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Re: [PATCH] Support for HWbreak/watchpoint accross fork/vfork on arm-native
- From: Omair Javaid <omair dot javaid at linaro dot org>
- To: gdb-patches at sourceware dot org
- Date: Fri, 31 Jan 2014 03:23:24 +0500
- Subject: Re: [PATCH] Support for HWbreak/watchpoint accross fork/vfork on arm-native
- Authentication-results: sourceware.org; auth=none
- References: <1391119790-6580-1-git-send-email-omair dot javaid at linaro dot org>
On 01/31/2014 03:09 AM, Omair Javaid wrote:
> ---
> gdb/arm-linux-nat.c | 417 ++++++++++++++++++++++++++++++++++------------------
> 1 file changed, 273 insertions(+), 144 deletions(-)
>
> diff --git a/gdb/arm-linux-nat.c b/gdb/arm-linux-nat.c
> index 6f56634..9a756c1 100644
> --- a/gdb/arm-linux-nat.c
> +++ b/gdb/arm-linux-nat.c
> @@ -787,70 +787,120 @@ struct arm_linux_hw_breakpoint
> arm_hwbp_control_t control;
> };
>
> -/* Structure containing arrays of the break and watch points which are have
> - active in each thread.
> -
> - The Linux ptrace interface to hardware break-/watch-points presents the
> - values in a vector centred around 0 (which is used fo generic information).
> - Positive indicies refer to breakpoint addresses/control registers, negative
> - indices to watchpoint addresses/control registers.
> -
> - The Linux vector is indexed as follows:
> - -((i << 1) + 2): Control register for watchpoint i.
> - -((i << 1) + 1): Address register for watchpoint i.
> - 0: Information register.
> - ((i << 1) + 1): Address register for breakpoint i.
> - ((i << 1) + 2): Control register for breakpoint i.
> -
> - This structure is used as a per-thread cache of the state stored by the
> - kernel, so that we don't need to keep calling into the kernel to find a
> - free breakpoint.
> -
> - We treat break-/watch-points with their enable bit clear as being deleted.
> - */
> -typedef struct arm_linux_thread_points
> +/* Since we cannot dynamically allocate subfields of arm_linux_process_info,
> + assume a maximum number of supported break-/watchpoints. */
> +#define MAX_BPTS 16
> +#define MAX_WPTS 16
> +
> +/* Per-process arch-specific data we want to keep. */
> +struct arm_linux_process_info
> {
> - /* Thread ID. */
> - int tid;
> - /* Breakpoints for thread. */
> - struct arm_linux_hw_breakpoint *bpts;
> - /* Watchpoint for threads. */
> - struct arm_linux_hw_breakpoint *wpts;
> -} *arm_linux_thread_points_p;
> -DEF_VEC_P (arm_linux_thread_points_p);
> -
> -/* Vector of hardware breakpoints for each thread. */
> -VEC(arm_linux_thread_points_p) *arm_threads = NULL;
> -
> -/* Find the list of hardware break-/watch-points for a thread with id TID.
