bootm: Support string substitution in bootargsWIP/04Dec2020-next

In some cases it is necessary to pass parameters to Linux so that it will
boot correctly. For example, the rootdev parameter is often used to
specify the root device. However the root device may change depending on
whence U-Boot loads the kernel. At present it is necessary to build up
the command line by adding device strings to it one by one.

It is often more convenient to provide a template for bootargs, with
U-Boot doing the substitution from other environment variables.

Add a way to substitute strings in the bootargs variable. This allows
things like "rootdev=${rootdev}" to be used in bootargs, with the
${rootdev} substitution providing the UUID of the root device.

For example, to substitute the GUID of the kernel partition:

  setenv bootargs "console=/dev/ttyS0 rootdev=${uuid}/PARTNROFF=1
		kern_guid=${uuid}"
  part uuid mmc 2:2 uuid
  bootm

This is particularly useful when the command line from another place. For
example, Chrome OS stores the command line next to the kernel itself. It
depends on the kernel version being used as well as the hardware features,
so it is extremely difficult to devise a U-Boot script that works on all
boards and kernel versions. With this feature, the command line can be
read from disk and used directly, with a few substitutions set up.

Signed-off-by: Simon Glass <sjg@chromium.org>

5 files changed, 172 insertions, 12 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index accd4df5b0..356193f9ec 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -147,6 +147,7 @@ config SANDBOX
 	imply CMD_PMC
 	imply CMD_CLONE
 	imply SILENT_CONSOLE
+	imply BOOTARGS_SUBST
 
 config SH
 	bool "SuperH architecture"
diff --git a/common/Kconfig.boot b/common/Kconfig.boot
index 3f6d9c1a25..1a302fd1a2 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -865,6 +865,23 @@ config BOOTARGS
 	  CONFIG_BOOTARGS goes into the environment value "bootargs". Note that
 	  this value will also override the "chosen" node in FDT blob.
 
+config BOOTARGS_SUBST
+	bool "Support substituting strings in boot arguments"
+	help
+	  This allows substituting string values in the boot arguments. These
+	  are applied after the commandline has been built. 
+
+	  One use for this is to insert the root-disk UUID into the command
+	  line where bootargs contains "root=${uuid}"
+
+		setenv bootargs "console= root=${uuid}"
+		# Set the 'uuid' environment variable
+		part uuid mmc 2:2 uuid
+
+		# Command-line substitution will put the real uuid into the
+		# kernel command line
+		bootm
+
 config USE_BOOTCOMMAND
 	bool "Enable a default value for bootcmd"
 	help
diff --git a/common/bootm.c b/common/bootm.c
index 020449db3f..6c286942a4 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -7,6 +7,7 @@
 #ifndef USE_HOSTCC
 #include <common.h>
 #include <bootstage.h>
+#include <cli.h>
 #include <cpu_func.h>
 #include <env.h>
 #include <errno.h>
@@ -542,6 +543,33 @@ static int fixup_silent_linux(char *buf, int maxlen)
 	return 0;
 }
 
+/**
+ * process_subst() - Handle substitution of ${...} fields in the environment
+ *
+ * Handle variable substitution in the provided buffer
+ *
+ * @buf: Buffer containing the string to process
+ * @maxlen: Maximum length of buffer
+ * @return 0 if OK, -ENOSPC if @maxlen is too small
+ */
+static int process_subst(char *buf, int maxlen)
+{
+	char *cmdline;
+	int size;
+	int ret;
+
+	/* Move to end of buffer */
+	size = strlen(buf) + 1;
+	cmdline = buf + maxlen - size;
+	if (buf + size > cmdline)
+		return -ENOSPC;
+	memmove(cmdline, buf, size);
+
+        ret = cli_simple_process_macros(cmdline, buf, cmdline - buf);
+
+	return ret;
+}
+
 int bootm_process_cmdline(char *buf, int maxlen, int flags)
 {
 	int ret;
@@ -554,6 +582,11 @@ int bootm_process_cmdline(char *buf, int maxlen, int flags)
 		if (ret)
 			return log_msg_ret("silent", ret);
 	}
+	if (IS_ENABLED(CONFIG_BOOTARGS_SUBST) && (flags & BOOTM_CL_SUBST)) {
+		ret = process_subst(buf, maxlen);
+		if (ret)
+			return log_msg_ret("silent", ret);
+	}
 
