[patch 1/2] x86, bts: fork and exit handling

[patch 1/2] x86, bts: fork and exit handling

[Markus Metzger]

Add arch_ptrace_untrace() function that is called when the tracer
detaches (either voluntarily or when the tracing task dies);
ptrace_disable() is only called on a voluntary detach.

Add ptrace_fork() and arch_ptrace_fork(). They are called when a
traced task is forked.

Clear DS and BTS related fields on fork.

Release DS resources and reclaim memory in ptrace_untrace(). This
releases resources already when the tracing task dies. We used to do
that when the traced task dies.


Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
---

Index: ftrace/arch/x86/kernel/process_32.c
===================================================================
--- ftrace.orig/arch/x86/kernel/process_32.c	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/arch/x86/kernel/process_32.c	2008-12-19 13:18:52.000000000 +0100
@@ -60,6 +60,7 @@
 #include <asm/idle.h>
 #include <asm/syscalls.h>
 #include <asm/smp.h>
+#include <asm/ds.h>
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
@@ -251,17 +252,8 @@
 		tss->x86_tss.io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
 		put_cpu();
 	}
-#ifdef CONFIG_X86_DS
-	/* Free any BTS tracers that have not been properly released. */
-	if (unlikely(current->bts)) {
-		ds_release_bts(current->bts);
-		current->bts = NULL;
-
-		kfree(current->bts_buffer);
-		current->bts_buffer = NULL;
-		current->bts_size = 0;
-	}
-#endif /* CONFIG_X86_DS */
+
+	ds_exit_thread(current);
 }
 
 void flush_thread(void)
@@ -343,6 +335,12 @@
 		kfree(p->thread.io_bitmap_ptr);
 		p->thread.io_bitmap_max = 0;
 	}
+
+	ds_copy_thread(p, current);
+
+	clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
+	p->thread.debugctlmsr = 0;
+
 	return err;
 }
 
Index: ftrace/arch/x86/kernel/process_64.c
===================================================================
--- ftrace.orig/arch/x86/kernel/process_64.c	2008-12-19 12:29:30.000000000 +0100
+++ ftrace/arch/x86/kernel/process_64.c	2008-12-19 12:29:41.000000000 +0100
@@ -54,6 +54,7 @@
 #include <asm/ia32.h>
 #include <asm/idle.h>
 #include <asm/syscalls.h>
+#include <asm/ds.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -248,17 +249,8 @@
 		t->io_bitmap_max = 0;
 		put_cpu();
 	}
-#ifdef CONFIG_X86_DS
-	/* Free any BTS tracers that have not been properly released. */
-	if (unlikely(current->bts)) {
-		ds_release_bts(current->bts);
-		current->bts = NULL;
-
-		kfree(current->bts_buffer);
-		current->bts_buffer = NULL;
-		current->bts_size = 0;
-	}
-#endif /* CONFIG_X86_DS */
+
+	ds_exit_thread(current);
 }
 
 void flush_thread(void)
@@ -388,6 +380,12 @@
 		if (err)
 			goto out;
 	}
+
+	ds_copy_thread(p, me);
+
+	clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR);
+	p->thread.debugctlmsr = 0;
+
 	err = 0;
 out:
 	if (err && p->thread.io_bitmap_ptr) {
Index: ftrace/kernel/fork.c
===================================================================
--- ftrace.orig/kernel/fork.c	2008-12-19 12:29:32.000000000 +0100
+++ ftrace/kernel/fork.c	2008-12-19 12:29:41.000000000 +0100
@@ -1102,6 +1102,8 @@
 #ifdef CONFIG_DEBUG_MUTEXES
 	p->blocked_on = NULL; /* not blocked yet */
 #endif
+	if (unlikely(ptrace_reparented(current)))
+		ptrace_fork(p, clone_flags);
 
 	/* Perform scheduler related setup. Assign this task to a CPU. */
 	sched_fork(p, clone_flags);
Index: ftrace/arch/x86/include/asm/ds.h
===================================================================
--- ftrace.orig/arch/x86/include/asm/ds.h	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/arch/x86/include/asm/ds.h	2008-12-19 12:29:41.000000000 +0100
@@ -252,12 +252,21 @@
  */
 extern void ds_switch_to(struct task_struct *prev, struct task_struct *next);
 