> - If no list exists for TID we return NULL if ALLOC_NEW is 0, otherwise we
> - create a new list and return that. */
> -static struct arm_linux_thread_points *
> -arm_linux_find_breakpoints_by_tid (int tid, int alloc_new)
> + /* Linked list. */
> + struct arm_linux_process_info *next;
> + /* The process identifier. */
> + pid_t pid;
> + /* Hardware breakpoints for this process. */
> + struct arm_linux_hw_breakpoint bpts[MAX_BPTS];
> + /* Hardware watchpoints for this process. */
> + struct arm_linux_hw_breakpoint wpts[MAX_WPTS];
> +};
> +
> +/* Per-thread arch-specific data we want to keep. */
> +struct arch_lwp_info
> {
> - int i;
> - struct arm_linux_thread_points *t;
> + /* Non-zero if our copy differs from what's recorded in the thread. */
> + char bpts_changed[MAX_BPTS];
> + char wpts_changed[MAX_WPTS];
> +};
>
> - for (i = 0; VEC_iterate (arm_linux_thread_points_p, arm_threads, i, t); ++i)
> - {
> - if (t->tid == tid)
> - return t;
> - }
> +static struct arm_linux_process_info *arm_linux_process_list = NULL;
> +
> +/* Find process data for process PID. */
>
> - t = NULL;
> +static struct arm_linux_process_info *
> +arm_linux_find_process_pid (pid_t pid)
> +{
> + struct arm_linux_process_info *proc;
> +
> + for (proc = arm_linux_process_list; proc; proc = proc->next)
> + if (proc->pid == pid)
> + return proc;
>
> - if (alloc_new)
> + return NULL;
> +}
> +
> +/* Add process data for process PID. Returns newly allocated info
> + object. */
> +
> +static struct arm_linux_process_info *
> +arm_linux_add_process (pid_t pid)
> +{
> + struct arm_linux_process_info *proc;
> +
> + proc = xcalloc (1, sizeof (*proc));
> + proc->pid = pid;
> +
> + proc->next = arm_linux_process_list;
> + arm_linux_process_list = proc;
> +
> + return proc;
> +}
> +
> +/* Get data specific info for process PID, creating it if necessary.
> + Never returns NULL. */
> +
> +static struct arm_linux_process_info *
> +arm_linux_process_info_get (pid_t pid)
> +{
> + struct arm_linux_process_info *proc;
> +
> + proc = arm_linux_find_process_pid (pid);
> + if (proc == NULL)
> + proc = arm_linux_add_process (pid);
> +
> + return proc;
> +}
> +
> +/* Called whenever GDB is no longer debugging process PID. It deletes
> + data structures that keep track of debug register state. */
> +
> +static void
> +arm_linux_forget_process (pid_t pid)
> +{
> + struct arm_linux_process_info *proc, **proc_link;
> +
> + proc = arm_linux_process_list;
> + proc_link = &arm_linux_process_list;
> +
> + while (proc != NULL)
> {
> - t = xmalloc (sizeof (struct arm_linux_thread_points));
> - t->tid = tid;
> - t->bpts = xzalloc (arm_linux_get_hw_breakpoint_count ()
> - * sizeof (struct arm_linux_hw_breakpoint));
> - t->wpts = xzalloc (arm_linux_get_hw_watchpoint_count ()
> - * sizeof (struct arm_linux_hw_breakpoint));
> - VEC_safe_push (arm_linux_thread_points_p, arm_threads, t);
> + if (proc->pid == pid)
> + {
> + *proc_link = proc->next;
> +
> + xfree (proc);
> + return;
> + }
> +
> + proc_link = &proc->next;
> + proc = *proc_link;
> }
> +}
> +
> +/* Get hardware breakpoint state for process PID. */
>
> - return t;
> +static struct arm_linux_hw_breakpoint *
> +arm_linux_get_hwbreak_state (pid_t pid)
> +{
> + return arm_linux_process_info_get (pid)->bpts;
> +}
> +
> +/* Get watchpoint state for process PID. */
> +
> +static struct arm_linux_hw_breakpoint *
> +arm_linux_get_watch_state (pid_t pid)
> +{
> + return arm_linux_process_info_get (pid)->wpts;
> }
>
> /* Initialize an ARM hardware break-/watch-point control register value.
