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Date: Thu, 17 Dec 2009 22:52:53 +0530
From: "K.Prasad" <prasad@...ux.vnet.ibm.com>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"mingo@...e.hu" <mingo@...e.hu>,
Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Subject: [Patch 1/1] Introduce register_user_hbp_by_pid() and
unregister_user_hbp_by_pid()
Provide an interface to (un)register user-space breakpoints using a
process' pid.
Signed-off-by: K.Prasad <prasad@...ux.vnet.ibm.com>
---
include/linux/hw_breakpoint.h | 8 +++
kernel/hw_breakpoint.c | 92 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 100 insertions(+)
Index: linux-2.6-tip.reg_by_pid/include/linux/hw_breakpoint.h
===================================================================
--- linux-2.6-tip.reg_by_pid.orig/include/linux/hw_breakpoint.h
+++ linux-2.6-tip.reg_by_pid/include/linux/hw_breakpoint.h
@@ -54,6 +54,10 @@ register_user_hw_breakpoint(struct perf_
perf_overflow_handler_t triggered,
struct task_struct *tsk);
+extern int register_user_hbp_by_pid(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ pid_t pid);
+extern void unregister_user_hbp_by_pid(pid_t pid);
/* FIXME: only change from the attr, and don't unregister */
extern int
modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr);
@@ -91,6 +95,10 @@ static inline struct perf_event *
register_user_hw_breakpoint(struct perf_event_attr *attr,
perf_overflow_handler_t triggered,
struct task_struct *tsk) { return NULL; }
+int register_user_hbp_by_pid(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ pid_t pid) { return 0; }
+void unregister_user_hbp_by_pid(pid_t pid) {}
static inline int
modify_user_hw_breakpoint(struct perf_event *bp,
struct perf_event_attr *attr) { return -ENOSYS; }
Index: linux-2.6-tip.reg_by_pid/kernel/hw_breakpoint.c
===================================================================
--- linux-2.6-tip.reg_by_pid.orig/kernel/hw_breakpoint.c
+++ linux-2.6-tip.reg_by_pid/kernel/hw_breakpoint.c
@@ -298,6 +298,98 @@ int register_perf_hw_breakpoint(struct p
return ret;
}
+/*
+ * Unregister breakpoints thread-by-thread, for all threads ranging from
+ * @start to @end.
+ */
+static inline void __unregister_user_hbp_for_threads(struct task_struct *start,
+ struct task_struct *end)
+{
+ struct perf_event *bp, *temp_bp;
+
+ do {
+ mutex_lock(&start->perf_event_mutex);
+ list_for_each_entry_safe(bp, temp_bp, &start->perf_event_list,
+ owner_entry) {
+ if (bp->attr.type != PERF_TYPE_BREAKPOINT)
+ continue;
+ unregister_hw_breakpoint(bp);
+ break;
+ }
+ mutex_unlock(&start->perf_event_mutex);
+ } while_each_thread(start, end);
+}
+
+/**
+ * register_user_hbp_by_pid - register a hardware breakpoint for user space using pid
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @pid: pid of the thread group for which breakpoints must be registered
+ */
+int register_user_hbp_by_pid(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ pid_t pid)
+{
+ int ret;
+ struct task_struct *t1, *t2;
+
+ t1 = t2 = find_task_by_vpid(pid);
+ if (t1 == NULL)
+ return -ESRCH;
+
+ /*
+ * Ensure that the breakpoint propogates to every new thread created in
+ * this thread_group.
+ */
+ attr->inherit = 1;
+ /*
+ * Register a breakpoint individually for every thread of the
+ * thread_group using register_user_hw_breakpoint() interface.
+ * Warning: Involves redundant validation checks using
+ * arch_validate_hwbkpt_settings().
+ */
+ do {
+ ret = IS_ERR(register_user_hw_breakpoint(attr, triggered, t1));
+ if (ret)
+ goto fail;
+ t1 = next_thread(t1);
+ } while (t1 != t2);
+
+ return 0;
+fail:
+ /*
+ * Check if the very first register_user_hw_breakpoint() request
+ * failed. If then, do nothing but return the error value.
+ */
+ if (t1 == t2)
+ return ret;
+ /*
+ * Since there exists a thread where the breakpoint request was not
+ * successful, we are unable to provide a process-wide breakpoint. Hence
+ * cleanup the breakpoints from the previously registered threads.
+ */
+ __unregister_user_hbp_for_threads(t2, t1);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(register_user_hbp_by_pid);
+
+/**
+ * unregister_hbp_by_pid - unregister a user-space hardware breakpoint previously registered using a pid
+ * @pid: pid of the process for which breakpoint must be unregistered
+ */
+void unregister_user_hbp_by_pid(pid_t pid)
+{
+ struct task_struct *t1, *t2;
+
+ t1 = t2 = find_task_by_vpid(pid);
+ if (t1 == NULL)
+ return;
+
+ __unregister_user_hbp_for_threads(t1, t2);
+}
+EXPORT_SYMBOL_GPL(unregister_user_hbp_by_pid);
+
/**
* register_user_hw_breakpoint - register a hardware breakpoint for user space
* @attr: breakpoint attributes
--
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