+/*
+ * Task clone/init and cleanup work
+ */
+extern void ds_copy_thread(struct task_struct *tsk, struct task_struct *father);
+extern void ds_exit_thread(struct task_struct *tsk);
+
 #else /* CONFIG_X86_DS */
 
 struct cpuinfo_x86;
 static inline void __cpuinit ds_init_intel(struct cpuinfo_x86 *ignored) {}
 static inline void ds_switch_to(struct task_struct *prev,
 				struct task_struct *next) {}
+static inline void ds_copy_thread(struct task_struct *tsk,
+				  struct task_struct *father) {}
+static inline void ds_exit_thread(struct task_struct *tsk) {}
 
 #endif /* CONFIG_X86_DS */
 #endif /* _ASM_X86_DS_H */
Index: ftrace/arch/x86/kernel/ds.c
===================================================================
--- ftrace.orig/arch/x86/kernel/ds.c	2008-12-19 12:29:30.000000000 +0100
+++ ftrace/arch/x86/kernel/ds.c	2008-12-19 12:29:41.000000000 +0100
@@ -1022,3 +1022,14 @@
 
 	update_debugctlmsr(next->thread.debugctlmsr);
 }
+
+void ds_copy_thread(struct task_struct *tsk, struct task_struct *father)
+{
+	clear_tsk_thread_flag(tsk, TIF_DS_AREA_MSR);
+	tsk->thread.ds_ctx = NULL;
+}
+
+void ds_exit_thread(struct task_struct *tsk)
+{
+	WARN_ON(tsk->thread.ds_ctx);
+}
Index: ftrace/arch/x86/kernel/ptrace.c
===================================================================
--- ftrace.orig/arch/x86/kernel/ptrace.c	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/arch/x86/kernel/ptrace.c	2008-12-19 13:17:47.000000000 +0100
@@ -769,8 +769,47 @@
 
 	return (trace->ds.top - trace->ds.begin) / trace->ds.size;
 }
+
+static void ptrace_bts_fork(struct task_struct *tsk)
+{
+	tsk->bts = NULL;
+	tsk->bts_buffer = NULL;
+	tsk->bts_size = 0;
+	tsk->thread.bts_ovfl_signal = 0;
+}
+
+static void ptrace_bts_untrace(struct task_struct *child)
+{
+	if (unlikely(child->bts)) {
+		ds_release_bts(child->bts);
+		child->bts = NULL;
+
+		kfree(child->bts_buffer);
+		child->bts_buffer = NULL;
+		child->bts_size = 0;
+	}
+}
+
+static void ptrace_bts_detach(struct task_struct *child)
+{
+	ptrace_bts_untrace(child);
+}
+#else
+static inline void ptrace_bts_fork(struct task_struct *tsk) {}
+static inline void ptrace_bts_detach(struct task_struct *child) {}
+static inline void ptrace_bts_untrace(struct task_struct *child) {}
 #endif /* CONFIG_X86_PTRACE_BTS */
 
+void x86_ptrace_fork(struct task_struct *child, unsigned long clone_flags)
+{
+	ptrace_bts_fork(child);
+}
+
+void x86_ptrace_untrace(struct task_struct *child)
+{
+	ptrace_bts_untrace(child);
+}
+
 /*
  * Called by kernel/ptrace.c when detaching..
  *
@@ -782,16 +821,7 @@
 #ifdef TIF_SYSCALL_EMU
 	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 #endif
-#ifdef CONFIG_X86_PTRACE_BTS
-	if (child->bts) {
-		ds_release_bts(child->bts);
-		child->bts = NULL;
-
-		kfree(child->bts_buffer);
-		child->bts_buffer = NULL;
-		child->bts_size = 0;
-	}
-#endif /* CONFIG_X86_PTRACE_BTS */
+	ptrace_bts_detach(child);
 }
 
