[COMMITTED, V2 2/6] gas: sframe: add support for .cfi_negate_ra_state

[Indu Bhagat <indu.bhagat@oracle.com>]

[Changes in V2]
  - bugfix: set merge_candidate to false when processing
    DW_CFA_GNU_window_save.
  - Instead of removing common-empty-4.s test in a later commit, remove
    the testcase common-empty-4 here in this commit.
[End of changes in V2]

DW_CFA_AARCH64_negate_ra_state in aarch64 is multiplexed with
DW_CFA_GNU_window_save in the DWARF format.

Remove the common-empty-4 testcase because the generated SFrame section
will not be be empty anymore.  A relevant test will be added in a later
commit.

ChangeLog:

	* gas/gen-sframe.c (sframe_v1_set_fre_info): Add new argument
	for mangled_ra_p.
	(sframe_set_fre_info): Likewise.
	(output_sframe_row_entry): Handle mangled_ra_p.
	(sframe_row_entry_new): Reset mangled_ra_p.
	(sframe_row_entry_initialize): Initialize mangled_ra_p.
	(sframe_xlate_do_gnu_window_save): New definition.
	(sframe_do_cfi_insn): Handle DW_CFA_GNU_window_save.
	* gas/gen-sframe.h (struct sframe_row_entry): New member.
	(struct sframe_version_ops): Add a new argument for
	mangled_ra_p.
	* gas/testsuite/gas/cfi-sframe/cfi-sframe.exp: Remove test.
	* gas/testsuite/gas/cfi-sframe/common-empty-4.d: Removed.
	* gas/testsuite/gas/cfi-sframe/common-empty-4.s: Removed.
---
 gas/gen-sframe.c                              | 42 +++++++++++++++----
 gas/gen-sframe.h                              |  6 ++-
 gas/testsuite/gas/cfi-sframe/cfi-sframe.exp   |  1 -
 gas/testsuite/gas/cfi-sframe/common-empty-4.d | 14 -------
 gas/testsuite/gas/cfi-sframe/common-empty-4.s | 17 --------
 5 files changed, 39 insertions(+), 41 deletions(-)
 delete mode 100644 gas/testsuite/gas/cfi-sframe/common-empty-4.d
 delete mode 100644 gas/testsuite/gas/cfi-sframe/common-empty-4.s

diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
index 075720facd6..9baf20bd873 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -243,10 +243,11 @@ static struct sframe_version_ops sframe_ver_ops;
 
 static unsigned char
 sframe_v1_set_fre_info (unsigned int base_reg, unsigned int num_offsets,
-			unsigned int offset_size)
+			unsigned int offset_size, bool mangled_ra_p)
 {
   unsigned char fre_info;
   fre_info = SFRAME_V1_FRE_INFO (base_reg, num_offsets, offset_size);
+  fre_info = SFRAME_V1_FRE_INFO_UPDATE_MANGLED_RA_P (mangled_ra_p, fre_info);
   return fre_info;
 }
 
@@ -275,10 +276,10 @@ sframe_set_version (uint32_t sframe_version __attribute__((unused)))
 
 static unsigned char
 sframe_set_fre_info (unsigned int base_reg, unsigned int num_offsets,
-		     unsigned int offset_size)
+		     unsigned int offset_size, bool mangled_ra_p)
 {
   return sframe_ver_ops.set_fre_info (base_reg, num_offsets,
-					 offset_size);
+				      offset_size, mangled_ra_p);
 }
 
 /* SFrame set func info. */
@@ -507,7 +508,7 @@ output_sframe_row_entry (symbolS *fde_start_addr,
   fre_num_offsets = get_fre_num_offsets (sframe_fre);
   fre_offset_size = sframe_get_fre_offset_size (sframe_fre);
   fre_info = sframe_set_fre_info (fre_base_reg, fre_num_offsets,
-				     fre_offset_size);
+				  fre_offset_size, sframe_fre->mangled_ra_p);
   out_one (fre_info);
 
   idx = sframe_fre_offset_func_map_index (fre_offset_size);
@@ -845,6 +846,9 @@ sframe_row_entry_new (void)
      for the supported arches.  */
   fre->cfa_base_reg = -1;
   fre->merge_candidate = true;
+  /* Reset the mangled RA status bit to zero by default.  We will initialize it in
+     sframe_row_entry_initialize () with the sticky bit if set.  */
+  fre->mangled_ra_p = false;
 
   return fre;
 }
@@ -890,6 +894,9 @@ sframe_row_entry_initialize (struct sframe_row_entry *cur_fre,
   cur_fre->bp_offset = prev_fre->bp_offset;
   cur_fre->ra_loc = prev_fre->ra_loc;
   cur_fre->ra_offset = prev_fre->ra_offset;
+  /* Treat RA mangling as a sticky bit.  It retains its value until another
+     .cfi_negate_ra_state is seen.  */
+  cur_fre->mangled_ra_p = prev_fre->mangled_ra_p;
 }
 
