Re: [PATCH v6 5/7] Support software single step on ARM in GDBServer.

[Yao Qi <qiyaoltc@gmail.com>]

Antoine Tremblay <antoine.tremblay@ericsson.com> writes:

> gdb/ChangeLog:
> 	* Makefile.in: Add arm-get-next-pcs.c/o, arm-linux.c/o.
> 	to all arm targets.

Please describe how Makefile.in is changed, as I suggested in previous patch.

> 	* aarch32-linux-nat.c: Include arch/arm-get-next-pcs.h.
> 	* arch/arm-get-next-pcs.c: New file.
> 	* arch/arm-get-next-pcs.h: New file.
> 	* arch/arm-linux.h: New file.
> 	* arch/arm-linux.c: New file.
> 	* arm-linux-nat.c: Include arch/arm.h, arch/arm-get-next-pcs.h
> 	arch/arm-linux.h.
> 	* arm-linux-tdep.c: Include arch/arm.h,arch/arm-get-next-pcs.h
> 	arch/arm-linux.h.
> 	(arm_linux_get_next_pcs_ops): New struct.
> 	(ARM_SIGCONTEXT_R0, ARM_UCONTEXT_SIGCONTEXT,
> 	ARM_OLD_RT_SIGFRAME_SIGINFO, ARM_OLD_RT_SIGFRAME_UCONTEXT,
> 	ARM_NEW_RT_SIGFRAME_UCONTEXT, ARM_NEW_SIGFRAME_MAGIC): Move stack
> 	layout defines to arch/arm-linux.h.
> 	(arm_linux_sigreturn_next_pc_offset): Move to arch/arm-linux.c.
> 	(arm_linux_software_single_step): Adjust for
> 	arm_get_next_pcs implementation.
> 	* arm-tdep.c: Include arch/arm-get-next-pcs.h.
> 	(arm_get_next_pcs_ops): New struct.
> 	(submask): Move macro to arm-get-next-pcs.h.
> 	(bit): Likewise.
> 	(bits): Likewise.
> 	(sbits): Likewise.
> 	(BranchDest): Likewise.

> 	(thumb_instruction_changes_pc): Move to arm-get-next-pcs.c
> 	(thumb2_instruction_changes_pc): Likewise.
> 	(arm_instruction_changes_pc): Likewise.

I feel they should be moved to arch/arm.c, because they are not about
getting the next pcs.

> 	(shifted_reg_val): Likewise.
> 	(thumb_advance_itstate): Likewise.

and this one.

> 	(thumb_get_next_pc_raw): Likewise.
> 	(arm_get_next_pc_raw): Likewise.
> 	(arm_get_next_pc): Likewise.
> 	(thumb_deal_with_atomic_sequence_raw): Likewise.
> 	(arm_deal_with_atomic_sequence_raw): Likewise.
> 	(arm_deal_with_atomic_sequence): Likewise.
> 	(arm_get_next_pcs_read_memory_unsigned_integer): New function.
> 	(arm_get_next_pcs_addr_bits_remove): Likewise.
> 	(arm_get_next_pcs_syscall_next_pc): Likewise.
> 	(arm_get_next_pcs_is_thumb): Likewise.
> 	(arm_software_single_step): Adjust for arm_get_next_pcs
> 	implementation.
> 	* arm-tdep.h: (arm_get_next_pc): Remove declaration.
> 	(arm_get_next_pcs_read_memory_unsigned_integer):
> 	New declaration.
> 	(arm_get_next_pcs_addr_bits_remove): Likewise.
> 	(arm_get_next_pcs_syscall_next_pc): Likewise.
> 	(arm_software_single_step): Likewise.
> 	(arm_deal_with_atomic_sequence: Remove declaration.
> 	(arm_get_next_pcs_is_thumb): New delcaration.
> 	* arm-wince-tdep.c: Include arch/arm-get-next-pcs.h.
> 	* armbsd-tdep.c: Likewise.
> 	* armnbsd-tdep.c: Likewise.
> 	* armobsd-tdep.c: Likewise.

Why do we need to include arm-get-next-pcs.h in these *-tdep.c files?

> 	* common/gdb_vecs.h: Add CORE_ADDR vector definition.
> 	* configure.tgt: Add arm-get-next-pcs.o, arm-linux.o to all
> 	relevent arm targets.
> 	* symtab.h: Move CORE_ADDR vector definition to gdb_vecs.h.
>
> gdb/gdbserver/ChangeLog:
> 	* Makefile.in : Add arm-get-next-pcs.c/o, arm-linux.c/o.

Please describe what are changed.

