[PATCH 1/2] trace-cmd: Fix crash when trace-cmd is executed with args "profile -F sleep 1"

[Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>]

A fix for https://bugzilla.kernel.org/show_bug.cgi?id=203411
When trace-cmd is running in "profile" mode, trace files are not generated.
Instead, pipes are used to collect trace data from recorder threads. Some
internal functions, originally designed for working with files, are reused
in pipes use case:
 init_cpu()
 allocate_page()
 get_next_page()
There was an undesired behaviour in those functions, when working with pipes,
which causes the segmentation fault, described in the bug report.

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@xxxxxxxxxx>
---
 lib/trace-cmd/trace-input.c | 69 ++++++++++++++++++++++++-------------
 1 file changed, 45 insertions(+), 24 deletions(-)

diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index ba20ef1..8d1001a 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -62,6 +62,7 @@ struct cpu_data {
 	struct list_head	page_maps;
 	struct page_map		*page_map;
 	struct page		**pages;
+	int			num_pages;
 	struct tep_record	*next;
 	struct page		*page;
 	struct kbuffer		*kbuf;
@@ -921,34 +922,50 @@ static struct page *allocate_page(struct tracecmd_input *handle,
 	struct cpu_data *cpu_data = &handle->cpu_data[cpu];
 	struct page *page;
 	int index;
+	int ret;
 
 	index = (offset - cpu_data->file_offset) / handle->page_size;
-	if (cpu_data->pages[index]) {
-		cpu_data->pages[index]->ref_count++;
-		return cpu_data->pages[index];
-	}
-
-	page = malloc(sizeof(*page));
-	if (!page)
+	if (index >= cpu_data->num_pages)
 		return NULL;
+	page = cpu_data->pages[index];
+	if (page && !handle->read_page) {
+		page->ref_count++;
+		return page;
+	}
 
-	memset(page, 0, sizeof(*page));
-	page->offset = offset;
-	page->handle = handle;
-	page->cpu = cpu;
+	if (!page) {
+		page = malloc(sizeof(*page));
+		if (!page)
+			return NULL;
 
-	page->map = allocate_page_map(handle, page, cpu, offset);
+		memset(page, 0, sizeof(*page));
+		page->offset = offset;
+		page->handle = handle;
+		page->cpu = cpu;
+	}
 
 	if (!page->map) {
-		free(page);
-		return NULL;
+		page->map = allocate_page_map(handle, page, cpu, offset);
+		if (!page->map) {
+			free(page);
+			return NULL;
+		}
+
+		cpu_data->pages[index] = page;
+		cpu_data->page_cnt++;
+		page->ref_count = 1;
+
+		return page;
 	}
 
-	cpu_data->pages[index] = page;
-	cpu_data->page_cnt++;
-	page->ref_count = 1;
+	if (handle->read_page) {
+		ret = read_page(handle, offset, cpu, page->map);
+		if (ret < 0)
+			return NULL;
+		return page;
+	}
 
-	return page;
+	return NULL;
 }
 
 static void __free_page(struct tracecmd_input *handle, struct page *page)
@@ -960,6 +977,8 @@ static void __free_page(struct tracecmd_input *handle, struct page *page)
 		die("Page ref count is zero!\n");
 
 	page->ref_count--;
+	if (cpu_data->page == page)
+		cpu_data->page = NULL;
 	if (page->ref_count)
 		return;
 
@@ -1125,7 +1144,7 @@ static int get_page(struct tracecmd_input *handle, int cpu,
 
 static int get_next_page(struct tracecmd_input *handle, int cpu)
 {
-	off64_t offset;
+	off64_t offset = 0;
 
 	if (!handle->cpu_data[cpu].page && !handle->use_pipe)
 		return 0;
@@ -1137,7 +1156,8 @@ static int get_next_page(struct tracecmd_input *handle, int cpu)
 		return 0;
 	}
 
-	offset = handle->cpu_data[cpu].offset + handle->page_size;
+	if (!handle->use_pipe)
+		offset = handle->cpu_data[cpu].offset + handle->page_size;
 
 	return get_page(handle, cpu, offset);
 }
@@ -2026,7 +2046,6 @@ tracecmd_read_prev(struct tracecmd_input *handle, struct tep_record *record)
 static int init_cpu(struct tracecmd_input *handle, int cpu)
 {
 	struct cpu_data *cpu_data = &handle->cpu_data[cpu];
-	int num_pages;
 	int i;
 
 	cpu_data->offset = cpu_data->file_offset;
@@ -2040,13 +2059,13 @@ static int init_cpu(struct tracecmd_input *handle, int cpu)
 		return 0;
 	}
 
-	num_pages = (cpu_data->size + handle->page_size - 1) / handle->page_size;
-	cpu_data->pages = calloc(num_pages + 1, sizeof(*cpu_data->pages));
+	cpu_data->num_pages = (cpu_data->size + handle->page_size - 1) / handle->page_size;
+	cpu_data->pages = calloc(cpu_data->num_pages + 1, sizeof(*cpu_data->pages));
 	if (!cpu_data->pages)
 		return -1;
 
 	/* Add stopper */
-	cpu_data->pages[num_pages] = PAGE_STOPPER;
+	cpu_data->pages[cpu_data->num_pages] = PAGE_STOPPER;
 
 	if (handle->use_pipe) {
 		/* Just make a page, it will be nuked later */
@@ -2056,8 +2075,10 @@ static int init_cpu(struct tracecmd_input *handle, int cpu)
 
 		memset(cpu_data->page, 0, sizeof(*cpu_data->page));
 		cpu_data->pages[0] = cpu_data->page;
+		cpu_data->num_pages = 1;
 		cpu_data->page_cnt = 1;
 		cpu_data->page->ref_count = 1;
+		cpu_data->page->cpu = cpu;
 		return 0;
 	}
 
-- 
2.20.1