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[PATCH, x86_64] Remove R_X86_64_PC32_BND and R_X86_64_PLT32_BND
- From: "Zamyatin, Igor" <igor dot zamyatin at intel dot com>
- To: "binutils at sourceware dot org" <binutils at sourceware dot org>
- Cc: "hjl dot tools at gmail dot com" <hjl dot tools at gmail dot com>
- Date: Fri, 14 Nov 2014 14:34:06 +0000
- Subject: [PATCH, x86_64] Remove R_X86_64_PC32_BND and R_X86_64_PLT32_BND
- Authentication-results: sourceware.org; auth=none
Hi!
It is appeared that for Intel MPX R_X86_64_*_BND relocations are not enough in case of indirect calls like eg in the following example:
foo:
movq fp@GOTPCREL(%rip), %rax
bnd jmp *(%rax)
.globl fp
.section .data.rel,"aw",@progbits
.align 8
.type fp, @object
.size fp, 8
fp:
.quad memcpy
There will be no R_X86_64_*_BND relocation but anyway linker needs to
generate extended PLT entry for memcpy.
The given patch contains changes that create separate linker option (-z bndplt) which forces
linker to create extended PLT entry for any call (this option will be passed to linker when compilation is in MPX mode).
Thus we can omit R_X86_64_*_BND relocations completely. (They left in the code just for backward compatibility).
MPX ABI changed accordingly (https://github.com/hjl-tools/x86-64-psABI/tree/hjl/mpx/master).
Thanks,
Igor
Changelogs:
bfd/ChangeLog
2014-11-14 Igor Zamyatin <igor.zamyatin@intel.com>
* elf64-x86-64.c (elf_x86_64_check_relocs): MPX PLT is now supported
for R_X86_64_PC32, R_X86_64_PLT32, R_X86_64_32 and R_X86_64_64 when
bndplt option is specified.
include/ChangeLog
2014-11-14 Igor Zamyatin <igor.zamyatin@intel.com>
* bfdlink.h (struct bfd_link_info): New field bndplt.
ld/ChangeLog
2014-11-14 Igor Zamyatin <igor.zamyatin@intel.com>
* emulparams/elf_x86_64.sh: Set BNDPLT for x86_64.
* emultempl/elf32.em: Handle bndplt option and add description for it.
* ld.texinfo: Add description for bndplt.
* testsuite/ld-x86-64/bnd-ifunc-1.d: Add bndplt option.
* testsuite/ld-x86-64/bnd-ifunc-2.d: Ditto.
* testsuite/ld-x86-64/bnd-plt-1.d: Ditto. Update dissassembly
sections.
* testsuite/ld-x86-64/mpx.exp: Handle mpx3 and mpx4 tests.
* testsuite/ld-x86-64/mpx3.dd: New file.
* testsuite/ld-x86-64/mpx3a.s: New file.
* testsuite/ld-x86-64/mpx3b.s: New file.
* testsuite/ld-x86-64/mpx4.dd: New file.
* testsuite/ld-x86-64/mpx4a.s: New file.
* testsuite/ld-x86-64/mpx4b.s: New file.
