[COMMITTED, V2 1/6] sframe.h: add support for .cfi_negate_ra_state

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

[No Changes in V2]

Use the last remaining bit in the 'SFrame FRE info' word to store whether
the RA is signed/unsigned with PAC authorization code: this bit is named
as the "mangled RA" bit.  This bit is still unused for x86-64.

The behaviour of the mangled-RA info bit in SFrame format closely
follows the behaviour of DW_CFA_AARCH64_negate_ra_state in DWARF.  During
unwinding, whenever an SFrame FRE with non-zero "mangled RA" bit is
encountered, it means the upper bits of the return address contain Pointer
Authentication code.  The unwinder, hence, must use appropriate means to
restore LR correctly in such cases.

include/ChangeLog:

	* sframe.h (SFRAME_V1_FRE_INFO_UPDATE_MANGLED_RA_P): New macro.
	(SFRAME_V1_FRE_MANGLED_RA_P): Likewise.
---
 include/sframe.h | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/include/sframe.h b/include/sframe.h
index 03a2d75dfd3..b2bd41a724e 100644
--- a/include/sframe.h
+++ b/include/sframe.h
@@ -227,11 +227,12 @@ typedef struct sframe_fre_info
      - 2 bits: information about size of the offsets (S) in bytes.
      Valid values are SFRAME_FRE_OFFSET_1B, SFRAME_FRE_OFFSET_2B,
      SFRAME_FRE_OFFSET_4B
-     - 1 bit: Unused.
-     -----------------------------------------------------------------------
-     |  Unused  |  Size of offsets   |   Number of offsets    |   base_reg |
-     -----------------------------------------------------------------------
-     8          7                    5                        1            0
+     - 1 bit: Mangled RA state bit (aarch64 only).
+     ----------------------------------------------------------------------------------
+     | Mangled-RA (aarch64) |  Size of offsets   |   Number of offsets    |   base_reg |
+     |  Unused (amd64)      |                    |                        |            |
+     ----------------------------------------------------------------------------------
+     8                     7                    5                        1            0
 
      */
   uint8_t fre_info;
@@ -239,13 +240,19 @@ typedef struct sframe_fre_info
 
 /* Macros to compose and decompose FRE info.  */
 
+/* Note: Set mangled_ra_p to zero by default.  */
 #define SFRAME_V1_FRE_INFO(base_reg_id, offset_num, offset_size) \
-  ((((offset_size) & 0x3) << 5) | (((offset_num) & 0xf) << 1) | \
-   ((base_reg_id) & 0x1))
+  (((0 & 0x1) << 7) | (((offset_size) & 0x3) << 5) | \
+   (((offset_num) & 0xf) << 1) | ((base_reg_id) & 0x1))
+
+/* Set the mangled_ra_p bit as indicated.  */
+#define SFRAME_V1_FRE_INFO_UPDATE_MANGLED_RA_P(mangled_ra_p, fre_info) \
+  ((((mangled_ra_p) & 0x1) << 7) | ((fre_info) & 0x7f))
 
 #define SFRAME_V1_FRE_CFA_BASE_REG_ID(data)	  ((data) & 0x1)
 #define SFRAME_V1_FRE_OFFSET_COUNT(data)	  (((data) >> 1) & 0xf)
-#define SFRAME_V1_FRE_OFFSET_SIZE(data)	  (((data) >> 5) & 0x3)
+#define SFRAME_V1_FRE_OFFSET_SIZE(data)		  (((data) >> 5) & 0x3)
+#define SFRAME_V1_FRE_MANGLED_RA_P(data)	  (((data) >> 7) & 0x1)
 
 /* SFrame Frame Row Entry definitions.
 
-- 
2.37.2