pxe: Clean up the use of bootfile

The 'bootfile' environment variable is read in the bowels of pxe_util to
provide a directory to which all loaded files are relative.

This is not obvious from the API to PXE and it is strange to make the
caller set an environment variable rather than pass this as a parameter.

The code is also convoluted, which this feature implemented by
get_bootfile_path().

Update the API to improve this. Unfortunately this means that
pxe_setup_ctx() can fail, so add error checking.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Artem Lapkin <email2tema@gmail.com>
Tested-by: Artem Lapkin <email2tema@gmail.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>

boot/pxe_utils.c

@@ -67,10 +67,10 @@ int format_mac_pxe(char *outbuf, size_t outbuf_len)
 /**
  * get_bootfile_path() - Figure out the path of a file to read
  *
- * Returns the directory the file specified in the 'bootfile' env variable is
+ * Copies the boot directory into the supplied buffer. If there is no boot
- * in. If bootfile isn't defined in the environment, return NULL, which should
+ * directory, set it to ""
- * be interpreted as "don't prepend anything to paths".
  *
+ * @ctx: PXE context
  * @file_path: File path to read (relative to the PXE file)
  * @bootfile_path: Place to put the bootfile path
  * @bootfile_path_size: Size of @bootfile_path in bytes
@@ -79,34 +79,25 @@ int format_mac_pxe(char *outbuf, size_t outbuf_len)
  * Returns 1 for success, -ENOSPC if bootfile_path_size is to small to hold the
  *	resulting path
  */
-static int get_bootfile_path(const char *file_path, char *bootfile_path,
+static int get_bootfile_path(struct pxe_context *ctx, const char *file_path,
-			     size_t bootfile_path_size, bool allow_abs_path)
+			     char *bootfile_path, size_t bootfile_path_size,
+			     bool allow_abs_path)
 {
-	char *bootfile, *last_slash;
 	size_t path_len = 0;
 
 	/* Only syslinux allows absolute paths */
 	if (file_path[0] == '/' && allow_abs_path)
 		goto ret;
 
-	bootfile = from_env("bootfile");
+	path_len = strlen(ctx->bootdir);
-	if (!bootfile)
+	if (bootfile_path_size < path_len + 1) {
-		goto ret;
-
-	last_slash = strrchr(bootfile, '/');
-	if (!last_slash)
-		goto ret;
-
-	path_len = (last_slash - bootfile) + 1;
-
-	if (bootfile_path_size < path_len) {
 		printf("bootfile_path too small. (%zd < %zd)\n",
 		       bootfile_path_size, path_len);
 
 		return -ENOSPC;
 	}
 
-	strncpy(bootfile_path, bootfile, path_len);
+	strncpy(bootfile_path, ctx->bootdir, path_len);
 
  ret:
 	bootfile_path[path_len] = '\0';
@@ -135,7 +126,7 @@ static int get_relfile(struct pxe_context *ctx, const char *file_path,
 	char addr_buf[18];
 	int err;
 
-	err = get_bootfile_path(file_path, relfile, sizeof(relfile),
+	err = get_bootfile_path(ctx, file_path, relfile, sizeof(relfile),
 				ctx->allow_abs_path);
 	if (err < 0)
 		return err;
@@ -1496,14 +1487,39 @@ void handle_pxe_menu(struct pxe_context *ctx, struct pxe_menu *cfg)
 	boot_unattempted_labels(ctx, cfg);
 }
 
-void pxe_setup_ctx(struct pxe_context *ctx, struct cmd_tbl *cmdtp,
+int pxe_setup_ctx(struct pxe_context *ctx, struct cmd_tbl *cmdtp,
-		   pxe_getfile_func getfile, void *userdata,
+		  pxe_getfile_func getfile, void *userdata,
-		   bool allow_abs_path)
+		  bool allow_abs_path, const char *bootfile)
 {
+	const char *last_slash;
+	size_t path_len = 0;
+
+	memset(ctx, '\0', sizeof(*ctx));
 	ctx->cmdtp = cmdtp;
 	ctx->getfile = getfile;
 	ctx->userdata = userdata;
 	ctx->allow_abs_path = allow_abs_path;
+
+	/* figure out the boot directory, if there is one */
+	if (bootfile && strlen(bootfile) >= MAX_TFTP_PATH_LEN)
+		return -ENOSPC;
+	ctx->bootdir = strdup(bootfile ? bootfile : "");
+	if (!ctx->bootdir)
+		return -ENOMEM;
+
+	if (bootfile) {
+		last_slash = strrchr(bootfile, '/');
+		if (last_slash)
+			path_len = (last_slash - bootfile) + 1;
+	}
+	ctx->bootdir[path_len] = '\0';
+
+	return 0;
+}
+
+void pxe_destroy_ctx(struct pxe_context *ctx)
+{
+	free(ctx->bootdir);
 }
 
 int pxe_process(struct pxe_context *ctx, ulong pxefile_addr_r, bool prompt)

cmd/pxe.c

@@ -121,8 +121,6 @@ do_pxe_get(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	struct pxe_context ctx;
 	int err, i = 0;
 
-	pxe_setup_ctx(&ctx, cmdtp, do_get_tftp, NULL, false);
-
 	if (argc != 1)
 		return CMD_RET_USAGE;
 
@@ -136,6 +134,11 @@ do_pxe_get(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	if (err < 0)
 		return 1;
 
