From: Indu Bhagat <indu.bhagat@oracle.com>
Date: Thu, 24 Apr 2025 21:59:56 +0000 (-0700)
Subject: include: libsframe: define new flag SFRAME_F_FDE_FUNC_START_ADDR_PCREL
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4880e6281f0c83df6108316f3e066d6efd1aaebe;p=thirdparty%2Fbinutils-gdb.git

include: libsframe: define new flag SFRAME_F_FDE_FUNC_START_ADDR_PCREL

Add a new flag SFRAME_F_FDE_FUNC_START_ADDR_PCREL to SFrame stack trace
format.  If set, this flag indicates that the function start address
field (sfde_func_start_address) is the offset to the function start
address from the SFrame FDE function start address field itself.

Such an encoding is friendlier to the exisitng PC-REL relocations
available in the ABIs supported in SFrame: AMD64 (R_X86_64_PC32) and
AArch64 (R_AARCH64_PREL32).  In subsequent patches, we will make the
implementation in gas and ld to both:
  - emit the values in the same (above-mentioned) encoding uniformly.
  - set the flag SFRAME_F_FDE_FUNC_START_ADDR_PCREL in the SFrame header
    for consumers to be able to distinguish.

include/
        * sframe.h (SFRAME_F_FDE_FUNC_START_ADDR_PCREL): New definition.
libsframe/
	* sframe-dump.c (MAX_NUM_FLAGS, flags_helper): Update to include
	the new flag.
	* sframe.c (sframe_header_sanity_check_p): Use uint8_t.
---

diff --git a/include/sframe.h b/include/sframe.h
index a965e23bdd1..9f5d0e78e89 100644
--- a/include/sframe.h
+++ b/include/sframe.h
@@ -82,9 +82,15 @@ extern "C"
 /* Various flags for SFrame.  */
 
 /* Function Descriptor Entries are sorted on PC.  */
-#define SFRAME_F_FDE_SORTED	0x1
+#define SFRAME_F_FDE_SORTED		    0x1
 /* Functions preserve frame pointer.  */
-#define SFRAME_F_FRAME_POINTER 0x2
+#define SFRAME_F_FRAME_POINTER		    (0x1 << 1)
+/* Function start address in SFrame FDE is encoded as the distance from the
+   location of the sfde_func_start_address to the start PC of the function.
+   If absent, the function start address in SFrame FDE is encoded as the
+   distance from the start of the SFrame FDE section to the start PC of the
+   function.  */
+#define SFRAME_F_FDE_FUNC_START_ADDR_PCREL  (0x1 << 2)
 
 #define SFRAME_CFA_FIXED_FP_INVALID 0
 #define SFRAME_CFA_FIXED_RA_INVALID 0
diff --git a/libsframe/sframe-dump.c b/libsframe/sframe-dump.c
index d6f838d4fc0..200530ffeb9 100644
--- a/libsframe/sframe-dump.c
+++ b/libsframe/sframe-dump.c
@@ -61,10 +61,11 @@ dump_sframe_header_flags (sframe_decoder_ctx *sfd_ctx)
   /* PS: Keep SFRAME_FLAGS_STR_MAX_LEN in sync if adding more members to
      this array.  */
 #define SFRAME_FLAGS_STR_MAX_LEN 50
-#define MAX_NUM_FLAGS 2
+#define MAX_NUM_FLAGS 3
   const struct dump_flags_helper flags_helper[MAX_NUM_FLAGS] = {
       { SFRAME_F_FDE_SORTED, "SFRAME_F_FDE_SORTED"},
-      { SFRAME_F_FRAME_POINTER, "SFRAME_F_FRAME_POINTER"}
+      { SFRAME_F_FRAME_POINTER, "SFRAME_F_FRAME_POINTER"},
+      { SFRAME_F_FDE_FUNC_START_ADDR_PCREL, "SFRAME_F_FDE_FUNC_START_ADDR_PCREL"}
   };
 
   /* Prepare SFrame section flags string.  */
diff --git a/libsframe/sframe.c b/libsframe/sframe.c
index 8e9990058b6..4de4151d0b2 100644
--- a/libsframe/sframe.c
+++ b/libsframe/sframe.c
@@ -204,7 +204,8 @@ flip_fde (sframe_func_desc_entry *fdep)
 static bool
 sframe_header_sanity_check_p (sframe_header *hp)
 {
-  unsigned char all_flags = SFRAME_F_FDE_SORTED | SFRAME_F_FRAME_POINTER;
+  uint8_t all_flags = (SFRAME_F_FDE_SORTED | SFRAME_F_FRAME_POINTER
+		       | SFRAME_F_FDE_FUNC_START_ADDR_PCREL);
   /* Check preamble is valid.  */
   if (hp->sfh_preamble.sfp_magic != SFRAME_MAGIC
       || (hp->sfh_preamble.sfp_version != SFRAME_VERSION_1