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index f71291e..8944ad1 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -1629,11 +1629,16 @@ elf_x86_64_check_relocs (bfd *abfd, struct bfd_link_info *info,
case R_X86_64_PC32_BND:
case R_X86_64_PLT32_BND:
+ case R_X86_64_PC32:
+ case R_X86_64_PLT32:
+ case R_X86_64_32:
+ case R_X86_64_64:
/* MPX PLT is supported only if elf_x86_64_arch_bed
is used in 64-bit mode. */
if (ABI_64_P (abfd)
- && (get_elf_x86_64_backend_data (abfd)
- == &elf_x86_64_arch_bed))
+ && info->bndplt
+ && (get_elf_x86_64_backend_data (abfd)
+ == &elf_x86_64_arch_bed))
{
elf_x86_64_hash_entry (h)->has_bnd_reloc = TRUE;
@@ -1675,11 +1680,7 @@ elf_x86_64_check_relocs (bfd *abfd, struct bfd_link_info *info,
}
case R_X86_64_32S:
- case R_X86_64_32:
- case R_X86_64_64:
- case R_X86_64_PC32:
case R_X86_64_PC64:
- case R_X86_64_PLT32:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCREL64:
if (htab->elf.dynobj == NULL)
diff --git a/include/bfdlink.h b/include/bfdlink.h
index fc14a9f..dc400a3 100644
--- a/include/bfdlink.h
+++ b/include/bfdlink.h
@@ -414,6 +414,9 @@ struct bfd_link_info
/* TRUE if the linker script contained an explicit PHDRS command. */
unsigned int user_phdrs: 1;
+ /* TRUE if BND prefix in PLT entries is always generated. */
+ unsigned int bndplt: 1;
+
/* Char that may appear as the first char of a symbol, but should be
skipped (like symbol_leading_char) when looking up symbols in
wrap_hash. Used by PowerPC Linux for 'dot' symbols. */
diff --git a/ld/emulparams/elf_x86_64.sh b/ld/emulparams/elf_x86_64.sh
index d8cb6bf..1e83a74 100644
--- a/ld/emulparams/elf_x86_64.sh
+++ b/ld/emulparams/elf_x86_64.sh
@@ -31,7 +31,10 @@ fi
case "$target" in
x86_64*-linux*|i[3-7]86-*-linux-*)
case "$EMULATION_NAME" in
- *64*) LIBPATH_SUFFIX=64 ;;
+ *64*)
+ LIBPATH_SUFFIX=64
+ BNDPLT=yes
+ ;;
esac
;;
*-*-solaris2*)
diff --git a/ld/emultempl/elf32.em b/ld/emultempl/elf32.em
index 39b4ccd..de5c5fb 100644
--- a/ld/emultempl/elf32.em
+++ b/ld/emultempl/elf32.em
@@ -2274,6 +2274,14 @@ fragment <<EOF
link_info.execstack = FALSE;
}
EOF
+
+if test x"$BNDPLT" = xyes; then
+fragment <<EOF
+ else if (strcmp (optarg, "bndplt") == 0)
+ link_info.bndplt = TRUE;
+EOF
+fi
+
if test x"$GENERATE_SHLIB_SCRIPT" = xyes; then
fragment <<EOF
else if (strcmp (optarg, "global") == 0)
@@ -2453,6 +2461,13 @@ fragment <<EOF
EOF
fi
+if test x"$BNDPLT" = xyes; then
+fragment <<EOF
+ fprintf (file, _("\
+ -z bndplt Always generate BND prefix in PLT entries\n"));
+EOF
+fi
+
if test -n "$PARSE_AND_LIST_OPTIONS" ; then
fragment <<EOF
$PARSE_AND_LIST_OPTIONS
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index 5762dc6..eaa925d 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -1104,6 +1104,10 @@ Specify a stack size for in an ELF @code{PT_GNU_STACK} segment.
Specifying zero will override any default non-zero sized
@code{PT_GNU_STACK} segment creation.
+@item bndplt
+Always generate BND prefix in PLT entries.
+Enabled for Linux/x86_64.
+
@end table
Other keywords are ignored for Solaris compatibility.
diff --git a/ld/testsuite/ld-x86-64/bnd-ifunc-1.d b/ld/testsuite/ld-x86-64/bnd-ifunc-1.d
index cdcb4f6..11313ab 100644
--- a/ld/testsuite/ld-x86-64/bnd-ifunc-1.d
+++ b/ld/testsuite/ld-x86-64/bnd-ifunc-1.d
@@ -1,5 +1,5 @@
#as: --64 -madd-bnd-prefix
-#ld: -shared -melf_x86_64
+#ld: -shared -melf_x86_64 -z bndplt
#objdump: -dw
#...