> @@ -950,45 +1000,76 @@ arm_linux_hw_breakpoint_equal (const struct arm_linux_hw_breakpoint *p1,
> return p1->address == p2->address && p1->control == p2->control;
> }
>
> +/* Callback to mark a watch-/breakpoint to be updated in all threads of
> + the current process. */
> +
> +struct update_registers_data
> +{
> + int watch;
> + int index;
> +};
> +
> +static int
> +update_registers_callback (struct lwp_info *lwp, void *arg)
> +{
> + struct update_registers_data *data = (struct update_registers_data *) arg;
> +
> + /* Force iterate_over_lwps to return matched lwp_info*. */
> + if (arg == NULL)
> + return 1;
> +
> + if (lwp->arch_private == NULL)
> + lwp->arch_private = XCNEW (struct arch_lwp_info);
> +
> + /* The actual update is done later just before resuming the lwp,
> + we just mark that the registers need updating. */
> + if (data->watch)
> + lwp->arch_private->wpts_changed[data->index] = 1;
> + else
> + lwp->arch_private->bpts_changed[data->index] = 1;
> +
> + /* If the lwp isn't stopped, force it to momentarily pause, so
> + we can update its breakpoint registers. */
> + if (!lwp->stopped)
> + linux_stop_lwp (lwp);
> +
> + return 0;
> +}
> +
> /* Insert the hardware breakpoint (WATCHPOINT = 0) or watchpoint (WATCHPOINT
> =1) BPT for thread TID. */
> static void
> arm_linux_insert_hw_breakpoint1 (const struct arm_linux_hw_breakpoint* bpt,
> - int tid, int watchpoint)
> + int watchpoint)
> {
> - struct arm_linux_thread_points *t = arm_linux_find_breakpoints_by_tid (tid, 1);
> + int pid;
> + ptid_t pid_ptid;
> gdb_byte count, i;
> struct arm_linux_hw_breakpoint* bpts;
> - int dir;
> + struct update_registers_data data;
>
> - gdb_assert (t != NULL);
> + pid = ptid_get_pid (inferior_ptid);
> + pid_ptid = pid_to_ptid (pid);
>
> if (watchpoint)
> {
> count = arm_linux_get_hw_watchpoint_count ();
> - bpts = t->wpts;
> - dir = -1;
> + bpts = arm_linux_get_watch_state(pid);
> }
> else
> {
> count = arm_linux_get_hw_breakpoint_count ();
> - bpts = t->bpts;
> - dir = 1;
> + bpts = arm_linux_get_hwbreak_state(pid);
> }
>
> for (i = 0; i < count; ++i)
> if (!arm_hwbp_control_is_enabled (bpts[i].control))
> {
> - errno = 0;
> - if (ptrace (PTRACE_SETHBPREGS, tid, dir * ((i << 1) + 1),
> - &bpt->address) < 0)
> - perror_with_name (_("Unexpected error setting breakpoint address"));
> - if (ptrace (PTRACE_SETHBPREGS, tid, dir * ((i << 1) + 2),
> - &bpt->control) < 0)
> - perror_with_name (_("Unexpected error setting breakpoint"));
> -
> - memcpy (bpts + i, bpt, sizeof (struct arm_linux_hw_breakpoint));
> - break;
> + data.watch = watchpoint;
> + data.index = i;
> + bpts[i] = *bpt;
> + iterate_over_lwps (pid_ptid, update_registers_callback, &data);
> + break;
> }
>
> gdb_assert (i != count);
> @@ -998,37 +1079,36 @@ arm_linux_insert_hw_breakpoint1 (const struct arm_linux_hw_breakpoint* bpt,
> (WATCHPOINT = 1) BPT for thread TID. */
> static void
> arm_linux_remove_hw_breakpoint1 (const struct arm_linux_hw_breakpoint *bpt,
> - int tid, int watchpoint)
> + int watchpoint)
> {
> - struct arm_linux_thread_points *t = arm_linux_find_breakpoints_by_tid (tid, 0);
> + int pid;
> gdb_byte count, i;
> - struct arm_linux_hw_breakpoint *bpts;
> - int dir;
> + ptid_t pid_ptid;
> + struct arm_linux_hw_breakpoint* bpts;
> + struct update_registers_data data;
>
> - gdb_assert (t != NULL);
> + pid = ptid_get_pid (inferior_ptid);
> + pid_ptid = pid_to_ptid (pid);
>
> if (watchpoint)
> {
> count = arm_linux_get_hw_watchpoint_count ();
