[RFA,v2] arm-pikeos: software single step
Commit Message
From: Jerome Guitton <guitton@adacore.com>
Hello,
Below is the updated version following Tom's comments. The only
changes are made are to fix the issues pointed out by Tom:
- Missing function documentation;
- Wrong casing in "PikeOS".
Thank you!
----------------------------------------------------------------------
On ARM, PikeOS does not support hardware single step, causing various
semi-random errors when trying to next/step over some user code. So
this patch changes this target to use software-single-step instead.
The challenge is that, up to now, the PikeOS target was in all respects
identical to a baremetal target as far as GDB was concerned, meaning
we were using the baremetal osabi for this target too. This is no longer
possible, and we need to introduce a new OSABI variant. Unfortunately,
there isn't anything in the object file that would allow us to
differentiate between the two platforms. So we have to rely on a
heuristic instead, where we look for some known symbols that are
required in a PikeOS application (these symbols are expected to be
defined by the default linker script, and correspond to routines used
to allocate the application stack).
gdb/ChangeLog:
* arm-pikeos-tdep.c: New file.
* configure.tgt: Add arm-pikeos-tdep.o to the case of ARM
embedded system.
* defs.h (enum gdb_osabi): Add GDB_OSABI_PIKEOS.
* osabi.c (gdb_osabi_names): Add name for GDB_OSABI_PIKEOS.
Tested on arm-pikeos and arm-elf using AdaCore's testsuite.
We also evaluated it on armhf-linux as a cross platform.
---
gdb/arm-pikeos-tdep.c | 102 +++++++++++++++++++++++++++++++++++++++++++++++++
gdb/configure.tgt | 1 +
gdb/defs.h | 1 +
gdb/osabi.c | 1 +
4 files changed, 105 insertions(+)
create mode 100644 gdb/arm-pikeos-tdep.c
Comments
(not sure why the From address is y@eu.adacore.com, I'll replace it with
Joel's).
> + symbol_table = (asymbol **) xmalloc (storage_needed);
> + make_cleanup (xfree, symbol_table);
It would make Tom really happy if you could avoid introducing a cleanup
:). I would suggest using an std::vector<asymbol *>. If you'd rather
not do it it's not a big deal, we can change it after.
> diff --git a/gdb/configure.tgt b/gdb/configure.tgt
> index 6d1a4df..a1f703f 100644
> --- a/gdb/configure.tgt
> +++ b/gdb/configure.tgt
> @@ -180,6 +180,7 @@ arm*-*-symbianelf*)
> ;;
> arm*-*-*)
> # Target: ARM embedded system
> + gdb_target_obs="arm-pikeos-tdep.o"
> gdb_sim=../sim/arm/libsim.a
> ;;
The object should be added to ALL_TARGETS_OBS in the Makefile, so it's
included in an enable-targets=all build.
Just to understand better why the object file needs to be added here,
what is the target triplet? arm-pikeos-something, arm-none-something?
Just wondering: when you connect to the target, you talk to a gdb stub
that is built right into the application/rtos?
Simon
>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:
Simon> (not sure why the From address is y@eu.adacore.com, I'll replace it
Simon> with Joel's).
>> + symbol_table = (asymbol **) xmalloc (storage_needed);
>> + make_cleanup (xfree, symbol_table);
Simon> It would make Tom really happy if you could avoid introducing a
Simon> cleanup :).
Wow, thanks. I sometimes check patches for new cleanups but I totally
missed it in this one :)
Tom
new file mode 100644
@@ -0,0 +1,102 @@
+/* Copyright (C) 2016-2018 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include "defs.h"
+#include "objfiles.h"
+#include "arm-tdep.h"
+#include "osabi.h"
+
+/* The gdbarch_register_osabi handler for ARM PikeOS; it performs
+ the gdbarch initialization for that platform. */
+
+static void
+arm_pikeos_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+ /* Single stepping. */
+ set_gdbarch_software_single_step (gdbarch, arm_software_single_step);
+}
+
+/* The ARM PikeOS OSABI sniffer (see gdbarch_register_osabi_sniffer).
+ Returns GDB_OSABI_PIKEOS if the given BFD is a PikeOS binary,
+ GDB_OSABI_UNKNOWN otherwise. */
+
+static enum gdb_osabi
+arm_pikeos_osabi_sniffer (bfd *abfd)
+{
+ long storage_needed;
+ asymbol **symbol_table;
+ long number_of_symbols;
+ long i;
+ int pikeos_stack_found = 0;
+ int pikeos_stack_size_found = 0;
+ struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
+
+ /* The BFD target of PikeOS is really just standard elf, so we
+ cannot use it to detect this variant. The only common thing that
+ may be found in PikeOS modules are symbols _vm_stack/__p4_stack and
+ _vm_stack_size/__p4_stack_end. They are used to specify the stack
+ location and size; and defined by the default linker script.
+
+ OS ABI sniffers are called before the minimal symtabs are
+ created. So inspect the symbol table using BFD. */
+
+ storage_needed = bfd_get_symtab_upper_bound (abfd);
+
+ if (storage_needed <= 0)
+ return GDB_OSABI_UNKNOWN;
+
+ symbol_table = (asymbol **) xmalloc (storage_needed);
+ make_cleanup (xfree, symbol_table);
+
+ number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
+
+ if (number_of_symbols < 0)
+ {
+ do_cleanups (old_chain);
+ return GDB_OSABI_UNKNOWN;
+ }
+
+ for (i = 0; i < number_of_symbols; i++)
+ {
+ const char *name = bfd_asymbol_name (symbol_table[i]);
+
+ if (strcmp (name, "_vm_stack") == 0
+ || strcmp (name, "__p4_stack") == 0)
+ pikeos_stack_found = 1;
+
+ if (strcmp (name, "_vm_stack_size") == 0
+ || strcmp (name, "__p4_stack_end") == 0)
+ pikeos_stack_size_found = 1;
+ }
+
+ do_cleanups (old_chain);
+
+ if (pikeos_stack_found && pikeos_stack_size_found)
+ return GDB_OSABI_PIKEOS;
+ else
+ return GDB_OSABI_UNKNOWN;
+}
+
+void
+_initialize_arm_pikeos_tdep (void)
+{
+ /* Register the sniffer for the PikeOS targets. */
+ gdbarch_register_osabi_sniffer (bfd_arch_arm, bfd_target_elf_flavour,
+ arm_pikeos_osabi_sniffer);
+ gdbarch_register_osabi (bfd_arch_arm, 0, GDB_OSABI_PIKEOS,
+ arm_pikeos_init_abi);
+}
@@ -180,6 +180,7 @@ arm*-*-symbianelf*)
;;
arm*-*-*)
# Target: ARM embedded system
+ gdb_target_obs="arm-pikeos-tdep.o"
gdb_sim=../sim/arm/libsim.a
;;
@@ -495,6 +495,7 @@ enum gdb_osabi
GDB_OSABI_LYNXOS178,
GDB_OSABI_NEWLIB,
GDB_OSABI_SDE,
+ GDB_OSABI_PIKEOS,
GDB_OSABI_INVALID /* keep this last */
};
@@ -80,6 +80,7 @@ static const struct osabi_names gdb_osabi_names[] =
{ "LynxOS178", NULL },
{ "Newlib", NULL },
{ "SDE", NULL },
+ { "PikeOS", NULL },
{ "<invalid>", NULL }
};