2001-05-10 Elena Zannoni <ezannoni@redhat.com>

[deliverable/binutils-gdb.git] / gdb / rs6000-tdep.c

diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 6ad71ef368c447ba8108aa5473d1017a09fc2574..3c0a7b9ad5aef076acfe7950116d9e9996abbca7 100644 (file)
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -299,7 +299,8 @@ rs6000_breakpoint_from_pc (CORE_ADDR *bp_addr, int *bp_size)
 /* AIX does not support PT_STEP. Simulate it. */
 
 void
-rs6000_software_single_step (unsigned int signal, int insert_breakpoints_p)
+rs6000_software_single_step (enum target_signal signal,
+                            int insert_breakpoints_p)
 {
 #define        INSNLEN(OPCODE)  4
 
@@ -1131,19 +1132,55 @@ rs6000_extract_return_value (struct type *valtype, char *regbuf, char *valbuf)
 
 static CORE_ADDR rs6000_struct_return_address;
 
-/* Indirect function calls use a piece of trampoline code to do context
-   switching, i.e. to set the new TOC table. Skip such code if we are on
-   its first instruction (as when we have single-stepped to here). 
-   Also skip shared library trampoline code (which is different from
+/* Return whether handle_inferior_event() should proceed through code
+   starting at PC in function NAME when stepping.
+
+   The AIX -bbigtoc linker option generates functions @FIX0, @FIX1, etc. to
+   handle memory references that are too distant to fit in instructions
+   generated by the compiler.  For example, if 'foo' in the following
+   instruction:
+
+     lwz r9,foo(r2)
+
+   is greater than 32767, the linker might replace the lwz with a branch to
+   somewhere in @FIX1 that does the load in 2 instructions and then branches
+   back to where execution should continue.
+
+   GDB should silently step over @FIX code, just like AIX dbx does.
+   Unfortunately, the linker uses the "b" instruction for the branches,
+   meaning that the link register doesn't get set.  Therefore, GDB's usual
+   step_over_function() mechanism won't work.
+
+   Instead, use the IN_SOLIB_RETURN_TRAMPOLINE and SKIP_TRAMPOLINE_CODE hooks
+   in handle_inferior_event() to skip past @FIX code.  */
+
+int
+rs6000_in_solib_return_trampoline (CORE_ADDR pc, char *name)
+{
+  return name && !strncmp (name, "@FIX", 4);
+}
+
+/* Skip code that the user doesn't want to see when stepping:
+
+   1. Indirect function calls use a piece of trampoline code to do context
+   switching, i.e. to set the new TOC table.  Skip such code if we are on
+   its first instruction (as when we have single-stepped to here).
+
+   2. Skip shared library trampoline code (which is different from
    indirect function call trampolines).
+
+   3. Skip bigtoc fixup code.
+
    Result is desired PC to step until, or NULL if we are not in
-   trampoline code.  */
+   code that should be skipped.  */
 
 CORE_ADDR
 rs6000_skip_trampoline_code (CORE_ADDR pc)
 {
   register unsigned int ii, op;
+  int rel;
   CORE_ADDR solib_target_pc;
+  struct minimal_symbol *msymbol;
 
   static unsigned trampoline_code[] =
   {
@@ -1157,6 +1194,21 @@ rs6000_skip_trampoline_code (CORE_ADDR pc)
     0
   };
 
+  /* Check for bigtoc fixup code.  */
+  msymbol = lookup_minimal_symbol_by_pc (pc);
+  if (msymbol && rs6000_in_solib_return_trampoline (pc, SYMBOL_NAME (msymbol)))
+    {
+      /* Double-check that the third instruction from PC is relative "b".  */
+      op = read_memory_integer (pc + 8, 4);
+      if ((op & 0xfc000003) == 0x48000000)
+       {
+         /* Extract bits 6-29 as a signed 24-bit relative word address and
+            add it to the containing PC.  */
+         rel = ((int)(op << 6) >> 6);
+         return pc + 8 + rel;
+       }
+    }
+
   /* If pc is in a shared library trampoline, return its target.  */
   solib_target_pc = find_solib_trampoline_target (pc);
   if (solib_target_pc)