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RE: [pushed][PATCH 4/7] Arch-specific remote follow fork


Thanks, I will take a look.  --Don

> -----Original Message-----
> From: Vidya Praveen [mailto:vidyapraveen@arm.com]
> Sent: Thursday, May 14, 2015 3:26 AM
> To: Breazeal, Don
> Cc: gdb-patches@sourceware.org
> Subject: Re: [pushed][PATCH 4/7] Arch-specific remote follow fork
> 
> Don,
> 
> There are several instances of xyz->private->arch_private where xyz is
> (struct process_info*). Assume it is a typo (should've been priv instead
> of private)?
> 
> I atleast see aarch64 build of this fail.
> 
> Regards
> VP.
> 
> 
> On Tue, May 12, 2015 at 06:28:12PM +0100, Don Breazeal wrote:
> > This is the version of the patch that I pushed.
> > Thanks
> > --Don
> >
> >
> > This patch implements the architecture-specific pieces of follow-fork
> > for remote and extended-remote Linux targets, which in the current
> > implementation copyies the parent's debug register state into the new
> > child's data structures.  This is required for x86, arm, aarch64, and
> > mips.
> >
> > This follows the native implementation as closely as possible by
> > implementing a new linux_target_ops function 'new_fork', which is
> > analogous to 'linux_nat_new_fork' in linux-nat.c.  In gdbserver, the
> > debug registers are stored in the process list, instead of an
> > architecture-specific list, so the function arguments are process_info
> > pointers instead of an lwp_info and a pid as in the native
> implementation.
> >
> > In the MIPS implementation the debug register mirror is stored
> > differently from x86, ARM, and aarch64, so instead of doing a simple
> > structure assignment I had to clone the list of watchpoint structures.
> >
> > Tested using gdb.threads/watchpoint-fork.exp on x86, and ran manual
> > tests on a MIPS board and an ARM board.  Aarch64 hasn't been tested.
> >
> > gdb/gdbserver/ChangeLog:
> >
> >         * linux-aarch64-low.c (aarch64_linux_new_fork): New function.
> >         (the_low_target) <new_fork>: Initialize new member.
> >         * linux-arm-low.c (arm_new_fork): New function.
> >         (the_low_target) <new_fork>: Initialize new member.
> >         * linux-low.c (handle_extended_wait): Call new target function
> >         new_fork.
> >         * linux-low.h (struct linux_target_ops) <new_fork>: New
> member.
> >         * linux-mips-low.c (mips_add_watchpoint): New function
> >         extracted from mips_insert_point.
> >         (the_low_target) <new_fork>: Initialize new member.
> >         (mips_linux_new_fork): New function.
> >         (mips_insert_point): Call mips_add_watchpoint.
> >         * linux-x86-low.c (x86_linux_new_fork): New function.
> >         (the_low_target) <new_fork>: Initialize new member.
> > ---
> >  gdb/gdbserver/ChangeLog           | 17 +++++++++
> >  gdb/gdbserver/linux-aarch64-low.c | 28 +++++++++++++++
> >  gdb/gdbserver/linux-arm-low.c     | 42 ++++++++++++++++++++++
> >  gdb/gdbserver/linux-low.c         |  4 +++
> >  gdb/gdbserver/linux-low.h         |  3 ++
> >  gdb/gdbserver/linux-mips-low.c    | 76
> ++++++++++++++++++++++++++++++++-------
> >  gdb/gdbserver/linux-x86-low.c     | 29 +++++++++++++++
> >  7 files changed, 187 insertions(+), 12 deletions(-)
> >
> > diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index
> > 0ef695c..0bdcdf3 100644
> > --- a/gdb/gdbserver/ChangeLog
> > +++ b/gdb/gdbserver/ChangeLog
> > @@ -1,5 +1,22 @@
> >  2015-05-12  Don Breazeal  <donb@codesourcery.com>
> >
> > +       * linux-aarch64-low.c (aarch64_linux_new_fork): New function.
> > +       (the_low_target) <new_fork>: Initialize new member.
> > +       * linux-arm-low.c (arm_new_fork): New function.
> > +       (the_low_target) <new_fork>: Initialize new member.
> > +       * linux-low.c (handle_extended_wait): Call new target function
> > +       new_fork.
> > +       * linux-low.h (struct linux_target_ops) <new_fork>: New
> member.
> > +       * linux-mips-low.c (mips_add_watchpoint): New function
> > +       extracted from mips_insert_point.
> > +       (the_low_target) <new_fork>: Initialize new member.
> > +       (mips_linux_new_fork): New function.
> > +       (mips_insert_point): Call mips_add_watchpoint.
