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Re: [RFC v3 3/8] Add basic Linux kernel support


Hi Philipp and Andreas,

I have some further comments on this patch specifically about copying
task_struct->pid into ptid->lwp and using task_struct address as tid.

I see that we are overriding lwp, tid which any target beneath might
be using differently.

So suggestion about storing task_struct->pid or task_struct address is
to use private_thread_info in binutils-gdb/gdb/gdbthread.h for this
information.

I also have reservation about use of old_ptid naming in struct
lk_private and > +struct lk_ptid_map.

old_ptid naming is a little confusing kindly choose a distinguishable
name for old_ptid varibles in both lk_private and lk_ptid_map.

Further Here's an implementation of bitmap_weight function from linux
kernel. Kindly see if your implementation can be improved and moved to
a generic area in gdb.

 10 int __bitmap_weight(const unsigned long *bitmap, int bits)
 11 {
 12         int k, w = 0, lim = bits/BITS_PER_LONG;
 13
 14         for (k = 0; k < lim; k++)
 15                 w += hweight_long(bitmap[k]);
 16
 17         if (bits % BITS_PER_LONG)
 18                 w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));
 19
 20         return w;
 21 }

Thanks!

--
Omair.

On 16 March 2017 at 21:57, Philipp Rudo <prudo@linux.vnet.ibm.com> wrote:
> This patch implements a basic target_ops for Linux kernel support. In
> particular it models Linux tasks as GDB threads such that you are able to
> change to a given thread, get backtraces, disassemble the current frame
> etc..
>
> Currently the target_ops is designed only to work with static targets, i.e.
> dumps. Thus it lacks implementation for hooks like to_wait, to_resume or
> to_store_registers. Furthermore the mapping between a CPU and the
> task_struct of the running task is only be done once at initialization. See
> cover letter for a detailed discussion.
>
> Nevertheless i made some design decisions different to Peter [1] which are
> worth discussing. Especially storing the private data in a htab (or
> std::unordered_map if i had the time...) instead of global variables makes
> the code much nicer and less memory consuming.
>
> [1] https://sourceware.org/ml/gdb-patches/2016-12/msg00382.html
>
> gdb/ChangeLog:
>
>     * gdbarch.sh (lk_init_private): New hook.
>     * gdbarch.h: Regenerated.
>     * gdbarch.c: Regenerated.
>     * lk-low.h: New file.
>     * lk-low.c: New file.
>     * lk-lists.h: New file.
>     * lk-lists.c: New file.
>     * Makefile.in (SFILES, ALLDEPFILES): Add lk-low.c and lk-lists.c.
>     (HFILES_NO_SRCDIR): Add lk-low.h and lk-lists.h.
>     (ALL_TARGET_OBS): Add lk-low.o and lk-lists.o.
>     * configure.tgt (lk_target_obs): New variable with object files for Linux
>       kernel support.
>       (s390*-*-linux*): Add lk_target_obs.
> ---
>  gdb/Makefile.in   |   8 +
>  gdb/configure.tgt |   6 +-
>  gdb/gdbarch.c     |  31 ++
>  gdb/gdbarch.h     |   7 +
>  gdb/gdbarch.sh    |   4 +
>  gdb/lk-lists.c    |  47 +++
>  gdb/lk-lists.h    |  56 ++++
>  gdb/lk-low.c      | 833 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  gdb/lk-low.h      | 310 ++++++++++++++++++++
>  9 files changed, 1301 insertions(+), 1 deletion(-)
>  create mode 100644 gdb/lk-lists.c
>  create mode 100644 gdb/lk-lists.h
>  create mode 100644 gdb/lk-low.c
>  create mode 100644 gdb/lk-low.h
>
> diff --git a/gdb/Makefile.in b/gdb/Makefile.in
> index 0818742..9387c66 100644
> --- a/gdb/Makefile.in
> +++ b/gdb/Makefile.in
> @@ -817,6 +817,8 @@ ALL_TARGET_OBS = \
>         iq2000-tdep.o \
>         linux-record.o \
>         linux-tdep.o \
> +       lk-lists.o \
> +       lk-low.o \
>         lm32-tdep.o \
>         m32c-tdep.o \
>         m32r-linux-tdep.o \
> @@ -1103,6 +1105,8 @@ SFILES = \
>         jit.c \
>         language.c \
>         linespec.c \
> +       lk-lists.c \
> +       lk-low.c \
>         location.c \
>         m2-exp.y \
>         m2-lang.c \
> @@ -1350,6 +1354,8 @@ HFILES_NO_SRCDIR = \
>         linux-nat.h \
>         linux-record.h \
>         linux-tdep.h \
> +       lk-lists.h \
> +       lk-low.h \
>         location.h \
>         m2-lang.h \
>         m32r-tdep.h \
> @@ -2547,6 +2553,8 @@ ALLDEPFILES = \
>         linux-fork.c \
>         linux-record.c \
>         linux-tdep.c \
> +       lk-lists.c \
> +       lk-low.c \
>         lm32-tdep.c \
>         m32r-linux-nat.c \
>         m32r-linux-tdep.c \
> diff --git a/gdb/configure.tgt b/gdb/configure.tgt
> index cb909e7..8d87fea 100644
> --- a/gdb/configure.tgt
> +++ b/gdb/configure.tgt
> @@ -34,6 +34,10 @@ case $targ in
>      ;;
>  esac
>
> +# List of objectfiles for Linux kernel support.  To be included into *-linux*
> +# targets wich support Linux kernel debugging.
> +lk_target_obs="lk-lists.o lk-low.o"
> +
>  # map target info into gdb names.
