Re: [PATCH] gdb: add support for handling core dumps on arm-none-eabi

[Paul Mathieu <paulmathieu@google.com>]

Hi Luis,

Thanks for the quick feedback!

It seems the e-mail client has messed up the proper formatting
> (spaces/tabs) of the patch. I'll defer formatting review until the patch
> comes through clean of e-mail client interferences.


Woops, sorry about this. I'm submitting a new patch, hopefully it will be
treated well by the email gods.


> Also, it would be nice to get rid of dead code (like "#if 0" blocks). If
> it is not functional, then there is little point in including such code.
>

Done.


> Who is generating such core files? Is there some way I can access the
> tool to give it a try? How can I test the patch itself?
>

I made one myself, with a python script that I wrote.
I have a live embedded target that I can use to dump memory regions and CPU
registers over a serial line. My python script then formats the memory
dumps into PT_LOAD segments, and the CPU registers into a NT_PRSTATUS note
segment, and stores it as an ELF32 core file.
I'm happy to share any material that would help testing this, including the
python script, an example of firmware and core file and some embedded
source code.

I addressed the rest of your feedback through essentially re-writing the
patch to not use `deprecated_add_core_fns`
In the new patch, I had to use the GDB_OSABI_LINUX, otherwise my core
wouldn't be recognized. I'm not sure if this can potentially interfere with
the arm-linux implementation. Since it has its own entry in configure.tgt,
I imagine not?

Thanks!

gdb/ChangeLog:
2018-09-29  Robin Haberkorn <robin.haberkorn@googlemail.com>
2020-10-02  Paul Mathieu <paulmathieu@google.com>
* arm-none-tdep.c: Source file added. Provide CPU registers from a core
file
* floating point registers not yet supported (FIXME)
---
 gdb/Makefile.in     |   2 +
 gdb/arm-none-tdep.c | 107 ++++++++++++++++++++++++++++++++++++++++++++
 gdb/configure.tgt   |   2 +-
 3 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 gdb/arm-none-tdep.c

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index dbede7a9cf..7f0e3ea0b0 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -720,6 +720,7 @@ ALL_TARGET_OBS = \
  arm-obsd-tdep.o \
  arm-pikeos-tdep.o \
  arm-symbian-tdep.o \
+ arm-none-tdep.o \
  arm-tdep.o \
  arm-wince-tdep.o \
  avr-tdep.o \
@@ -2150,6 +2151,7 @@ ALLDEPFILES = \
  arm-nbsd-tdep.c \
  arm-obsd-tdep.c \
  arm-symbian-tdep.c \
+ arm-none-tdep.c \
  arm-tdep.c \
  avr-tdep.c \
  bfin-linux-tdep.c \
diff --git a/gdb/arm-none-tdep.c b/gdb/arm-none-tdep.c
new file mode 100644
index 0000000000..bdf346bdc3
--- /dev/null
+++ b/gdb/arm-none-tdep.c
@@ -0,0 +1,107 @@
+/* Native-dependent code for GDB targetting embedded ARM.
+
+   Copyright (C) 2020 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 "osabi.h"
+
+#include "arch/arm.h"
+#include "gdbarch.h"
+#include "regcache.h"
+#include "regset.h"
+
+struct arm_none_reg
+{
+  uint32_t reg[13];
+  uint32_t sp;
+  uint32_t lr;
+  uint32_t pc;
+  uint32_t cpsr;
+  uint32_t orig_r0;
+};
+
+extern int arm_apcs_32;
+
+static void
+arm_none_supply_gregset (const struct regset *regset,
+                         struct regcache *regcache, int regnum,
+                         const void *gregs, size_t len)
+{
+  const arm_none_reg *gregset = static_cast<const arm_none_reg *> (gregs);
+  gdb_assert (len >= sizeof (arm_none_reg));
+
+  /* Integer registers.  */
+  for (int i = ARM_A1_REGNUM; i < ARM_SP_REGNUM; i++)
+    if (regnum == -1 || regnum == i)
+      regcache->raw_supply (i, (char *)&gregset->reg[i]);
+
+  if (regnum == -1 || regnum == ARM_SP_REGNUM)
+    regcache->raw_supply (ARM_SP_REGNUM, (char *)&gregset->sp);
+
+  if (regnum == -1 || regnum == ARM_LR_REGNUM)
+    regcache->raw_supply (ARM_LR_REGNUM, (char *)&gregset->lr);
+
+  if (regnum == -1 || regnum == ARM_PC_REGNUM)
+    {
+      CORE_ADDR r_pc
+          = gdbarch_addr_bits_remove (regcache->arch (), gregset->pc);
+      regcache->raw_supply (ARM_PC_REGNUM, (char *)&r_pc);
+    }
+
+  if (regnum == -1 || regnum == ARM_PS_REGNUM)
+    {
+      if (arm_apcs_32)
+        regcache->raw_supply (ARM_PS_REGNUM, (char *)&gregset->cpsr);
+      else
+        regcache->raw_supply (ARM_PS_REGNUM, (char *)&gregset->pc);
+    }
+}
+
+static const struct regset arm_none_regset
+    = { nullptr, arm_none_supply_gregset,
+        /* We don't need a collect function because we only use this
reading
+           registers (via iterate_over_regset_sections and
+           fetch_regs/fetch_register).  */
+        nullptr, 0 };
+
+static void
+arm_none_iterate_over_regset_sections (struct gdbarch *gdbarch,
+                                       iterate_over_regset_sections_cb *cb,
+                                       void *cb_data,
+                                       const struct regcache *regcache)
+{
+  cb (".reg", sizeof (arm_none_reg), sizeof (arm_none_reg),
&arm_none_regset,
+      NULL, cb_data);
+}
+
+static void arm_none_elf_init_abi (struct gdbarch_info info,
+                                   struct gdbarch *gdbarch);
+static void
+arm_none_elf_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+  set_gdbarch_iterate_over_regset_sections (
+      gdbarch, arm_none_iterate_over_regset_sections);
+}
+
+void _initialize_arm_none_tdep (void);
+void
+_initialize_arm_none_tdep (void)
+{
+  gdbarch_register_osabi (bfd_arch_arm, 0, GDB_OSABI_LINUX,
+                          arm_none_elf_init_abi);
+}
diff --git a/gdb/configure.tgt b/gdb/configure.tgt
index a3e11c4b9b..0cf05efdd1 100644
--- a/gdb/configure.tgt
+++ b/gdb/configure.tgt
@@ -189,7 +189,7 @@ arm*-*-symbianelf*)
  ;;
 arm*-*-*)
  # Target: ARM embedded system
- gdb_target_obs="arm-pikeos-tdep.o"
+ gdb_target_obs="arm-pikeos-tdep.o arm-none-tdep.o"
  gdb_sim=../sim/arm/libsim.a
  ;;

--