[PATCH 2/3] arc: Add evaluation of long jump targets

[Anton Kolesov <Anton.Kolesov@synopsys.com>]

Standard get_longjmp_target implementation, similar to what is in arm-tdep.c.
Actual value of jb_pc should be set in init_osabi methods of particular OS/ABI
implementations.

gdb/ChangeLog:

	* arc-tdep.h (gdbarch_tdep): Add jb_pc.
	* arc-tdep.c (arc_get_longjmp_target): New function.
	(arc_gdbarch_init): Set get_longjmp_target if jb_pc is non-negative.
	(arc_dump_tdep): Print jb_pc.
---
 gdb/arc-tdep.c | 36 +++++++++++++++++++++++++++++++++++-
 gdb/arc-tdep.h |  3 +++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
index 58de8e9..bc8bb98 100644
--- a/gdb/arc-tdep.c
+++ b/gdb/arc-tdep.c
@@ -557,6 +557,34 @@ arc_store_return_value (struct gdbarch *gdbarch, struct type *type,
     error (_("arc_store_return_value: type length too large."));
 }
 
+/* Implement the "get_longjmp_target" gdbarch method.
+
+   Detemine the address the longjmp will jump to.  We need to use the frame
+   info to get the register pointing to the jmp_buf, then extract the PC from
+   that.  Since jmp_buf is the first argument to longjmp () it will be in r0.
+   Where we then go depends on the OS - OS/ABI initialization should set offset
+   from jmp_buf start to the stored PC location.  */
+
+static int
+arc_get_longjmp_target (struct frame_info *frame, CORE_ADDR *pc)
+{
+  if (arc_debug)
+    debug_printf ("arc: get_longjmp_target\n");
+
+  struct gdbarch *gdbarch = get_frame_arch (frame);
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+  int pc_offset = tdep->jb_pc * ARC_REGISTER_SIZE;
+  gdb_byte buf[ARC_REGISTER_SIZE];
+  CORE_ADDR jb_addr = get_frame_register_unsigned (frame, ARC_FIRST_ARG_REGNUM);
+
+  if (target_read_memory (jb_addr + pc_offset, buf, ARC_REGISTER_SIZE))
+    return 0; /* Failed to read from memory.  */
+
+  *pc = extract_unsigned_integer (buf, ARC_REGISTER_SIZE,
+				  gdbarch_byte_order (gdbarch));
+  return 1;
+}
+
 /* Implement the "return_value" gdbarch method.  */
 
 static enum return_value_convention
@@ -1162,6 +1190,7 @@ arc_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   /* Allocate the ARC-private target-dependent information structure, and the
      GDB target-independent information structure.  */
   struct gdbarch_tdep *tdep = XCNEW (struct gdbarch_tdep);
+  tdep->jb_pc = -1; /* No longjmp support by default.  */
   struct gdbarch *gdbarch = gdbarch_alloc (&info, tdep);
 
   /* Data types.  */
@@ -1246,6 +1275,9 @@ arc_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
      It can override functions set earlier.  */
   gdbarch_init_osabi (info, gdbarch);
 
+  if (tdep->jb_pc >= 0)
+    set_gdbarch_get_longjmp_target (gdbarch, arc_get_longjmp_target);
+
   tdesc_use_registers (gdbarch, tdesc, tdesc_data);
 
   return gdbarch;
@@ -1256,7 +1288,9 @@ arc_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 static void
 arc_dump_tdep (struct gdbarch *gdbarch, struct ui_file *file)
 {
-  /* Empty for now.  */
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  fprintf_unfiltered (file, "arc_dump_tdep: jb_pc = %i\n", tdep->jb_pc);
 }
 
 /* Suppress warning from -Wmissing-prototypes.  */
diff --git a/gdb/arc-tdep.h b/gdb/arc-tdep.h
index ea34b9e..1e792b9 100644
--- a/gdb/arc-tdep.h
+++ b/gdb/arc-tdep.h
@@ -81,6 +81,9 @@ extern int arc_debug;
 
 struct gdbarch_tdep
 {
+  /* Offset to PC value in jump buffer.  If this is negative, longjmp
+     support will be disabled.  */
+  int jb_pc;
 };
 
 /* Utility functions used by other ARC-specific modules.  */
-- 
2.8.1