[gdb_6_0-branch commit] PPC64: convert_from_func_ptr_addr method

[Jim Blandy <jimb@redhat.com>]

I've committed this to the 6.0 branch, with verbal approval on the
phone from Kevin Buettner, the PPC Linux maintainer.  It is already
committed to the trunk.

2003-06-11  Jim Blandy  <jimb@redhat.com>

	* ppc-linux-tdep.c (ppc64_linux_convert_from_func_ptr_addr): New
	function.
	(ppc_linux_init_abi): Register it as the
	CONVERT_FROM_FUNC_PTR_ADDR method under the PPC64 Linux ABI.

Index: gdb/ppc-linux-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/ppc-linux-tdep.c,v
retrieving revision 1.28.8.17
diff -c -r1.28.8.17 ppc-linux-tdep.c
*** gdb/ppc-linux-tdep.c	12 Jun 2003 21:09:22 -0000	1.28.8.17
--- gdb/ppc-linux-tdep.c	12 Jun 2003 21:09:42 -0000
***************
*** 894,899 ****
--- 894,934 ----
  }
  
  
+ /* Support for CONVERT_FROM_FUNC_PTR_ADDR(ADDR) on PPC64 Linux.
+ 
+    Usually a function pointer's representation is simply the address
+    of the function. On Linux on the 64-bit PowerPC however, a function
+    pointer is represented by a pointer to a TOC entry. This TOC entry
+    contains three words, the first word is the address of the
+    function, the second word is the TOC pointer (r2), and the third
+    word is the static chain value.  Throughout GDB it is currently
+    assumed that a function pointer contains the address of the
+    function, which is not easy to fix.  In addition, the conversion of
+    a function address to a function pointer would require allocation
+    of a TOC entry in the inferior's memory space, with all its
+    drawbacks.  To be able to call C++ virtual methods in the inferior
+    (which are called via function pointers), find_function_addr uses
+    this function to get the function address from a function
+    pointer.  */
+ 
+ /* Return real function address if ADDR (a function pointer) is in the data
+    space and is therefore a special function pointer.  */
+ 
+ static CORE_ADDR
+ ppc64_linux_convert_from_func_ptr_addr (CORE_ADDR addr)
+ {
+   struct obj_section *s;
+ 
+   s = find_pc_section (addr);
+   if (s && s->the_bfd_section->flags & SEC_CODE)
+     return addr;
+ 
+   /* ADDR is in the data space, so it's a pointer to a descriptor, not
+      the entry point.  */
+   return ppc64_desc_entry_point (addr);
+ }
+ 
+ 
  /* On 64-bit PowerPC Linux, the ELF header's e_entry field is the
     address of a function descriptor for the entry point function, not
     the actual entry point itself.  So to find the actual address at
***************
*** 1027,1032 ****
--- 1062,1072 ----
    
    if (tdep->wordsize == 8)
      {
+       /* Handle PPC64 Linux function pointers (which are really
+          function descriptors).  */
+       set_gdbarch_convert_from_func_ptr_addr
+         (gdbarch, ppc64_linux_convert_from_func_ptr_addr);
+ 
        set_gdbarch_call_dummy_address (gdbarch, ppc64_call_dummy_address);
  
        set_gdbarch_in_solib_call_trampoline