Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 537 insertions, 0 deletions

diff --git a/lib/kunit/string-stream-test.c b/lib/kunit/string-stream-test.c
new file mode 100644
index 000000000..7734e3315
--- /dev/null
+++ b/lib/kunit/string-stream-test.c
@@ -0,0 +1,537 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for struct string_stream.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <kunit/static_stub.h>
+#include <kunit/test.h>
+#include <linux/ktime.h>
+#include <linux/prandom.h>
+#include <linux/slab.h>
+#include <linux/timekeeping.h>
+
+#include "string-stream.h"
+
+struct string_stream_test_priv {
+	/* For testing resource-managed free. */
+	struct string_stream *expected_free_stream;
+	bool stream_was_freed;
+	bool stream_free_again;
+};
+
+/* Avoids a cast warning if kfree() is passed direct to kunit_add_action(). */
+KUNIT_DEFINE_ACTION_WRAPPER(kfree_wrapper, kfree, const void *);
+
+/* Avoids a cast warning if string_stream_destroy() is passed direct to kunit_add_action(). */
+KUNIT_DEFINE_ACTION_WRAPPER(cleanup_raw_stream, string_stream_destroy, struct string_stream *);
+
+static char *get_concatenated_string(struct kunit *test, struct string_stream *stream)
+{
+	char *str = string_stream_get_string(stream);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, str);
+	kunit_add_action(test, kfree_wrapper, (void *)str);
+
+	return str;
+}
+
+/* Managed string_stream object is initialized correctly. */
+static void string_stream_managed_init_test(struct kunit *test)
+{
+	struct string_stream *stream;
+
+	/* Resource-managed initialization. */
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	KUNIT_EXPECT_EQ(test, stream->length, 0);
+	KUNIT_EXPECT_TRUE(test, list_empty(&stream->fragments));
+	KUNIT_EXPECT_TRUE(test, (stream->gfp == GFP_KERNEL));
+	KUNIT_EXPECT_FALSE(test, stream->append_newlines);
+	KUNIT_EXPECT_TRUE(test, string_stream_is_empty(stream));
+}
+
+/* Unmanaged string_stream object is initialized correctly. */
+static void string_stream_unmanaged_init_test(struct kunit *test)
+{
+	struct string_stream *stream;
+
+	stream = alloc_string_stream(GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+	kunit_add_action(test, cleanup_raw_stream, stream);
+
+	KUNIT_EXPECT_EQ(test, stream->length, 0);
+	KUNIT_EXPECT_TRUE(test, list_empty(&stream->fragments));
+	KUNIT_EXPECT_TRUE(test, (stream->gfp == GFP_KERNEL));
+	KUNIT_EXPECT_FALSE(test, stream->append_newlines);
+
+	KUNIT_EXPECT_TRUE(test, string_stream_is_empty(stream));
+}
+
+static void string_stream_destroy_stub(struct string_stream *stream)
+{
+	struct kunit *fake_test = kunit_get_current_test();
+	struct string_stream_test_priv *priv = fake_test->priv;
+
+	/* The kunit could own string_streams other than the one we are testing. */
+	if (stream == priv->expected_free_stream) {
+		if (priv->stream_was_freed)
+			priv->stream_free_again = true;
+		else
+			priv->stream_was_freed = true;
+	}
+
+	/*
+	 * Calling string_stream_destroy() will only call this function again
+	 * because the redirection stub is still active.
+	 * Avoid calling deactivate_static_stub() or changing current->kunit_test
+	 * during cleanup.
+	 */
+	string_stream_clear(stream);
+	kfree(stream);
+}
+
+/* kunit_free_string_stream() calls string_stream_desrtoy() */
+static void string_stream_managed_free_test(struct kunit *test)
+{
+	struct string_stream_test_priv *priv = test->priv;
+
+	priv->expected_free_stream = NULL;
+	priv->stream_was_freed = false;
+	priv->stream_free_again = false;
+
+	kunit_activate_static_stub(test,
+				   string_stream_destroy,
+				   string_stream_destroy_stub);
+
+	priv->expected_free_stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->expected_free_stream);
+
+	/* This should call the stub function. */
+	kunit_free_string_stream(test, priv->expected_free_stream);
+
+	KUNIT_EXPECT_TRUE(test, priv->stream_was_freed);
+	KUNIT_EXPECT_FALSE(test, priv->stream_free_again);
+}
+
+/* string_stream object is freed when test is cleaned up. */
+static void string_stream_resource_free_test(struct kunit *test)
+{
+	struct string_stream_test_priv *priv = test->priv;
+	struct kunit *fake_test;
+
+	fake_test = kunit_kzalloc(test, sizeof(*fake_test), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_test);
+
+	kunit_init_test(fake_test, "string_stream_fake_test", NULL);
+	fake_test->priv = priv;
+
+	/*
+	 * Activate stub before creating string_stream so the
+	 * string_stream will be cleaned up first.