diff --git a/ld/testsuite/ld-x86-64/bnd-ifunc-2.d b/ld/testsuite/ld-x86-64/bnd-ifunc-2.d
index 43e3356..6be8290 100644
--- a/ld/testsuite/ld-x86-64/bnd-ifunc-2.d
+++ b/ld/testsuite/ld-x86-64/bnd-ifunc-2.d
@@ -1,5 +1,5 @@
#as: --64 -madd-bnd-prefix
-#ld: -shared -melf_x86_64
+#ld: -shared -melf_x86_64 -z bndplt
#objdump: -dw
#...
diff --git a/ld/testsuite/ld-x86-64/bnd-plt-1.d b/ld/testsuite/ld-x86-64/bnd-plt-1.d
index 3cfe9e6..d76a7a7 100644
--- a/ld/testsuite/ld-x86-64/bnd-plt-1.d
+++ b/ld/testsuite/ld-x86-64/bnd-plt-1.d
@@ -1,6 +1,6 @@
#source: bnd-branch-1.s
#as: --64
-#ld: -shared -melf_x86_64
+#ld: -shared -melf_x86_64 -z bndplt
#objdump: -dw
.*: +file format .*
@@ -13,8 +13,8 @@ Disassembly of section .plt:
[ ]*[a-f0-9]+: f2 ff 25 83 01 20 00 bnd jmpq \*0x200183\(%rip\) # 200440 <_GLOBAL_OFFSET_TABLE_\+0x10>
[ ]*[a-f0-9]+: 0f 1f 00 nopl \(%rax\)
[ ]*[a-f0-9]+: 68 00 00 00 00 pushq \$0x0
-[ ]*[a-f0-9]+: e9 e6 ff ff ff jmpq 2b0 <foo2@plt-0x50>
-[ ]*[a-f0-9]+: 66 0f 1f 44 00 00 nopw 0x0\(%rax,%rax,1\)
+[ ]*[a-f0-9]+: f2 e9 e5 ff ff ff bnd jmpq 2b0 <foo2@plt-0x50>
+[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
[ ]*[a-f0-9]+: 68 01 00 00 00 pushq \$0x1
[ ]*[a-f0-9]+: f2 e9 d5 ff ff ff bnd jmpq 2b0 <foo2@plt-0x50>
[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
@@ -22,14 +22,14 @@ Disassembly of section .plt:
[ ]*[a-f0-9]+: f2 e9 c5 ff ff ff bnd jmpq 2b0 <foo2@plt-0x50>
[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
[ ]*[a-f0-9]+: 68 03 00 00 00 pushq \$0x3
-[ ]*[a-f0-9]+: e9 b6 ff ff ff jmpq 2b0 <foo2@plt-0x50>
-[ ]*[a-f0-9]+: 66 0f 1f 44 00 00 nopw 0x0\(%rax,%rax,1\)
+[ ]*[a-f0-9]+: f2 e9 b5 ff ff ff bnd jmpq 2b0 <foo2@plt-0x50>
+[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
Disassembly of section .plt.bnd:
0+300 <foo2@plt>:
-[ ]*[a-f0-9]+: ff 25 42 01 20 00 jmpq \*0x200142\(%rip\) # 200448 <_GLOBAL_OFFSET_TABLE_\+0x18>
-[ ]*[a-f0-9]+: 66 90 xchg %ax,%ax
+[ ]*[a-f0-9]+: f2 ff 25 41 01 20 00 bnd jmpq \*0x200141\(%rip\) # 200448 <_GLOBAL_OFFSET_TABLE_\+0x18>
+[ ]*[a-f0-9]+: 90 nop
0+308 <foo3@plt>:
[ ]*[a-f0-9]+: f2 ff 25 41 01 20 00 bnd jmpq \*0x200141\(%rip\) # 200450 <_GLOBAL_OFFSET_TABLE_\+0x20>
@@ -40,8 +40,8 @@ Disassembly of section .plt.bnd:
[ ]*[a-f0-9]+: 90 nop
0+318 <foo4@plt>:
-[ ]*[a-f0-9]+: ff 25 42 01 20 00 jmpq \*0x200142\(%rip\) # 200460 <_GLOBAL_OFFSET_TABLE_\+0x30>
