[gas] arm: Add support for new unwinder directive ".pacspval".

This patch adds the assembler support for the new unwinder
directive ".pacspval" and encodes this directives with opcode
"0xb5". This opcode indicates the unwinder to use effective
vsp as modifier for PAC validation.

gas/ChangeLog:

2022-11-07  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

        * doc/c-arm.texi: Document directive.
        * config/tc-arm.c (s_arm_unwind_pacspval): Define function.
        (md_pseudo_table): Add entry for pacspval directive.
        * testsuite/gas/arm/ehabi-pacbti-m.d: New test.
        * testsuite/gas/arm/ehabi-pacbti-m.s: Likewise.

4 files changed, 76 insertions, 0 deletions

diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index 8864286..8f0e8b0 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -4929,6 +4929,22 @@ s_arm_unwind_pad (int ignored ATTRIBUTE_UNUSED)
   demand_empty_rest_of_line ();
 }
 
+/* Parse an unwind_pacspval directive.  */
+
+static void
+s_arm_unwind_pacspval (int ignored ATTRIBUTE_UNUSED)
+{
+  valueT op;
+
+  if (!unwind.proc_start)
+    as_bad (MISSING_FNSTART);
+
+  demand_empty_rest_of_line ();
+
+  op = 0xb5;
+  add_unwind_opcode (op, 1);
+}
+
 /* Parse an unwind_setfp directive.  */
 
 static void
@@ -5205,6 +5221,7 @@ const pseudo_typeS md_pseudo_table[] =
   { "vsave",		s_arm_unwind_save,	1 },
   { "movsp",		s_arm_unwind_movsp,	0 },
   { "pad",		s_arm_unwind_pad,	0 },
+  { "pacspval",		s_arm_unwind_pacspval,	0 },
   { "setfp",		s_arm_unwind_setfp,	0 },
   { "unwind_raw",	s_arm_unwind_raw,	0 },
   { "eabi_attribute",	s_arm_eabi_attribute,	0 },
diff --git a/gas/doc/c-arm.texi b/gas/doc/c-arm.texi
index 0605d32..0f43272 100644
--- a/gas/doc/c-arm.texi
+++ b/gas/doc/c-arm.texi
@@ -1086,6 +1086,12 @@ This directive writes 12-byte packed floating-point values to the
 output section.  These are not compatible with current ARM processors
 or ABIs.
 
+@anchor{arm_pacspval}
+@cindex @code{.pacspval} directive, ARM
+@item .pacspval
+Generate unwinder annotations to use effective vsp as modifier in PAC
+validation.
+
 @anchor{arm_pad}
 @cindex @code{.pad} directive, ARM
 @item .pad #@var{count}
diff --git a/gas/testsuite/gas/arm/ehabi-pacbti-m.d b/gas/testsuite/gas/arm/ehabi-pacbti-m.d
new file mode 100644
index 0000000..6039945
--- /dev/null
+++ b/gas/testsuite/gas/arm/ehabi-pacbti-m.d
@@ -0,0 +1,15 @@
+# name: Unwind Stack Frame information for Armv8.1-M.Mainline PAC extension
+# source: ehabi-pacbti-m.s
+# as: -march=armv8.1-m.main+mve+pacbti
+# readelf: -u
+
+Unwind section '.ARM.exidx' at offset 0x5c contains 1 entry:
+
+0x0: @0x0
+  Compact model index: 1
+  0xb1 0x08 pop {r3}
+  0x80 0x08 pop {r7}
+  0xb4      pop {ra_auth_code}
+  0x84 0x00 pop {r14}
+  0xb1 0x0f pop {r0, r1, r2, r3}
+  0xb5      vsp as modifier for PAC validation
diff --git a/gas/testsuite/gas/arm/ehabi-pacbti-m.s b/gas/testsuite/gas/arm/ehabi-pacbti-m.s
new file mode 100644
index 0000000..1018548
--- /dev/null
+++ b/gas/testsuite/gas/arm/ehabi-pacbti-m.s
@@ -0,0 +1,38 @@
+        .syntax unified
+        .thumb
+        .thumb_func
+	.fnstart
+	.cfi_startproc
+	.pacspval
+	pac	ip, lr, sp
+	.cfi_register 143, 12
+	push	{r0, r1, r2, r3}
+	.save {r0, r1, r2, r3}
+	.cfi_def_cfa_offset 16
+	.cfi_offset 0, -16
+	.cfi_offset 1, -12
+	.cfi_offset 2, -8
+	.cfi_offset 3, -4
+	push	{r3, r7, ip, lr}
+	.save {r3, r7, ra_auth_code, lr}
+	.cfi_def_cfa_offset 32
+	.cfi_offset 3, -32
+	.cfi_offset 7, -28
+	.cfi_offset 143, -24
+	.cfi_offset 14, -20
+	pop	{r3, r7, ip, lr}
+	.cfi_restore 14
+	.cfi_restore 143
+	.cfi_restore 7
+	.cfi_restore 3
+	.cfi_def_cfa_offset 0
+	add	sp, sp, #16
+	.cfi_restore 3
+	.cfi_restore 2
+	.cfi_restore 1
+	.cfi_restore 0
+	.cfi_def_cfa_offset -16
+	aut	ip, lr, sp
+	bx	lr
+	.cfi_endproc
+	.fnend