+	 */
+	priv->expected_free_stream = NULL;
+	priv->stream_was_freed = false;
+	priv->stream_free_again = false;
+
+	kunit_activate_static_stub(fake_test,
+				   string_stream_destroy,
+				   string_stream_destroy_stub);
+
+	priv->expected_free_stream = kunit_alloc_string_stream(fake_test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->expected_free_stream);
+
+	/* Set current->kunit_test to fake_test so the static stub will be called. */
+	current->kunit_test = fake_test;
+
+	/* Cleanup test - the stub function should be called */
+	kunit_cleanup(fake_test);
+
+	/* Set current->kunit_test back to current test. */
+	current->kunit_test = test;
+
+	KUNIT_EXPECT_TRUE(test, priv->stream_was_freed);
+	KUNIT_EXPECT_FALSE(test, priv->stream_free_again);
+}
+
+/*
+ * Add a series of lines to a string_stream. Check that all lines
+ * appear in the correct order and no characters are dropped.
+ */
+static void string_stream_line_add_test(struct kunit *test)
+{
+	struct string_stream *stream;
+	char line[60];
+	char *concat_string, *pos, *string_end;
+	size_t len, total_len;
+	int num_lines, i;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	/* Add series of sequence numbered lines */
+	total_len = 0;
+	for (i = 0; i < 100; ++i) {
+		len = snprintf(line, sizeof(line),
+			"The quick brown fox jumps over the lazy penguin %d\n", i);
+
+		/* Sanity-check that our test string isn't truncated */
+		KUNIT_ASSERT_LT(test, len, sizeof(line));
+
+		string_stream_add(stream, line);
+		total_len += len;
+	}
+	num_lines = i;
+
+	concat_string = get_concatenated_string(test, stream);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, concat_string);
+	KUNIT_EXPECT_EQ(test, strlen(concat_string), total_len);
+
+	/*
+	 * Split the concatenated string at the newlines and check that
+	 * all the original added strings are present.
+	 */
+	pos = concat_string;
+	for (i = 0; i < num_lines; ++i) {
+		string_end = strchr(pos, '\n');
+		KUNIT_EXPECT_NOT_NULL(test, string_end);
+
+		/* Convert to NULL-terminated string */
+		*string_end = '\0';
+
+		snprintf(line, sizeof(line),
+			 "The quick brown fox jumps over the lazy penguin %d", i);
+		KUNIT_EXPECT_STREQ(test, pos, line);
+
+		pos = string_end + 1;
+	}
+
+	/* There shouldn't be any more data after this */
+	KUNIT_EXPECT_EQ(test, strlen(pos), 0);
+}
+
+/* Add a series of lines of variable length to a string_stream. */
+static void string_stream_variable_length_line_test(struct kunit *test)
+{
+	static const char line[] =
+		"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+		" 0123456789!$%^&*()_-+={}[]:;@'~#<>,.?/|";
+	struct string_stream *stream;
+	struct rnd_state rnd;
+	char *concat_string, *pos, *string_end;
+	size_t offset, total_len;
+	int num_lines, i;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	/*
+	 * Log many lines of varying lengths until we have created
+	 * many fragments.
+	 * The "randomness" must be repeatable.
+	 */
+	prandom_seed_state(&rnd, 3141592653589793238ULL);
+	total_len = 0;
+	for (i = 0; i < 100; ++i) {
+		offset = prandom_u32_state(&rnd) % (sizeof(line) - 1);
+		string_stream_add(stream, "%s\n", &line[offset]);
+		total_len += sizeof(line) - offset;
+	}
+	num_lines = i;
+
+	concat_string = get_concatenated_string(test, stream);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, concat_string);
+	KUNIT_EXPECT_EQ(test, strlen(concat_string), total_len);
+
+	/*
+	 * Split the concatenated string at the newlines and check that
+	 * all the original added strings are present.
