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[gas] Implement .cfi_negate_ra_state directive

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This patch implements the .cfi_negate_ra_state to be consistent with
LLVM (https://reviews.llvm.org/D50136). The relevant DWARF code DW_CFA_AARCH64_negate_ra_state
is multiplexed on top of DW_CFA_GNU_window_save, as per
https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00753.html

I believe this is the simplest patch implementing this and is needed to
allow users to build, for example, the Linux kernel with Armv8.3-A
pointer authentication support with Clang while using gas as the
assembler, which is a common usecase.

gas/
2019-12-06  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

    * dw2gencfi.c (cfi_pseudo_table): Add cfi_negate_ra_state.
    * testsuite/gas/aarch64/pac_negate_ra_state.s: New file.
    * testsuite/gas/aarch64/pac_negate_ra_state.d: Likewise.
This commit is contained in:
Kyrylo Tkachov 2019-12-06 10:46:32 +00:00
parent e6b39f6f8e
commit e8dc9b5bfd
4 changed files with 53 additions and 0 deletions
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6
gas/ChangeLog
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@ -1,3 +1,9 @@
2019-12-06 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* dw2gencfi.c (cfi_pseudo_table): Add cfi_negate_ra_state.
* testsuite/gas/aarch64/pac_negate_ra_state.s: New file.
* testsuite/gas/aarch64/pac_negate_ra_state.d: Likewise.
2019-12-05 Jan Beulich <jbeulich@suse.com>
* config/tc-aarch64.c (aarch64_features): Drop redundant AES and

1
gas/dw2gencfi.c
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@ -726,6 +726,7 @@ const pseudo_typeS cfi_pseudo_table[] =
{ "cfi_remember_state", dot_cfi, DW_CFA_remember_state },
{ "cfi_restore_state", dot_cfi, DW_CFA_restore_state },
{ "cfi_window_save", dot_cfi, DW_CFA_GNU_window_save },
{ "cfi_negate_ra_state", dot_cfi, DW_CFA_AARCH64_negate_ra_state },
{ "cfi_escape", dot_cfi_escape, 0 },
{ "cfi_signal_frame", dot_cfi, CFI_signal_frame },
{ "cfi_personality", dot_cfi_personality, 0 },

26
gas/testsuite/gas/aarch64/pac_negate_ra_state.d Normal file
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@ -0,0 +1,26 @@
#objdump: --dwarf=frames
.+: file .+
Contents of the .eh_frame section:
00000000 0000000000000010 00000000 CIE
Version: 1
Augmentation: "zR"
Code alignment factor: 4
Data alignment factor: -8
Return address column: 30
Augmentation data: 1b
DW_CFA_def_cfa: r31 \(sp\) ofs 0
00000014 0000000000000018 00000018 FDE cie=00000000 pc=0000000000000000..0000000000000008
DW_CFA_advance_loc: 4 to 0000000000000004
DW_CFA_GNU_window_save
DW_CFA_advance_loc: 4 to 0000000000000008
DW_CFA_def_cfa_offset: 16
DW_CFA_offset: r29 \(x29\) at cfa-16
DW_CFA_offset: r30 \(x30\) at cfa-8
DW_CFA_nop
DW_CFA_nop

20
gas/testsuite/gas/aarch64/pac_negate_ra_state.s Normal file
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@ -0,0 +1,20 @@
.arch armv8-a
.text
.align 2
.global _Z5foo_av
.type _Z5foo_av, %function
_Z5foo_av:
.LFB0:
.cfi_startproc
hint 25 // paciasp
.cfi_negate_ra_state
stp x29, x30, [sp, -16]!
.cfi_def_cfa_offset 16
.cfi_offset 29, -16
.cfi_offset 30, -8
.cfi_endproc
.LFE0:
.size _Z5foo_av, .-_Z5foo_av
.align 2
.global _Z5foo_bv
.type _Z5foo_bv, %function