1 files changed, 203 insertions, 36 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index a240bdc0f2d8..6edd70e45807 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -42,6 +42,9 @@
 
 static void update_pages_handler(struct work_struct *work);
 
+struct ring_buffer_meta {
+};
+
 /*
  * The ring buffer header is special. We must manually up keep it.
  */
@@ -342,7 +345,8 @@ struct buffer_page {
 	local_t		 entries;	/* entries on this page */
 	unsigned long	 real_end;	/* real end of data */
 	unsigned	 order;		/* order of the page */
-	u32		 id;		/* ID for external mapping */
+	u32		 id:30;		/* ID for external mapping */
+	u32		 range:1;	/* Mapped via a range */
 	struct buffer_data_page *page;	/* Actual data page */
 };
 
@@ -373,7 +377,9 @@ static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
 
 static void free_buffer_page(struct buffer_page *bpage)
 {
-	free_pages((unsigned long)bpage->page, bpage->order);
+	/* Range pages are not to be freed */
+	if (!bpage->range)
+		free_pages((unsigned long)bpage->page, bpage->order);
 	kfree(bpage);
 }
 
@@ -524,6 +530,9 @@ struct trace_buffer {
 	struct rb_irq_work		irq_work;
 	bool				time_stamp_abs;
 
+	unsigned long			range_addr_start;
+	unsigned long			range_addr_end;
+
 	unsigned int			subbuf_size;
 	unsigned int			subbuf_order;
 	unsigned int			max_data_size;
@@ -1491,9 +1500,70 @@ static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
 	}
 }
 
+/*
+ * Take an address, add the meta data size as well as the array of
+ * array subbuffer indexes, then align it to a subbuffer size.
+ *
+ * This is used to help find the next per cpu subbuffer within a mapped range.
+ */
+static unsigned long
+rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
+{
+	addr += sizeof(struct ring_buffer_meta) +
+		sizeof(int) * nr_subbufs;
+	return ALIGN(addr, subbuf_size);
+}
+
+/*
+ * Return a specific sub-buffer for a given @cpu defined by @idx.
+ */
+static void *rb_range_buffer(struct trace_buffer *buffer, int cpu, int nr_pages, int idx)
+{
+	unsigned long ptr;
+	int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
+	int nr_subbufs;
+
+	/* Include the reader page */
+	nr_subbufs = nr_pages + 1;
+
+	/*
+	 * The first chunk may not be subbuffer aligned, where as
+	 * the rest of the chunks are.
+	 */
+	ptr = buffer->range_addr_start;
+	ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
+	if (cpu) {
+		unsigned long p;
+
+		ptr += subbuf_size * nr_subbufs;
+
+		/* Save the beginning of this CPU chunk */
+		p = ptr;
+
+		ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
+
+		/* We can use multiplication to find chunks greater than 1 */
+		if (cpu > 1) {
+			unsigned long size;
+
+			ptr += subbuf_size * nr_subbufs;
+
+			/* Now all chunks after this are the same size */
+			size = ptr - p;
+			ptr += size * (cpu - 2);
+
+			ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
+		}
+	}
+	if (ptr + subbuf_size * nr_subbufs > buffer->range_addr_end)
+		return NULL;
+	return (void *)ptr;
+}
+
 static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 		long nr_pages, struct list_head *pages)
 {
+	struct trace_buffer *buffer = cpu_buffer->buffer;
 	struct buffer_page *bpage, *tmp;
 	bool user_thread = current->mm != NULL;
 	gfp_t mflags;
@@ -1530,6 +1600,7 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 		set_current_oom_origin();
 	for (i = 0; i < nr_pages; i++) {
 		struct page *page;
+		int cpu = cpu_buffer->cpu;
 
 		bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
 				    mflags, cpu_to_node(cpu_buffer->cpu));
@@ -1538,14 +1609,26 @@ static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
 
 		rb_check_bpage(cpu_buffer, bpage);
 
-		list_add(&bpage->list, pages);
-
-		page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
-					mflags | __GFP_COMP | __GFP_ZERO,
-					cpu_buffer->buffer->subbuf_order);
-		if (!page)
-			goto free_pages;
-		bpage->page = page_address(page);
+		/*
+		 * Append the pages as for mapped buffers we want to keep
+		 * the order
+		 */
+		list_add_tail(&bpage->list, pages);
+
+		if (buffer->range_addr_start) {
+			/* A range was given. Use that for the buffer page */
+			bpage->page = rb_range_buffer(buffer, cpu, nr_pages, i + 1);
+			if (!bpage->page)
+				goto free_pages;
+			bpage->range = 1;
+		} else {
+			page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
+						mflags | __GFP_COMP | __GFP_ZERO,
+						cpu_buffer->buffer->subbuf_order);
+			if (!page)
+				goto free_pages;
+			bpage->page = page_address(page);
+		}
 		bpage->order = cpu_buffer->buffer->subbuf_order;
 		rb_init_page(bpage->page);
 
@@ -1627,11 +1710,19 @@ rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
 
 	cpu_buffer->reader_page = bpage;
 
-	page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
-				cpu_buffer->buffer->subbuf_order);
-	if (!page)
-		goto fail_free_reader;
-	bpage->page = page_address(page);
+	if (buffer->range_addr_start) {
+		bpage->page = rb_range_buffer(buffer, cpu, nr_pages, 0);
+		if (!bpage->page)
+			goto fail_free_reader;
+		bpage->range = 1;
+	} else {
+		page = alloc_pages_node(cpu_to_node(cpu),
+					GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
+					cpu_buffer->buffer->subbuf_order);
+		if (!page)
+			goto fail_free_reader;
+		bpage->page = page_address(page);
+	}
 	rb_init_page(bpage->page);
 