> 	* configure.srv: Add arm-get-next-pcs.o, arm-linux.o
> 	to needed arm targets.
> 	* linux-arm-low.c: Include arch/arm-linux.h,
> 	aarch/arm-get-next-pcs.h.
> 	(get_next_pcs_ops): New struct.
> 	(get_next_pcs_addr_bits_remove): New function.
> 	(get_next_pcs_is_thumb): New function.
> 	(get_next_pcs_read_memory_unsigned_integer): Likewise.
> 	(arm_sigreturn_next_pc): Likewise.
> 	(get_next_pcs_syscall_next_pc): Likewise.
> 	(arm_gdbserver_get_next_pcs): Likewise.
> 	(struct linux_target_ops) <arm_gdbserver_get_next_pcs>:
> 	Initialize.
> 	* linux-low.h: Move CORE_ADDR vector definition to gdb_vecs.h.
> 	* server.h: Include gdb_vecs.h.
> ---
>  gdb/Makefile.in               |   16 +-
>  gdb/aarch32-linux-nat.c       |    1 +
>  gdb/arch/arm-get-next-pcs.c   | 1216 +++++++++++++++++++++++++++++++++
>  gdb/arch/arm-get-next-pcs.h   |   95 +++
>  gdb/arch/arm-linux.c          |   59 ++
>  gdb/arch/arm-linux.h          |   73 ++
>  gdb/arm-linux-nat.c           |    2 +
>  gdb/arm-linux-tdep.c          |  136 ++--
>  gdb/arm-tdep.c                | 1495 +++++------------------------------------
>  gdb/arm-tdep.h                |   18 +-
>  gdb/arm-wince-tdep.c          |    1 +
>  gdb/armbsd-tdep.c             |    1 +
>  gdb/armnbsd-tdep.c            |    1 +
>  gdb/armobsd-tdep.c            |    1 +
>  gdb/common/gdb_vecs.h         |    2 +
>  gdb/configure.tgt             |   20 +-
>  gdb/gdbserver/Makefile.in     |    9 +-
>  gdb/gdbserver/configure.srv   |    2 +
>  gdb/gdbserver/linux-arm-low.c |  144 +++-
>  gdb/gdbserver/linux-low.h     |    2 -
>  gdb/gdbserver/server.h        |    1 +
>  gdb/symtab.h                  |    2 -
>  22 files changed, 1871 insertions(+), 1426 deletions(-)
>  create mode 100644 gdb/arch/arm-get-next-pcs.c
>  create mode 100644 gdb/arch/arm-get-next-pcs.h
>  create mode 100644 gdb/arch/arm-linux.c
>  create mode 100644 gdb/arch/arm-linux.h
>



> +
> +/* Checks for an atomic sequence of instructions beginning with a LDREX{,B,H,D}
> +   instruction and ending with a STREX{,B,H,D} instruction.  If such a sequence
> +   is found, attempt to step through it.  The end of the sequence address is
> +   added to the next_pcs list.  */
> +
> +static int
> +thumb_deal_with_atomic_sequence_raw (struct arm_get_next_pcs *self,
> +				     CORE_ADDR pc,
> +				     VEC (CORE_ADDR) **next_pcs)

We can return VEC (CORE_ADDR) * here, if it is NULL, the sequence is not
found, otherwise, the end of the sequence addresses are returned in the vector.

> +
> +/* Checks for an atomic sequence of instructions beginning with a LDREX{,B,H,D}
> +   instruction and ending with a STREX{,B,H,D} instruction.  If such a sequence
> +   is found, attempt to step through it.  The end of the sequence address is
> +   added to the next_pcs list.  */
> +
> +static int
> +arm_deal_with_atomic_sequence_raw (struct arm_get_next_pcs *self,
> +				   CORE_ADDR pc,
> +				   VEC (CORE_ADDR) **next_pcs)

Likewise.

> +
> +/* See arm-get-next-pcs.h.  */
> +
> +VEC (CORE_ADDR) *
> +arm_get_next_pcs (struct arm_get_next_pcs *self, CORE_ADDR pc)
> +{
> +  VEC (CORE_ADDR) *next_pcs = NULL;
> +
> +  if (self->ops->is_thumb (self))
> +    {
> +      if (!thumb_deal_with_atomic_sequence_raw (self, pc, &next_pcs))
> +	return thumb_get_next_pcs_raw (self, pc, &next_pcs);

Why do we need to pass next_pcs to thumb_get_next_pcs_raw?  Isn't
simpler to write it like this,

        next_pcs = thumb_deal_with_atomic_sequence_raw (self, pc);
        if (next_pcs == NULL)
          next_pcs = thumb_get_next_pcs_raw (self, pc);

> +    }
> +  else
> +    {
> +      if (!arm_deal_with_atomic_sequence_raw (self, pc, &next_pcs))
> +	return arm_get_next_pcs_raw (self, pc, &next_pcs);
> +    }
> +
> +  return next_pcs;
> +}

> diff --git a/gdb/arch/arm-get-next-pcs.h b/gdb/arch/arm-get-next-pcs.h
> new file mode 100644
> index 0000000..39921e0
> --- /dev/null
> +++ b/gdb/arch/arm-get-next-pcs.h
> @@ -0,0 +1,95 @@
> +/* Common code for ARM software single stepping support.
> +
> +   Copyright (C) 1988-2015 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/>.  */
> +
> +#ifndef ARM_GET_NEXT_PCS_H
> +#define ARM_GET_NEXT_PCS_H 1
> +
> +/* Support routines for instruction parsing.  */
> +#define submask(x) ((1L << ((x) + 1)) - 1)
> +#define bits(obj,st,fn) (((obj) >> (st)) & submask ((fn) - (st)))
> +#define bit(obj,st) (((obj) >> (st)) & 1)
> +#define sbits(obj,st,fn) \
> +  ((long) (bits(obj,st,fn) | ((long) bit(obj,fn) * ~ submask (fn - st))))
> +#define BranchDest(addr,instr) \
> +  ((CORE_ADDR) (((unsigned long) (addr)) + 8 + (sbits (instr, 0, 23) << 2)))
> +

These macros should be moved to arch/arm.h.

-- 
Yao (齐尧)