sframebt: Factor register access code into a header file

ChangeLog:

	* libsframe/sframe-backtrace-regs.h: New file.
	* libsframe/sframe-backtrace.c: Use the new abstractions.

2 files changed, 84 insertions, 14 deletions

diff --git a/libsframe/sframe-backtrace-regs.h b/libsframe/sframe-backtrace-regs.h
new file mode 100644
index 0000000..1932869
--- /dev/null
+++ b/libsframe/sframe-backtrace-regs.h
@@ -0,0 +1,77 @@
+/* The SFrame backtracer - accessing target registers.
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of libsframebt.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <stdint.h>
+#include <ucontext.h>
+
+#if defined (__x86_64__)
+
+static inline uint64_t
+get_context_pc (ucontext_t *cp)
+{
+  return cp->uc_mcontext.gregs[REG_RIP];
+}
+
+static inline uint64_t
+get_context_rsp (ucontext_t *cp)
+{
+  return cp->uc_mcontext.gregs[REG_RSP];
+}
+
+static inline uint64_t
+get_context_rfp (ucontext_t *cp)
+{
+  return cp->uc_mcontext.gregs[REG_RBP];
+}
+
+static inline uint64_t
+get_context_ra (ucontext_t *cp)
+{
+  return 0;	/* SFRAME_CFA_FIXED_RA_INVALID  */
+}
+
+#elif defined (__aarch64__)
+
+static inline uint64_t
+get_context_pc (ucontext_t *cp)
+{
+  return cp->uc_mcontext.pc;
+}
+
+static inline uint64_t
+get_context_rsp (ucontext_t *cp)
+{
+  return cp->uc_mcontext.sp;
+}
+
+static inline uint64_t
+get_context_rfp (ucontext_t *cp)
+{
+#define UNWIND_AARCH64_X29              29      /* 64-bit frame pointer.  */
+  return cp->uc_mcontext.regs[UNWIND_AARCH64_X29];
+}
+
+static inline uint64_t
+get_context_ra (ucontext_t *cp)
+{
+#define UNWIND_AARCH64_X30              30      /* 64-bit link pointer.  */
+  return cp->uc_mcontext.regs[UNWIND_AARCH64_X30];
+}
+
+#endif
diff --git a/libsframe/sframe-backtrace.c b/libsframe/sframe-backtrace.c
index 1280b00..65fa018 100644
--- a/libsframe/sframe-backtrace.c
+++ b/libsframe/sframe-backtrace.c
@@ -33,6 +33,7 @@
 #include "ansidecl.h"
 #include "sframe-api.h"
 #include "sframe-backtrace-api.h"
+#include "sframe-backtrace-regs.h"
 
 #ifndef PT_SFRAME
 #define PT_SFRAME 0x6474e554		/* FIXME.  */
@@ -41,7 +42,7 @@
 #define _sf_printflike_(string_index, first_to_check) ATTRIBUTE_PRINTF (1, 2)
 
 static bool _sframe_unwind_debug;	/* Control for printing out debug info.  */
-static int no_of_entries = NUM_OF_DSOS;
+static const int no_of_entries = NUM_OF_DSOS;
 
 /* SFrame decode data for the main module or a DSO.  */
 struct sframe_decode_data
@@ -460,7 +461,7 @@ sframe_unwind (struct sframe_unwind_info *sf, void **ra_lst,
   sframe_decoder_ctx *ctx;
   int cfa_offset, rfp_offset, errnum, i, count;
   sframe_frame_row_entry fred, *frep = &fred;
-  uint64_t pc, rfp, rsp, cfi_vma;
+  uint64_t pc, rfp, rsp, ra, cfi_vma;
   ucontext_t context, *cp = &context;
 
   if (sf == NULL || ra_lst == NULL || ra_size == NULL)
@@ -477,18 +478,10 @@ sframe_unwind (struct sframe_unwind_info *sf, void **ra_lst,
     }
   sframe_bt_set_errno (errp, SFRAME_BT_OK);
 
-#if defined (__x86_64__)
-  pc = cp->uc_mcontext.gregs[REG_RIP];
-  rsp = cp->uc_mcontext.gregs[REG_RSP];
-  rfp = cp->uc_mcontext.gregs[REG_RBP];
-#elif defined (__aarch64__)
-#define UNWIND_AARCH64_X29		29	/* 64-bit frame pointer.  */
-#define UNWIND_AARCH64_X30		30	/* 64-bit link pointer.  */
-  pc = cp->uc_mcontext.pc;
-  rsp = cp->uc_mcontext.sp;
-  rfp = cp->uc_mcontext.regs[UNWIND_AARCH64_X29];
-  uint64_t ra = cp->uc_mcontext.regs[UNWIND_AARCH64_X30];
-#endif
+  pc = get_context_pc (cp);
+  rsp = get_context_rsp (cp);
+  rfp = get_context_rfp (cp);
+  ra = get_context_ra (cp);
 
   /* Load and set up the decoder.  */
   ctx = sframe_load_ctx (sf, pc);