2 files changed, 268 insertions, 7 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ea055aa21cd9..12539f72f4a5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -11,31 +11,30 @@
  *  Copyright (C) 2004-2006 Ingo Molnar
  *  Copyright (C) 2004 William Lee Irwin III
  */
+#include <linux/ring_buffer.h>
 #include <linux/utsrelease.h>
+#include <linux/stacktrace.h>
+#include <linux/writeback.h>
 #include <linux/kallsyms.h>
 #include <linux/seq_file.h>
 #include <linux/notifier.h>
+#include <linux/irqflags.h>
 #include <linux/debugfs.h>
 #include <linux/pagemap.h>
 #include <linux/hardirq.h>
 #include <linux/linkage.h>
 #include <linux/uaccess.h>
+#include <linux/kprobes.h>
 #include <linux/ftrace.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
+#include <linux/splice.h>
 #include <linux/kdebug.h>
 #include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/poll.h>
 #include <linux/gfp.h>
 #include <linux/fs.h>
-#include <linux/kprobes.h>
-#include <linux/writeback.h>
-#include <linux/splice.h>
-
-#include <linux/stacktrace.h>
-#include <linux/ring_buffer.h>
-#include <linux/irqflags.h>
 
 #include "trace.h"
 #include "trace_output.h"
@@ -3005,6 +3004,246 @@ static struct file_operations tracing_mark_fops = {
         .write          = tracing_mark_write,
 };
 
