citrun

commit 3ac0a43822a62c4f72e326059fe60df7032dd3f9
parent 95a73422904fbe77f511cc7f1e4f2a7f326d35a7
Author: Kyle Milz <kyle@0x30.net>
Date:   Sat, 24 Sep 2016 21:13:43 -0600

src/rt: add comments and improve naming

Diffstat:
M
src/rt.c
 | 
113
+++++++++++++++++++++++++++++++++++++++++++++++++------------------------------

1 file changed, 70 insertions(+), 43 deletions(-)
diff --git a/src/rt.c b/src/rt.c
@@ -58,8 +58,14 @@ add_str(uint8_t *shm, size_t shm_pos, const char *str, uint16_t len)
 	return shm_pos + len;
 }
 
+/*
+ * Extends the memory mapping of shm_fd some number of bytes rounded up to the
+ * next page size.
+ * Exits on error, returns a pointer to the beginning of the extended memory
+ * region on success.
+ */
 static uint8_t *
-add_new_region(int bytes)
+shm_extend(int bytes)
 {
 	uint8_t		*shm;
 	int		 page_size = getpagesize();
@@ -68,32 +74,39 @@ add_new_region(int bytes)
 
 	aligned_bytes = ((bytes) + page_mask) & ~page_mask;
 
+	/* Increase the length of the file descriptor. */
 	if (ftruncate(shm_fd, shm_len + aligned_bytes) < 0)
 		err(1, "ftruncate from %zu to %zu", shm_len, shm_len + aligned_bytes);
 
+	/* Increase the size of the memory mapping. */
 	shm = mmap(NULL, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
 			shm_fd, shm_len);
 
 	if (shm == MAP_FAILED)
 		err(1, "mmap %i bytes @ %zu", bytes, shm_len);
 
+	/* Increase internal length field. */
 	shm_len += aligned_bytes;
 	return shm;
 }
 
 /*
- * These are written into shared memory, offset 0:
+ * Add a header region to a newly created shared memory file.
+ * The header contains:
  * - version major and minor
  * - process id, parent process id, group process id
  * - program name
  * - current working directory
+ * Exits or asserts on error.
  */
 static void
-write_header()
+shm_add_header()
 {
 	char		*cwd_buf;
 	const char	*progname;
-	size_t		 sz = 0;
+	uint8_t		*shm;
+	size_t		 sz;
+	size_t		 shm_pos;
 	uint16_t	 prog_sz, cwd_sz;
 
 	progname = getprogname();
@@ -103,6 +116,7 @@ write_header()
 	prog_sz = strnlen(progname, PATH_MAX);
 	cwd_sz = strnlen(cwd_buf, PATH_MAX);
 
+	sz = 0;
 	sz += sizeof(uint8_t) * 2;
 	sz += sizeof(uint32_t) * 3;
 	sz += sizeof(prog_sz);
@@ -110,9 +124,9 @@ write_header()
 	sz += sizeof(cwd_sz);
 	sz += cwd_sz;
 
-	uint8_t *shm = add_new_region(sz);
+	shm = shm_extend(sz);
 
-	size_t shm_pos = 0;
+	shm_pos = 0;
 	shm_pos = add_1(shm, shm_pos, citrun_major);
 	shm_pos = add_1(shm, shm_pos, citrun_minor);
 
@@ -126,46 +140,23 @@ write_header()
 	assert(shm_pos == sz);
 }
 
+/*
+ * Adds a new memory region for a given citrun_node.
+ * The data format is described in the instrumentation header generation code.
+ * Exits on failure.
+ */
 static void
-create_memory_file()
-{
-	char memfile_path[23];
-	char *template = "/tmp/citrun/XXXXXXXXXX";
-	char *process_dir  = "/tmp/citrun";
-
-	assert(shm_fd == 0);
-	assert(shm_len == 0);
-
-	if (getenv("CITRUN_TOOLS") != NULL) {
-		if ((shm_fd = open("procfile.shm", O_RDWR | O_CREAT,
-		    S_IRUSR | S_IWUSR)) == -1)
-			err(1, "open");
-	} else {
-		/* Existing directory is OK. */
-		if (mkdir(process_dir, S_IRWXU) && errno != EEXIST)
-			err(1, "mkdir '%s'", process_dir);
-
-		strlcpy(memfile_path, template, sizeof(memfile_path));
-
-		if ((shm_fd = mkstemp(memfile_path)) == -1)
-			err(1, "mkstemp");
-	}
-
-	init++;
-	write_header();
-}
-
-static void
-node_add(struct citrun_node *n)
+shm_add_node(struct citrun_node *n)
 {
-	size_t sz = 0;
-	uint16_t comp_sz, abs_sz;
-	uint8_t *shm;
-	size_t shm_pos = 0;
+	uint8_t		*shm;
+	size_t		 sz;
+	size_t		 shm_pos;
+	uint16_t	 comp_sz, abs_sz;
 
 	comp_sz = strnlen(n->comp_file_path, PATH_MAX);
 	abs_sz = strnlen(n->abs_file_path, PATH_MAX);
 
+	sz = 0;
 	sz += sizeof(uint32_t);
 	sz += sizeof(comp_sz);
 	sz += comp_sz;
@@ -173,8 +164,9 @@ node_add(struct citrun_node *n)
 	sz += abs_sz;
 	sz += n->size * sizeof(uint64_t);
 
-	shm = add_new_region(sz);
+	shm = shm_extend(sz);
 
+	shm_pos = 0;
 	shm_pos = add_4(shm, shm_pos, n->size);
 	shm_pos = add_str(shm, shm_pos, n->comp_file_path, comp_sz);
 	shm_pos = add_str(shm, shm_pos, n->abs_file_path, abs_sz);
@@ -186,6 +178,41 @@ node_add(struct citrun_node *n)
 }
 
 /*
+ * Usually opens a file descriptor with a random file name in a known directory.
+ * Should only ever be called once per process.  Adds a header to the created
+ * file containing program meta information.
+ * Exits on failure.
+ */
+static void
+shm_create()
+{
+	char	 memfile_path[23];
+	char	*template = "/tmp/citrun/XXXXXXXXXX";
+	char	*process_dir  = "/tmp/citrun";
+
+	assert(shm_fd == 0);
+	assert(shm_len == 0);
+
+	if (getenv("CITRUN_TOOLS") != NULL) {
+		if ((shm_fd = open("procfile.shm", O_RDWR | O_CREAT,
+		    S_IRUSR | S_IWUSR)) == -1)
+			err(1, "open");
+	} else {
+		/* Existing directory is OK. */
+		if (mkdir(process_dir, S_IRWXU) && errno != EEXIST)
+			err(1, "mkdir '%s'", process_dir);
+
+		strlcpy(memfile_path, template, sizeof(memfile_path));
+
+		if ((shm_fd = mkstemp(memfile_path)) == -1)
+			err(1, "mkstemp");
+	}
+
+	init++;
+	shm_add_header();
+}
+
+/*
  * Public interface: Add a node to shared memory.
  */
 void
@@ -200,7 +227,7 @@ citrun_node_add(uint8_t node_major, uint8_t node_minor, struct citrun_node *n)
 			citrun_major, citrun_minor, node_major, node_minor);
 
 	if (!init)
-		create_memory_file();
+		shm_create();
 
-	node_add(n);
+	shm_add_node(n);
 }