Merge branch 'rfc/splice/tip/tracing/ftrace' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into tracing/ftrace

3 files changed, 352 insertions, 41 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index a8c275c01e8..f2a163db52f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -61,6 +61,8 @@ enum {
 
 static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
 
+#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
+
 /**
  * tracing_on - enable all tracing buffers
  *
@@ -132,7 +134,7 @@ void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
 
-#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
+#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
 #define RB_ALIGNMENT            4U
 #define RB_MAX_SMALL_DATA       28
 
@@ -234,6 +236,18 @@ static void rb_init_page(struct buffer_data_page *bpage)
         local_set(&bpage->commit, 0);
 }
 
+/**
+ * ring_buffer_page_len - the size of data on the page.
+ * @page: The page to read
+ *
+ * Returns the amount of data on the page, including buffer page header.
+ */
+size_t ring_buffer_page_len(void *page)
+{
+        return local_read(&((struct buffer_data_page *)page)->commit)
+                + BUF_PAGE_HDR_SIZE;
+}
+
 /*
  * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
  * this issue out.
@@ -254,7 +268,7 @@ static inline int test_time_stamp(u64 delta)
         return 0;
 }
 
-#define BUF_PAGE_SIZE (PAGE_SIZE - offsetof(struct buffer_data_page, data))
+#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
 
 /*
  * head_page == tail_page && head == tail then buffer is empty.
@@ -2378,8 +2392,8 @@ static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,
  */
 void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
 {
-        unsigned long addr;
         struct buffer_data_page *bpage;
+        unsigned long addr;
 
         addr = __get_free_page(GFP_KERNEL);
         if (!addr)
@@ -2387,6 +2401,8 @@ void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
 
         bpage = (void *)addr;
 
+        rb_init_page(bpage);
+
         return bpage;
 }
 
@@ -2406,6 +2422,7 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
  * ring_buffer_read_page - extract a page from the ring buffer
  * @buffer: buffer to extract from
  * @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @len: amount to extract
  * @cpu: the cpu of the buffer to extract
  * @full: should the extraction only happen when the page is full.
  *
@@ -2418,7 +2435,7 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
  *      rpage = ring_buffer_alloc_read_page(buffer);
  *      if (!rpage)
  *              return error;
- *      ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
+ *      ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
  *      if (ret >= 0)
  *              process_page(rpage, ret);
  *
@@ -2435,70 +2452,103 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
  *  <0 if no data has been transferred.
  */
 int ring_buffer_read_page(struct ring_buffer *buffer,
-                            void **data_page, int cpu, int full)
+                          void **data_page, size_t len, int cpu, int full)
 {
         struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
         struct ring_buffer_event *event;
         struct buffer_data_page *bpage;
+        struct buffer_page *reader;
         unsigned long flags;
+        unsigned int commit;
         unsigned int read;
         int ret = -1;
 
+        /*
+         * If len is not big enough to hold the page header, then
+         * we can not copy anything.
+         */
+        if (len <= BUF_PAGE_HDR_SIZE)
+                return -1;
+
+        len -= BUF_PAGE_HDR_SIZE;
+
         if (!data_page)
-                return 0;
+                return -1;
 
         bpage = *data_page;
         if (!bpage)
-                return 0;
+                return -1;
 
         spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
 
-        /*
-         * rb_buffer_peek will get the next ring buffer if
-         * the current reader page is empty.
-         */
-        event = rb_buffer_peek(buffer, cpu, NULL);
-        if (!event)
+        reader = rb_get_reader_page(cpu_buffer);
+        if (!reader)
                 goto out;
 
-        /* check for data */
-        if (!local_read(&cpu_buffer->reader_page->page->commit))
-                goto out;
+        event = rb_reader_event(cpu_buffer);
+
+        read = reader->read;
+        commit = rb_page_commit(reader);
 
-        read = cpu_buffer->reader_page->read;
         /*
-         * If the writer is already off of the read page, then simply
-         * switch the read page with the given page. Otherwise
-         * we need to copy the data from the reader to the writer.
+         * If this page has been partially read or
+         * if len is not big enough to read the rest of the page or
+         * a writer is still on the page, then
+         * we must copy the data from the page to the buffer.
+         * Otherwise, we can simply swap the page with the one passed in.
          */
-        if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
-                unsigned int commit = rb_page_commit(cpu_buffer->reader_page);
+        if (read || (len < (commit - read)) ||
+            cpu_buffer->reader_page == cpu_buffer->commit_page) {
                 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
+                unsigned int rpos = read;
+                unsigned int pos = 0;
+                unsigned int size;
 
                 if (full)
                         goto out;
-                /* The writer is still on the reader page, we must copy */
-                memcpy(bpage->data + read, rpage->data + read, commit - read);
 
-                /* consume what was read */
-                cpu_buffer->reader_page->read = commit;
+                if (len > (commit - read))
+                        len = (commit - read);
+
+                size = rb_event_length(event);
+
+                if (len < size)
+                        goto out;
+
+                /* Need to copy one event at a time */
+                do {
+                        memcpy(bpage->data + pos, rpage->data + rpos, size);
+
+                        len -= size;
+
+                        rb_advance_reader(cpu_buffer);
+                        rpos = reader->read;
+                        pos += size;
+
+                        event = rb_reader_event(cpu_buffer);
+                        size = rb_event_length(event);
+                } while (len > size);
 
                 /* update bpage */
-                local_set(&bpage->commit, commit);
-                if (!read)
-                        bpage->time_stamp = rpage->time_stamp;
+                local_set(&bpage->commit, pos);
+                bpage->time_stamp = rpage->time_stamp;
+
+                /* we copied everything to the beginning */
+                read = 0;
         } else {
                 /* swap the pages */
                 rb_init_page(bpage);
-                bpage = cpu_buffer->reader_page->page;
-                cpu_buffer->reader_page->page = *data_page;
-                cpu_buffer->reader_page->read = 0;
+                bpage = reader->page;
+                reader->page = *data_page;
+                local_set(&reader->write, 0);
+                reader->read = 0;
                 *data_page = bpage;
+
+                /* update the entry counter */
+                rb_remove_entries(cpu_buffer, bpage, read);
         }
         ret = read;
 
-        /* update the entry counter */
-        rb_remove_entries(cpu_buffer, bpage, read);
  out:
         spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ea055aa21cd..12539f72f4a 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 e606633fb49..561bb5c5d98 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;