>
>  case "${targ}" in
> @@ -479,7 +483,7 @@ powerpc*-*-*)
>  s390*-*-linux*)
>         # Target: S390 running Linux
>         gdb_target_obs="s390-linux-tdep.o solib-svr4.o linux-tdep.o \
> -                       linux-record.o"
> +                       linux-record.o ${lk_target_obs}"
>         build_gdbserver=yes
>         ;;
>
> diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
> index 87eafb2..5509a6c 100644
> --- a/gdb/gdbarch.c
> +++ b/gdb/gdbarch.c
> @@ -349,6 +349,7 @@ struct gdbarch
>    gdbarch_addressable_memory_unit_size_ftype *addressable_memory_unit_size;
>    char ** disassembler_options;
>    const disasm_options_t * valid_disassembler_options;
> +  gdbarch_lk_init_private_ftype *lk_init_private;
>  };
>
>  /* Create a new ``struct gdbarch'' based on information provided by
> @@ -1139,6 +1140,12 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file)
>                        "gdbarch_dump: iterate_over_regset_sections = <%s>\n",
>                        host_address_to_string (gdbarch->iterate_over_regset_sections));
>    fprintf_unfiltered (file,
> +                      "gdbarch_dump: gdbarch_lk_init_private_p() = %d\n",
> +                      gdbarch_lk_init_private_p (gdbarch));
> +  fprintf_unfiltered (file,
> +                      "gdbarch_dump: lk_init_private = <%s>\n",
> +                      host_address_to_string (gdbarch->lk_init_private));
> +  fprintf_unfiltered (file,
>                        "gdbarch_dump: long_bit = %s\n",
>                        plongest (gdbarch->long_bit));
>    fprintf_unfiltered (file,
> @@ -5008,6 +5015,30 @@ set_gdbarch_valid_disassembler_options (struct gdbarch *gdbarch,
>    gdbarch->valid_disassembler_options = valid_disassembler_options;
>  }
>
> +int
> +gdbarch_lk_init_private_p (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  return gdbarch->lk_init_private != NULL;
> +}
> +
> +void
> +gdbarch_lk_init_private (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  gdb_assert (gdbarch->lk_init_private != NULL);
> +  if (gdbarch_debug >= 2)
> +    fprintf_unfiltered (gdb_stdlog, "gdbarch_lk_init_private called\n");
> +  gdbarch->lk_init_private (gdbarch);
> +}
> +
> +void
> +set_gdbarch_lk_init_private (struct gdbarch *gdbarch,
> +                             gdbarch_lk_init_private_ftype lk_init_private)
> +{
> +  gdbarch->lk_init_private = lk_init_private;
> +}
> +
>
>  /* Keep a registry of per-architecture data-pointers required by GDB
>     modules.  */
> diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
> index 34f82a7..c03bf00 100644
> --- a/gdb/gdbarch.h
> +++ b/gdb/gdbarch.h
> @@ -1553,6 +1553,13 @@ extern void set_gdbarch_disassembler_options (struct gdbarch *gdbarch, char ** d
>
>  extern const disasm_options_t * gdbarch_valid_disassembler_options (struct gdbarch *gdbarch);
>  extern void set_gdbarch_valid_disassembler_options (struct gdbarch *gdbarch, const disasm_options_t * valid_disassembler_options);
> +/* Initiate architecture dependent private data for the linux-kernel target. */
> +
> +extern int gdbarch_lk_init_private_p (struct gdbarch *gdbarch);
> +
> +typedef void (gdbarch_lk_init_private_ftype) (struct gdbarch *gdbarch);
> +extern void gdbarch_lk_init_private (struct gdbarch *gdbarch);
> +extern void set_gdbarch_lk_init_private (struct gdbarch *gdbarch, gdbarch_lk_init_private_ftype *lk_init_private);
>
>  /* Definition for an unknown syscall, used basically in error-cases.  */
>  #define UNKNOWN_SYSCALL (-1)
> diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
> index 39b1f94..cad45d1 100755
> --- a/gdb/gdbarch.sh
> +++ b/gdb/gdbarch.sh
> @@ -1167,6 +1167,10 @@ m:int:addressable_memory_unit_size:void:::default_addressable_memory_unit_size::
>  v:char **:disassembler_options:::0:0::0:pstring_ptr (gdbarch->disassembler_options)
>  v:const disasm_options_t *:valid_disassembler_options:::0:0::0:host_address_to_string (gdbarch->valid_disassembler_options)
>
> +# Initialize architecture dependent private data for the linux-kernel
> +# target.
> +M:void:lk_init_private:void:
> +
>  EOF
>  }
>
> diff --git a/gdb/lk-lists.c b/gdb/lk-lists.c
> new file mode 100644
> index 0000000..55d11bd
> --- /dev/null
> +++ b/gdb/lk-lists.c
> @@ -0,0 +1,47 @@
> +/* Iterators for internal data structures of the Linux kernel.
> +
> +   Copyright (C) 2016 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 "inferior.h"
> +#include "lk-lists.h"
> +#include "lk-low.h"
> +
> +/* Returns next entry from struct list_head CURR while iterating field
> +   SNAME->FNAME.  */
> +
> +CORE_ADDR
> +lk_list_head_next (CORE_ADDR curr, const char *sname, const char *fname)
> +{
> +  CORE_ADDR next, next_prev;
> +
> +  /* We must always assume that the data we handle is corrupted.  Thus use
> +     curr->next->prev == curr as sanity check.  */
> +  next = lk_read_addr (curr + LK_OFFSET (list_head, next));
> +  next_prev = lk_read_addr (next + LK_OFFSET (list_head, prev));
> +
> +  if (!curr || curr != next_prev)
> +    {
> +      error (_("Memory corruption detected while iterating list_head at "\
> +              "0x%s belonging to list %s->%s."),
> +            phex (curr, lk_builtin_type_size (unsigned_long)) , sname, fname);
> +    }
> +
> +  return next;
> +}
> diff --git a/gdb/lk-lists.h b/gdb/lk-lists.h
> new file mode 100644
> index 0000000..f9c2a85
> --- /dev/null
> +++ b/gdb/lk-lists.h
> @@ -0,0 +1,56 @@
> +/* Iterators for internal data structures of the Linux kernel.
> +
> +   Copyright (C) 2016 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 __LK_LISTS_H__
> +#define __LK_LISTS_H__
> +
> +extern CORE_ADDR lk_list_head_next (CORE_ADDR curr, const char *sname,
> +                                   const char *fname);
> +
> +/* Iterator over field SNAME->FNAME of type struct list_head starting at
> +   address START of type struct list_head.  This iterator is intended to be
> +   used for lists initiated with macro LIST_HEAD (include/linux/list.h) in
> +   the kernel, i.e. lists that START is a global variable of type struct
> +   list_head and _not_ of type struct SNAME as the rest of the list.  Thus
> +   START will not be iterated over but only be used to start/terminate the
> +   iteration.  */
> +
> +#define lk_list_for_each(next, start, sname, fname)            \
> +  for ((next) = lk_list_head_next ((start), #sname, #fname);   \
> +       (next) != (start);                                      \
> +       (next) = lk_list_head_next ((next), #sname, #fname))
> +
> +/* Iterator over struct SNAME linked together via field SNAME->FNAME of type
> +   struct list_head starting at address START of type struct SNAME.  In
> +   contrast to the iterator above, START is a "full" member of the list and
> +   thus will be iterated over.  */
> +
> +#define lk_list_for_each_container(cont, start, sname, fname)  \
> +  CORE_ADDR _next;                                             \
> +  bool _first_loop = true;                                     \
> +  for ((cont) = (start),                                       \
> +       _next = (start) + LK_OFFSET (sname, fname);             \
> +                                                               \
> +       (cont) != (start) || _first_loop;                       \
> +                                                               \
> +       _next = lk_list_head_next (_next, #sname, #fname),      \
> +       (cont) = LK_CONTAINER_OF (_next, sname, fname),         \
> +       _first_loop = false)
> +
> +#endif /* __LK_LISTS_H__ */
> diff --git a/gdb/lk-low.c b/gdb/lk-low.c
> new file mode 100644
> index 0000000..768f228
> --- /dev/null
> +++ b/gdb/lk-low.c
> @@ -0,0 +1,833 @@
> +/* Basic Linux kernel support, architecture independent.
