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Re: [RFC v3 3/8] Add basic Linux kernel support
- From: Philipp Rudo <prudo at linux dot vnet dot ibm dot com>
- To: Yao Qi <qiyaoltc at gmail dot com>
- Cc: gdb-patches at sourceware dot org, Yao Qi <yao dot qi at linaro dot org>, Peter Griffin <peter dot griffin at linaro dot org>, Omair Javaid <omair dot javaid at linaro dot org>, Andreas Arnez <arnez at linux dot vnet dot ibm dot com>
- Date: Wed, 3 May 2017 17:36:26 +0200
- Subject: Re: [RFC v3 3/8] Add basic Linux kernel support
- Authentication-results: sourceware.org; auth=none
- References: <20170316165739.88524-1-prudo@linux.vnet.ibm.com> <20170316165739.88524-4-prudo@linux.vnet.ibm.com> <86d1br8q8v.fsf@gmail.com>
Hi Yao,
On Tue, 02 May 2017 12:14:40 +0100
Yao Qi <qiyaoltc@gmail.com> wrote:
> Philipp Rudo <prudo@linux.vnet.ibm.com> writes:
>
> Hi Philipp,
>
> > +/* 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."));
> > +}
> > +
>
> > +
> > +/* 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
>
> "private" here is a little confusing. How about rename it to "linux_kernel"?
I called it "private" as it is the targets private data stored in its to_data
hook. But I don't mind renaming it. Especially ...
> > +{
> > + /* 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;
> > +};
> > +
>
> Secondly, can we change it to a class and function pointers in
> lk_private_hooks become virtual functions. gdbarch_lk_init_private
> returns a pointer to an instance of sub-class of "linux_kernel".
>
> lk_init_private_data can be put the constructor of base class, to add
> entries to "data", and sub-class (in each gdbarch) can add their own
> specific stuff.
... when classifying the struct, which already is on my long ToDo-list. This
struct is a left over from when I started working on the project shortly before
gdb-7.12 was released. I didn't think that the C++-yfication would kick off
that fast and started with plain C ...
Thanks
Philipp
> > +
> > +/* 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);
>
> > +
> > +/* 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;
> > +};
>