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Re: [PATCH] Fix gdb1476.exp on s390*
- From: Andrew Cagney <cagney at gnu dot org>
- To: Ulrich Weigand <weigand at i1 dot informatik dot uni-erlangen dot de>
- Cc: gdb-patches at sources dot redhat dot com
- Date: Mon, 22 Mar 2004 16:58:51 -0500
- Subject: Re: [PATCH] Fix gdb1476.exp on s390*
- References: <200403221905.UAA12203@faui1d.informatik.uni-erlangen.de>
Andrew Cagney wrote:
> Hello,
>
> this patch fixes the gdb.base/gdb1476.exp test case (backtrace from NULL
> function pointer call).
>
> When calling via an invalid function pointer, what we should do is simply
> unwind the PC from the return address register and continue. This is
> exactly what is done to unwind from a PLT stub as well, so the patch
> simply uses the PLT frame unwinder to handle this case as well.
While that might be true, I don't know that its the job of something
called "PLTSTUB".
Yes, the name's a bit unfortunate. What this unwinder does is basically
unwind from any situation where we don't have a proper function prolog.
It could in theory handle all kinds of stubs, trampolines etc.
I can think of either:
- renaming pltstub to something that matches its new purpose (just "stub"?)
This would be my preferred solution.
Try the attached.
Andrew
- using the default unwinder
The default unwinder as it is now would handle the situation incorrectly.
I could build the stub detection logic into the default unwinder, but that
would make it even more complex than it already is; I would think with the
new frame logic it is preferable to have multiple unwinders rather than a
single one that handles everything.
Bye,
Ulrich
2004-03-22 Andrew Cagney <cagney@redhat.com>
* s390-tdep.c (struct s390_stub_unwind_cache): Rename
s390_pltstub_unwind_cache.
(s390_stub_frame_unwind_cache): Rename
s390_pltstub_frame_unwind_cache.
(s390_stub_frame_this_id): Rename s390_pltstub_frame_this_id.
(s390_stub_frame_prev_register): Rename
s390_pltstub_frame_prev_register.
(s390_stub_frame_unwind): Rename s390_pltstub_frame_unwind.
(s390_stub_frame_sniffer): Rename s390_stub_frame_sniffer.
From Ulrich Weigand:
* s390-tdep.c (s390_pltstub_frame_sniffer): Handle invalid function
pointer calls like PLT calls.
Index: s390-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/s390-tdep.c,v
retrieving revision 1.129
diff -u -r1.129 s390-tdep.c
--- s390-tdep.c 26 Feb 2004 23:48:01 -0000 1.129
+++ s390-tdep.c 22 Mar 2004 21:55:33 -0000
@@ -2037,27 +2037,29 @@
}
-/* PLT stub stack frames. */
-
-struct s390_pltstub_unwind_cache {
+/* Code stubs and their stack frames. For things like PLTs and NULL
+ function calls (where there is no true frame and the return address
+ is in the RETADDR register). */
+struct s390_stub_unwind_cache
+{
CORE_ADDR frame_base;
struct trad_frame_saved_reg *saved_regs;
};
-static struct s390_pltstub_unwind_cache *
-s390_pltstub_frame_unwind_cache (struct frame_info *next_frame,
- void **this_prologue_cache)
+static struct s390_stub_unwind_cache *
+s390_stub_frame_unwind_cache (struct frame_info *next_frame,
+ void **this_prologue_cache)
{
struct gdbarch *gdbarch = get_frame_arch (next_frame);
int word_size = gdbarch_ptr_bit (gdbarch) / 8;
- struct s390_pltstub_unwind_cache *info;
+ struct s390_stub_unwind_cache *info;
ULONGEST reg;
if (*this_prologue_cache)
return *this_prologue_cache;
- info = FRAME_OBSTACK_ZALLOC (struct s390_pltstub_unwind_cache);
+ info = FRAME_OBSTACK_ZALLOC (struct s390_stub_unwind_cache);
*this_prologue_cache = info;
info->saved_regs = trad_frame_alloc_saved_regs (next_frame);
@@ -2072,41 +2074,47 @@
}
static void
-s390_pltstub_frame_this_id (struct frame_info *next_frame,
- void **this_prologue_cache,
- struct frame_id *this_id)
+s390_stub_frame_this_id (struct frame_info *next_frame,
+ void **this_prologue_cache,
+ struct frame_id *this_id)
{
- struct s390_pltstub_unwind_cache *info
- = s390_pltstub_frame_unwind_cache (next_frame, this_prologue_cache);
+ struct s390_stub_unwind_cache *info
+ = s390_stub_frame_unwind_cache (next_frame, this_prologue_cache);
*this_id = frame_id_build (info->frame_base, frame_pc_unwind (next_frame));
}
static void
-s390_pltstub_frame_prev_register (struct frame_info *next_frame,
- void **this_prologue_cache,
- int regnum, int *optimizedp,
- enum lval_type *lvalp, CORE_ADDR *addrp,
- int *realnump, void *bufferp)
+s390_stub_frame_prev_register (struct frame_info *next_frame,
+ void **this_prologue_cache,
+ int regnum, int *optimizedp,
+ enum lval_type *lvalp, CORE_ADDR *addrp,
+ int *realnump, void *bufferp)
{
- struct s390_pltstub_unwind_cache *info
- = s390_pltstub_frame_unwind_cache (next_frame, this_prologue_cache);
+ struct s390_stub_unwind_cache *info
+ = s390_stub_frame_unwind_cache (next_frame, this_prologue_cache);
trad_frame_prev_register (next_frame, info->saved_regs, regnum,
optimizedp, lvalp, addrp, realnump, bufferp);
}
-static const struct frame_unwind s390_pltstub_frame_unwind = {
+static const struct frame_unwind s390_stub_frame_unwind = {
NORMAL_FRAME,
- s390_pltstub_frame_this_id,
- s390_pltstub_frame_prev_register
+ s390_stub_frame_this_id,
+ s390_stub_frame_prev_register
};
static const struct frame_unwind *
-s390_pltstub_frame_sniffer (struct frame_info *next_frame)
+s390_stub_frame_sniffer (struct frame_info *next_frame)
{
- if (!in_plt_section (frame_pc_unwind (next_frame), NULL))
- return NULL;
+ CORE_ADDR pc = frame_pc_unwind (next_frame);
+ bfd_byte insn[S390_MAX_INSTR_SIZE];
- return &s390_pltstub_frame_unwind;
+ /* If the current PC points to non-readable memory, we assume we
+ have trapped due to an invalid function pointer call. We handle
+ the non-existing current function like a PLT stub. */
+ if (in_plt_section (pc, NULL)
+ || s390_readinstruction (insn, pc) < 0)
+ return &s390_stub_frame_unwind;
+ return NULL;
}
@@ -3028,7 +3036,7 @@
dwarf2_frame_set_init_reg (gdbarch, s390_dwarf2_frame_init_reg);
frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
frame_base_append_sniffer (gdbarch, dwarf2_frame_base_sniffer);
- frame_unwind_append_sniffer (gdbarch, s390_pltstub_frame_sniffer);
+ frame_unwind_append_sniffer (gdbarch, s390_stub_frame_sniffer);
frame_unwind_append_sniffer (gdbarch, s390_sigtramp_frame_sniffer);
frame_unwind_append_sniffer (gdbarch, s390_frame_sniffer);
frame_base_set_default (gdbarch, &s390_frame_base);