> +
> +   Copyright (C) 2016 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 "block.h"
> +#include "exceptions.h"
> +#include "frame.h"
> +#include "gdbarch.h"
> +#include "gdbcore.h"
> +#include "gdbthread.h"
> +#include "gdbtypes.h"
> +#include "inferior.h"
> +#include "lk-lists.h"
> +#include "lk-low.h"
> +#include "objfiles.h"
> +#include "observer.h"
> +#include "solib.h"
> +#include "target.h"
> +#include "value.h"
> +
> +#include <algorithm>
> +
> +struct target_ops *linux_kernel_ops = NULL;
> +
> +/* Initialize a private data entry for an address, where NAME is the name
> +   of the symbol, i.e. variable name in Linux, ALIAS the name used to
> +   retrieve the entry from hashtab, and SILENT a flag to determine if
> +   errors should be ignored.
> +
> +   Returns a pointer to the new entry.  In case of an error, either returns
> +   NULL (SILENT = TRUE) or throws an error (SILENT = FALSE).  If SILENT = TRUE
> +   the caller is responsible to check for errors.
> +
> +   Do not use directly, use LK_DECLARE_* macros defined in lk-low.h instead.  */
> +
> +struct lk_private_data *
> +lk_init_addr (const char *name, const char *alias, int silent)
> +{
> +  struct lk_private_data *data;
> +  struct bound_minimal_symbol bmsym;
> +  void **new_slot;
> +  void *old_slot;
> +
> +  if ((old_slot = lk_find (alias)) != NULL)
> +    return (struct lk_private_data *) old_slot;
> +
> +  bmsym = lookup_minimal_symbol (name, NULL, NULL);
> +
> +  if (bmsym.minsym == NULL)
> +    {
> +      if (!silent)
> +       error (_("Could not find address %s.  Aborting."), alias);
> +      return NULL;
> +    }
> +
> +  data = XCNEW (struct lk_private_data);
> +  data->alias = alias;
> +  data->data.addr = BMSYMBOL_VALUE_ADDRESS (bmsym);
> +
> +  new_slot = lk_find_slot (alias);
> +  *new_slot = data;
> +
> +  return data;
> +}
> +
> +/* Same as lk_init_addr but for structs.  */
> +
> +struct lk_private_data *
> +lk_init_struct (const char *name, const char *alias, int silent)
> +{
> +  struct lk_private_data *data;
> +  const struct block *global;
> +  const struct symbol *sym;
> +  struct type *type;
> +  void **new_slot;
> +  void *old_slot;
> +
> +  if ((old_slot = lk_find (alias)) != NULL)
> +    return (struct lk_private_data *) old_slot;
> +
> +  global = block_global_block(get_selected_block (0));
> +  sym = lookup_symbol (name, global, STRUCT_DOMAIN, NULL).symbol;
> +
> +  if (sym != NULL)
> +    {
> +      type = SYMBOL_TYPE (sym);
> +      goto out;
> +    }
> +
> +  /*  Chek for "typedef struct { ... } name;"-like definitions.  */
> +  sym = lookup_symbol (name, global, VAR_DOMAIN, NULL).symbol;
> +  if (sym == NULL)
> +    goto error;
> +
> +  type = check_typedef (SYMBOL_TYPE (sym));
> +
> +  if (TYPE_CODE (type) == TYPE_CODE_STRUCT)
> +    goto out;
> +
> +error:
> +  if (!silent)
> +    error (_("Could not find %s.  Aborting."), alias);
> +
> +  return NULL;
> +
> +out:
> +  data = XCNEW (struct lk_private_data);
> +  data->alias = alias;
> +  data->data.type = type;
> +
> +  new_slot = lk_find_slot (alias);
> +  *new_slot = data;
> +
> +  return data;
> +}
> +
> +/* Nearly the same as lk_init_addr, with the difference that two names are
> +   needed, i.e. the struct name S_NAME containing the field with name
> +   F_NAME.  */
> +
> +struct lk_private_data *
> +lk_init_field (const char *s_name, const char *f_name,
> +              const char *s_alias, const char *f_alias,
> +              int silent)
> +{
> +  struct lk_private_data *data;
> +  struct lk_private_data *parent;
> +  struct field *first, *last, *field;
> +  void **new_slot;
> +  void *old_slot;
> +
> +  if ((old_slot = lk_find (f_alias)) != NULL)
> +    return (struct lk_private_data *) old_slot;
> +
> +  parent = lk_find (s_alias);
> +  if (parent == NULL)
> +    {
> +      parent = lk_init_struct (s_name, s_alias, silent);
> +
> +      /* Only SILENT == true needed, as otherwise lk_init_struct would throw
> +        an error.  */
> +      if (parent == NULL)
> +       return NULL;
> +    }
> +
> +  first = TYPE_FIELDS (parent->data.type);
> +  last = first + TYPE_NFIELDS (parent->data.type);
> +  for (field = first; field < last; field ++)
> +    {
> +      if (streq (field->name, f_name))
> +       break;
> +    }
> +
> +  if (field == last)
> +    {
> +      if (!silent)
> +       error (_("Could not find field %s->%s.  Aborting."), s_alias, f_name);
> +      return NULL;
> +    }
> +
> +  data = XCNEW (struct lk_private_data);
> +  data->alias = f_alias;
> +  data->data.field = field;
> +
> +  new_slot = lk_find_slot (f_alias);
> +  *new_slot = data;
> +
> +  return data;
> +}
> +
> +/* Map cpu number CPU to the original PTID from target beneath.  */
> +
> +static ptid_t
> +lk_cpu_to_old_ptid (const int cpu)
> +{
> +  struct lk_ptid_map *ptid_map;
> +
> +  for (ptid_map = LK_PRIVATE->old_ptid; ptid_map;
> +       ptid_map = ptid_map->next)
> +    {
> +      if (ptid_map->cpu == cpu)
> +       return ptid_map->old_ptid;
> +    }
> +
> +  error (_("Could not map CPU %d to original PTID.  Aborting."), cpu);
> +}
> +
> +/* Helper functions to read and return basic types at a given ADDRess.  */
> +
> +/* Read and return the integer value at address ADDR.  */
> +
> +int
> +lk_read_int (CORE_ADDR addr)
> +{
> +  size_t int_size = lk_builtin_type_size (int);
> +  enum bfd_endian endian = gdbarch_byte_order (current_inferior ()->gdbarch);
> +  return read_memory_integer (addr, int_size, endian);
> +}
> +
> +/* Read and return the unsigned integer value at address ADDR.  */
> +
> +unsigned int
> +lk_read_uint (CORE_ADDR addr)
> +{
> +  size_t uint_size = lk_builtin_type_size (unsigned_int);
> +  enum bfd_endian endian = gdbarch_byte_order (current_inferior ()->gdbarch);
> +  return read_memory_integer (addr, uint_size, endian);
> +}
> +
> +/* Read and return the long integer value at address ADDR.  */
> +
> +LONGEST
> +lk_read_long (CORE_ADDR addr)