+	if (pxe_setup_ctx(&ctx, cmdtp, do_get_tftp, NULL, false,
+			  env_get("bootfile"))) {
+		printf("Out of memory\n");
+		return CMD_RET_FAILURE;
+	}
 	/*
 	 * Keep trying paths until we successfully get a file we're looking
 	 * for.
@@ -144,6 +147,7 @@ do_pxe_get(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	    pxe_mac_path(&ctx, pxefile_addr_r) > 0 ||
 	    pxe_ipaddr_paths(&ctx, pxefile_addr_r) > 0) {
 		printf("Config file found\n");
+		pxe_destroy_ctx(&ctx);
 
 		return 0;
 	}
@@ -152,12 +156,14 @@ do_pxe_get(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 		if (get_pxelinux_path(&ctx, pxe_default_paths[i],
 				      pxefile_addr_r) > 0) {
 			printf("Config file found\n");
+			pxe_destroy_ctx(&ctx);
 			return 0;
 		}
 		i++;
 	}
 
 	printf("Config file not found\n");
+	pxe_destroy_ctx(&ctx);
 
 	return 1;
 }
@@ -175,8 +181,6 @@ do_pxe_boot(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 	struct pxe_context ctx;
 	int ret;
 
-	pxe_setup_ctx(&ctx, cmdtp, do_get_tftp, NULL, false);
-
 	if (argc == 1) {
 		pxefile_addr_str = from_env("pxefile_addr_r");
 		if (!pxefile_addr_str)
@@ -193,7 +197,13 @@ do_pxe_boot(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 		return 1;
 	}
 
+	if (pxe_setup_ctx(&ctx, cmdtp, do_get_tftp, NULL, false,
+			  env_get("bootfile"))) {
+		printf("Out of memory\n");
+		return CMD_RET_FAILURE;
+	}
 	ret = pxe_process(&ctx, pxefile_addr_r, false);
+	pxe_destroy_ctx(&ctx);
 	if (ret)
 		return CMD_RET_FAILURE;
 

cmd/sysboot.c

@@ -59,6 +59,7 @@ static int do_sysboot(struct cmd_tbl *cmdtp, int flag, int argc,
 		      char *const argv[])
 {
 	unsigned long pxefile_addr_r;
+	pxe_getfile_func getfile;
 	struct pxe_context ctx;
 	char *pxefile_addr_str;
 	char *filename;
@@ -89,13 +90,12 @@ static int do_sysboot(struct cmd_tbl *cmdtp, int flag, int argc,
 		env_set("bootfile", filename);
 	}
 
-	pxe_setup_ctx(&ctx, cmdtp, NULL, NULL, true);
 	if (strstr(argv[3], "ext2")) {
-		ctx.getfile = do_get_ext2;
+		getfile = do_get_ext2;
 	} else if (strstr(argv[3], "fat")) {
-		ctx.getfile = do_get_fat;
+		getfile = do_get_fat;
 	} else if (strstr(argv[3], "any")) {
-		ctx.getfile = do_get_any;
+		getfile = do_get_any;
 	} else {
 		printf("Invalid filesystem: %s\n", argv[3]);
 		return 1;
@@ -108,12 +108,19 @@ static int do_sysboot(struct cmd_tbl *cmdtp, int flag, int argc,
 		return 1;
 	}
 
+	if (pxe_setup_ctx(&ctx, cmdtp, getfile, NULL, true, filename)) {
+		printf("Out of memory\n");
+		return CMD_RET_FAILURE;
+	}
+
 	if (get_pxe_file(&ctx, filename, pxefile_addr_r) < 0) {
 		printf("Error reading config file\n");
+		pxe_destroy_ctx(&ctx);
 		return 1;
 	}
 
 	ret = pxe_process(&ctx, pxefile_addr_r, prompt);
+	pxe_destroy_ctx(&ctx);
 	if (ret)
 		return CMD_RET_FAILURE;
 

include/pxe_utils.h

@@ -86,6 +86,8 @@ typedef int (*pxe_getfile_func)(struct pxe_context *ctx, const char *file_path,
  * @getfile: Function called by PXE to read a file
  * @userdata: Data the caller requires for @getfile
  * @allow_abs_path: true to allow absolute paths
+ * @bootdir: Directory that files are loaded from ("" if no directory). This is
+ *	allocated
  */
 struct pxe_context {
 	struct cmd_tbl *cmdtp;
@@ -102,6 +104,7 @@ struct pxe_context {
 
 	void *userdata;
 	bool allow_abs_path;
+	char *bootdir;
 };
 
 /**
@@ -197,10 +200,20 @@ int format_mac_pxe(char *outbuf, size_t outbuf_len);
  * @getfile: Function to call to read a file
  * @userdata: Data the caller requires for @getfile - stored in ctx->userdata
  * @allow_abs_path: true to allow absolute paths
+ * @bootfile: Bootfile whose directory loaded files are relative to, NULL if
+ *	none
+ * @return 0 if OK, -ENOMEM if out of memory
  */
-void pxe_setup_ctx(struct pxe_context *ctx, struct cmd_tbl *cmdtp,
+int pxe_setup_ctx(struct pxe_context *ctx, struct cmd_tbl *cmdtp,
-		   pxe_getfile_func getfile, void *userdata,
+		  pxe_getfile_func getfile, void *userdata,
-		   bool allow_abs_path);
+		  bool allow_abs_path, const char *bootfile);
+
+/**
+ * pxe_destroy_ctx() - Destroy a PXE context
+ *
+ * @ctx: Context to destroy
+ */
+void pxe_destroy_ctx(struct pxe_context *ctx);
 
 /**
  * pxe_process() - Process a PXE file through to boot