+	 */
+	prandom_seed_state(&rnd, 3141592653589793238ULL);
+	pos = concat_string;
+	for (i = 0; i < num_lines; ++i) {
+		string_end = strchr(pos, '\n');
+		KUNIT_EXPECT_NOT_NULL(test, string_end);
+
+		/* Convert to NULL-terminated string */
+		*string_end = '\0';
+
+		offset = prandom_u32_state(&rnd) % (sizeof(line) - 1);
+		KUNIT_EXPECT_STREQ(test, pos, &line[offset]);
+
+		pos = string_end + 1;
+	}
+
+	/* There shouldn't be any more data after this */
+	KUNIT_EXPECT_EQ(test, strlen(pos), 0);
+}
+
+/* Appending the content of one string stream to another. */
+static void string_stream_append_test(struct kunit *test)
+{
+	static const char * const strings_1[] = {
+		"one", "two", "three", "four", "five", "six",
+		"seven", "eight", "nine", "ten",
+	};
+	static const char * const strings_2[] = {
+		"Apple", "Pear", "Orange", "Banana", "Grape", "Apricot",
+	};
+	struct string_stream *stream_1, *stream_2;
+	const char *stream1_content_before_append, *stream_2_content;
+	char *combined_content;
+	size_t combined_length;
+	int i;
+
+	stream_1 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_1);
+
+	stream_2 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_2);
+
+	/* Append content of empty stream to empty stream */
+	string_stream_append(stream_1, stream_2);
+	KUNIT_EXPECT_EQ(test, strlen(get_concatenated_string(test, stream_1)), 0);
+
+	/* Add some data to stream_1 */
+	for (i = 0; i < ARRAY_SIZE(strings_1); ++i)
+		string_stream_add(stream_1, "%s\n", strings_1[i]);
+
+	stream1_content_before_append = get_concatenated_string(test, stream_1);
+
+	/* Append content of empty stream to non-empty stream */
+	string_stream_append(stream_1, stream_2);
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream_1),
+			   stream1_content_before_append);
+
+	/* Add some data to stream_2 */
+	for (i = 0; i < ARRAY_SIZE(strings_2); ++i)
+		string_stream_add(stream_2, "%s\n", strings_2[i]);
+
+	/* Append content of non-empty stream to non-empty stream */
+	string_stream_append(stream_1, stream_2);
+
+	/*
+	 * End result should be the original content of stream_1 plus
+	 * the content of stream_2.
+	 */
+	stream_2_content = get_concatenated_string(test, stream_2);
+	combined_length = strlen(stream1_content_before_append) + strlen(stream_2_content);
+	combined_length++; /* for terminating \0 */
+	combined_content = kunit_kmalloc(test, combined_length, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, combined_content);
+	snprintf(combined_content, combined_length, "%s%s",
+		 stream1_content_before_append, stream_2_content);
+
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream_1), combined_content);
+
+	/* Append content of non-empty stream to empty stream */
+	kunit_free_string_stream(test, stream_1);
+
+	stream_1 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_1);
+
+	string_stream_append(stream_1, stream_2);
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream_1), stream_2_content);
+}
+
+/* Appending the content of one string stream to one with auto-newlining. */
+static void string_stream_append_auto_newline_test(struct kunit *test)
+{
+	struct string_stream *stream_1, *stream_2;
+
+	/* Stream 1 has newline appending enabled */
+	stream_1 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_1);
+	string_stream_set_append_newlines(stream_1, true);
+	KUNIT_EXPECT_TRUE(test, stream_1->append_newlines);
+
+	/* Stream 2 does not append newlines */
+	stream_2 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_2);
+
+	/* Appending a stream with a newline should not add another newline */
+	string_stream_add(stream_1, "Original string\n");
+	string_stream_add(stream_2, "Appended content\n");
+	string_stream_add(stream_2, "More stuff\n");
+	string_stream_append(stream_1, stream_2);
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream_1),
+			   "Original string\nAppended content\nMore stuff\n");
+
+	kunit_free_string_stream(test, stream_2);
+	stream_2 = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream_2);
+
+	/*
+	 * Appending a stream without newline should add a final newline.
+	 * The appended string_stream is treated as a single string so newlines
+	 * should not be inserted between fragments.
+	 */
+	string_stream_add(stream_2, "Another");
+	string_stream_add(stream_2, "And again");
+	string_stream_append(stream_1, stream_2);
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream_1),
+			   "Original string\nAppended content\nMore stuff\nAnotherAnd again\n");
+}
+
+/* Adding an empty string should not create a fragment. */
+static void string_stream_append_empty_string_test(struct kunit *test)
+{
+	struct string_stream *stream;
+	int original_frag_count;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	/* Formatted empty string */
+	string_stream_add(stream, "%s", "");
+	KUNIT_EXPECT_TRUE(test, string_stream_is_empty(stream));
+	KUNIT_EXPECT_TRUE(test, list_empty(&stream->fragments));
+
+	/* Adding an empty string to a non-empty stream */
+	string_stream_add(stream, "Add this line");
+	original_frag_count = list_count_nodes(&stream->fragments);
+
+	string_stream_add(stream, "%s", "");
+	KUNIT_EXPECT_EQ(test, list_count_nodes(&stream->fragments), original_frag_count);
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream), "Add this line");
+}
+
+/* Adding strings without automatic newline appending */
+static void string_stream_no_auto_newline_test(struct kunit *test)
+{
+	struct string_stream *stream;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	/*
+	 * Add some strings with and without newlines. All formatted newlines
+	 * should be preserved. It should not add any extra newlines.
