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[binutils-gdb] x86-64: Improve GOTPCREL relocation conversion
- From: H.J.Lu <hjl at sourceware dot org>
- To: bfd-cvs at sourceware dot org
- Date: 5 Sep 2017 18:27:22 -0000
- Subject: [binutils-gdb] x86-64: Improve GOTPCREL relocation conversion
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=8b43e456886c5b3aaba1ef93195ed888b15de242
commit 8b43e456886c5b3aaba1ef93195ed888b15de242
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Tue Sep 5 11:24:01 2017 -0700
x86-64: Improve GOTPCREL relocation conversion
When GOTPCREL relocation conversion leads to relocation overflow, we
may get a mysterious linker message, like
relocation truncated to fit: R_X86_64_32S against symbol `foo'
This patch changes the linker message to
failed to convert GOTPCREL relocation; relink with --no-relax
bfd/
* elf64-x86-64.c (elf_x86_64_convert_load_reloc): Remove the sec
argument. Don't check relocation overflow. Avoid relocation
overflow if --no-relax is used. Set converted_reloc on symbol
if a GOTPCREL relocation is converted.
(elf_x86_64_relocate_section): Issue a fatal error and suggest
--no-relax if GOTPCREL relocation conversion leads to relocation
overflow.
* elfxx-x86.h (elf_x86_link_hash_entry): Add converted_reloc.
ld/
* testsuite/ld-x86-64/pr19609-4e.d: Updated.
* testsuite/ld-x86-64/pr19609-6a.d: Likewise.
Diff:
---
bfd/ChangeLog | 11 +++
bfd/elf64-x86-64.c | 132 +++++++-----------------------------
bfd/elfxx-x86.h | 5 ++
ld/ChangeLog | 5 ++
ld/testsuite/ld-x86-64/pr19609-4e.d | 4 +-
ld/testsuite/ld-x86-64/pr19609-6a.d | 2 +-
6 files changed, 49 insertions(+), 110 deletions(-)
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 1957ca9..551891d 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,14 @@
+2017-09-05 H.J. Lu <hongjiu.lu@intel.com>
+
+ * elf64-x86-64.c (elf_x86_64_convert_load_reloc): Remove the sec
+ argument. Don't check relocation overflow. Avoid relocation
+ overflow if --no-relax is used. Set converted_reloc on symbol
+ if a GOTPCREL relocation is converted.
+ (elf_x86_64_relocate_section): Issue a fatal error and suggest
+ --no-relax if GOTPCREL relocation conversion leads to relocation
+ overflow.
+ * elfxx-x86.h (elf_x86_link_hash_entry): Add converted_reloc.
+
2017-09-05 Alexander Fedotov <alexander.fedotov@nxp.com>
Edmar Wienskoski <edmar.wienskoski@nxp.com
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index fa295a5..ddbf133 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -1438,7 +1438,7 @@ elf_x86_64_need_pic (struct bfd_link_info *info,
instructions. */
static bfd_boolean
-elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
+elf_x86_64_convert_load_reloc (bfd *abfd,
bfd_byte *contents,
Elf_Internal_Rela *irel,
struct elf_link_hash_entry *h,
@@ -1447,17 +1447,15 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
{
struct elf_x86_link_hash_table *htab;
bfd_boolean is_pic;
- bfd_boolean require_reloc_pc32;
+ bfd_boolean no_overflow;
bfd_boolean relocx;
bfd_boolean to_reloc_pc32;
asection *tsec;
- char symtype;
bfd_signed_vma raddend;
unsigned int opcode;
unsigned int modrm;
unsigned int r_type = ELF32_R_TYPE (irel->r_info);
unsigned int r_symndx;
- bfd_vma toff;
bfd_vma roff = irel->r_offset;
if (roff < (r_type == R_X86_64_REX_GOTPCRELX ? 3 : 2))
@@ -1474,10 +1472,8 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
relocx = (r_type == R_X86_64_GOTPCRELX
|| r_type == R_X86_64_REX_GOTPCRELX);
- /* TRUE if we can convert only to R_X86_64_PC32. Enable it for
- --no-relax. */
- require_reloc_pc32
- = link_info->disable_target_specific_optimizations > 1;
+ /* TRUE if --no-relax is used. */
+ no_overflow = link_info->disable_target_specific_optimizations > 1;
r_symndx = htab->r_sym (irel->r_info);
@@ -1496,12 +1492,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
/* We convert only to R_X86_64_PC32:
1. Branch.
2. R_X86_64_GOTPCREL since we can't modify REX byte.
- 3. require_reloc_pc32 is true.
