perf_counter: executable mmap() information

Currently the profiling information returns userspace IPs but no way
to correlate them to userspace code. Userspace could look into
/proc/$pid/maps but that might not be current or even present anymore
at the time of analyzing the IPs.

Therefore provide means to track the mmap information and provide it
in the output stream.

XXX: only covers mmap()/munmap(), mremap() and mprotect() are missing.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Mackerras <paulus@samba.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Orig-LKML-Reference: <20090330171023.417259499@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 145 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index c95e92329b9..f35e89e3d6a 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -25,6 +25,7 @@
 #include <linux/anon_inodes.h>
 #include <linux/kernel_stat.h>
 #include <linux/perf_counter.h>
+#include <linux/dcache.h>
 
 #include <asm/irq_regs.h>
 
@@ -1844,6 +1845,150 @@ void perf_counter_output(struct perf_counter *counter,
 }
 
 /*
+ * mmap tracking
+ */
+
+struct perf_mmap_event {
+	struct file	*file;
+	char		*file_name;
+	int		file_size;
+
+	struct {
+		struct perf_event_header	header;
+
+		u32				pid;
+		u32				tid;
+		u64				start;
+		u64				len;
+		u64				pgoff;
+	} event;
+};
+
+static void perf_counter_mmap_output(struct perf_counter *counter,
+				     struct perf_mmap_event *mmap_event)
+{
+	struct perf_output_handle handle;
+	int size = mmap_event->event.header.size;
+	int ret = perf_output_begin(&handle, counter, size);
+
+	if (ret)
+		return;
+
+	perf_output_put(&handle, mmap_event->event);
+	perf_output_copy(&handle, mmap_event->file_name,
+				   mmap_event->file_size);
+	perf_output_end(&handle, 0);
+}
+
+static int perf_counter_mmap_match(struct perf_counter *counter,
+				   struct perf_mmap_event *mmap_event)
+{
+	if (counter->hw_event.mmap &&
+	    mmap_event->event.header.type == PERF_EVENT_MMAP)
+		return 1;
+
+	if (counter->hw_event.munmap &&
+	    mmap_event->event.header.type == PERF_EVENT_MUNMAP)
+		return 1;
+
+	return 0;
+}
+
+static void perf_counter_mmap_ctx(struct perf_counter_context *ctx,
+				  struct perf_mmap_event *mmap_event)
+{
+	struct perf_counter *counter;
+
+	if (system_state != SYSTEM_RUNNING || list_empty(&ctx->event_list))
+		return;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {
+		if (perf_counter_mmap_match(counter, mmap_event))
+			perf_counter_mmap_output(counter, mmap_event);
+	}
+	rcu_read_unlock();
+}
+
+static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
+{
+	struct perf_cpu_context *cpuctx;
+	struct file *file = mmap_event->file;
+	unsigned int size;
+	char tmp[16];
+	char *buf = NULL;
+	char *name;
+
+	if (file) {
+		buf = kzalloc(PATH_MAX, GFP_KERNEL);
+		if (!buf) {
+			name = strncpy(tmp, "//enomem", sizeof(tmp));
+			goto got_name;
+		}
+		name = dentry_path(file->f_dentry, buf, PATH_MAX);
+		if (IS_ERR(name)) {
+			name = strncpy(tmp, "//toolong", sizeof(tmp));
+			goto got_name;
+		}
+	} else {
+		name = strncpy(tmp, "//anon", sizeof(tmp));
+		goto got_name;
+	}
+
+got_name:
+	size = ALIGN(strlen(name), sizeof(u64));
+
+	mmap_event->file_name = name;
+	mmap_event->file_size = size;
+
+	mmap_event->event.header.size = sizeof(mmap_event->event) + size;
+
+	cpuctx = &get_cpu_var(perf_cpu_context);
+	perf_counter_mmap_ctx(&cpuctx->ctx, mmap_event);
+	put_cpu_var(perf_cpu_context);
+
+	perf_counter_mmap_ctx(&current->perf_counter_ctx, mmap_event);
+
+	kfree(buf);
+}
+
+void perf_counter_mmap(unsigned long addr, unsigned long len,
+		       unsigned long pgoff, struct file *file)
+{
+	struct perf_mmap_event mmap_event = {
+		.file   = file,
+		.event  = {
+			.header = { .type = PERF_EVENT_MMAP, },
+			.pid	= current->group_leader->pid,
+			.tid	= current->pid,
+			.start  = addr,
+			.len    = len,
+			.pgoff  = pgoff,
+		},
+	};
+
+	perf_counter_mmap_event(&mmap_event);
+}
+
+void perf_counter_munmap(unsigned long addr, unsigned long len,
+			 unsigned long pgoff, struct file *file)
+{
+	struct perf_mmap_event mmap_event = {
+		.file   = file,
+		.event  = {
+			.header = { .type = PERF_EVENT_MUNMAP, },
+			.pid	= current->group_leader->pid,
+			.tid	= current->pid,
+			.start  = addr,
+			.len    = len,
+			.pgoff  = pgoff,
+		},
+	};
+
+	perf_counter_mmap_event(&mmap_event);
+}
+
+/*
  * Generic software counter infrastructure
  */