-[ ]*[a-f0-9]+: 66 90 xchg %ax,%ax
+[ ]*[a-f0-9]+: f2 ff 25 41 01 20 00 bnd jmpq \*0x200141\(%rip\) # 200460 <_GLOBAL_OFFSET_TABLE_\+0x30>
+[ ]*[a-f0-9]+: 90 nop
Disassembly of section .text:
diff --git a/ld/testsuite/ld-x86-64/mpx.exp b/ld/testsuite/ld-x86-64/mpx.exp
index f2a50d4..a4e3254 100644
--- a/ld/testsuite/ld-x86-64/mpx.exp
+++ b/ld/testsuite/ld-x86-64/mpx.exp
@@ -59,6 +59,21 @@ set build_tests {
run_cc_link_tests $build_tests
+run_ld_link_tests {
+ {"Build libcall.so"
+ "-shared -z bndplt" "" ""
+ {mpx3b.s} {} "libcall.so"}
+ {"Build mpx3"
+ "tmpdir/libcall.so -z bndplt" "" ""
+ {mpx3a.s} {{objdump -dw mpx3.dd}} "mpx3"}
+ {"Build libcall1.so"
+ "-shared -z bndplt" "" ""
+ {mpx4b.s} {} "libcall1.so"}
+ {"Build mpx4"
+ "tmpdir/libcall1.so -z bndplt" "" ""
+ {mpx4a.s} {{objdump -dw mpx4.dd}} "mpx4"}
+}
+
set run_tests {
{"Run mpx1"
"tmpdir/mpx1a.o tmpdir/mpx1b.o tmpdir/mpx1c.o" ""
diff --git a/ld/testsuite/ld-x86-64/mpx3.dd b/ld/testsuite/ld-x86-64/mpx3.dd
new file mode 100644
index 0000000..2a8356d
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx3.dd
@@ -0,0 +1,35 @@
+.*: +file format .*
+
+
+Disassembly of section .plt:
+
+0+400290 <.plt>:
+[ ]*[a-f0-9]+: ff 35 6a 01 20 00 pushq 0x20016a\(%rip\) # 600400 <_GLOBAL_OFFSET_TABLE_\+0x8>
+[ ]*[a-f0-9]+: f2 ff 25 6b 01 20 00 bnd jmpq \*0x20016b\(%rip\) # 600408 <_GLOBAL_OFFSET_TABLE_\+0x10>
+[ ]*[a-f0-9]+: 0f 1f 00 nopl \(%rax\)
+[ ]*[a-f0-9]+: 68 00 00 00 00 pushq \$0x0
+[ ]*[a-f0-9]+: f2 e9 e5 ff ff ff bnd jmpq 400290 <call1@plt-0x30>
+[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
+[ ]*[a-f0-9]+: 68 01 00 00 00 pushq \$0x1
+[ ]*[a-f0-9]+: f2 e9 d5 ff ff ff bnd jmpq 400290 <call1@plt-0x30>
+[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
+
+Disassembly of section .plt.bnd:
+
+0+4002c0 <call1@plt>:
+[ ]*[a-f0-9]+: f2 ff 25 49 01 20 00 bnd jmpq \*0x200149\(%rip\) # 600410 <_GLOBAL_OFFSET_TABLE_\+0x18>
+[ ]*[a-f0-9]+: 90 nop
+
+0+4002c8 <call2@plt>:
+[ ]*[a-f0-9]+: f2 ff 25 49 01 20 00 bnd jmpq \*0x200149\(%rip\) # 600418 <_GLOBAL_OFFSET_TABLE_\+0x20>
+[ ]*[a-f0-9]+: 90 nop
+
+Disassembly of section .text:
+
+0+4002d0 <_start>:
+[ ]*[a-f0-9]+: bf c0 02 40 00 mov \$0x4002c0,%edi
+[ ]*[a-f0-9]+: f2 ff d7 bnd callq \*%rdi
+[ ]*[a-f0-9]+: 48 8b 3d 41 01 20 00 mov 0x200141\(%rip\),%rdi # 600420 <func>
+[ ]*[a-f0-9]+: f2 ff d7 bnd callq \*%rdi
+[ ]*[a-f0-9]+: c3 retq
+#pass