> - bpts = t->wpts;
> - dir = -1;
> + bpts = arm_linux_get_watch_state(pid);
> }
> else
> {
> count = arm_linux_get_hw_breakpoint_count ();
> - bpts = t->bpts;
> - dir = 1;
> + bpts = arm_linux_get_hwbreak_state(pid);
> }
>
> for (i = 0; i < count; ++i)
> if (arm_linux_hw_breakpoint_equal (bpt, bpts + i))
> {
> - errno = 0;
> - bpts[i].control = arm_hwbp_control_disable (bpts[i].control);
> - if (ptrace (PTRACE_SETHBPREGS, tid, dir * ((i << 1) + 2),
> - &bpts[i].control) < 0)
> - perror_with_name (_("Unexpected error clearing breakpoint"));
> - break;
> + data.watch = watchpoint;
> + data.index = i;
> + bpts[i].control = arm_hwbp_control_disable (bpts[i].control);
> + iterate_over_lwps (pid_ptid, update_registers_callback, &data);
> + break;
> }
>
> gdb_assert (i != count);
> @@ -1046,8 +1126,8 @@ arm_linux_insert_hw_breakpoint (struct gdbarch *gdbarch,
> return -1;
>
> arm_linux_hw_breakpoint_initialize (gdbarch, bp_tgt, &p);
> - ALL_LWPS (lp)
> - arm_linux_insert_hw_breakpoint1 (&p, ptid_get_lwp (lp->ptid), 0);
> +
> + arm_linux_insert_hw_breakpoint1 (&p, 0);
>
> return 0;
> }
> @@ -1064,8 +1144,8 @@ arm_linux_remove_hw_breakpoint (struct gdbarch *gdbarch,
> return -1;
>
> arm_linux_hw_breakpoint_initialize (gdbarch, bp_tgt, &p);
> - ALL_LWPS (lp)
> - arm_linux_remove_hw_breakpoint1 (&p, ptid_get_lwp (lp->ptid), 0);
> +
> + arm_linux_remove_hw_breakpoint1 (&p, 0);
>
> return 0;
> }
> @@ -1115,8 +1195,8 @@ arm_linux_insert_watchpoint (CORE_ADDR addr, int len, int rw,
> return -1;
>
> arm_linux_hw_watchpoint_initialize (addr, len, rw, &p);
> - ALL_LWPS (lp)
> - arm_linux_insert_hw_breakpoint1 (&p, ptid_get_lwp (lp->ptid), 1);
> +
> + arm_linux_insert_hw_breakpoint1 (&p, 1);
>
> return 0;
> }
> @@ -1133,8 +1213,8 @@ arm_linux_remove_watchpoint (CORE_ADDR addr, int len, int rw,
> return -1;
>
> arm_linux_hw_watchpoint_initialize (addr, len, rw, &p);
> - ALL_LWPS (lp)
> - arm_linux_remove_hw_breakpoint1 (&p, ptid_get_lwp (lp->ptid), 1);
> +
> + arm_linux_remove_hw_breakpoint1 (&p, 1);
>
> return 0;
> }
> @@ -1190,63 +1270,108 @@ arm_linux_watchpoint_addr_within_range (struct target_ops *target,
> static void
> arm_linux_new_thread (struct lwp_info *lp)
> {
> - int tid = ptid_get_lwp (lp->ptid);
> - const struct arm_linux_hwbp_cap *info = arm_linux_get_hwbp_cap ();
> + int i;
> + struct arch_lwp_info *info = XCNEW (struct arch_lwp_info);
>
> - if (info != NULL)
> + /* Mark that all the hardware breakpoint/watchpoint register pairs
> + for this thread need to be initialized. */
> +
> + for (i = 0; i < MAX_BPTS; i++)
> {
> - int i;
> - struct arm_linux_thread_points *p;
> - struct arm_linux_hw_breakpoint *bpts;
> -
> - if (VEC_empty (arm_linux_thread_points_p, arm_threads))
> - return;
> -
> - /* Get a list of breakpoints from any thread. */
> - p = VEC_last (arm_linux_thread_points_p, arm_threads);
> -
> - /* Copy that thread's breakpoints and watchpoints to the new thread. */
> - for (i = 0; i < info->bp_count; i++)
> - if (arm_hwbp_control_is_enabled (p->bpts[i].control))
> - arm_linux_insert_hw_breakpoint1 (p->bpts + i, tid, 0);
> - for (i = 0; i < info->wp_count; i++)
> - if (arm_hwbp_control_is_enabled (p->wpts[i].control))
> - arm_linux_insert_hw_breakpoint1 (p->wpts + i, tid, 1);
> + info->bpts_changed[i] = 1;
> + info->wpts_changed[i] = 1;
> }
> +
> + lp->arch_private = info;
> }
>
> -/* Handle thread exit. Tidy up the memory that has been allocated for the
> - thread. */
> +/* Called when resuming a thread.
