Fix linker script alignment of TLS sections

binutils-2.20/ld/scripttempl/naclelf.sc

 #
 # Unusual variables checked by this code:
 #       NOP - four byte opcode for no-op (defaults to 0)
 #       NO_SMALL_DATA - no .sbss/.sbss2/.sdata/.sdata2 sections if not
 #               empty.
 #       SMALL_DATA_CTOR - .ctors contains small data.
 #       SMALL_DATA_DTOR - .dtors contains small data.
 #       DATA_ADDR - if end-of-text-plus-one-page isn't right for data start
 #       INITIAL_READONLY_SECTIONS - at start of text segment
 #       OTHER_READONLY_SECTIONS - other than .text .init .rodata ...
@@ skipping 440 matching lines @@
   ${CREATE_PIE+${RELOCATING+. = ${SHLIB_DATA_ADDR-${DATA_SEGMENT_ALIGN}};}}
 
   /* Exception handling  */
   .eh_frame     ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame)) }
   .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { *(.gcc_except_table .gcc_except_table.*) }
 
   /* Thread Local Storage sections  */
   /* The total size of the TLS template area must be a multiple of 0x20,
    * but it's size calculation is hardcoded in bfd_elf_final_link function
    * so the only thing we can do is align segments here properly */
-  .tdata        : ${RELOCATING+ALIGN(0x20)} {
+  .tdata        ${RELOCATING+ALIGN(0x20)}${RELOCATING-0} : ALIGN(0x10) {

[krasin, 2011/10/12 19:56:07]

The line itself looks fine (modulo my linker script illiteration). My concern is
that it would be absolutely impossible to avoid a regression in the future.

I'm fine to write a test myself, though.

     ${RELOCATING+PROVIDE (__tls_template_start = .);}
     *(.tdata${RELOCATING+ .tdata.* .gnu.linkonce.td.*})
     ${RELOCATING+. = ALIGN(0x20);}
     ${RELOCATING+PROVIDE (__tls_template_tdata_end = .);}
   }
-  .tbss         : ${RELOCATING+ALIGN(0x20)} {
+  .tbss         ${RELOCATING+ALIGN(0x20)}${RELOCATING-0} : ALIGN(0x10) {

[krasin, 2011/10/12 19:56:07]

I'm not sure, if this line is required. bss is put right after tdata and the
code in src/untrusted/nacl/tls.c does not care about alignment tbss. At the same
time, since .tdata size is a multiply of 0x20 and it's aligned by 0x10, .tbss
will be automatically aligned by 0x10.

     *(.tbss${RELOCATING+ .tbss.* .gnu.linkonce.tb.*})${RELOCATING+ *(.tcommon)}
     ${RELOCATING+. = ALIGN(0x20);}
   }
   /* . does not advance for tbss because it is not loaded. */
   ${RELOCATING+PROVIDE (__tls_template_end = . + SIZEOF(.tbss));}
   .preinit_array   ${RELOCATING-0} :
   {
     ${RELOCATING+${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__preinit_array_start = .);}}
     KEEP (*(.preinit_array))
     ${RELOCATING+${CREATE_SHLIB-PROVIDE_HIDDEN (${USER_LABEL_PREFIX}__preinit_array_end = .);}}
@@ skipping 135 matching lines @@
   ${TINY_DATA_SECTION}
   ${TINY_BSS_SECTION}
 
   ${STACK_ADDR+${STACK}}
   ${ATTRS_SECTIONS}
   ${OTHER_SECTIONS}
   ${RELOCATING+${OTHER_SYMBOLS}}
   ${RELOCATING+${DISCARDED}}
 }
 EOF