> +{
> +  size_t long_size = lk_builtin_type_size (long);
> +  enum bfd_endian endian = gdbarch_byte_order (current_inferior ()->gdbarch);
> +  return read_memory_integer (addr, long_size, endian);
> +}
> +
> +/* Read and return the unsigned long integer value at address ADDR.  */
> +
> +ULONGEST
> +lk_read_ulong (CORE_ADDR addr)
> +{
> +  size_t ulong_size = lk_builtin_type_size (unsigned_long);
> +  enum bfd_endian endian = gdbarch_byte_order (current_inferior ()->gdbarch);
> +  return read_memory_unsigned_integer (addr, ulong_size, endian);
> +}
> +
> +/* Read and return the address value at address ADDR.  */
> +
> +CORE_ADDR
> +lk_read_addr (CORE_ADDR addr)
> +{
> +  return (CORE_ADDR) lk_read_ulong (addr);
> +}
> +
> +/* Reads a bitmap at a given ADDRess of size SIZE (in bits). Allocates and
> +   returns an array of ulongs.  The caller is responsible to free the array
> +   after it is no longer needed.  */
> +
> +ULONGEST *
> +lk_read_bitmap (CORE_ADDR addr, size_t size)
> +{
> +  ULONGEST *bitmap;
> +  size_t ulong_size, len;
> +
> +  ulong_size = lk_builtin_type_size (unsigned_long);
> +  len = LK_DIV_ROUND_UP (size, ulong_size * LK_BITS_PER_BYTE);
> +  bitmap = XNEWVEC (ULONGEST, len);
> +
> +  for (size_t i = 0; i < len; i++)
> +    bitmap[i] = lk_read_ulong (addr + i * ulong_size);
> +
> +  return bitmap;
> +}
> +
> +/* Return the next set bit in bitmap BITMAP of size SIZE (in bits)
> +   starting from bit (index) BIT.  Return SIZE when the end of the bitmap
> +   was reached.  To iterate over all set bits use macro
> +   LK_BITMAP_FOR_EACH_SET_BIT defined in lk-low.h.  */
> +
> +size_t
> +lk_bitmap_find_next_bit (ULONGEST *bitmap, size_t size, size_t bit)
> +{
> +  size_t ulong_size, bits_per_ulong, elt;
> +
> +  ulong_size = lk_builtin_type_size (unsigned_long);
> +  bits_per_ulong = ulong_size * LK_BITS_PER_BYTE;
> +  elt = bit / bits_per_ulong;
> +
> +  while (bit < size)
> +    {
> +      /* FIXME: Explain why using lsb0 bit order.  */
> +      if (bitmap[elt] & (1UL << (bit % bits_per_ulong)))
> +       return bit;
> +
> +      bit++;
> +      if (bit % bits_per_ulong == 0)
> +       elt++;
> +    }
> +
> +  return size;
> +}
> +
> +/* Returns the Hamming weight, i.e. number of set bits, of bitmap BITMAP
> +   with size SIZE (in bits).  */
> +
> +size_t
> +lk_bitmap_hweight (ULONGEST *bitmap, size_t size)
> +{
> +  size_t ulong_size, bit, bits_per_ulong, elt, retval;
> +
> +  ulong_size = lk_builtin_type_size (unsigned_long);
> +  bits_per_ulong = ulong_size * LK_BITS_PER_BYTE;
> +  elt = bit = 0;
> +  retval = 0;
> +
> +  while (bit < size)
> +    {
> +      if (bitmap[elt] & (1 << bit % bits_per_ulong))
> +       retval++;
> +
> +      bit++;
> +      if (bit % bits_per_ulong == 0)
> +       elt++;
> +    }
> +
> +  return retval;
> +}
> +
> +/* Provide the per_cpu_offset of cpu CPU.  See comment in lk-low.h for
> +   details.  */
> +
> +CORE_ADDR
> +lk_get_percpu_offset (unsigned int cpu)
> +{
> +  size_t ulong_size = lk_builtin_type_size (unsigned_long);
> +  CORE_ADDR percpu_elt;
> +
> +  /* Give the architecture a chance to overwrite default behaviour.  */
> +  if (LK_HOOK->get_percpu_offset)
> +      return LK_HOOK->get_percpu_offset (cpu);
> +
> +  percpu_elt = LK_ADDR (__per_cpu_offset) + (ulong_size * cpu);
> +  return lk_read_addr (percpu_elt);
> +}
> +
> +
> +/* Test if a given task TASK is running.  See comment in lk-low.h for
> +   details.  */
> +
> +unsigned int
> +lk_task_running (CORE_ADDR task)
> +{
> +  ULONGEST *cpu_online_mask;
> +  size_t size;
> +  unsigned int cpu;
> +  struct cleanup *old_chain;
> +
> +  size = LK_BITMAP_SIZE (cpumask);
> +  cpu_online_mask = lk_read_bitmap (LK_ADDR (cpu_online_mask), size);
> +  old_chain = make_cleanup (xfree, cpu_online_mask);
> +
> +  LK_BITMAP_FOR_EACH_SET_BIT (cpu_online_mask, size, cpu)
> +    {
> +      CORE_ADDR rq;
> +      CORE_ADDR curr;
> +
> +      rq = LK_ADDR (runqueues) + lk_get_percpu_offset (cpu);
> +      curr = lk_read_addr (rq + LK_OFFSET (rq, curr));
> +
> +      if (curr == task)
> +       break;
> +    }
> +
> +  if (cpu == size)
> +    cpu = LK_CPU_INVAL;
> +
> +  do_cleanups (old_chain);
> +  return cpu;
> +}
> +
> +/* Update running tasks with information from struct rq->curr. */
> +
> +static void
> +lk_update_running_tasks ()
> +{
> +  ULONGEST *cpu_online_mask;
> +  size_t size;
> +  unsigned int cpu;
> +  struct cleanup *old_chain;
> +
> +  size = LK_BITMAP_SIZE (cpumask);
> +  cpu_online_mask = lk_read_bitmap (LK_ADDR (cpu_online_mask), size);
> +  old_chain = make_cleanup (xfree, cpu_online_mask);
> +
> +  LK_BITMAP_FOR_EACH_SET_BIT (cpu_online_mask, size, cpu)
> +    {
> +      struct thread_info *tp;
> +      CORE_ADDR rq, curr;
> +      LONGEST pid, inf_pid;
> +      ptid_t new_ptid, old_ptid;
> +
> +      rq = LK_ADDR (runqueues) + lk_get_percpu_offset (cpu);
> +      curr = lk_read_addr (rq + LK_OFFSET (rq, curr));
> +      pid = lk_read_int (curr + LK_OFFSET (task_struct, pid));
> +      inf_pid = current_inferior ()->pid;
> +
> +      new_ptid = ptid_build (inf_pid, pid, curr);
> +      old_ptid = lk_cpu_to_old_ptid (cpu); /* FIXME not suitable for
> +                                             running targets? */
> +
> +      tp = find_thread_ptid (old_ptid);
> +      if (tp && tp->state != THREAD_EXITED)
> +       thread_change_ptid (old_ptid, new_ptid);
> +    }
> +  do_cleanups (old_chain);
> +}
> +
> +/* Update sleeping tasks by walking the task_structs starting from
> +   init_task.  */
> +
> +static void
> +lk_update_sleeping_tasks ()
> +{
> +  CORE_ADDR init_task, task, thread;
> +  int inf_pid;
> +
> +  inf_pid = current_inferior ()->pid;
> +  init_task = LK_ADDR (init_task);
> +
> +  lk_list_for_each_container (task, init_task, task_struct, tasks)
> +    {
> +      lk_list_for_each_container (thread, task, task_struct, thread_group)
> +       {
