RE: TLS transition error

["King, Steven R" <steven dot r dot king at intel dot com>]

> -----Original Message-----
> From: David Miller [mailto:davem@davemloft.net]
> Sent: Friday, February 19, 2010 4:44 PM
> To: King, Steven R
> Cc: binutils@sourceware.org
> Subject: Re: TLS transition error
> 
> From: "King, Steven R" <steven.r.king@intel.com>
> Date: Fri, 19 Feb 2010 16:36:26 -0800
> 
> > libc.a(malloc.o): TLS transition from R_386_TLS_IE to R_386_TLS_LE_32
> against `__libc_tsd_MALLOC' at 0x9c in section `.text' failed
> > libc.a: could not read symbols: Bad value
> >
> > I did an objdump -x of malloc.o and libc.a but don't see R_386_TLS_LE_32
> anywhere.
> >
> > I've stepped through the BFD code around the error, but there are many
> mystery constants in play and I am not making much progress.
> >
> > Can someone please point me in the right direction?
> 
> The R_386_TLS_LE_32 relocation is being produced internally by the
> i386 BFD backend during linking when it optimizes TLS relocations.
> 
> Start by studying elf_i386_tls_transition().

Thank you for the help.  elf_i386_tls_transition() eventually calls elf_i386_check_tls_transition(), which eventually returns false (failure) in the case statement below.  Where do I look to understand the meaning of 0xa1, 0x8b and x3 comparison values?  At runtime, my val = 0x3D and type = 0x2B.  What do these values imply?

Thanks again for help!
-steve

   case R_386_TLS_IE:
      /* Check transition from IE access model:
		movl foo@indntpoff(%rip), %eax
		movl foo@indntpoff(%rip), %reg
		addl foo@indntpoff(%rip), %reg
       */

      if (offset < 1 || (offset + 4) > sec->size)
	return FALSE;

      /* Check "movl foo@tpoff(%rip), %eax" first.  */
      val = bfd_get_8 (abfd, contents + offset - 1);
      
      if (val == 0xa1)
	return TRUE;

      if (offset < 2)
	return FALSE;

      /* Check movl|addl foo@tpoff(%rip), %reg.   */
      type = bfd_get_8 (abfd, contents + offset - 2);
      
      return ((type == 0x8b || type == 0x03)
	      && (val & 0xc7) == 0x05);