+struct ftrace_buffer_info {
+        struct trace_array      *tr;
+        void                    *spare;
+        int                     cpu;
+        unsigned int            read;
+};
+
+static int tracing_buffers_open(struct inode *inode, struct file *filp)
+{
+        int cpu = (int)(long)inode->i_private;
+        struct ftrace_buffer_info *info;
+
+        if (tracing_disabled)
+                return -ENODEV;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                return -ENOMEM;
+
+        info->tr        = &global_trace;
+        info->cpu       = cpu;
+        info->spare     = ring_buffer_alloc_read_page(info->tr->buffer);
+        /* Force reading ring buffer for first read */
+        info->read      = (unsigned int)-1;
+        if (!info->spare)
+                goto out;
+
+        filp->private_data = info;
+
+        return 0;
+
+ out:
+        kfree(info);
+        return -ENOMEM;
+}
+
+static ssize_t
+tracing_buffers_read(struct file *filp, char __user *ubuf,
+                     size_t count, loff_t *ppos)
+{
+        struct ftrace_buffer_info *info = filp->private_data;
+        unsigned int pos;
+        ssize_t ret;
+        size_t size;
+
+        /* Do we have previous read data to read? */
+        if (info->read < PAGE_SIZE)
+                goto read;
+
+        info->read = 0;
+
+        ret = ring_buffer_read_page(info->tr->buffer,
+                                    &info->spare,
+                                    count,
+                                    info->cpu, 0);
+        if (ret < 0)
+                return 0;
+
+        pos = ring_buffer_page_len(info->spare);
+
+        if (pos < PAGE_SIZE)
+                memset(info->spare + pos, 0, PAGE_SIZE - pos);
+
+read:
+        size = PAGE_SIZE - info->read;
+        if (size > count)
+                size = count;
+
+        ret = copy_to_user(ubuf, info->spare + info->read, size);
+        if (ret)
+                return -EFAULT;
+        *ppos += size;
+        info->read += size;
+
+        return size;
+}
+
+static int tracing_buffers_release(struct inode *inode, struct file *file)
+{
+        struct ftrace_buffer_info *info = file->private_data;
+
+        ring_buffer_free_read_page(info->tr->buffer, info->spare);
+        kfree(info);
+
+        return 0;
+}
+
+struct buffer_ref {
+        struct ring_buffer      *buffer;
+        void                    *page;
+        int                     ref;
+};
+
+static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
+                                    struct pipe_buffer *buf)
+{
+        struct buffer_ref *ref = (struct buffer_ref *)buf->private;
+
+        if (--ref->ref)
+                return;
+
+        ring_buffer_free_read_page(ref->buffer, ref->page);
+        kfree(ref);
+        buf->private = 0;
+}
+
+static int buffer_pipe_buf_steal(struct pipe_inode_info *pipe,
+                                 struct pipe_buffer *buf)
+{
+        return 1;
+}
+
+static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
+                                struct pipe_buffer *buf)
+{
+        struct buffer_ref *ref = (struct buffer_ref *)buf->private;
+
+        ref->ref++;
+}
+
+/* Pipe buffer operations for a buffer. */
+static struct pipe_buf_operations buffer_pipe_buf_ops = {
+        .can_merge              = 0,
+        .map                    = generic_pipe_buf_map,
+        .unmap                  = generic_pipe_buf_unmap,
+        .confirm                = generic_pipe_buf_confirm,
+        .release                = buffer_pipe_buf_release,
+        .steal                  = buffer_pipe_buf_steal,
+        .get                    = buffer_pipe_buf_get,
+};
+
+/*
+ * Callback from splice_to_pipe(), if we need to release some pages
+ * at the end of the spd in case we error'ed out in filling the pipe.
+ */
+static void buffer_spd_release(struct splice_pipe_desc *spd, unsigned int i)
+{
+        struct buffer_ref *ref =
+                (struct buffer_ref *)spd->partial[i].private;
+
+        if (--ref->ref)
+                return;
+
+        ring_buffer_free_read_page(ref->buffer, ref->page);
+        kfree(ref);
+        spd->partial[i].private = 0;
+}
+
+static ssize_t
+tracing_buffers_splice_read(struct file *file, loff_t *ppos,
+                            struct pipe_inode_info *pipe, size_t len,
+                            unsigned int flags)
+{
+        struct ftrace_buffer_info *info = file->private_data;
+        struct partial_page partial[PIPE_BUFFERS];
+        struct page *pages[PIPE_BUFFERS];
+        struct splice_pipe_desc spd = {
+                .pages          = pages,
+                .partial        = partial,
+                .flags          = flags,
+                .ops            = &buffer_pipe_buf_ops,
+                .spd_release    = buffer_spd_release,
+        };
+        struct buffer_ref *ref;
+        int size, i;
+        size_t ret;
+
+        /*
+         * We can't seek on a buffer input
+         */
+        if (unlikely(*ppos))
+                return -ESPIPE;
+
+
+        for (i = 0; i < PIPE_BUFFERS && len; i++, len -= size) {
+                struct page *page;
+                int r;
+
+                ref = kzalloc(sizeof(*ref), GFP_KERNEL);
+                if (!ref)
+                        break;
+
+                ref->buffer = info->tr->buffer;
+                ref->page = ring_buffer_alloc_read_page(ref->buffer);
+                if (!ref->page) {
+                        kfree(ref);
+                        break;
+                }
+
+                r = ring_buffer_read_page(ref->buffer, &ref->page,
+                                          len, info->cpu, 0);
+                if (r < 0) {
+                        ring_buffer_free_read_page(ref->buffer,
+                                                   ref->page);
+                        kfree(ref);
+                        break;
+                }
+
+                /*
+                 * zero out any left over data, this is going to
+                 * user land.
+                 */
+                size = ring_buffer_page_len(ref->page);
+                if (size < PAGE_SIZE)
+                        memset(ref->page + size, 0, PAGE_SIZE - size);
+
+                page = virt_to_page(ref->page);
+
+                spd.pages[i] = page;
+                spd.partial[i].len = PAGE_SIZE;
+                spd.partial[i].offset = 0;
+                spd.partial[i].private = (unsigned long)ref;
+                spd.nr_pages++;
+        }
+
+        spd.nr_pages = i;
+
+        /* did we read anything? */
+        if (!spd.nr_pages) {
+                if (flags & SPLICE_F_NONBLOCK)
+                        ret = -EAGAIN;
+                else
+                        ret = 0;
+                /* TODO: block */
+                return ret;
+        }
+
+        ret = splice_to_pipe(pipe, &spd);
+
+        return ret;
+}
+
+static const struct file_operations tracing_buffers_fops = {
+        .open           = tracing_buffers_open,
+        .read           = tracing_buffers_read,
+        .release        = tracing_buffers_release,
+        .splice_read    = tracing_buffers_splice_read,
+        .llseek         = no_llseek,
+};
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 int __weak ftrace_arch_read_dyn_info(char *buf, int size)
@@ -3399,6 +3638,7 @@ static __init void create_trace_options_dir(void)
 static __init int tracer_init_debugfs(void)
 {
         struct dentry *d_tracer;
+        struct dentry *buffers;
         struct dentry *entry;
         int cpu;
 
@@ -3471,6 +3711,26 @@ static __init int tracer_init_debugfs(void)
                 pr_warning("Could not create debugfs "
                            "'trace_marker' entry\n");
 
+        buffers = debugfs_create_dir("binary_buffers", d_tracer);
+
+        if (!buffers)
+                pr_warning("Could not create buffers directory\n");
+        else {
+                int cpu;
+                char buf[64];
+
+                for_each_tracing_cpu(cpu) {
+                        sprintf(buf, "%d", cpu);
+
+                        entry = debugfs_create_file(buf, 0444, buffers,
+                                                    (void *)(long)cpu,
+                                                    &tracing_buffers_fops);
+                        if (!entry)
+                                pr_warning("Could not create debugfs buffers "
+                                           "'%s' entry\n", buf);
+                }
+        }
+
 #ifdef CONFIG_DYNAMIC_FTRACE
         entry = debugfs_create_file("dyn_ftrace_total_info", 0444, d_tracer,
                                     &ftrace_update_tot_cnt,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index e606633fb498..561bb5c5d988 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -217,6 +217,7 @@ enum trace_flag_type {
  */
 struct trace_array_cpu {
         atomic_t                disabled;
+        void                    *buffer_page;   /* ring buffer spare */
 
         /* these fields get copied into max-trace: */
         unsigned long           trace_idx;