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Fix GOT[1] for MIPS n64
- From: Richard Sandiford <rsandifo at nildram dot co dot uk>
- To: binutils at sourceware dot org
- Date: Wed, 19 Mar 2008 21:12:47 +0000
- Subject: Fix GOT[1] for MIPS n64
The MIPS psABI reserves GOT[0] for the runtime resolver, but as an
extension, GNU ld also reserves GOT[1]. We set the top bit of GOT[1]
to indicate that it has been reserved. The GNU dynamic loader checks
that this bit is set before using the entry; if the entry hasn't been
reserved, the resolver uses a slower fallback instead. (FWIW, uClibc's
loader uses the entry unconditionally, presumably because it doesn't
have as much historical baggage to support.)
However, the static linker gets this wrong for n64: it sets bit 31
instead of bit 63. The GNU dynamic loader therefore treats GOT[1]
like any other local GOT entry.
Tested on mips{,64}{,el}-linux-gnu and mips64{,el}-elf. OK to install?
Richard
bfd/
* elfxx-mips.c (MIPS_ELF_GNU_GOT1_MASK): New macro.
(_bfd_mips_elf_finish_dynamic_sections): Use it instead of 0x80000000.
ld/testsuite/
* ld-mips-elf/elf-rel-got-n64-linux.d: Expect bit 63 rather than
bit 31 of the second GOT entry to be set.
* ld-mips-elf/elf-rel-got-n64.d: Likewise.
* ld-mips-elf/elf-rel-xgot-n64-linux.d: Likewise.
* ld-mips-elf/elf-rel-xgot-n64.d: Likewise.
Index: bfd/elfxx-mips.c
===================================================================
--- bfd/elfxx-mips.c 2008-03-17 18:29:21.000000000 +0000
+++ bfd/elfxx-mips.c 2008-03-19 19:31:08.000000000 +0000
@@ -648,6 +648,12 @@ #define MINUS_TWO (((bfd_vma)0) - 2)
#define MIPS_RESERVED_GOTNO(INFO) \
(mips_elf_hash_table (INFO)->is_vxworks ? 3 : 2)
+/* The value to write into got[1] for SVR4 targets, to identify it is
+ a GNU object. The dynamic linker can then use got[1] to store the
+ module pointer. */
+#define MIPS_ELF_GNU_GOT1_MASK(abfd) \
+ ((bfd_vma) 1 << (ABI_64_P (abfd) ? 63 : 31))
+
/* The offset of $gp from the beginning of the .got section. */
#define ELF_MIPS_GP_OFFSET(INFO) \
(mips_elf_hash_table (INFO)->is_vxworks ? 0x0 : 0x7ff0)
@@ -9230,7 +9236,7 @@ _bfd_mips_elf_finish_dynamic_sections (b
runtime. The second entry will be used by some runtime loaders.
This isn't the case of IRIX rld. */
MIPS_ELF_PUT_WORD (output_bfd, (bfd_vma) 0, sgot->contents);
- MIPS_ELF_PUT_WORD (output_bfd, (bfd_vma) 0x80000000,
+ MIPS_ELF_PUT_WORD (output_bfd, MIPS_ELF_GNU_GOT1_MASK (output_bfd),
sgot->contents + MIPS_ELF_GOT_SIZE (output_bfd));
}
@@ -9254,7 +9260,8 @@ _bfd_mips_elf_finish_dynamic_sections (b
MIPS_ELF_PUT_WORD (output_bfd, 0, sgot->contents
+ index++ * MIPS_ELF_GOT_SIZE (output_bfd));
- MIPS_ELF_PUT_WORD (output_bfd, 0x80000000, sgot->contents
+ MIPS_ELF_PUT_WORD (output_bfd, MIPS_ELF_GNU_GOT1_MASK (output_bfd),
+ sgot->contents
+ index++ * MIPS_ELF_GOT_SIZE (output_bfd));
if (! info->shared)
Index: ld/testsuite/ld-mips-elf/elf-rel-got-n64-linux.d
===================================================================
--- ld/testsuite/ld-mips-elf/elf-rel-got-n64-linux.d 2008-03-13 10:15:06.000000000 +0000
+++ ld/testsuite/ld-mips-elf/elf-rel-got-n64-linux.d 2008-03-19 19:31:08.000000000 +0000
@@ -294,7 +294,8 @@ Disassembly of section \.got:
00000001200105e0 <_GLOBAL_OFFSET_TABLE_>:
\.\.\.
- 1200105ec: 80000000 .*
+ 1200105e8: 80000000 .*
+ 1200105ec: 00000000 .*
1200105f0: 00000001 .*
1200105f4: 20010000 .*
1200105f8: 00000001 .*
Index: ld/testsuite/ld-mips-elf/elf-rel-got-n64.d
===================================================================
--- ld/testsuite/ld-mips-elf/elf-rel-got-n64.d 2008-03-13 10:15:06.000000000 +0000
+++ ld/testsuite/ld-mips-elf/elf-rel-got-n64.d 2008-03-19 19:31:08.000000000 +0000
@@ -293,7 +293,8 @@ Disassembly of section \.got:
00000000101005e0 <_GLOBAL_OFFSET_TABLE_>:
\.\.\.
- 101005ec: 80000000 .*
+ 101005e8: 80000000 .*
+ 101005ec: 00000000 .*
101005f0: 00000000 .*
101005f4: 1010052c .*
101005f8: 00000000 .*
Index: ld/testsuite/ld-mips-elf/elf-rel-xgot-n64-linux.d
===================================================================
--- ld/testsuite/ld-mips-elf/elf-rel-xgot-n64-linux.d 2008-03-13 10:15:06.000000000 +0000
+++ ld/testsuite/ld-mips-elf/elf-rel-xgot-n64-linux.d 2008-03-19 19:31:08.000000000 +0000
@@ -418,7 +418,8 @@ Disassembly of section \.got:
00000001200107d0 <_GLOBAL_OFFSET_TABLE_>:
\.\.\.
- 1200107dc: 80000000 .*
+ 1200107d8: 80000000 .*
+ 1200107dc: 00000000 .*
1200107e0: 00000001 .*
1200107e4: 20010000 .*
1200107e8: 00000001 .*
Index: ld/testsuite/ld-mips-elf/elf-rel-xgot-n64.d
===================================================================
--- ld/testsuite/ld-mips-elf/elf-rel-xgot-n64.d 2008-03-13 10:15:06.000000000 +0000
+++ ld/testsuite/ld-mips-elf/elf-rel-xgot-n64.d 2008-03-19 19:31:08.000000000 +0000
@@ -417,7 +417,8 @@ Disassembly of section \.got:
00000000101007d0 <_GLOBAL_OFFSET_TABLE_>:
\.\.\.
- 101007dc: 80000000 .*
+ 101007d8: 80000000 .*
+ 101007dc: 00000000 .*
101007e0: 00000000 .*
101007e4: 10100000 .*
101007e8: 00000000 .*