+ 3. no_overflow is true.
4. PIC.
*/
to_reloc_pc32 = (opcode == 0xff
|| !relocx
- || require_reloc_pc32
+ || no_overflow
|| is_pic);
/* Get the symbol referred to by the reloc. */
@@ -1514,8 +1510,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
if (isym->st_shndx == SHN_UNDEF)
return TRUE;
- symtype = ELF_ST_TYPE (isym->st_info);
-
if (isym->st_shndx == SHN_ABS)
tsec = bfd_abs_section_ptr;
else if (isym->st_shndx == SHN_COMMON)
@@ -1524,8 +1518,6 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
tsec = &_bfd_elf_large_com_section;
else
tsec = bfd_section_from_elf_index (abfd, isym->st_shndx);
-
- toff = isym->st_value;
}
else
{
@@ -1545,7 +1537,7 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
{
/* Skip for branch instructions since R_X86_64_PC32
may overflow. */
- if (require_reloc_pc32)
+ if (no_overflow)
return TRUE;
}
else if (relocx)
@@ -1586,13 +1578,11 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
&& h->root.u.def.section == bfd_und_section_ptr))))
{
/* Skip since R_X86_64_32/R_X86_64_32S may overflow. */
- if (require_reloc_pc32)
+ if (no_overflow)
return TRUE;
goto convert;
}
tsec = h->root.u.def.section;
- toff = h->root.u.def.value;
- symtype = h->type;
}
else
return TRUE;
@@ -1603,92 +1593,12 @@ elf_x86_64_convert_load_reloc (bfd *abfd, asection *sec,
&& (elf_section_flags (tsec) & SHF_X86_64_LARGE) != 0)
return TRUE;
- /* We can only estimate relocation overflow for R_X86_64_PC32. */
- if (!to_reloc_pc32)
- goto convert;
-
- if (tsec->sec_info_type == SEC_INFO_TYPE_MERGE)
- {
- /* At this stage in linking, no SEC_MERGE symbol has been
- adjusted, so all references to such symbols need to be
- passed through _bfd_merged_section_offset. (Later, in
- relocate_section, all SEC_MERGE symbols *except* for
- section symbols have been adjusted.)
-
- gas may reduce relocations against symbols in SEC_MERGE
- sections to a relocation against the section symbol when
- the original addend was zero. When the reloc is against
- a section symbol we should include the addend in the
- offset passed to _bfd_merged_section_offset, since the
- location of interest is the original symbol. On the
- other hand, an access to "sym+addend" where "sym" is not
- a section symbol should not include the addend; Such an
- access is presumed to be an offset from "sym"; The
- location of interest is just "sym". */
- if (symtype == STT_SECTION)
- toff += raddend;
-
- toff = _bfd_merged_section_offset (abfd, &tsec,
- elf_section_data (tsec)->sec_info,
- toff);
-
- if (symtype != STT_SECTION)
- toff += raddend;
- }
- else
- toff += raddend;
-
- /* Don't convert if R_X86_64_PC32 relocation overflows. */
- if (tsec->output_section == sec->output_section)
- {
- if ((toff - roff + 0x80000000) > 0xffffffff)
- return TRUE;
- }
- else
- {
- bfd_signed_vma distance;
-
- /* At this point, we don't know the load addresses of TSEC
- section nor SEC section. We estimate the distrance between
- SEC and TSEC. We store the estimated distances in the
- compressed_size field of the output section, which is only
- used to decompress the compressed input section. */
- if (sec->output_section->compressed_size == 0)
- {
- asection *asect;
- bfd_size_type size = 0;
- for (asect = link_info->output_bfd->sections;
- asect != NULL;
- asect = asect->next)
- /* Skip debug sections since compressed_size is used to
- compress debug sections. */
- if ((asect->flags & SEC_DEBUGGING) == 0)
- {
- asection *i;
- for (i = asect->map_head.s;
- i != NULL;
- i = i->map_head.s)
- {
- size = align_power (size, i->alignment_power);
