[PATCH] x86-64: Convert load to mov only for GOTPCRELX relocations
H.J. Lu
hjl.tools@gmail.com
Sat Dec 5 03:00:36 GMT 2020
On Fri, Dec 4, 2020 at 6:57 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Since converting load to mov needs to rewrite the REX byte and we don't
> know if there is a REX byte with GOTPCREL relocation, do it only for
> GOTPCRELX relocations.
>
> bfd/
>
> PR ld/27016
> * elf64-x86-64.c (elf_x86_64_convert_load_reloc): Convert load
> to mov only for GOTPCRELX relocations.
>
> ld/
>
> PR ld/27016
> * testsuite/ld-x86-64/x86-64.exp: Run pr27016a and pr27016b.
> * testsuite/ld-x86-64/pr27016a.d: New file.
> * testsuite/ld-x86-64/pr27016a.s: Likewise.
> * testsuite/ld-x86-64/pr27016b.d: Likewise.
> * testsuite/ld-x86-64/pr27016b.s: Likewise.
> ---
> bfd/ChangeLog | 6 ++++++
> bfd/elf64-x86-64.c | 2 +-
> ld/ChangeLog | 9 +++++++++
> ld/testsuite/ld-x86-64/pr27016a.d | 23 +++++++++++++++++++++++
> ld/testsuite/ld-x86-64/pr27016a.s | 23 +++++++++++++++++++++++
> ld/testsuite/ld-x86-64/pr27016b.d | 23 +++++++++++++++++++++++
> ld/testsuite/ld-x86-64/pr27016b.s | 4 ++++
> ld/testsuite/ld-x86-64/x86-64.exp | 2 ++
> 8 files changed, 91 insertions(+), 1 deletion(-)
> create mode 100644 ld/testsuite/ld-x86-64/pr27016a.d
> create mode 100644 ld/testsuite/ld-x86-64/pr27016a.s
> create mode 100644 ld/testsuite/ld-x86-64/pr27016b.d
> create mode 100644 ld/testsuite/ld-x86-64/pr27016b.s
>
> diff --git a/bfd/ChangeLog b/bfd/ChangeLog
> index fa29df2267..2d1e4da18f 100644
> --- a/bfd/ChangeLog
> +++ b/bfd/ChangeLog
> @@ -1,3 +1,9 @@
> +2020-12-04 H.J. Lu <hongjiu.lu@intel.com>
> +
> + PR ld/27016
> + * elf64-x86-64.c (elf_x86_64_convert_load_reloc): Convert load
> + to mov only for GOTPCRELX relocations.
> +
> 2020-12-04 Alan Modra <amodra@gmail.com>
>
> PR 26978
> diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
> index 549a8be6a6..bb33967171 100644
> --- a/bfd/elf64-x86-64.c
> +++ b/bfd/elf64-x86-64.c
> @@ -1731,7 +1731,7 @@ elf_x86_64_convert_load_reloc (bfd *abfd,
>
> if (opcode == 0x8b)
> {
> - if (abs_symbol && local_ref)
> + if (abs_symbol && local_ref && relocx)
> to_reloc_pc32 = FALSE;
>
> if (to_reloc_pc32)
> diff --git a/ld/ChangeLog b/ld/ChangeLog
> index 0bbb576c56..f33bd41b01 100644
> --- a/ld/ChangeLog
> +++ b/ld/ChangeLog
> @@ -1,3 +1,12 @@
> +2020-12-04 H.J. Lu <hongjiu.lu@intel.com>
> +
> + PR ld/27016
> + * testsuite/ld-x86-64/x86-64.exp: Run pr27016a and pr27016b.
> + * testsuite/ld-x86-64/pr27016a.d: New file.
> + * testsuite/ld-x86-64/pr27016a.s: Likewise.
> + * testsuite/ld-x86-64/pr27016b.d: Likewise.
> + * testsuite/ld-x86-64/pr27016b.s: Likewise.