 	INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
@@ -1682,22 +1773,14 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
 	kfree(cpu_buffer);
 }
 
-/**
- * __ring_buffer_alloc - allocate a new ring_buffer
- * @size: the size in bytes per cpu that is needed.
- * @flags: attributes to set for the ring buffer.
- * @key: ring buffer reader_lock_key.
- *
- * Currently the only flag that is available is the RB_FL_OVERWRITE
- * flag. This flag means that the buffer will overwrite old data
- * when the buffer wraps. If this flag is not set, the buffer will
- * drop data when the tail hits the head.
- */
-struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
-					struct lock_class_key *key)
+static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
+					 int order, unsigned long start,
+					 unsigned long end,
+					 struct lock_class_key *key)
 {
 	struct trace_buffer *buffer;
 	long nr_pages;
+	int subbuf_size;
 	int bsize;
 	int cpu;
 	int ret;
@@ -1711,14 +1794,13 @@ struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
 		goto fail_free_buffer;
 
-	/* Default buffer page size - one system page */
-	buffer->subbuf_order = 0;
-	buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
+	buffer->subbuf_order = order;
+	subbuf_size = (PAGE_SIZE << order);
+	buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
 
 	/* Max payload is buffer page size - header (8bytes) */
 	buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
 
-	nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
 	buffer->flags = flags;
 	buffer->clock = trace_clock_local;
 	buffer->reader_lock_key = key;
@@ -1726,10 +1808,6 @@ struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
 	init_waitqueue_head(&buffer->irq_work.waiters);
 
-	/* need at least two pages */
-	if (nr_pages < 2)
-		nr_pages = 2;
-
 	buffer->cpus = nr_cpu_ids;
 
 	bsize = sizeof(void *) * nr_cpu_ids;
@@ -1738,6 +1816,54 @@ struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	if (!buffer->buffers)
 		goto fail_free_cpumask;
 
+	/* If start/end are specified, then that overrides size */
+	if (start && end) {
+		unsigned long ptr;
+		int n;
+
+		size = end - start;
+		size = size / nr_cpu_ids;
+
+		/*
+		 * The number of sub-buffers (nr_pages) is determined by the
+		 * total size allocated minus the meta data size.
+		 * Then that is divided by the number of per CPU buffers
+		 * needed, plus account for the integer array index that
+		 * will be appended to the meta data.
+		 */
+		nr_pages = (size - sizeof(struct ring_buffer_meta)) /
+			(subbuf_size + sizeof(int));
+		/* Need at least two pages plus the reader page */
+		if (nr_pages < 3)
+			goto fail_free_buffers;
+
+ again:
+		/* Make sure that the size fits aligned */
+		for (n = 0, ptr = start; n < nr_cpu_ids; n++) {
+			ptr += sizeof(struct ring_buffer_meta) +
+				sizeof(int) * nr_pages;
+			ptr = ALIGN(ptr, subbuf_size);
+			ptr += subbuf_size * nr_pages;
+		}
+		if (ptr > end) {
+			if (nr_pages <= 3)
+				goto fail_free_buffers;
+			nr_pages--;
+			goto again;
+		}
+
+		/* nr_pages should not count the reader page */
+		nr_pages--;
+		buffer->range_addr_start = start;
+		buffer->range_addr_end = end;
+	} else {
+
+		/* need at least two pages */
+		nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
+		if (nr_pages < 2)
+			nr_pages = 2;
+	}
+
 	cpu = raw_smp_processor_id();
 	cpumask_set_cpu(cpu, buffer->cpumask);
 	buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
@@ -1766,9 +1892,50 @@ struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	kfree(buffer);
 	return NULL;
 }
+
+/**
+ * __ring_buffer_alloc - allocate a new ring_buffer
+ * @size: the size in bytes per cpu that is needed.
+ * @flags: attributes to set for the ring buffer.
+ * @key: ring buffer reader_lock_key.
+ *
+ * Currently the only flag that is available is the RB_FL_OVERWRITE
+ * flag. This flag means that the buffer will overwrite old data
+ * when the buffer wraps. If this flag is not set, the buffer will
+ * drop data when the tail hits the head.
+ */
+struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
+					struct lock_class_key *key)
+{
+	/* Default buffer page size - one system page */
+	return alloc_buffer(size, flags, 0, 0, 0,key);
+
+}
 EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
 
 /**
+ * __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory
+ * @size: the size in bytes per cpu that is needed.
+ * @flags: attributes to set for the ring buffer.
+ * @start: start of allocated range
+ * @range_size: size of allocated range
+ * @order: sub-buffer order
+ * @key: ring buffer reader_lock_key.
+ *
+ * Currently the only flag that is available is the RB_FL_OVERWRITE
+ * flag. This flag means that the buffer will overwrite old data
+ * when the buffer wraps. If this flag is not set, the buffer will
+ * drop data when the tail hits the head.
+ */
+struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
+					       int order, unsigned long start,
+					       unsigned long range_size,
+					       struct lock_class_key *key)
+{
+	return alloc_buffer(size, flags, order, start, start + range_size, key);
+}
+
+/**
  * ring_buffer_free - free a ring buffer.
  * @buffer: the buffer to free.
  */