x86, bts, ptrace: move BTS buffer allocation from ds.c into ptrace.c

Impact: restructure DS memory allocation to be done by the usage site of DS

Require pre-allocated buffers in ds.h.

Move the BTS buffer allocation for ptrace into ptrace.c.
The pointer to the allocated buffer is stored in the traced task's
task_struct together with the handle returned by ds_request_bts().

Removes memory accounting code.
Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/ds.h

@@ -7,13 +7,12 @@
  *
  * It manages:
  * - per-thread and per-cpu allocation of BTS and PEBS
- * - buffer memory allocation (optional)
- * - buffer overflow handling
+ * - buffer overflow handling (to be done)
  * - buffer access
  *
  * It assumes:
- * - get_task_struct on all parameter tasks
- * - current is allowed to trace parameter tasks
+ * - get_task_struct on all traced tasks
+ * - current is allowed to trace tasks
  *
  *
  * Copyright (C) 2007-2008 Intel Corporation.
@@ -54,8 +53,7 @@ typedef void (*pebs_ovfl_callback_t)(struct pebs_tracer *);
  * task: the task to request recording for;
  *       NULL for per-cpu recording on the current cpu
  * base: the base pointer for the (non-pageable) buffer;
- *       NULL if buffer allocation requested
- * size: the size of the requested or provided buffer in bytes
+ * size: the size of the provided buffer in bytes
  * ovfl: pointer to a function to be called on buffer overflow;
  *       NULL if cyclic buffer requested
  * th: the interrupt threshold in records from the end of the buffer;
@@ -72,8 +70,6 @@ extern struct pebs_tracer *ds_request_pebs(struct task_struct *task,
 /*
  * Release BTS or PEBS resources
  *
- * Frees buffers allocated on ds_request.
- *
  * Returns 0 on success; -Eerrno otherwise
  *
  * tracer: the tracer handle returned from ds_request_~()

arch/x86/kernel/ds.c

@@ -7,13 +7,12 @@
  *
  * It manages:
  * - per-thread and per-cpu allocation of BTS and PEBS
- * - buffer memory allocation (optional)
- * - buffer overflow handling
+ * - buffer overflow handling (to be done)
  * - buffer access
  *
  * It assumes:
- * - get_task_struct on all parameter tasks
- * - current is allowed to trace parameter tasks
+ * - get_task_struct on all traced tasks
+ * - current is allowed to trace tasks
  *
  *
  * Copyright (C) 2007-2008 Intel Corporation.
@@ -57,8 +56,6 @@ struct ds_tracer {
 	/* the buffer provided on ds_request() and its size in bytes */
 	void *buffer;
 	size_t size;
-	/* the number of allocated pages for on-request allocated buffers */
-	unsigned int pages;
 };
 
 struct bts_tracer {
@@ -141,8 +138,7 @@ static inline void ds_set(unsigned char *base, enum ds_qualifier qual,
 
 
 /*
- * Locking is done only for allocating BTS or PEBS resources and for
- * guarding context and buffer memory allocation.
+ * Locking is done only for allocating BTS or PEBS resources.
  */
 static spinlock_t ds_lock = __SPIN_LOCK_UNLOCKED(ds_lock);
 
@@ -292,50 +288,6 @@ static void ds_overflow(struct ds_context *context, enum ds_qualifier qual)
 }
 
 
-/*
- * Allocate a non-pageable buffer of the parameter size.
- * Checks the memory and the locked memory rlimit.
- *
- * Returns the buffer, if successful;
- *         NULL, if out of memory or rlimit exceeded.
- *
- * size: the requested buffer size in bytes
- * pages (out): if not NULL, contains the number of pages reserved
- */
-static inline void *ds_allocate_buffer(size_t size, unsigned int *pages)
-{
-	unsigned long rlim, vm, pgsz;
-	void *buffer = NULL;
-
-	pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
-
-	down_write(&current->mm->mmap_sem);
-
-	rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
-	vm   = current->mm->total_vm  + pgsz;
-	if (rlim < vm)
-		goto out;
-
-	rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
-	vm   = current->mm->locked_vm  + pgsz;
-	if (rlim < vm)
-		goto out;
-
-	buffer = kzalloc(size, GFP_KERNEL);
-	if (!buffer)
-		goto out;
-
-	current->mm->total_vm  += pgsz;
-	current->mm->locked_vm += pgsz;
-
-	if (pages)
-		*pages = pgsz;
-
- out:
-	up_write(&current->mm->mmap_sem);
-	return buffer;
-}
-
 static void ds_install_ds_config(struct ds_context *context,
 				 enum ds_qualifier qual,
 				 void *base, size_t size, size_t ith)
@@ -382,6 +334,10 @@ static int ds_request(struct ds_tracer *tracer, enum ds_qualifier qual,
 	if (!ds_cfg.sizeof_ds)
 		goto out;
 