> +         int pid;
> +         ptid_t ptid;
> +         struct thread_info *tp;
> +
> +         pid = lk_read_int (thread + LK_OFFSET (task_struct, pid));
> +         ptid = ptid_build (inf_pid, pid, thread);
> +
> +         tp = find_thread_ptid (ptid);
> +         if (tp == NULL || tp->state == THREAD_EXITED)
> +           add_thread (ptid);
> +       }
> +    }
> +}
> +
> +/* Function for targets to_update_thread_list hook.  */
> +
> +static void
> +lk_update_thread_list (struct target_ops *target)
> +{
> +  prune_threads ();
> +  lk_update_running_tasks ();
> +  lk_update_sleeping_tasks ();
> +}
> +
> +/* Function for targets to_fetch_registers hook.  */
> +
> +static void
> +lk_fetch_registers (struct target_ops *target,
> +                   struct regcache *regcache, int regnum)
> +{
> +  CORE_ADDR task;
> +  unsigned int cpu;
> +
> +  task = (CORE_ADDR) ptid_get_tid (regcache_get_ptid (regcache));
> +  cpu = lk_task_running (task);
> +
> +  /* Let the target beneath fetch registers of running tasks.  */
> +  if (cpu != LK_CPU_INVAL)
> +    {
> +      struct cleanup *old_inferior_ptid;
> +
> +      old_inferior_ptid = save_inferior_ptid ();
> +      inferior_ptid = lk_cpu_to_old_ptid (cpu);
> +      linux_kernel_ops->beneath->to_fetch_registers (target, regcache, regnum);
> +      do_cleanups (old_inferior_ptid);
> +    }
> +  else
> +    {
> +      struct gdbarch *gdbarch;
> +      unsigned int i;
> +
> +      LK_HOOK->get_registers (task, target, regcache, regnum);
> +
> +      /* Mark all registers not found as unavailable.  */
> +      gdbarch = get_regcache_arch (regcache);
> +      for (i = 0; i < gdbarch_num_regs (gdbarch); i++)
> +       {
> +         if (regcache_register_status (regcache, i) == REG_UNKNOWN)
> +           regcache_raw_supply (regcache, i, NULL);
> +       }
> +    }
> +}
> +
> +/* Function for targets to_pid_to_str hook.  Marks running tasks with an
> +   asterisk "*".  */
> +
> +static char *
> +lk_pid_to_str (struct target_ops *target, ptid_t ptid)
> +{
> +  static char buf[64];
> +  long pid;
> +  CORE_ADDR task;
> +
> +  pid = ptid_get_lwp (ptid);
> +  task = (CORE_ADDR) ptid_get_tid (ptid);
> +
> +  xsnprintf (buf, sizeof (buf), "PID: %5li%s, 0x%s",
> +            pid, ((lk_task_running (task) != LK_CPU_INVAL) ? "*" : ""),
> +            phex (task, lk_builtin_type_size (unsigned_long)));
> +
> +  return buf;
> +}
> +
> +/* Function for targets to_thread_name hook.  */
> +
> +static const char *
> +lk_thread_name (struct target_ops *target, struct thread_info *ti)
> +{
> +  static char buf[LK_TASK_COMM_LEN + 1];
> +  char tmp[LK_TASK_COMM_LEN + 1];
> +  CORE_ADDR task, comm;
> +  size_t size;
> +
> +  size = std::min ((unsigned int) LK_TASK_COMM_LEN,
> +                  LK_ARRAY_LEN(LK_FIELD (task_struct, comm)));
> +
> +  task = (CORE_ADDR) ptid_get_tid (ti->ptid);
> +  comm = task + LK_OFFSET (task_struct, comm);
> +  read_memory (comm, (gdb_byte *) tmp, size);
> +
> +  xsnprintf (buf, sizeof (buf), "%-16s", tmp);
> +
> +  return buf;
> +}
> +
> +/* Functions to initialize and free target_ops and its private data.  As well
> +   as functions for targets to_open/close/detach hooks.  */
> +
> +/* Check if OBFFILE is a Linux kernel.  */
> +
> +static int
> +lk_is_linux_kernel (struct objfile *objfile)
> +{
> +  int ok = 0;
> +
> +  if (objfile == NULL || !(objfile->flags & OBJF_MAINLINE))
> +    return 0;
> +
> +  ok += lookup_minimal_symbol ("linux_banner", NULL, objfile).minsym != NULL;
> +  ok += lookup_minimal_symbol ("_stext", NULL, objfile).minsym != NULL;
> +  ok += lookup_minimal_symbol ("_etext", NULL, objfile).minsym != NULL;
> +
> +  return (ok > 2);
> +}
> +
> +/* Initialize struct lk_private.  */
> +
> +static void
> +lk_init_private ()
> +{
> +  linux_kernel_ops->to_data = XCNEW (struct lk_private);
> +  LK_PRIVATE->hooks = XCNEW (struct lk_private_hooks);
> +  LK_PRIVATE->data = htab_create_alloc (31, (htab_hash) lk_hash_private_data,
> +                                       (htab_eq) lk_private_data_eq, NULL,
> +                                       xcalloc, xfree);
> +}
> +
> +/* Initialize architecture independent private data.  Must be called
> +   _after_ symbol tables were initialized.  */
> +
> +static void
> +lk_init_private_data ()
> +{
> +  if (LK_PRIVATE->data != NULL)
> +    htab_empty (LK_PRIVATE->data);
> +
> +  LK_DECLARE_FIELD (task_struct, tasks);
> +  LK_DECLARE_FIELD (task_struct, pid);
> +  LK_DECLARE_FIELD (task_struct, tgid);
> +  LK_DECLARE_FIELD (task_struct, thread_group);
> +  LK_DECLARE_FIELD (task_struct, comm);
> +  LK_DECLARE_FIELD (task_struct, thread);
> +
> +  LK_DECLARE_FIELD (list_head, next);
> +  LK_DECLARE_FIELD (list_head, prev);
> +
> +  LK_DECLARE_FIELD (rq, curr);
> +
> +  LK_DECLARE_FIELD (cpumask, bits);
> +
> +  LK_DECLARE_ADDR (init_task);
> +  LK_DECLARE_ADDR (runqueues);
> +  LK_DECLARE_ADDR (__per_cpu_offset);
> +  LK_DECLARE_ADDR (init_mm);
> +
> +  LK_DECLARE_ADDR_ALIAS (__cpu_online_mask, cpu_online_mask);  /* linux 4.5+ */
> +  LK_DECLARE_ADDR_ALIAS (cpu_online_bits, cpu_online_mask);    /* linux -4.4 */
> +  if (LK_ADDR (cpu_online_mask) == -1)
> +    error (_("Could not find address cpu_online_mask.  Aborting."));
> +}
> +
> +/* Frees the cpu to old ptid map.  */
> +
> +static void
> +lk_free_ptid_map ()
> +{
> +  while (LK_PRIVATE->old_ptid)
> +    {
> +      struct lk_ptid_map *tmp;
> +
> +      tmp = LK_PRIVATE->old_ptid;
> +      LK_PRIVATE->old_ptid = tmp->next;
> +      XDELETE (tmp);
> +    }
> +}
> +
> +/* Initialize the cpu to old ptid map.  Prefer the arch dependent
> +   map_running_task_to_cpu hook if provided, else assume that the PID used
> +   by target beneath is the same as in task_struct PID task_struct.  See
> +   comment on lk_ptid_map in lk-low.h for details.  */
> +
> +static void
> +lk_init_ptid_map ()
> +{
> +  struct thread_info *ti;
> +  ULONGEST *cpu_online_mask;