> > +       * linux-x86-low.c (x86_linux_new_fork): New function.
> > +       (the_low_target) <new_fork>: Initialize new member.
> > +
> > +2015-05-12  Don Breazeal  <donb@codesourcery.com>
> > +
> >         * linux-low.c (handle_extended_wait): Implement return value,
> >         rename argument 'event_child' to 'event_lwp', handle
> >         PTRACE_EVENT_FORK, call internal_error for unrecognized event.
> > diff --git a/gdb/gdbserver/linux-aarch64-low.c
> > b/gdb/gdbserver/linux-aarch64-low.c
> > index d44175e..7e6e9ac 100644
> > --- a/gdb/gdbserver/linux-aarch64-low.c
> > +++ b/gdb/gdbserver/linux-aarch64-low.c
> > @@ -1135,6 +1135,33 @@ aarch64_linux_new_thread (struct lwp_info *lwp)
> >    lwp->arch_private = info;
> >  }
> >
> > +static void
> > +aarch64_linux_new_fork (struct process_info *parent,
> > +                       struct process_info *child) {
> > +  /* These are allocated by linux_add_process.  */
> > +  gdb_assert (parent->private != NULL
> > +             && parent->private->arch_private != NULL);
> > +  gdb_assert (child->private != NULL
> > +             && child->private->arch_private != NULL);
> > +
> > +  /* Linux kernel before 2.6.33 commit
> > +     72f674d203cd230426437cdcf7dd6f681dad8b0d
> > +     will inherit hardware debug registers from parent
> > +     on fork/vfork/clone.  Newer Linux kernels create such tasks with
> > +     zeroed debug registers.
> > +
> > +     GDB core assumes the child inherits the watchpoints/hw
> > +     breakpoints of the parent, and will remove them all from the
> > +     forked off process.  Copy the debug registers mirrors into the
> > +     new process so that all breakpoints and watchpoints can be
> > +     removed together.  The debug registers mirror will become zeroed
> > +     in the end before detaching the forked off process, thus making
> > +     this compatible with older Linux kernels too.  */
> > +
> > +  *child->private->arch_private = *parent->private->arch_private; }
> > +
> >  /* Called when resuming a thread.
> >     If the debug regs have changed, update the thread's copies.  */
> >
> > @@ -1299,6 +1326,7 @@ struct linux_target_ops the_low_target =
> >    NULL,
> >    aarch64_linux_new_process,
> >    aarch64_linux_new_thread,
> > +  aarch64_linux_new_fork,
> >    aarch64_linux_prepare_to_resume,
> >  };
> >
> > diff --git a/gdb/gdbserver/linux-arm-low.c
> > b/gdb/gdbserver/linux-arm-low.c index d408dcd..3420dea 100644
> > --- a/gdb/gdbserver/linux-arm-low.c
> > +++ b/gdb/gdbserver/linux-arm-low.c
> > @@ -717,6 +717,47 @@ arm_new_thread (struct lwp_info *lwp)
> >    lwp->arch_private = info;
> >  }
> >
> > +static void
> > +arm_new_fork (struct process_info *parent, struct process_info
> > +*child) {
> > +  struct arch_process_info *parent_proc_info =
> > +parent->private->arch_private;
> > +  struct arch_process_info *child_proc_info =
> > +child->private->arch_private;
> > +  struct lwp_info *child_lwp;
> > +  struct arch_lwp_info *child_lwp_info;
> > +  int i;
> > +
> > +  /* These are allocated by linux_add_process.  */  gdb_assert
> > + (parent->private != NULL
> > +             && parent->private->arch_private != NULL);  gdb_assert
> > + (child->private != NULL
> > +             && child->private->arch_private != NULL);
> > +
> > +  /* Linux kernel before 2.6.33 commit
> > +     72f674d203cd230426437cdcf7dd6f681dad8b0d
> > +     will inherit hardware debug registers from parent
> > +     on fork/vfork/clone.  Newer Linux kernels create such tasks with
> > +     zeroed debug registers.
> > +
> > +     GDB core assumes the child inherits the watchpoints/hw
> > +     breakpoints of the parent, and will remove them all from the
> > +     forked off process.  Copy the debug registers mirrors into the
> > +     new process so that all breakpoints and watchpoints can be
> > +     removed together.  The debug registers mirror will become zeroed
> > +     in the end before detaching the forked off process, thus making
> > +     this compatible with older Linux kernels too.  */
> > +
> > +  *child_proc_info = *parent_proc_info;
> > +
> > +  /* Mark all the hardware breakpoints and watchpoints as changed to
> > +     make sure that the registers will be updated.  */
> > +  child_lwp = find_lwp_pid (ptid_of (child));
> > +  child_lwp_info = child_lwp->arch_private;
> > +  for (i = 0; i < MAX_BPTS; i++)
> > +    child_lwp_info->bpts_changed[i] = 1;
> > +  for (i = 0; i < MAX_WPTS; i++)
> > +    child_lwp_info->wpts_changed[i] = 1; }
> > +
> >  /* Called when resuming a thread.