> + The hardware debug registers are updated when there is any change. */
> +
> static void
> -arm_linux_thread_exit (struct thread_info *tp, int silent)
> +arm_linux_prepare_to_resume (struct lwp_info *lwp)
> {
> - const struct arm_linux_hwbp_cap *info = arm_linux_get_hwbp_cap ();
> + int pid, i;
> + struct arm_linux_hw_breakpoint *bpts, *wpts;
> + struct arch_lwp_info *arm_lwp_info = lwp->arch_private;
> +
> + /* NULL means this is the main thread still going through the shell,
> + or, no watchpoint has been set yet. In that case, there's
> + nothing to do. */
> + if (arm_lwp_info == NULL)
> + return;
>
> - if (info != NULL)
> - {
> - int i;
> - int tid = ptid_get_lwp (tp->ptid);
> - struct arm_linux_thread_points *t = NULL, *p;
> + for (i = 0; i < arm_linux_get_hw_breakpoint_count (); i++)
> + if (arm_lwp_info->bpts_changed[i])
> + {
> + errno = 0;
> + pid = ptid_get_lwp (lwp->ptid);
> + bpts = arm_linux_get_hwbreak_state (ptid_get_pid (lwp->ptid));
>
> - for (i = 0;
> - VEC_iterate (arm_linux_thread_points_p, arm_threads, i, p); i++)
> - {
> - if (p->tid == tid)
> - {
> - t = p;
> - break;
> - }
> - }
> + if (arm_hwbp_control_is_enabled (bpts[i].control))
> + if (ptrace (PTRACE_SETHBPREGS, pid,
> + (PTRACE_TYPE_ARG3) ((i << 1) + 1), &bpts[i].address) < 0)
> + perror_with_name ("Unexpected error setting breakpoint address");
>
> - if (t == NULL)
> - return;
> + if (bpts[i].control != 0)
> + if (ptrace (PTRACE_SETHBPREGS, pid,
> + (PTRACE_TYPE_ARG3) ((i << 1) + 2), &bpts[i].control) < 0)
> + perror_with_name ("Unexpected error setting breakpoint");
>
> - VEC_unordered_remove (arm_linux_thread_points_p, arm_threads, i);
> + arm_lwp_info->bpts_changed[i] = 0;
> + }
>
> - xfree (t->bpts);
> - xfree (t->wpts);
> - xfree (t);
> - }
> + for (i = 0; i < arm_linux_get_hw_watchpoint_count (); i++)
> + if (arm_lwp_info->wpts_changed[i])
> + {
> + errno = 0;
> + pid = ptid_get_lwp (lwp->ptid);
> + wpts = arm_linux_get_watch_state (ptid_get_pid (lwp->ptid));
> +
> + if (arm_hwbp_control_is_enabled (wpts[i].control))
> + if (ptrace (PTRACE_SETHBPREGS, pid,
> + (PTRACE_TYPE_ARG3) -((i << 1) + 1), &wpts[i].address) < 0)
> + perror_with_name ("Unexpected error setting watchpoint address");
> +
> + if (wpts[i].control != 0)
> + if (ptrace (PTRACE_SETHBPREGS, pid,
> + (PTRACE_TYPE_ARG3) -((i << 1) + 2), &wpts[i].control) < 0)
> + perror_with_name ("Unexpected error setting watchpoint");
> +
> + arm_lwp_info->wpts_changed[i] = 0;
> + }
> +}
> +
> +/* linux_nat_new_fork hook. */
> +
> +static void
> +arm_linux_new_fork (struct lwp_info *parent, pid_t child_pid)
> +{
> + pid_t parent_pid;
> + struct arm_linux_hw_breakpoint *parent_point_state;
> + struct arm_linux_hw_breakpoint *child_point_state;
> +
> + /* NULL means no watchpoint has ever been set in the parent. In