> +  size_t size;
> +  unsigned int cpu;
> +  struct cleanup *old_chain;
> +
> +  if (LK_PRIVATE->old_ptid != NULL)
> +    lk_free_ptid_map ();
> +
> +  size = LK_BITMAP_SIZE (cpumask);
> +  cpu_online_mask = lk_read_bitmap (LK_ADDR (cpu_online_mask), size);
> +  old_chain = make_cleanup (xfree, cpu_online_mask);
> +
> +  ALL_THREADS (ti)
> +    {
> +      struct lk_ptid_map *ptid_map = XCNEW (struct lk_ptid_map);
> +      CORE_ADDR rq, curr;
> +      int pid;
> +
> +      /* Give the architecture a chance to overwrite default behaviour.  */
> +      if (LK_HOOK->map_running_task_to_cpu)
> +       {
> +         ptid_map->cpu = LK_HOOK->map_running_task_to_cpu (ti);
> +       }
> +      else
> +       {
> +         LK_BITMAP_FOR_EACH_SET_BIT (cpu_online_mask, size, cpu)
> +           {
> +             rq = LK_ADDR (runqueues) + lk_get_percpu_offset (cpu);
> +             curr = lk_read_addr (rq + LK_OFFSET (rq, curr));
> +             pid = lk_read_int (curr + LK_OFFSET (task_struct, pid));
> +
> +             if (pid == ptid_get_lwp (ti->ptid))
> +               {
> +                 ptid_map->cpu = cpu;
> +                 break;
> +               }
> +           }
> +         if (cpu == size)
> +           error (_("Could not map thread with pid %d, lwp %lu to a cpu."),
> +                  ti->ptid.pid, ti->ptid.lwp);
> +       }
> +      ptid_map->old_ptid = ti->ptid;
> +      ptid_map->next = LK_PRIVATE->old_ptid;
> +      LK_PRIVATE->old_ptid = ptid_map;
> +    }
> +
> +  do_cleanups (old_chain);
> +}
> +
> +/* Initializes all private data and pushes the linux kernel target, if not
> +   already done.  */
> +
> +static void
> +lk_try_push_target ()
> +{
> +  struct gdbarch *gdbarch;
> +
> +  gdbarch = current_inferior ()->gdbarch;
> +  if (!(gdbarch && gdbarch_lk_init_private_p (gdbarch)))
> +    error (_("Linux kernel debugging not supported on %s."),
> +          gdbarch_bfd_arch_info (gdbarch)->printable_name);
> +
> +  lk_init_private ();
> +  lk_init_private_data ();
> +  gdbarch_lk_init_private (gdbarch);
> +  /* Check for required arch hooks.  */
> +  gdb_assert (LK_HOOK->get_registers);
> +
> +  lk_init_ptid_map ();
> +  lk_update_thread_list (linux_kernel_ops);
> +
> +  if (!target_is_pushed (linux_kernel_ops))
> +    push_target (linux_kernel_ops);
> +}
> +
> +/* Function for targets to_open hook.  */
> +
> +static void
> +lk_open (const char *args, int from_tty)
> +{
> +  struct objfile *objfile;
> +
> +  if (target_is_pushed (linux_kernel_ops))
> +    {
> +      printf_unfiltered (_("Linux kernel target already pushed.  Aborting\n"));
> +      return;
> +    }
> +
> +  for (objfile = current_program_space->objfiles; objfile;
> +       objfile = objfile->next)
> +    {
> +      if (lk_is_linux_kernel (objfile)
> +         && ptid_get_pid (inferior_ptid) != 0)
> +       {
> +         lk_try_push_target ();
> +         return;
> +       }
> +    }
> +  printf_unfiltered (_("Could not find a valid Linux kernel object file.  "
> +                      "Aborting.\n"));
> +}
> +
> +/* Function for targets to_close hook.  Deletes all private data.  */
> +
> +static void
> +lk_close (struct target_ops *ops)
> +{
> +  htab_delete (LK_PRIVATE->data);
> +  lk_free_ptid_map ();
> +  XDELETE (LK_PRIVATE->hooks);
> +
> +  XDELETE (LK_PRIVATE);
> +  linux_kernel_ops->to_data = NULL;
> +}
> +
> +/* Function for targets to_detach hook.  */
> +
> +static void
> +lk_detach (struct target_ops *t, const char *args, int from_tty)
> +{
> +  struct target_ops *beneath = linux_kernel_ops->beneath;
> +
> +  unpush_target (linux_kernel_ops);
> +  reinit_frame_cache ();
> +  if (from_tty)
> +    printf_filtered (_("Linux kernel target detached.\n"));
> +
> +  beneath->to_detach (beneath, args, from_tty);
> +}
> +
> +/* Function for new objfile observer.  */
> +
> +static void
> +lk_observer_new_objfile (struct objfile *objfile)
> +{
> +  if (lk_is_linux_kernel (objfile)
> +      && ptid_get_pid (inferior_ptid) != 0)
> +    lk_try_push_target ();
> +}
> +
> +/* Function for inferior created observer.  */
> +
> +static void
> +lk_observer_inferior_created (struct target_ops *ops, int from_tty)
> +{
> +  struct objfile *objfile;
> +
> +  if (ptid_get_pid (inferior_ptid) == 0)
> +    return;
> +
> +  for (objfile = current_inferior ()->pspace->objfiles; objfile;
> +       objfile = objfile->next)
> +    {
> +      if (lk_is_linux_kernel (objfile))
> +       {
> +         lk_try_push_target ();
> +         return;
> +       }
> +    }
> +}
> +
> +/* Initialize linux kernel target.  */
> +
> +static void
> +init_linux_kernel_ops (void)
> +{
> +  struct target_ops *t;
> +
> +  if (linux_kernel_ops != NULL)
> +    return;
> +
> +  t = XCNEW (struct target_ops);
> +  t->to_shortname = "linux-kernel";
> +  t->to_longname = "linux kernel support";
> +  t->to_doc = "Adds support to debug the Linux kernel";
> +
> +  /* set t->to_data = struct lk_private in lk_init_private.  */
> +
> +  t->to_open = lk_open;
> +  t->to_close = lk_close;
> +  t->to_detach = lk_detach;
> +  t->to_fetch_registers = lk_fetch_registers;
> +  t->to_update_thread_list = lk_update_thread_list;
> +  t->to_pid_to_str = lk_pid_to_str;
> +  t->to_thread_name = lk_thread_name;
> +
> +  t->to_stratum = thread_stratum;
> +  t->to_magic = OPS_MAGIC;
> +
> +  linux_kernel_ops = t;
> +
> +  add_target (t);
> +}
> +
> +/* Provide a prototype to silence -Wmissing-prototypes.  */
> +extern initialize_file_ftype _initialize_linux_kernel;
> +
> +void
> +_initialize_linux_kernel (void)
> +{
> +  init_linux_kernel_ops ();
> +
> +  observer_attach_new_objfile (lk_observer_new_objfile);
> +  observer_attach_inferior_created (lk_observer_inferior_created);
> +}
> diff --git a/gdb/lk-low.h b/gdb/lk-low.h
> new file mode 100644
> index 0000000..292ef97
> --- /dev/null
> +++ b/gdb/lk-low.h
> @@ -0,0 +1,310 @@
> +/* Basic Linux kernel support, architecture independent.