diff --git a/ld/testsuite/ld-x86-64/mpx3a.s b/ld/testsuite/ld-x86-64/mpx3a.s
new file mode 100644
index 0000000..dbb1361
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx3a.s
@@ -0,0 +1,17 @@
+ .text
+ .globl _start
+ .type _start, @function
+_start:
+ movl $call1, %edi
+ bnd call *%rdi
+ movq func(%rip), %rdi
+ bnd call *%rdi
+ ret
+ .size _start, .-_start
+ .globl func
+ .data
+ .type func, @object
+ .size func, 8
+func:
+ .quad call2
+
diff --git a/ld/testsuite/ld-x86-64/mpx3b.s b/ld/testsuite/ld-x86-64/mpx3b.s
new file mode 100644
index 0000000..171f1dd
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx3b.s
@@ -0,0 +1,12 @@
+ .text
+ .globl call1
+ .type call1, @function
+call1:
+ ret
+ .size call1, .-call1
+ .globl call2
+ .type call2, @function
+call2:
+ ret
+ .size call2, .-call2
+
diff --git a/ld/testsuite/ld-x86-64/mpx4.dd b/ld/testsuite/ld-x86-64/mpx4.dd
new file mode 100644
index 0000000..0cf0f75
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx4.dd
@@ -0,0 +1,24 @@
+.*: +file format .*
+
+
+Disassembly of section .plt:
+
+0+400260 <.plt>:
+[ ]*[a-f0-9]+: ff 35 42 01 20 00 pushq 0x200142\(%rip\) # 6003a8 <_GLOBAL_OFFSET_TABLE_\+0x8>
+[ ]*[a-f0-9]+: f2 ff 25 43 01 20 00 bnd jmpq \*0x200143\(%rip\) # 6003b0 <_GLOBAL_OFFSET_TABLE_\+0x10>
+[ ]*[a-f0-9]+: 0f 1f 00 nopl \(%rax\)
+[ ]*[a-f0-9]+: 68 00 00 00 00 pushq \$0x0
+[ ]*[a-f0-9]+: f2 e9 e5 ff ff ff bnd jmpq 400260 <call1@plt-0x20>
+[ ]*[a-f0-9]+: 0f 1f 44 00 00 nopl 0x0\(%rax,%rax,1\)
+
+Disassembly of section .plt.bnd:
+
+0+400280 <call1@plt>:
+[ ]*[a-f0-9]+: f2 ff 25 31 01 20 00 bnd jmpq \*0x200131\(%rip\) # 6003b8 <_GLOBAL_OFFSET_TABLE_\+0x18>
+[ ]*[a-f0-9]+: 90 nop
+
+Disassembly of section .text:
+
+0+400288 <_start>:
+[ ]*[a-f0-9]+: bf 80 02 40 00 mov \$0x400280,%edi
+[ ]*[a-f0-9]+: f2 ff d7 bnd callq \*%rdi
diff --git a/ld/testsuite/ld-x86-64/mpx4a.s b/ld/testsuite/ld-x86-64/mpx4a.s
new file mode 100644
index 0000000..56f0fab
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx4a.s
@@ -0,0 +1,7 @@
+.text
+ .globl _start
+ .type _start, @function
+_start:
+ movl $call1, %edi
+ bnd call *%rdi
+
diff --git a/ld/testsuite/ld-x86-64/mpx4b.s b/ld/testsuite/ld-x86-64/mpx4b.s
new file mode 100644
index 0000000..a456de0
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/mpx4b.s
@@ -0,0 +1,6 @@
+.text
+ .globl call1
+ .type call1, @function
+call1:
+ ret
+