[RFC] PPC: Skip call to __eabi in main()

[Kevin Buettner]

Some versions of gcc now generate a call to __eabi in main() for the
powerpc-eabi and powerpc-eabispe targets.  The patch below causes this
call to be skipped when placing a breakpoint at the first line of
main(), thus fixing quite a few failures when running the test suite.

I've tested this patch against powerpc-eabi and powerpc-eabispe
running on the simulator.

Comments?

	* rs6000-tdep.c (rs6000_skip_main_prologue): New function.
	(rs6000_gdb_arch_init): Register rs6000_skip_main_prologue.

Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/rs6000-tdep.c,v
retrieving revision 1.318
diff -u -p -r1.318 rs6000-tdep.c
--- rs6000-tdep.c	15 Jul 2008 18:32:06 -0000	1.318
+++ rs6000-tdep.c	21 Jul 2008 22:39:00 -0000
@@ -1769,6 +1769,32 @@ rs6000_skip_prologue (struct gdbarch *gd
   return pc;
 }
 
+/* Check that the code pointed to by PC corresponds to a call to
+   __eabi, skip it if so.  Return PC otherwise.  */
+
+CORE_ADDR
+rs6000_skip_main_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
+{
+  gdb_byte buf[4];
+  unsigned long op;
+
+  if (target_read_memory (pc, buf, 4))
+    return pc;
+  op = extract_unsigned_integer (buf, 4);
+
+  if ((op & 0xfc000001) == 0x48000001)
+    {
+      CORE_ADDR displ = op & 0x03fffffc;
+      CORE_ADDR call_dest = pc + 4 + displ;
+      struct minimal_symbol *s = lookup_minimal_symbol_by_pc (call_dest);
+
+      if (s != NULL
+          && SYMBOL_LINKAGE_NAME (s) != NULL
+	  && strcmp (SYMBOL_LINKAGE_NAME (s), "__eabi") == 0)
+	pc += 4;
+    }
+  return pc;
+}
 
 /* All the ABI's require 16 byte alignment.  */
 static CORE_ADDR
@@ -3238,6 +3264,7 @@ rs6000_gdbarch_init (struct gdbarch_info
 
   set_gdbarch_skip_prologue (gdbarch, rs6000_skip_prologue);
   set_gdbarch_in_function_epilogue_p (gdbarch, rs6000_in_function_epilogue_p);
+  set_gdbarch_skip_main_prologue (gdbarch, rs6000_skip_main_prologue);
 
   set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
   set_gdbarch_breakpoint_from_pc (gdbarch, rs6000_breakpoint_from_pc);