > in elf_machine_rela() > > + case R_68K_NONE: /* Alright, Wilbur. */ > + break; > > but forbid R_68K_NONE for lazy relocations > in elf_machine_lazy_rel() Because the latter must never happen. Please file a binutils bug with a self-contained test case. Andreas.
On Sun, 30 Oct 2016 12:04:59 +0100 Andreas Schwab <schwab@linux-m68k.org> wrote: > On Okt 30 2016, Sergei Trofimovich <slyich@gmail.com> wrote: > > > Is there a reason to allow R_68K_NONE for non-lazy relocations > > in elf_machine_rela() > > > > + case R_68K_NONE: /* Alright, Wilbur. */ > > + break; > > > > but forbid R_68K_NONE for lazy relocations > > in elf_machine_lazy_rel() > > Because the latter must never happen. Please file a binutils bug with a > self-contained test case. Finally extracted one. Filed as: https://sourceware.org/bugzilla/show_bug.cgi?id=20796 It is triggered by a mix of -Wl,--gc-sections, -u buggy_symbol and a shared library where 'buggy_symbol' comes from. And while at it filed minor bug about R_68K_NONE relocations to be present in final binaries: https://sourceware.org/bugzilla/show_bug.cgi?id=20797
diff --git a/sysdeps/m68k/dl-machine.h b/sysdeps/m68k/dl-machine.h index 41c179c..1b6b6a4 100644 --- a/sysdeps/m68k/dl-machine.h +++ b/sysdeps/m68k/dl-machine.h @@ -312,6 +312,8 @@ elf_machine_lazy_rel (struct link_map *map, Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset); if (ELF32_R_TYPE (reloc->r_info) == R_68K_JMP_SLOT) *reloc_addr += l_addr; + else if (ELF32_R_TYPE (reloc->r_info) == R_68K_NONE) + return; else _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 1); }