+	error = -EINVAL;
+	if (!base)
+		goto out;
+
 	/* we require some space to do alignment adjustments below */
 	error = -EINVAL;
 	if (size < (DS_ALIGNMENT + ds_cfg.sizeof_rec[qual]))
@@ -395,13 +351,6 @@ static int ds_request(struct ds_tracer *tracer, enum ds_qualifier qual,
 			goto out;
 	}
 
-	error = -ENOMEM;
-	if (!base) {
-		base = ds_allocate_buffer(size, &tracer->pages);
-		if (!base)
-			goto out;
-	}
-
 	tracer->buffer = base;
 	tracer->size = size;
 
@@ -466,7 +415,7 @@ struct bts_tracer *ds_request_bts(struct task_struct *task,
 	return tracer;
 
  out_tracer:
-	(void)ds_release_bts(tracer);
+	kfree(tracer);
  out:
 	return ERR_PTR(error);
 }
@@ -496,31 +445,18 @@ struct pebs_tracer *ds_request_pebs(struct task_struct *task,
 	return tracer;
 
  out_tracer:
-	(void)ds_release_pebs(tracer);
+	kfree(tracer);
  out:
 	return ERR_PTR(error);
 }
 
 static void ds_release(struct ds_tracer *tracer, enum ds_qualifier qual)
 {
-	if (tracer->context) {
-		BUG_ON(tracer->context->owner[qual] != tracer);
-		tracer->context->owner[qual] = NULL;
-
-		put_tracer(tracer->context->task);
-		ds_put_context(tracer->context);
-	}
+	BUG_ON(tracer->context->owner[qual] != tracer);
+	tracer->context->owner[qual] = NULL;
 
-	if (tracer->pages) {
-		kfree(tracer->buffer);
-
-		down_write(&current->mm->mmap_sem);
-
-		current->mm->total_vm  -= tracer->pages;
-		current->mm->locked_vm -= tracer->pages;
-
-		up_write(&current->mm->mmap_sem);
-	}
+	put_tracer(tracer->context->task);
+	ds_put_context(tracer->context);
 }
 
 int ds_release_bts(struct bts_tracer *tracer)

arch/x86/kernel/ptrace.c

@@ -758,6 +758,10 @@ static int ptrace_bts_config(struct task_struct *child,
 		bts_ovfl_callback_t ovfl = NULL;
 		unsigned int sig = 0;
 
+		error = -EINVAL;
+		if (cfg.size < (10 * bts_cfg.sizeof_bts))
+			goto errout;
+
 		if (cfg.flags & PTRACE_BTS_O_SIGNAL) {
 			if (!cfg.signal)
 				goto errout;
@@ -768,14 +772,26 @@ static int ptrace_bts_config(struct task_struct *child,
 			sig  = cfg.signal;
 		}
 
-		if (child->bts)
+		if (child->bts) {
 			(void)ds_release_bts(child->bts);
+			kfree(child->bts_buffer);
+
+			child->bts = NULL;
+			child->bts_buffer = NULL;
+		}
+
+		error = -ENOMEM;
+		child->bts_buffer = kzalloc(cfg.size, GFP_KERNEL);
+		if (!child->bts_buffer)
+			goto errout;
 
-		child->bts = ds_request_bts(child, /* base = */ NULL, cfg.size,
+		child->bts = ds_request_bts(child, child->bts_buffer, cfg.size,
 					    ovfl, /* th = */ (size_t)-1);
 		if (IS_ERR(child->bts)) {
 			error = PTR_ERR(child->bts);
+			kfree(child->bts_buffer);
 			child->bts = NULL;
+			child->bts_buffer = NULL;
 			goto errout;
 		}
 
@@ -972,6 +988,8 @@ void ptrace_disable(struct task_struct *child)
 #ifdef CONFIG_X86_PTRACE_BTS
 	if (child->bts) {
 		(void)ds_release_bts(child->bts);
+		kfree(child->bts_buffer);
+		child->bts_buffer = NULL;
 
 		child->thread.debugctlmsr &= ~bts_cfg.debugctl_mask;
 		if (!child->thread.debugctlmsr)

include/linux/sched.h

@@ -1168,6 +1168,10 @@ struct task_struct {
 	 * This field actually belongs to the ptracer task.
 	 */
 	struct bts_tracer *bts;
+	/*
+	 * The buffer to hold the BTS data.
+	 */
+	void *bts_buffer;
 #endif /* CONFIG_X86_PTRACE_BTS */
 
 	/* PID/PID hash table linkage. */