 /* Translate DW_CFA_advance_loc into SFrame context.
@@ -1150,6 +1157,23 @@ sframe_xlate_do_restore (struct sframe_xlate_ctx *xlate_ctx,
   return SFRAME_XLATE_OK;
 }
 
+/* Translate DW_CFA_GNU_window_save into SFrame context.
+   Return SFRAME_XLATE_OK if success.  */
+
+static int
+sframe_xlate_do_gnu_window_save (struct sframe_xlate_ctx *xlate_ctx,
+				 struct cfi_insn_data *cfi_insn ATTRIBUTE_UNUSED)
+{
+  struct sframe_row_entry *cur_fre = xlate_ctx->cur_fre;
+
+  gas_assert (cur_fre);
+  /* Toggle the mangled RA status bit.  */
+  cur_fre->mangled_ra_p = !cur_fre->mangled_ra_p;
+  cur_fre->merge_candidate = false;
+
+  return SFRAME_XLATE_OK;
+}
+
 /* Process CFI_INSN and update the translation context with the FRE
    information.
 
@@ -1195,6 +1219,11 @@ sframe_do_cfi_insn (struct sframe_xlate_ctx *xlate_ctx,
     case DW_CFA_restore:
       err = sframe_xlate_do_restore (xlate_ctx, cfi_insn);
       break;
+    /* DW_CFA_AARCH64_negate_ra_state is multiplexed with
+       DW_CFA_GNU_window_save.  */
+    case DW_CFA_GNU_window_save:
+      err = sframe_xlate_do_gnu_window_save (xlate_ctx, cfi_insn);
+      break;
     case DW_CFA_undefined:
     case DW_CFA_same_value:
       break;
@@ -1207,10 +1236,7 @@ sframe_do_cfi_insn (struct sframe_xlate_ctx *xlate_ctx,
 	    - ...
 
 	   Following skipped operations do, however, impact the asynchronicity:
-	     - CFI_escape,
-	     - DW_CFA_GNU_window_save,
-	     - DW_CFA_AARCH64_negate_ra_state (multiplexed with
-	       DW_CFA_GNU_window_save)  */
+	     - CFI_escape  */
 
 	err = SFRAME_XLATE_ERR_NOTREPRESENTED;
 	// printf (_("SFrame Unsupported or unknown Dwarf CFI number: %#x\n"), op);
diff --git a/gas/gen-sframe.h b/gas/gen-sframe.h
index 93af499278c..5d5702a57ca 100644
--- a/gas/gen-sframe.h
+++ b/gas/gen-sframe.h
@@ -50,6 +50,9 @@ struct sframe_row_entry
      on it.  */
   bool merge_candidate;
 
+  /* Whether the return address is mangled with pauth code.  */
+  bool mangled_ra_p;
+
   /* Track CFA base (architectural) register ID.  */
   unsigned int cfa_base_reg;
   /* Offset from the CFA base register for recovering CFA.  */
@@ -140,7 +143,8 @@ struct sframe_version_ops
 {
   unsigned char format_version;    /* SFrame format version.  */
   /* set SFrame FRE info.  */
-  unsigned char (*set_fre_info) (unsigned int, unsigned int, unsigned int);
+  unsigned char (*set_fre_info) (unsigned int, unsigned int, unsigned int,
+				 bool);
   /* set SFrame Func info.  */
   unsigned char (*set_func_info) (unsigned int, unsigned int);
 };
diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
index eb6da614c2f..8129e86ccce 100644
--- a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
+++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
@@ -82,7 +82,6 @@ if  { ([istarget "x86_64-*-*"] || [istarget "aarch64*-*-*"]) \
     run_dump_test "common-empty-1"
     run_dump_test "common-empty-2"
     run_dump_test "common-empty-3"
-    run_dump_test "common-empty-4"
 }
 
 # x86-64 specific tests
diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-4.d b/gas/testsuite/gas/cfi-sframe/common-empty-4.d
deleted file mode 100644
index f7a6062d392..00000000000
--- a/gas/testsuite/gas/cfi-sframe/common-empty-4.d
+++ /dev/null
@@ -1,14 +0,0 @@
-#as: --gsframe
-#objdump: --sframe=.sframe
-#name: SFrame supports only default return column
-#...
-Contents of the SFrame section .sframe:
-
-  Header :
-
-    Version: SFRAME_VERSION_1
-    Flags: NONE
-    Num FDEs: 0
-    Num FREs: 0
-
-#pass
diff --git a/gas/testsuite/gas/cfi-sframe/common-empty-4.s b/gas/testsuite/gas/cfi-sframe/common-empty-4.s
deleted file mode 100644
index f97ca2f7ff9..00000000000
--- a/gas/testsuite/gas/cfi-sframe/common-empty-4.s
+++ /dev/null
@@ -1,17 +0,0 @@
-## ARMv8.3 addded support 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 unwinder 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 used to convey this information.
-##
-## SFrame does not have any means to represent this information at this time.
-	.cfi_startproc
-	.long 0
-	.cfi_def_cfa_offset 16
-	.cfi_negate_ra_state
-	.long 0
-	.cfi_endproc
-- 
2.37.2