Re: [RFA 1/2] mips: Switch inferior function calls to ON_STACK method.

[Joel Brobecker <brobecker@adacore.com>]

[-- Attachment #1: Type: text/plain, Size: 332 bytes --]

> gdb/ChangeLog:
> 
>         * mips-tdep.c (mips_push_dummy_code): New function.
>         (mips_gdbarch_init): Set the gdbarch call_dummy_location to
>         ON_STACK and install mips_push_dummy_code as our gdbarch
>         push_dummy_code routine.

Second version of this patch with Mark's style comments addressed.

-- 
Joel

[-- Attachment #2: mips-on-stack-v2.diff --]
[-- Type: text/x-diff, Size: 2787 bytes --]

commit d7f93872c27075342da02ab2ee57062d8b9511c9
Author: Joel Brobecker <brobecker@adacore.com>
Date:   Wed May 2 20:39:57 2012 -0400

    mips: Switch inferior function calls to ON_STACK method.
    
    This patch switches the mips code to use the ON_STACK method
    for function calls instead of AT_SYMBOL, which we want to remove.
    
    gdb/ChangeLog:
    
            * mips-tdep.c (mips_push_dummy_code): New function.
            (mips_gdbarch_init): Set the gdbarch call_dummy_location to
            ON_STACK and install mips_push_dummy_code as our gdbarch
            push_dummy_code routine.

diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 9a3c7fb..5faf114 100644
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -3009,6 +3009,37 @@ mips_frame_align (struct gdbarch *gdbarch, CORE_ADDR addr)
   return align_down (addr, 16);
 }
 
+/* Implement the push_dummy_code gdbarch method for mips targets.  */
+
+static CORE_ADDR
+mips_push_dummy_code (struct gdbarch *gdbarch, CORE_ADDR sp,
+		      CORE_ADDR funaddr, struct value **args,
+		      int nargs, struct type *value_type,
+		      CORE_ADDR *real_pc, CORE_ADDR *bp_addr,
+		      struct regcache *regcache)
+{
+  int bp_len;
+  gdb_byte null_insn[4] = { 0 };
+
+  *bp_addr = mips_frame_align (gdbarch, sp);
+  gdbarch_breakpoint_from_pc (gdbarch, bp_addr, &bp_len);
+
+  /* The breakpoint layer automatically adjusts the address of
+     breakpoints inserted in a branch delay slot.  With enough
+     bad luck, the 4 bytes located just before our breakpoint
+     instruction could look like a branch instruction, and thus
+     trigger the adjustement, and break the function call entirely.
+     So, we reserve those 4 bytes and write a null instruction
+     to prevent that from happening.  */
+  write_memory (*bp_addr - bp_len, null_insn, sizeof (null_insn));
+  sp = mips_frame_align (gdbarch, *bp_addr - 2 * bp_len);
+
+  /* Inferior resumes at the function entry point.  */
+  *real_pc = funaddr;
+
+  return sp;
+}
+
 static CORE_ADDR
 mips_eabi_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
 			   struct regcache *regcache, CORE_ADDR bp_addr,
@@ -6906,10 +6937,8 @@ mips_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 
   /* MIPS version of CALL_DUMMY.  */
 
-  /* NOTE: cagney/2003-08-05: Eventually call dummy location will be
-     replaced by a command, and all targets will default to on stack
-     (regardless of the stack's execute status).  */
-  set_gdbarch_call_dummy_location (gdbarch, AT_SYMBOL);
+  set_gdbarch_call_dummy_location (gdbarch, ON_STACK);
+  set_gdbarch_push_dummy_code (gdbarch, mips_push_dummy_code);
   set_gdbarch_frame_align (gdbarch, mips_frame_align);
 
   set_gdbarch_convert_register_p (gdbarch, mips_convert_register_p);