[ppc64-linux]: register CONVERT_FROM_FUNC_PTR_ADDR method

Jim Blandy
2003-06-11T08:52:43Z

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 1.28.8.14
diff -c -r1.28.8.14 ppc-linux-tdep.c
*** gdb/ppc-linux-tdep.c 11 Jun 2003 06:46:17 -0000 1.28.8.14
--- gdb/ppc-linux-tdep.c 11 Jun 2003 08:48:28 -0000
***************
*** 894,899 ****
--- 894,932 ----
}

+ /* Support for CONVERT_FROM_FUNC_PTR_ADDR(ADDR).
+
+ Usually a function pointer's representation is simply the address
+ of the function. On the RS/6000 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 special function pointer. */
+ 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
***************
*** 1028,1033 ****
--- 1061,1071 ----
if (tdep->wordsize == 8)
{
set_gdbarch_long_double_bit (gdbarch, 16 * TARGET_CHAR_BIT);
+
+ /* 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);