+	 */
+	string_stream_add(stream, "One");
+	string_stream_add(stream, "Two\n");
+	string_stream_add(stream, "%s\n", "Three");
+	string_stream_add(stream, "%s", "Four\n");
+	string_stream_add(stream, "Five\n%s", "Six");
+	string_stream_add(stream, "Seven\n\n");
+	string_stream_add(stream, "Eight");
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream),
+			   "OneTwo\nThree\nFour\nFive\nSixSeven\n\nEight");
+}
+
+/* Adding strings with automatic newline appending */
+static void string_stream_auto_newline_test(struct kunit *test)
+{
+	struct string_stream *stream;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	string_stream_set_append_newlines(stream, true);
+	KUNIT_EXPECT_TRUE(test, stream->append_newlines);
+
+	/*
+	 * Add some strings with and without newlines. Newlines should
+	 * be appended to lines that do not end with \n, but newlines
+	 * resulting from the formatting should not be changed.
+	 */
+	string_stream_add(stream, "One");
+	string_stream_add(stream, "Two\n");
+	string_stream_add(stream, "%s\n", "Three");
+	string_stream_add(stream, "%s", "Four\n");
+	string_stream_add(stream, "Five\n%s", "Six");
+	string_stream_add(stream, "Seven\n\n");
+	string_stream_add(stream, "Eight");
+	KUNIT_EXPECT_STREQ(test, get_concatenated_string(test, stream),
+			   "One\nTwo\nThree\nFour\nFive\nSix\nSeven\n\nEight\n");
+}
+
+/*
+ * This doesn't actually "test" anything. It reports time taken
+ * and memory used for logging a large number of lines.
+ */
+static void string_stream_performance_test(struct kunit *test)
+{
+	struct string_stream_fragment *frag_container;
+	struct string_stream *stream;
+	char test_line[101];
+	ktime_t start_time, end_time;
+	size_t len, bytes_requested, actual_bytes_used, total_string_length;
+	int offset, i;
+
+	stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+	memset(test_line, 'x', sizeof(test_line) - 1);
+	test_line[sizeof(test_line) - 1] = '\0';
+
+	start_time = ktime_get();
+	for (i = 0; i < 10000; i++) {
+		offset = i % (sizeof(test_line) - 1);
+		string_stream_add(stream, "%s: %d\n", &test_line[offset], i);
+	}
+	end_time = ktime_get();
+
+	/*
+	 * Calculate memory used. This doesn't include invisible
+	 * overhead due to kernel allocator fragment size rounding.
+	 */
+	bytes_requested = sizeof(*stream);
+	actual_bytes_used = ksize(stream);
+	total_string_length = 0;
+
+	list_for_each_entry(frag_container, &stream->fragments, node) {
+		bytes_requested += sizeof(*frag_container);
+		actual_bytes_used += ksize(frag_container);
+
+		len = strlen(frag_container->fragment);
+		total_string_length += len;
+		bytes_requested += len + 1; /* +1 for '\0' */
+		actual_bytes_used += ksize(frag_container->fragment);
+	}
+
+	kunit_info(test, "Time elapsed:           %lld us\n",
+		   ktime_us_delta(end_time, start_time));
+	kunit_info(test, "Total string length:    %zu\n", total_string_length);
+	kunit_info(test, "Bytes requested:        %zu\n", bytes_requested);
+	kunit_info(test, "Actual bytes allocated: %zu\n", actual_bytes_used);
+}
+
+static int string_stream_test_init(struct kunit *test)
+{
+	struct string_stream_test_priv *priv;
+
+	priv = kunit_kzalloc(test, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	test->priv = priv;
+
+	return 0;
+}
+
+static struct kunit_case string_stream_test_cases[] = {
+	KUNIT_CASE(string_stream_managed_init_test),
+	KUNIT_CASE(string_stream_unmanaged_init_test),
+	KUNIT_CASE(string_stream_managed_free_test),
+	KUNIT_CASE(string_stream_resource_free_test),
+	KUNIT_CASE(string_stream_line_add_test),
+	KUNIT_CASE(string_stream_variable_length_line_test),
+	KUNIT_CASE(string_stream_append_test),
+	KUNIT_CASE(string_stream_append_auto_newline_test),
+	KUNIT_CASE(string_stream_append_empty_string_test),
+	KUNIT_CASE(string_stream_no_auto_newline_test),
+	KUNIT_CASE(string_stream_auto_newline_test),
+	KUNIT_CASE(string_stream_performance_test),
+	{}
+};
+
+static struct kunit_suite string_stream_test_suite = {
+	.name = "string-stream-test",
+	.test_cases = string_stream_test_cases,
+	.init = string_stream_test_init,
+};
+kunit_test_suites(&string_stream_test_suite);