Arch-specific remote follow fork

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.

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 0ef695c43ac54fe8e2119bfd3816a2af0c6bc5c5..0bdcdf36c368d29202e2011397d5c67ae79123f6 100644 (file)
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,20 @@
+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,

diff --git a/gdb/gdbserver/linux-aarch64-low.c b/gdb/gdbserver/linux-aarch64-low.c
index d44175ef8e0a5a321fa3e328b5719aa6fb584412..7e6e9ac830d0e75012553344348a066afd1fa8f9 100644 (file)
--- 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 d408dcda2ef1ba0c468153d1f5eadf804a34c7a9..3420dea73ac8c9d6a49a0cdeb38d59386bb6dddc 100644 (file)
--- 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 b280c174a971a5989e3fcade4d4539962c418deb..d9053ad6048e000a501f0a3869bceb946e8a283d 100644 (file)
--- 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 41067d65ce558da6b8c0262428983a5bd8c829c7..3300da96c65f6e644a250a86ba2c6208cf60902a 100644 (file)
--- 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 7988d073dacc591385aa5b923d14df2babed7bed..4601ad06fcb77156d1c99dce73b99549b81f0119 100644 (file)
--- 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 763df081f7a9647a95d7db3297a70d7ef42af65a..4aef7b79825e0a65ddc508244e76b073b5233848 100644 (file)
--- 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,