> >     If the debug regs have changed, update the thread's copies.  */
> > static void @@ -920,6 +961,7 @@ struct linux_target_ops the_low_target
> > = {
> >    NULL, /* siginfo_fixup */
> >    arm_new_process,
> >    arm_new_thread,
> > +  arm_new_fork,
> >    arm_prepare_to_resume,
> >  };
> >
> > diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
> > index b280c17..d9053ad 100644
> > --- a/gdb/gdbserver/linux-low.c
> > +++ b/gdb/gdbserver/linux-low.c
> > @@ -489,6 +489,10 @@ handle_extended_wait (struct lwp_info *event_lwp,
> int wstat)
> >           child_proc->tdesc = tdesc;
> >           child_lwp->must_set_ptrace_flags = 1;
> >
> > +         /* Clone arch-specific process data.  */
> > +         if (the_low_target.new_fork != NULL)
> > +           the_low_target.new_fork (parent_proc, child_proc);
> > +
> >           /* Save fork info in the parent thread.  */
> >           event_lwp->waitstatus.kind = TARGET_WAITKIND_FORKED;
> >           event_lwp->waitstatus.value.related_pid = ptid; diff --git
> > a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h index
> > 41067d6..3300da9 100644
> > --- a/gdb/gdbserver/linux-low.h
> > +++ b/gdb/gdbserver/linux-low.h
> > @@ -187,6 +187,9 @@ struct linux_target_ops
> >       allocate it here.  */
> >    void (*new_thread) (struct lwp_info *);
> >
> > +  /* Hook to call, if any, when a new fork is attached.  */  void
> > + (*new_fork) (struct process_info *parent, struct process_info
> > + *child);
> > +
> >    /* Hook to call prior to resuming a thread.  */
> >    void (*prepare_to_resume) (struct lwp_info *);
> >
> > diff --git a/gdb/gdbserver/linux-mips-low.c
> > b/gdb/gdbserver/linux-mips-low.c index 7988d07..4601ad0 100644
> > --- a/gdb/gdbserver/linux-mips-low.c
> > +++ b/gdb/gdbserver/linux-mips-low.c
> > @@ -344,6 +344,68 @@ mips_linux_new_thread (struct lwp_info *lwp)
> >    lwp->arch_private = info;
> >  }
> >
> > +/* Create a new mips_watchpoint and add it to the list.  */
> > +
> > +static void
> > +mips_add_watchpoint (struct arch_process_info *private, CORE_ADDR
> addr,
> > +                    int len, int watch_type) {
> > +  struct mips_watchpoint *new_watch;
> > +  struct mips_watchpoint **pw;
> > +
> > +  new_watch = xmalloc (sizeof (struct mips_watchpoint));
> > + new_watch->addr = addr;  new_watch->len = len;  new_watch->type =
> > + watch_type;  new_watch->next = NULL;
> > +
> > +  pw = &private->current_watches;
> > +  while (*pw != NULL)
> > +    pw = &(*pw)->next;
> > +  *pw = new_watch;
> > +}
> > +
> > +/* Hook to call when a new fork is attached.  */
> > +
> > +static void
> > +mips_linux_new_fork (struct process_info *parent,
> > +                       struct process_info *child) {
> > +  struct arch_process_info *parent_private;
> > +  struct arch_process_info *child_private;
> > +  struct mips_watchpoint *wp;
> > +
> > +  /* These are allocated by linux_add_process.  */  gdb_assert
> > + (parent->private != NULL
> > +             && parent->private->arch_private != NULL);  gdb_assert
> > + (child->private != NULL
> > +             && child->private->arch_private != NULL);
> > +
> > +  /* Linux kernel before 2.6.33 commit
> > +     72f674d203cd230426437cdcf7dd6f681dad8b0d
> > +     will inherit hardware debug registers from parent
> > +     on fork/vfork/clone.  Newer Linux kernels create such tasks with
> > +     zeroed debug registers.
