aarch64: make explicit that CFI gnu_window_save is for Sparc, not AArch64

- add a detailed comment when parsing DW_CFA_GNU_window_save in SFrame to
  explain why we are checking whether the targeted architecture is AArch64,
  whereas this CFI is a Sparc extension.
- replace .cfi_gnu_window_save by .cfi_negate_ra_state in existing AArch64
  DWARF tests as this is the preferred directive since GCC 15.
- add a new AArch64 test to check backward compatibility with old GCC
  versions that emits .cfi_gnu_window_save.

Approved-by: Indu Bhagat <indu.bhagat@oracle.com>
Approved-by: Richard Earnshaw <richard.earnshaw@arm.com>

4 files changed, 73 insertions, 3 deletions

diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
index 71296f2..960c22e 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -1273,7 +1273,13 @@ sframe_xlate_do_aarch64_negate_ra_state (struct sframe_xlate_ctx *xlate_ctx,
 }
 
 /* Translate DW_CFA_GNU_window_save into SFrame context.
-   DW_CFA_AARCH64_negate_ra_state is multiplexed with DW_CFA_GNU_window_save.
+   DW_CFA_GNU_window_save is a DWARF Sparc extension, but is multiplexed with a
+   directive of DWARF AArch64 extension: DW_CFA_AARCH64_negate_ra_state.
+   The AArch64 backend of GCC 14 and older versions was emitting mistakenly the
+   Sparc CFI directive (.cfi_window_save).  From GCC 15, the AArch64 backend
+   only emits .cfi_negate_ra_state.  For backward compatibility, the handler for
+   .cfi_window_save needs to check whether the directive was used in a AArch64
+   ABI context or not.
    Return SFRAME_XLATE_OK if success.  */
 
 static int
diff --git a/gas/testsuite/gas/aarch64/pac_ab_key.s b/gas/testsuite/gas/aarch64/pac_ab_key.s
index 4b328e7..3b81919 100644
--- a/gas/testsuite/gas/aarch64/pac_ab_key.s
+++ b/gas/testsuite/gas/aarch64/pac_ab_key.s
@@ -7,7 +7,7 @@ _Z5foo_av:
 .LFB0:
 	.cfi_startproc
 	hint	25 // paciasp
-	.cfi_window_save
+	.cfi_negate_ra_state
 	stp	x29, x30, [sp, -16]!
 	.cfi_def_cfa_offset 16
 	.cfi_offset 29, -16
@@ -23,7 +23,7 @@ _Z5foo_bv:
 	.cfi_startproc
 	.cfi_b_key_frame
 	hint	27 // pacibsp
-	.cfi_window_save
+	.cfi_negate_ra_state
 	stp	x29, x30, [sp, -16]!
 	.cfi_def_cfa_offset 16
 	.cfi_offset 29, -16
diff --git a/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.d b/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.d
new file mode 100644
index 0000000..8e59086
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.d
@@ -0,0 +1,44 @@
+#objdump: --dwarf=frames
+# This test is only valid on ELF based ports.
+#notarget: *-*-*coff *-*-pe *-*-wince *-*-*aout* *-*-netbsd
+
+## ARMv8.3 adds support for a new security feature named Pointer Authentication.
+## The main idea behind this is to use the unused bits in the pointer values.
+## Each pointer is patched with a PAC before writing to memory, and is verified
+## before using it.
+## When the pointers are mangled, the stack trace generator needs to know so it
+## can mask off the PAC from the pointer value to recover the return address,
+## and conversely, skip doing so if the pointers are not mangled.
+##
+## .cfi_negate_ra_state CFI directive is usually used to convey this information.
+## .cfi_negate_ra_state and .cfi_window_save are both in the processor-specific
+## numbering space, but use the same code value in the dwarf tables.
+## In GCC 14 and older, the Sparc DWARF extension .cfi_window_save is emitted
+## instead of .cfi_negate_ra_state, but it mapped to the same value. GCC 15 fixed
+## this naming issue and there is no change to the object file created when the
+## source is assembled. Nevertheless the support for the SPARC directive is
+## preserved in binutils for backward compatibility with existing GCC releases,
+## hence this test.
+
+.+:     file .+
+
+Contents of the .eh_frame section:
+
+0+ 0+10 0+ 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
+
+0+14 0+18 0+18 FDE cie=0+ pc=0+\.\.0+8
+  DW_CFA_advance_loc: 4 to 0+4
+  DW_CFA_AARCH64_negate_ra_state
+  DW_CFA_advance_loc: 4 to 0+8
+  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
diff --git a/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.s b/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.s
new file mode 100644
index 0000000..92a54f3
--- /dev/null
+++ b/gas/testsuite/gas/aarch64/pac_compat_cfi_window_save.s
@@ -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_window_save // really .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