> +
> +   Copyright (C) 2016 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 __LK_LOW_H__
> +#define __LK_LOW_H__
> +
> +#include "target.h"
> +
> +extern struct target_ops *linux_kernel_ops;
> +
> +/* Copy constants defined in Linux kernel.  */
> +#define LK_TASK_COMM_LEN 16
> +#define LK_BITS_PER_BYTE 8
> +
> +/* Definitions used in linux kernel target.  */
> +#define LK_CPU_INVAL -1U
> +
> +/* Private data structs for this target.  */
> +/* Forward declarations.  */
> +struct lk_private_hooks;
> +struct lk_ptid_map;
> +
> +/* Short hand access to private data.  */
> +#define LK_PRIVATE ((struct lk_private *) linux_kernel_ops->to_data)
> +#define LK_HOOK (LK_PRIVATE->hooks)
> +
> +struct lk_private
> +{
> +  /* Hashtab for needed addresses, structs and fields.  */
> +  htab_t data;
> +
> +  /* Linked list to map between cpu number and original ptid from target
> +     beneath.  */
> +  struct lk_ptid_map *old_ptid;
> +
> +  /* Hooks for architecture dependent functions.  */
> +  struct lk_private_hooks *hooks;
> +};
> +
> +/* We use the following convention for PTIDs:
> +
> +   ptid->pid = inferiors PID
> +   ptid->lwp = PID from task_stuct
> +   ptid->tid = address of task_struct
> +
> +   The task_structs address as TID has two reasons.  First, we need it quite
> +   often and there is no other reasonable way to pass it down.  Second, it
> +   helps us to distinguish swapper tasks as they all have PID = 0.
> +
> +   Furthermore we cannot rely on the target beneath to use the same PID as the
> +   task_struct. Thus we need a mapping between our PTID and the PTID of the
> +   target beneath. Otherwise it is impossible to pass jobs, e.g. fetching
> +   registers of running tasks, to the target beneath.  */
> +
> +/* Private data struct to map between our and the target beneath PTID.  */
> +
> +struct lk_ptid_map
> +{
> +  struct lk_ptid_map *next;
> +  unsigned int cpu;
> +  ptid_t old_ptid;
> +};
> +
> +/* Private data struct to be stored in hashtab.  */
> +
> +struct lk_private_data
> +{
> +  const char *alias;
> +
> +  union
> +  {
> +    CORE_ADDR addr;
> +    struct type *type;
> +    struct field *field;
> +  } data;
> +};
> +
> +/* Wrapper for htab_hash_string to work with our private data.  */
> +
> +static inline hashval_t
> +lk_hash_private_data (const struct lk_private_data *entry)
> +{
> +  return htab_hash_string (entry->alias);
> +}
> +
> +/* Function for htab_eq to work with our private data.  */
> +
> +static inline int
> +lk_private_data_eq (const struct lk_private_data *entry,
> +                   const struct lk_private_data *element)
> +{
> +  return streq (entry->alias, element->alias);
> +}
> +
> +/* Wrapper for htab_find_slot to work with our private data.  Do not use
> +   directly, use the macros below instead.  */
> +
> +static inline void **
> +lk_find_slot (const char *alias)
> +{
> +  const struct lk_private_data dummy = { alias };
> +  return htab_find_slot (LK_PRIVATE->data, &dummy, INSERT);
> +}
> +
> +/* Wrapper for htab_find to work with our private data.  Do not use
> +   directly, use the macros below instead.  */
> +
> +static inline struct lk_private_data *
> +lk_find (const char *alias)
> +{
> +  const struct lk_private_data dummy = { alias };
> +  return (struct lk_private_data *) htab_find (LK_PRIVATE->data, &dummy);
> +}
> +
> +/* Functions to initialize private data.  Do not use directly, use the
> +   macros below instead.  */
> +
> +extern struct lk_private_data *lk_init_addr (const char *name,
> +                                            const char *alias, int silent);
> +extern struct lk_private_data *lk_init_struct (const char *name,
> +                                              const char *alias, int silent);
> +extern struct lk_private_data *lk_init_field (const char *s_name,
> +                                             const char *f_name,
> +                                             const char *s_alias,
> +                                             const char *f_alias, int silent);
> +
> +/* The names we use to store our private data in the hashtab.  */
> +
> +#define LK_STRUCT_ALIAS(s_name) ("struct " #s_name)
> +#define LK_FIELD_ALIAS(s_name, f_name) (#s_name " " #f_name)
> +
> +/* Macros to initiate addresses and fields, where (S_/F_)NAME is the variables
> +   name as used in Linux.  LK_DECLARE_FIELD also initializes the corresponding
> +   struct entry.  Throws an error, if no symbol with the given name is found.
> + */
> +
> +#define LK_DECLARE_ADDR(name) \
> +  lk_init_addr (#name, #name, 0)
> +#define LK_DECLARE_FIELD(s_name, f_name) \
> +  lk_init_field (#s_name, #f_name, LK_STRUCT_ALIAS (s_name), \
> +                LK_FIELD_ALIAS (s_name, f_name), 0)
> +
> +/* Same as LK_DECLARE_*, but returns NULL instead of throwing an error if no
> +   symbol was found.  The caller is responsible to check for possible errors.
