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Re: [RFC] PPC: Skip call to __eabi in main()
I've done some further testing of my patch and have found that
an additional test is needed to accomodate -fleading-underscore.
(See the comment in the patch below...)
I've also expanded the comment that precedes rs6000_skip_main_prologue().
I'll wait a few more days before committing this change.
Kevin
* rs6000-tdep.c (BL_MASK, BL_INSTRUCTION, BL_DISPLACEMENT_MASK):
New macros.
(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 29 Jul 2008 00:11:52 -0000
@@ -1146,6 +1146,20 @@ bl_to_blrl_insn_p (CORE_ADDR pc, int ins
return 0;
}
+/* Masks for decoding a branch-and-link (bl) instruction.
+
+ BL_MASK and BL_INSTRUCTION are used in combination with each other.
+ The former is anded with the opcode in question; if the result of
+ this masking operation is equal to BL_INSTRUCTION, then the opcode in
+ question is a ``bl'' instruction.
+
+ BL_DISPLACMENT_MASK is anded with the opcode in order to extract
+ the branch displacement. */
+
+#define BL_MASK 0xfc000001
+#define BL_INSTRUCTION 0x48000001
+#define BL_DISPLACEMENT_MASK 0x03fffffc
+
/* return pc value after skipping a function prologue and also return
information about a function frame.
@@ -1769,6 +1783,41 @@ rs6000_skip_prologue (struct gdbarch *gd
return pc;
}
+/* When compiling for EABI, some versions of GCC emit a call to __eabi
+ in the prologue of main().
+
+ The function below examines the code pointed at by PC and checks to
+ see if it corresponds to a call to __eabi. If so, it returns the
+ address of the instruction following that call. Otherwise, it simply
+ returns PC. */
+
+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 & BL_MASK) == BL_INSTRUCTION)
+ {
+ CORE_ADDR displ = op & BL_DISPLACEMENT_MASK;
+ CORE_ADDR call_dest = pc + 4 + displ;
+ struct minimal_symbol *s = lookup_minimal_symbol_by_pc (call_dest);
+
+ /* We check for ___eabi (three leading underscores) in addition
+ to __eabi in case the GCC option "-fleading-underscore" was
+ used to compile the program. */
+ if (s != NULL
+ && SYMBOL_LINKAGE_NAME (s) != NULL
+ && (strcmp (SYMBOL_LINKAGE_NAME (s), "__eabi") == 0
+ || strcmp (SYMBOL_LINKAGE_NAME (s), "___eabi") == 0))
+ pc += 4;
+ }
+ return pc;
+}
/* All the ABI's require 16 byte alignment. */
static CORE_ADDR
@@ -3238,6 +3287,7 @@ 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);