 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
Index: ftrace/include/linux/ptrace.h
===================================================================
--- ftrace.orig/include/linux/ptrace.h	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/include/linux/ptrace.h	2008-12-19 12:29:41.000000000 +0100
@@ -94,6 +94,7 @@
 extern void __ptrace_link(struct task_struct *child,
 			  struct task_struct *new_parent);
 extern void __ptrace_unlink(struct task_struct *child);
+extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);
 #define PTRACE_MODE_READ   1
 #define PTRACE_MODE_ATTACH 2
 /* Returns 0 on success, -errno on denial. */
@@ -313,6 +314,27 @@
 #define arch_ptrace_stop(code, info)		do { } while (0)
 #endif
 
+#ifndef arch_ptrace_untrace
+/*
+ * Do machine-specific work before untracing child.
+ *
+ * This is called for a normal detach as well as from ptrace_exit()
+ * when the tracing task dies.
+ *
+ * Called with write_lock(&tasklist_lock) held.
+ */
+#define arch_ptrace_untrace(task)		do { } while (0)
+#endif
+
+#ifndef arch_ptrace_fork
+/*
+ * Do machine-specific work to initialize a new task.
+ *
+ * This is called from copy_process().
+ */
+#define arch_ptrace_fork(child, clone_flags)	do { } while (0)
+#endif
+
 extern int task_current_syscall(struct task_struct *target, long *callno,
 				unsigned long args[6], unsigned int maxargs,
 				unsigned long *sp, unsigned long *pc);
Index: ftrace/kernel/ptrace.c
===================================================================
--- ftrace.orig/kernel/ptrace.c	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/kernel/ptrace.c	2008-12-19 12:29:41.000000000 +0100
@@ -25,6 +25,17 @@
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 
+
+/*
+ * Initialize a new task whose father had been ptraced.
+ *
+ * Called from copy_process().
+ */
+void ptrace_fork(struct task_struct *child, unsigned long clone_flags)
+{
+	arch_ptrace_fork(child, clone_flags);
+}
+
 /*
  * ptrace a task: make the debugger its new parent and
  * move it to the ptrace list.
@@ -72,6 +83,7 @@
 	child->parent = child->real_parent;
 	list_del_init(&child->ptrace_entry);
 
+	arch_ptrace_untrace(child);
 	if (task_is_traced(child))
 		ptrace_untrace(child);
 }
Index: ftrace/arch/x86/include/asm/ptrace.h
===================================================================
--- ftrace.orig/arch/x86/include/asm/ptrace.h	2008-12-19 12:28:23.000000000 +0100
+++ ftrace/arch/x86/include/asm/ptrace.h	2008-12-19 12:29:41.000000000 +0100
@@ -235,6 +235,13 @@
 extern int do_set_thread_area(struct task_struct *p, int idx,
 			      struct user_desc __user *info, int can_allocate);
 
+extern void x86_ptrace_untrace(struct task_struct *);
+extern void x86_ptrace_fork(struct task_struct *child,
+			    unsigned long clone_flags);
+
+#define arch_ptrace_untrace(tsk) x86_ptrace_untrace(tsk)
+#define arch_ptrace_fork(child, flags) x86_ptrace_fork(child, flags)
+
 #endif /* __KERNEL__ */
 
 #endif /* !__ASSEMBLY__ */
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Re: [patch 1/2] x86, bts: fork and exit handling

[Ingo Molnar]

* Markus Metzger <markus.t.metzger@intel.com> wrote:

> Add arch_ptrace_untrace() function that is called when the tracer
> detaches (either voluntarily or when the tracing task dies);
> ptrace_disable() is only called on a voluntary detach.
> 
> Add ptrace_fork() and arch_ptrace_fork(). They are called when a
> traced task is forked.
> 
> Clear DS and BTS related fields on fork.
> 
> Release DS resources and reclaim memory in ptrace_untrace(). This
> releases resources already when the tracing task dies. We used to do
> that when the traced task dies.
> 
> Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>

applied to tip/tracing/hw-branch-tracer, thanks Markus! It's a nice 
cleanup too - to tear down any arch-level ptrace state that might come 
around.

	Ingo