- size += i->size;
- }
- asect->compressed_size = size;
- }
- }
-
- /* Don't convert GOTPCREL relocations if TSEC isn't placed
- after SEC. */
- distance = (tsec->output_section->compressed_size
- - sec->output_section->compressed_size);
- if (distance < 0)
- return TRUE;
+ /* Skip since R_X86_64_PC32/R_X86_64_32/R_X86_64_32S may overflow. */
+ if (no_overflow)
+ return TRUE;
- /* Take PT_GNU_RELRO segment into account by adding
- maxpagesize. */
- if ((toff + distance + get_elf_backend_data (abfd)->maxpagesize
- - roff + 0x80000000) > 0xffffffff)
- return TRUE;
- }
+ if (h != NULL)
+ ((struct elf_x86_link_hash_entry *) h)->converted_reloc = 1;
convert:
if (opcode == 0xff)
@@ -2467,7 +2377,7 @@ _bfd_x86_64_elf_convert_load (bfd *abfd, asection *sec,
continue;
converted = FALSE;
- if (!elf_x86_64_convert_load_reloc (abfd, sec, contents, irel, h,
+ if (!elf_x86_64_convert_load_reloc (abfd, contents, irel, h,
&converted, link_info))
goto error_return;
@@ -4099,9 +4009,17 @@ check_relocation_error:
}
if (r == bfd_reloc_overflow)
- (*info->callbacks->reloc_overflow)
- (info, (h ? &h->root : NULL), name, howto->name,
- (bfd_vma) 0, input_bfd, input_section, rel->r_offset);
+ {
+ if (eh != NULL && eh->converted_reloc)
+ {
+ info->callbacks->einfo
+ (_("%F%P: failed to convert GOTPCREL relocation; relink with --no-relax\n"));
+ return FALSE;
+ }
+ (*info->callbacks->reloc_overflow)
+ (info, (h ? &h->root : NULL), name, howto->name,
+ (bfd_vma) 0, input_bfd, input_section, rel->r_offset);
+ }
else
{
_bfd_error_handler
diff --git a/bfd/elfxx-x86.h b/bfd/elfxx-x86.h
index 9c0dcbbe..775e025 100644
--- a/bfd/elfxx-x86.h
+++ b/bfd/elfxx-x86.h
@@ -110,6 +110,11 @@ struct elf_x86_link_hash_entry
is only used by x86-64. */
unsigned int needs_copy : 1;
+ /* TRUE if a symbol with GOTPCREL relocations which have been converted
+ to R_X86_64_PC32, R_X86_64_32 or R_X86_64_32S. This is only used by
+ x86-64 for now. */
+ unsigned int converted_reloc : 1;
+
/* Reference count of C/C++ function pointer relocations in read-write
section which can be resolved at run-time. */
bfd_signed_vma func_pointer_refcount;
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 1fbec40..983c471 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,8 @@
+2017-09-05 H.J. Lu <hongjiu.lu@intel.com>
+
+ * testsuite/ld-x86-64/pr19609-4e.d: Updated.
+ * testsuite/ld-x86-64/pr19609-6a.d: Likewise.
+
2017-09-03 H.J. Lu <hongjiu.lu@intel.com>
PR ld/22071
diff --git a/ld/testsuite/ld-x86-64/pr19609-4e.d b/ld/testsuite/ld-x86-64/pr19609-4e.d
index 527fe5d..f263494 100644
--- a/ld/testsuite/ld-x86-64/pr19609-4e.d
+++ b/ld/testsuite/ld-x86-64/pr19609-4e.d
@@ -9,5 +9,5 @@
Disassembly of section .text:
0+70000000 <_start>:
-[ ]*[a-f0-9]+: 48 8d 05 f9 ff ff 2f lea 0x2ffffff9\(%rip\),%rax # a0000000 <foo>
-[ ]*[a-f0-9]+: 4c 8d 1d f2 ff ff 2f lea 0x2ffffff2\(%rip\),%r11 # a0000000 <foo>
+[ ]*[a-f0-9]+: 48 8b 05 ([0-9a-f]{2} ){4} * mov [-]?0x[a-f0-9]+\(%rip\),%rax # [a-f0-9]+ <.got>
+[ ]*[a-f0-9]+: 4c 8b 1d ([0-9a-f]{2} ){4} * mov [-]?0x[a-f0-9]+\(%rip\),%r11 # [a-f0-9]+ <.got>
diff --git a/ld/testsuite/ld-x86-64/pr19609-6a.d b/ld/testsuite/ld-x86-64/pr19609-6a.d
index 4802ffe..3c011d9 100644
--- a/ld/testsuite/ld-x86-64/pr19609-6a.d
+++ b/ld/testsuite/ld-x86-64/pr19609-6a.d
@@ -1,4 +1,4 @@
#source: pr19609-6.s
#as: --64 -mrelax-relocations=yes
#ld: -melf_x86_64 --defsym foobar=0x80000000
-#error: .*relocation truncated to fit: R_X86_64_32S .*
+#error: failed to convert GOTPCREL relocation; relink with --no-relax