> + that case, there's nothing to do. */
> + if (parent->arch_private == NULL)
> + return;
> +
> + /* 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. */
> +
> + parent_pid = ptid_get_pid (parent->ptid);
> + parent_point_state = arm_linux_get_hwbreak_state (parent_pid);
> + child_point_state = arm_linux_get_hwbreak_state (child_pid);
> + memcpy (child_point_state, parent_point_state,
> + sizeof (struct arm_linux_hw_breakpoint) * MAX_BPTS);
> +
> + parent_point_state = arm_linux_get_watch_state (parent_pid);
> + child_point_state = arm_linux_get_watch_state (child_pid);
> + memcpy (child_point_state, parent_point_state,
> + sizeof (struct arm_linux_hw_breakpoint) * MAX_BPTS);
> }
>
> void _initialize_arm_linux_nat (void);
> @@ -1279,7 +1404,11 @@ _initialize_arm_linux_nat (void)
> /* Register the target. */
> linux_nat_add_target (t);
>
> - /* Handle thread creation and exit */
> - observer_attach_thread_exit (arm_linux_thread_exit);
> + /* Handle thread creation and exit. */
> linux_nat_set_new_thread (t, arm_linux_new_thread);
> + linux_nat_set_prepare_to_resume (t, arm_linux_prepare_to_resume);
> +
> + /* Handle process creation and exit. */
> + linux_nat_set_new_fork (t, arm_linux_new_fork);
> + linux_nat_set_forget_process (t, arm_linux_forget_process);
> }
>
Accidentally missed the patch description and changelog:
This patch updates arm native support for hardware breakpoints and watchpoints
to accommodate watchpoint/breakpoints across fork/vfork. Previously for arm
native a record of breakpoints at thread level was being kept which has been
changed to a process level record to come in sync with gdb-linux calls to
threads and process creation/destruction hooks.
gdb:
2014-01-31 Omair Javaid <omair.javaid@linaro.org>
* arm-linux-nat.c (struct arm_linux_thread_points): Removed.
(MAX_BPTS): Define.
(MAX_WPTS): Define.
(struct arm_linux_process_info): New.
(DEF_VEC_P (arm_linux_thread_points_p)): Removed.
(VEC(arm_linux_thread_points_p) *arm_threads): Removed.
(arm_linux_find_breakpoints_by_tid): Removed.
(struct arch_lwp_info): New.
(arm_linux_find_process_pid): New functions.
(arm_linux_add_process): New functions.
(arm_linux_process_info_get): New functions.
(arm_linux_forget_process): New function.
(arm_linux_get_hwbreak_state): New function.
(arm_linux_get_watch_state): New function.
(struct update_registers_data): New.
(update_registers_callback): New function.
(arm_linux_insert_hw_breakpoint1): Updated.
(arm_linux_remove_hw_breakpoint1): Updated.
(arm_linux_insert_hw_breakpoint): Updated.
(arm_linux_remove_hw_breakpoint): Updated.
(arm_linux_insert_watchpoint): Updated.
(arm_linux_remove_watchpoint): Updated.
(arm_linux_new_thread): Updated.
(arm_linux_prepare_to_resume): New function.
(arm_linux_new_fork): New function.
(_initialize_arm_linux_nat): Updated.