> +
> 2020-12-04 Alan Modra <amodra@gmail.com>
>
> * testsuite/ld-elf/pr26978a.d,
> diff --git a/ld/testsuite/ld-x86-64/pr27016a.d b/ld/testsuite/ld-x86-64/pr27016a.d
> new file mode 100644
> index 0000000000..88fba0a37f
> --- /dev/null
> +++ b/ld/testsuite/ld-x86-64/pr27016a.d
> @@ -0,0 +1,23 @@
> +#source: pr27016a.s
> +#source: pr27016b.s
> +#as: --64 -mx86-used-note=no -mrelax-relocations=no
> +#ld: -m elf_x86_64 -z max-page-size=0x200000 -z noseparate-code -e main
> +#objdump: -dw
> +
> +.*: +file format .*
> +
> +
> +Disassembly of section .text:
> +
> +0+4000e8 <main>:
> + +[a-f0-9]+: 55 push %rbp
> + +[a-f0-9]+: 48 89 e5 mov %rsp,%rbp
> + +[a-f0-9]+: 4c 8d 1d 39 3f 00 00 lea 0x3f39\(%rip\),%r11 # 40402c <thesym>
> + +[a-f0-9]+: 41 8b 03 mov \(%r11\),%eax
> + +[a-f0-9]+: 8d 50 01 lea 0x1\(%rax\),%edx
> + +[a-f0-9]+: 4c 8d 1d 2c 3f 00 00 lea 0x3f2c\(%rip\),%r11 # 40402c <thesym>
> + +[a-f0-9]+: 41 89 13 mov %edx,\(%r11\)
> + +[a-f0-9]+: b8 00 00 00 00 mov \$0x0,%eax
> + +[a-f0-9]+: 5d pop %rbp
> + +[a-f0-9]+: c3 ret
> +#pass
> diff --git a/ld/testsuite/ld-x86-64/pr27016a.s b/ld/testsuite/ld-x86-64/pr27016a.s
> new file mode 100644
> index 0000000000..b64851a5ff
> --- /dev/null
> +++ b/ld/testsuite/ld-x86-64/pr27016a.s
> @@ -0,0 +1,23 @@
> + .text
> + .comm global_int,4,4
> + .globl main
> + .type main, @function
> +main:
> + .cfi_startproc
> + pushq %rbp
> + .cfi_def_cfa_offset 16
> + .cfi_offset 6, -16
> + movq %rsp, %rbp
> + .cfi_def_cfa_register 6
> + movq thesym@GOTPCREL(%rip), %r11
> + movl (%r11), %eax
> + leal 1(%rax), %edx
> + movq thesym@GOTPCREL(%rip), %r11
> + movl %edx, (%r11)
> + movl $0, %eax
> + popq %rbp
> + .cfi_def_cfa 7, 8
> + ret
> + .cfi_endproc
> + .size main, .-main
> + .section .note.GNU-stack,"",@progbits
> diff --git a/ld/testsuite/ld-x86-64/pr27016b.d b/ld/testsuite/ld-x86-64/pr27016b.d
> new file mode 100644
> index 0000000000..b172736321
> --- /dev/null
> +++ b/ld/testsuite/ld-x86-64/pr27016b.d
> @@ -0,0 +1,23 @@
> +#source: pr27016a.s
> +#source: pr27016b.s
> +#as: --64 -mx86-used-note=no -mrelax-relocations=yes
> +#ld: -m elf_x86_64 -z max-page-size=0x200000 -z noseparate-code -e main
> +#objdump: -dw
> +
> +.*: +file format .*
> +
> +
> +Disassembly of section .text:
> +
> +0+4000e8 <main>:
> + +[a-f0-9]+: 55 push %rbp
> + +[a-f0-9]+: 48 89 e5 mov %rsp,%rbp
> + +[a-f0-9]+: 49 c7 c3 2c 40 40 00 mov \$0x40402c,%r11
> + +[a-f0-9]+: 41 8b 03 mov \(%r11\),%eax
> + +[a-f0-9]+: 8d 50 01 lea 0x1\(%rax\),%edx
> + +[a-f0-9]+: 49 c7 c3 2c 40 40 00 mov \$0x40402c,%r11
> + +[a-f0-9]+: 41 89 13 mov %edx,\(%r11\)
> + +[a-f0-9]+: b8 00 00 00 00 mov \$0x0,%eax
> + +[a-f0-9]+: 5d pop %rbp
> + +[a-f0-9]+: c3 ret
> +#pass
> diff --git a/ld/testsuite/ld-x86-64/pr27016b.s b/ld/testsuite/ld-x86-64/pr27016b.s
> new file mode 100644
> index 0000000000..ded8d7a826
> --- /dev/null
> +++ b/ld/testsuite/ld-x86-64/pr27016b.s
> @@ -0,0 +1,4 @@
> + .globl thesym
> +thesym = 0x40402c
> +
> + .section .note.GNU-stack,"",@progbits
> diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
> index 99c8a33c3e..41d385bf05 100644
> --- a/ld/testsuite/ld-x86-64/x86-64.exp
> +++ b/ld/testsuite/ld-x86-64/x86-64.exp
> @@ -661,6 +661,8 @@ run_dump_test "pr22048"
> run_dump_test "pr22929"
> run_dump_test "pr26939"
> run_dump_test "pr26939-x32"
> +run_dump_test "pr27016a"
> +run_dump_test "pr27016b"
>
> proc undefined_weak {cflags ldflags} {
> set testname "Undefined weak symbol"
> --
> 2.28.0
>
I am backporting it to 2.35 branch.
--
H.J.
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