> + */
> +
> +#define LK_DECLARE_ADDR_SILENT(name) \
> +  lk_init_addr (#name, #name, 1)
> +#define LK_DECLARE_FIELD_SILENT(s_name, f_name) \
> +  lk_init_field (#s_name, #f_name, LK_STRUCT_ALIAS (s_name), \
> +                LK_FIELD_ALIAS (s_name, f_name), 1)
> +
> +/* Same as LK_DECLARE_*_SILENT, but allows you to give an ALIAS name.  If used
> +   for a struct, the struct has to be declared explicitly _before_ any of its
> +   fields.  They are ment to be used, when a variable in the kernel was simply
> +   renamed (at least from our point of view).  The caller is responsible to
> +   check for possible errors.  */
> +
> +#define LK_DECLARE_ADDR_ALIAS(name, alias) \
> +  lk_init_addr (#name, #alias, 1)
> +#define LK_DECLARE_STRUCT_ALIAS(s_name, alias) \
> +  lk_init_struct (#s_name, LK_STRUCT_ALIAS (alias), 1)
> +#define LK_DECLARE_FIELD_ALIAS(s_alias, f_name, f_alias) \
> +  lk_init_field (NULL, #f_name, LK_STRUCT_ALIAS (s_alias), \
> +                LK_FIELD_ALIAS (s_alias, f_alias), 1)
> +
> +/* Macros to retrieve private data from hashtab. Returns NULL (-1) if no entry
> +   with the given ALIAS exists. The caller only needs to check for possible
> +   errors if not done so at initialization.  */
> +
> +#define LK_ADDR(alias) \
> +  (lk_find (#alias) ? (lk_find (#alias))->data.addr : -1)
> +#define LK_STRUCT(alias) \
> +  (lk_find (LK_STRUCT_ALIAS (alias)) \
> +   ? (lk_find (LK_STRUCT_ALIAS (alias)))->data.type \
> +   : NULL)
> +#define LK_FIELD(s_alias, f_alias) \
> +  (lk_find (LK_FIELD_ALIAS (s_alias, f_alias)) \
> +   ? (lk_find (LK_FIELD_ALIAS (s_alias, f_alias)))->data.field \
> +   : NULL)
> +
> +
> +/* Definitions for architecture dependent hooks.  */
> +/* Hook to read registers from the target and supply their content
> +   to the regcache.  */
> +typedef void (*lk_hook_get_registers) (CORE_ADDR task,
> +                                      struct target_ops *target,
> +                                      struct regcache *regcache,
> +                                      int regnum);
> +
> +/* Hook to return the per_cpu_offset of cpu CPU.  Only architectures that
> +   do not use the __per_cpu_offset array to determin the offset have to
> +   supply this hook.  */
> +typedef CORE_ADDR (*lk_hook_get_percpu_offset) (unsigned int cpu);
> +
> +/* Hook to map a running task to a logical CPU.  Required if the target
> +   beneath uses a different PID as struct rq.  */
> +typedef unsigned int (*lk_hook_map_running_task_to_cpu) (struct thread_info *ti);
> +
> +struct lk_private_hooks
> +{
> +  /* required */
> +  lk_hook_get_registers get_registers;
> +
> +  /* optional, required if __per_cpu_offset array is not used to determine
> +     offset.  */
> +  lk_hook_get_percpu_offset get_percpu_offset;
> +
> +  /* optional, required if the target beneath uses a different PID as struct
> +     rq.  */
> +  lk_hook_map_running_task_to_cpu map_running_task_to_cpu;
> +};
> +
> +/* Helper functions to read and return a value at a given ADDRess.  */
> +extern int lk_read_int (CORE_ADDR addr);
> +extern unsigned int lk_read_uint (CORE_ADDR addr);
> +extern LONGEST lk_read_long (CORE_ADDR addr);
> +extern ULONGEST lk_read_ulong (CORE_ADDR addr);
> +extern CORE_ADDR lk_read_addr (CORE_ADDR addr);
> +
> +/* Reads a bitmap at a given ADDRess of size SIZE (in bits). Allocates and
> +   returns an array of ulongs.  The caller is responsible to free the array
> +   after it is no longer needed.  */
> +extern ULONGEST *lk_read_bitmap (CORE_ADDR addr, size_t size);
> +
> +/* Walks the bitmap BITMAP of size SIZE from bit (index) BIT.
> +   Returns the index of the next set bit or SIZE, when the end of the bitmap
> +   was reached.  To iterate over all set bits use macro
> +   LK_BITMAP_FOR_EACH_SET_BIT defined below.  */
> +extern size_t lk_bitmap_find_next_bit (ULONGEST *bitmap, size_t bit,
> +                                      size_t size);
> +#define LK_BITMAP_FOR_EACH_SET_BIT(bitmap, size, bit)                  \
> +  for ((bit) = lk_bitmap_find_next_bit ((bitmap), (size), 0);          \
> +       (bit) < (size);                                                 \
> +       (bit) = lk_bitmap_find_next_bit ((bitmap), (size), (bit) + 1))
> +
> +/* Returns the size of BITMAP in bits.  */
> +#define LK_BITMAP_SIZE(bitmap) \
> +  (FIELD_SIZE (LK_FIELD (bitmap, bits)) * LK_BITS_PER_BYTE)
> +
> +/* Returns the Hamming weight, i.e. number of set bits, of bitmap BITMAP with
> +   size SIZE (in bits).  */
> +extern size_t lk_bitmap_hweight (ULONGEST *bitmap, size_t size);
> +
> +
> +/* Short hand access to current gdbarchs builtin types and their
> +   size (in byte).  For TYPE replace spaces " " by underscore "_", e.g.
> +   "unsigned int" => "unsigned_int".  */
> +#define lk_builtin_type(type)                                  \
> +  (builtin_type (current_inferior ()->gdbarch)->builtin_##type)
> +#define lk_builtin_type_size(type)             \
> +  (lk_builtin_type (type)->length)
> +
> +/* If field FIELD is an array returns its length (in #elements).  */
> +#define LK_ARRAY_LEN(field)                    \
> +  (FIELD_SIZE (field) / FIELD_TARGET_SIZE (field))
> +
> +/* Short hand access to the offset of field F_NAME in struct S_NAME.  */
> +#define LK_OFFSET(s_name, f_name)              \
> +  (FIELD_OFFSET (LK_FIELD (s_name, f_name)))
> +
> +/* Returns the container of field FNAME of struct SNAME located at address
> +   ADDR.  */
> +#define LK_CONTAINER_OF(addr, sname, fname)            \
> +  ((addr) - LK_OFFSET (sname, fname))
> +
> +/* Divides numinator N by demoniator D and rounds up the result.  */
> +#define LK_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
> +
> +
> +/* Additional access macros to fields in the style of gdbtypes.h */
> +/* Returns the size of field FIELD (in bytes). If FIELD is an array returns
> +   the size of the whole array.  */
> +#define FIELD_SIZE(field)                      \
> +  TYPE_LENGTH (check_typedef (FIELD_TYPE (*field)))
> +
> +/* Returns the size of the target type of field FIELD (in bytes).  If FIELD is
> +   an array returns the size of its elements.  */
> +#define FIELD_TARGET_SIZE(field)               \
> +  TYPE_LENGTH (check_typedef (TYPE_TARGET_TYPE (FIELD_TYPE (*field))))
> +
> +/* Returns the offset of field FIELD (in bytes).  */
> +#define FIELD_OFFSET(field)                    \
> +  (FIELD_BITPOS (*field) / TARGET_CHAR_BIT)
> +
> +/* Provides the per_cpu_offset of cpu CPU.  If the architecture
> +   provides a get_percpu_offset hook, the call is passed to it.  Otherwise
> +   returns the __per_cpu_offset[CPU] element.  */
> +extern CORE_ADDR lk_get_percpu_offset (unsigned int cpu);
> +
> +/* Tests if a given task TASK is running. Returns either the cpu-id
> +   if running or LK_CPU_INVAL if not.  */
> +extern unsigned int lk_task_running (CORE_ADDR task);
> +#endif /* __LK_LOW_H__ */
> --
> 2.8.4
>


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