Bug 214440

Split off from bug 202096 (ia64: unaligned accesses during dmraid execution at
startup)

ld generates unaligned access faults on ia64 linking dmraid.so to dmraid.

The faulting instruction lies in _dl_relocate_object:

dmraid(4716): unaligned access to 0x20000000000ae0be, ip=0x2000000000018080

Breakpoint 2, 0x2000000000018090 in _dl_relocate_object () from
/lib/ld-linux-ia64.so.2
(gdb) bt
#0  0x2000000000018090 in _dl_relocate_object () from /lib/ld-linux-ia64.so.2
#1  0x2000000000008450 in dl_main () from /lib/ld-linux-ia64.so.2
#2  0x200000000002c5e0 in _dl_sysdep_start () from /lib/ld-linux-ia64.so.2
#3  0x2000000000004bf0 in _dl_start () from /lib/ld-linux-ia64.so.2
#4  0x2000000000001590 in _start () from /lib/ld-linux-ia64.so.2

Intel further pinned this down to:

sysdeps/ia64/dl-machine.h.

elf_machine_rela_relative (Elf64_Addr l_addr, const Elf64_Rela *reloc,
                           void *const reloc_addr_arg)
{
  Elf64_Addr *const reloc_addr = reloc_addr_arg;
  /* ??? Ignore MSB and Instruction format for now.  */
  assert (ELF64_R_TYPE (reloc->r_info) == R_IA64_REL64LSB);

  *reloc_addr += l_addr; <--------
}

It sems like the faults happen relocating an array of packed structs:

struct format_member {
        const unsigned short offset;
        const unsigned char flags;
        const char *msg;
} __attribute__ ((packed));

static struct format_member format_member[] = {
        ...
};

A patch was pasted into bug 202096 that makes _dl_relocate_object check for
unaligned accesses and work around them - will attach here also.