> > +
> > +     GDB core assumes the child inherits the watchpoints/hw
> > +     breakpoints of the parent, and will remove them all from the
> > +     forked off process.  Copy the debug registers mirrors into the
> > +     new process so that all breakpoints and watchpoints can be
> > +     removed together.  The debug registers mirror will become zeroed
> > +     in the end before detaching the forked off process, thus making
> > +     this compatible with older Linux kernels too.  */
> > +
> > +  parent_private = parent->private->arch_private;  child_private =
> > + child->private->arch_private;
> > +
> > +  child_private->watch_readback_valid =
> > + parent_private->watch_readback_valid;
> > +  child_private->watch_readback = parent_private->watch_readback;
> > +
> > +  for (wp = parent_private->current_watches; wp != NULL; wp = wp-
> >next)
> > +    mips_add_watchpoint (child_private, wp->addr, wp->len, wp->type);
> > +
> > +  child_private->watch_mirror = parent_private->watch_mirror; }
> >  /* This is the implementation of linux_target_ops method
> >     prepare_to_resume.  If the watch regs have changed, update the
> >     thread's copies.  */
> > @@ -397,8 +459,6 @@ mips_insert_point (enum raw_bkpt_type type,
> CORE_ADDR addr,
> >    struct process_info *proc = current_process ();
> >    struct arch_process_info *priv = proc->priv->arch_private;
> >    struct pt_watch_regs regs;
> > -  struct mips_watchpoint *new_watch;
> > -  struct mips_watchpoint **pw;
> >    int pid;
> >    long lwpid;
> >    enum target_hw_bp_type watch_type;
> > @@ -425,16 +485,7 @@ mips_insert_point (enum raw_bkpt_type type,
> CORE_ADDR addr,
> >      return -1;
> >
> >    /* It fit.  Stick it on the end of the list.  */
> > -  new_watch = xmalloc (sizeof (struct mips_watchpoint));
> > -  new_watch->addr = addr;
> > -  new_watch->len = len;
> > -  new_watch->type = watch_type;
> > -  new_watch->next = NULL;
> > -
> > -  pw = &priv->current_watches;
> > -  while (*pw != NULL)
> > -    pw = &(*pw)->next;
> > -  *pw = new_watch;
> > +  mips_add_watchpoint (priv, addr, len, watch_type);
> >
> >    priv->watch_mirror = regs;
> >
> > @@ -845,6 +896,7 @@ struct linux_target_ops the_low_target = {
> >    NULL, /* siginfo_fixup */
> >    mips_linux_new_process,
> >    mips_linux_new_thread,
> > +  mips_linux_new_fork,
> >    mips_linux_prepare_to_resume
> >  };
> >
> > diff --git a/gdb/gdbserver/linux-x86-low.c
> > b/gdb/gdbserver/linux-x86-low.c index 763df08..4aef7b7 100644
> > --- a/gdb/gdbserver/linux-x86-low.c
> > +++ b/gdb/gdbserver/linux-x86-low.c
> > @@ -634,6 +634,34 @@ x86_linux_new_process (void)
> >    return info;
> >  }
> >
> > +/* Target routine for linux_new_fork.  */
> > +
> > +static void
> > +x86_linux_new_fork (struct process_info *parent, struct process_info
> > +*child) {
> > +  /* These are allocated by linux_add_process.  */
> > +  gdb_assert (parent->priv != NULL
> > +             && parent->priv->arch_private != NULL);
> > +  gdb_assert (child->priv != NULL
> > +             && child->priv->arch_private != NULL);
> > +
> > +  /* Linux kernel before 2.6.33 commit
> > +     72f674d203cd230426437cdcf7dd6f681dad8b0d
> > +     will inherit hardware debug registers from parent
> > +     on fork/vfork/clone.  Newer Linux kernels create such tasks with
> > +     zeroed debug registers.
> > +
> > +     GDB core assumes the child inherits the watchpoints/hw
> > +     breakpoints of the parent, and will remove them all from the
> > +     forked off process.  Copy the debug registers mirrors into the
> > +     new process so that all breakpoints and watchpoints can be
> > +     removed together.  The debug registers mirror will become zeroed
> > +     in the end before detaching the forked off process, thus making
> > +     this compatible with older Linux kernels too.  */
> > +
> > +  *child->priv->arch_private = *parent->priv->arch_private; }
> > +
> >  /* See nat/x86-dregs.h.  */
> >
> >  struct x86_debug_reg_state *
> > @@ -3263,6 +3291,7 @@ struct linux_target_ops the_low_target =
> >    x86_siginfo_fixup,
> >    x86_linux_new_process,
> >    x86_linux_new_thread,
> > +  x86_linux_new_fork,
> >    x86_linux_prepare_to_resume,
> >    x86_linux_process_qsupported,
> >    x86_supports_tracepoints,
> > --
> > 1.8.1.1
> >


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