Re: [patch] Fixes problem setting breakpoint in dynamic loader

PAUL GILLIAM
2006-06-23T21:33:59Z

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It's been just about a month, so I thought I try again (and use the new
patch tracker!)

:ADDPATCH PowerPC-64:

> On Thu, 2006-05-25 at 18:58 -0400, Daniel Jacobowitz wrote:

> > I don't feel that I can really review this; I'm going to wait a while
> > and hope someone more familiar with a function descriptor platform
> > responds.

I have attached the patches again. 'loader_break.diff' applied cleanly
to cvs-head, but I had to do a trivial tweak to 'rs6000.diff' so that it
would.

OK to commit?

-=# Paul #=-

[-- Attachment #2: loader_break.diff --]
[-- Type: text/x-patch, Size: 3392 bytes --]

2006-05-25 Paul Gilliam <pgilliam@us.ibm.com

* solib-svr4.c: Remove "._dl_debug_state" from the list of symbols at
which to try setting a breakpoint for tracking solibs.
(enable_break): Resolve break address when the symbol is found in
the data section.

Index: solib-svr4.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-svr4.c,v
retrieving revision 1.58
diff -a -u -r1.58 solib-svr4.c
--- solib-svr4.c 18 May 2006 20:38:56 -0000 1.58
+++ solib-svr4.c 25 May 2006 22:12:55 -0000
@@ -85,16 +85,6 @@
"rtld_db_dlactivity",
"_rtld_debug_state",

- /* On the 64-bit PowerPC, the linker symbol with the same name as
- the C function points to a function descriptor, not to the entry
- point. The linker symbol whose name is the C function name
- prefixed with a '.' points to the function's entry point. So
- when we look through this table, we ignore symbols that point
- into the data section (thus skipping the descriptor's symbol),
- and eventually try this one, giving us the real entry point
- address. */
- "._dl_debug_state",
-
NULL
};

@@ -1043,20 +1033,45 @@
/* Now try to set a breakpoint in the dynamic linker. */
for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
{
- /* On ABI's that use function descriptors, there are usually
- two linker symbols associated with each C function: one
- pointing at the actual entry point of the machine code,
- and one pointing at the function's descriptor. The
- latter symbol has the same name as the C function.
-
- What we're looking for here is the machine code entry
- point, so we are only interested in symbols in code
- sections. */
+ /* What we're looking for here is the machine code entry point,
+ so we are only interested in symbols in code sections.
+
+ On ABI's that use function descriptors, the linker symbol with
+ the same name as a C funtion points to that functions descriptor.
+ when those function descriptors are in the code section, they
+ contain executable code and we can set a breakpoint there. */
sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep, SEC_CODE);
if (sym_addr != 0)
break;
}

+ if (sym_addr == 0)
+ {
+ CORE_ADDR sect_offset;
+
+ /* No symbol was found in a code section, so look in the data
+ sections. This will only happen when the linker symbol points
+ to a function descriptor that is in a data section. */
+ for (bkpt_namep = solib_break_names; *bkpt_namep!=NULL; bkpt_namep++)
+ {
+ /* On ABI's that use function descriptors that are in the data
+ section, */
+ sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep, SEC_DATA);
+ if (sym_addr != 0)
+ break;
+ }
+ if (sym_addr == 0)
+ {
+ target_close (tmp_bfd_target, 0);
+ goto bkpt_at_symbol;
+ }
+
+ /* Convert 'sym_addr' from a function pointer to an address. */
+ sym_addr = gdbarch_convert_from_func_ptr_addr (current_gdbarch,
+ sym_addr,
+ tmp_bfd_target);
+ }
+
/* We're done with both the temporary bfd and target. Remember,
closing the target closes the underlying bfd. */
target_close (tmp_bfd_target, 0);

[-- Attachment #3: rs6000.diff --]
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2006-05-25 Paul Gilliam <pgilliam@us.ibm.com

*rs6000-tdep.c (rs6000_convert_from_func_ptr_addr): Use target_ops.

Index: rs6000-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/rs6000-tdep.c,v
retrieving revision 1.258
diff -a -u -r1.258 rs6000-tdep.c
--- rs6000-tdep.c 23 Apr 2006 14:15:01 -0000 1.258
+++ rs6000-tdep.c 23 Jun 2006 21:22:32 -0000
@@ -2338,7 +2338,8 @@
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. */
+ function address from a function pointer. It is also used by
+ enable_break from svr4_solib_create_inferior_hook. */

/* Return real function address if ADDR (a function pointer) is in the data
space and is therefore a special function pointer. */
@@ -2355,7 +2356,9 @@
return addr;

/* ADDR is in the data space, so it's a special function pointer. */
- return read_memory_addr (addr, gdbarch_tdep (current_gdbarch)->wordsize);
+
+ return get_target_memory_unsigned (targ, addr,
+ gdbarch_tdep (current_gdbarch)->wordsize);
}
\f