From 2971b56ba623542a0232473f110922758588fe2c Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Tue, 20 Apr 2010 22:38:54 +0000 Subject: [PATCH] [AIX] Memory error while checking if pointer is descriptor. 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. --- gdb/ChangeLog | 7 +++++++ gdb/rs6000-aix-tdep.c | 20 +++++++++++++++++--- 2 files changed, 24 insertions(+), 3 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index fe8bcb790c..e56a6a12d7 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,10 @@ +2010-04-20 Joel Brobecker + + * 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 * ada-typeprint.c (ada_print_typedef): New function. diff --git a/gdb/rs6000-aix-tdep.c b/gdb/rs6000-aix-tdep.c index 530c12e2a6..927cfe2da2 100644 --- a/gdb/rs6000-aix-tdep.c +++ b/gdb/rs6000-aix-tdep.c @@ -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; -- 2.34.1