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[AIX] Memory error while checking if pointer is descriptor.

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A long time ago (Oct 2009), I noticed a problem on AIX, where something
failed with an error while the debugger was checking whether an address
was a descriptor or not.  Unfortunately, like an idiot, I forgot to write
notes about the scenario where the problem occured - I am usually pretty
meticulous about that because my memory of these things is really bad.
I hope you'll forgive me for not providing a solid testcase - if it's
any consolation, I've searched for a long time before giving up :-(.

Based on the testsuite reports that I have, I think that this happened
while inserting a breakpoint, as follow:

    (gdb) break x
    Cannot access memory at address 0x200093b4

What happened is that rs6000_convert_from_func_ptr_addr tried to read
the memory at the given address, and fail because of an exception.
It seems pretty clear that, if the address was in fact a descriptor,
GDB would have been able to read the target memory region.

So this patch protects the memory-read against exceptions, and treats
such exceptions as an indication that our address is not a descriptor.

gdb/ChangeLog:

        * rs6000-aix-tdep.c: #include exceptions.h.
        (rs6000_convert_from_func_ptr_addr): If an exception is thrown
        while reading the memory at ADDR, then ADDR cannot be a function
        descriptor.
This commit is contained in:
Joel Brobecker 2010-04-20 22:38:54 +00:00
parent be9425454f
commit 2971b56ba6
2 changed files with 24 additions and 3 deletions
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7
gdb/ChangeLog
View file

@ -1,3 +1,10 @@
2010-04-20 Joel Brobecker <brobecker@adacore.com>
* rs6000-aix-tdep.c: #include exceptions.h.
(rs6000_convert_from_func_ptr_addr): If an exception is thrown
while reading the memory at ADDR, then ADDR cannot be a function
descriptor.
2010-04-20 Joel Brobecker <brobecker@adacore.com>
* ada-typeprint.c (ada_print_typedef): New function.

20
gdb/rs6000-aix-tdep.c
View file

@ -34,6 +34,7 @@
#include "breakpoint.h"
#include "rs6000-tdep.h"
#include "ppc-tdep.h"
#include "exceptions.h"
/* Hook for determining the TOC address when calling functions in the
inferior under AIX. The initialization code in rs6000-nat.c sets
@ -582,9 +583,22 @@ rs6000_convert_from_func_ptr_addr (struct gdbarch *gdbarch,
the target address itself points to a section that is executable. */
if (s && (s->the_bfd_section->flags & SEC_CODE) == 0)
{
CORE_ADDR pc =
read_memory_unsigned_integer (addr, tdep->wordsize, byte_order);
struct obj_section *pc_section = find_pc_section (pc);
CORE_ADDR pc;
struct obj_section *pc_section;
struct gdb_exception e;
TRY_CATCH (e, RETURN_MASK_ERROR)
{
pc = read_memory_unsigned_integer (addr, tdep->wordsize, byte_order);
}
if (e.reason < 0)
{
/* An error occured during reading. Probably a memory error
due to the section not being loaded yet. This address
cannot be a function descriptor. */
return addr;
}
pc_section = find_pc_section (pc);
if (pc_section && (pc_section->the_bfd_section->flags & SEC_CODE))
return pc;