 	return 0;
 }
@@ -569,7 +602,7 @@ int bootm_process_cmdline_env(int flags)
 	/* First check if any action is needed */
 	do_silent = IS_ENABLED(CONFIG_SILENT_CONSOLE) &&
 	    !IS_ENABLED(CONFIG_SILENT_U_BOOT_ONLY) && (flags & BOOTM_CL_SILENT);
-	if (!do_silent)
+	if (!do_silent && !IS_ENABLED(CONFIG_BOOTARGS_SUBST))
 		return 0;
 
 	env = env_get("bootargs");
@@ -702,8 +735,7 @@ int do_bootm_states(struct cmd_tbl *cmdtp, int flag, int argc,
 	if (!ret && (states & BOOTM_STATE_OS_BD_T))
 		ret = boot_fn(BOOTM_STATE_OS_BD_T, argc, argv, images);
 	if (!ret && (states & BOOTM_STATE_OS_PREP)) {
-		ret = bootm_process_cmdline_env(images->os.os == IH_OS_LINUX ?
-						BOOTM_CL_SILENT : 0);
+		ret = bootm_process_cmdline_env(images->os.os == IH_OS_LINUX);
 		if (ret) {
 			printf("Cmdline setup failed (err=%d)\n", ret);
 			ret = CMD_RET_FAILURE;
diff --git a/include/bootm.h b/include/bootm.h
index 8d95fb2a90..7f88ec718b 100644
--- a/include/bootm.h
+++ b/include/bootm.h
@@ -78,8 +78,9 @@ void switch_to_non_secure_mode(void);
 /* Flags to control bootm_process_cmdline() */
 enum bootm_cmdline_t {
 	BOOTM_CL_SILENT	= 1 << 0,	/* Do silent console processing */
+	BOOTM_CL_SUBST	= 1 << 1,	/* Do substitution */
 
-	BOOTM_CL_ALL	= 1,		/* All substitutions */
+	BOOTM_CL_ALL	= 3,		/* All substitutions */
 };
 
 /**
@@ -95,7 +96,10 @@ void board_preboot_os(void);
 /*
  * bootm_process_cmdline() - Process fix-ups for the command line
  *
- * This handles: making Linux boot silently if requested ('silent_linux' envvar)
+ * This handles:
+ *
+ *  - making Linux boot silently if requested ('silent_linux' envvar)
+ *  - performing substitutions in the command line ('bootargs_subst' envvar)
  *
  * @maxlen must provide enough space for the string being processed plus the
  * resulting string
@@ -111,8 +115,10 @@ int bootm_process_cmdline(char *buf, int maxlen, int flags);
 /**
  * bootm_process_cmdline_env() - Process fix-ups for the command line
  *
- * Updates the 'bootargs' envvar as required. This handles making Linux boot
- * silently if requested ('silent_linux' envvar)
+ * Updates the 'bootargs' envvar as required. This handles:
+ *
+ *  - making Linux boot silently if requested ('silent_linux' envvar)
+ *  - performing substitutions in the command line ('bootargs_subst' envvar)
  *
  * @flags: Flags to control what happens (see bootm_cmdline_t)
  * @return 0 if OK, -ENOMEM if out of memory
diff --git a/test/bootm.c b/test/bootm.c
index d0b29441d6..92dc2b6e17 100644
--- a/test/bootm.c
+++ b/test/bootm.c
@@ -116,22 +116,126 @@ static int bootm_test_silent(struct unit_test_state *uts)
 }
 BOOTM_TEST(bootm_test_silent, 0);
 
+/* Test substitution processing */
+static int bootm_test_subst(struct unit_test_state *uts)
+{
+	char buf[BUF_SIZE];
+
+	/* try with an unset variable */
+	ut_assertok(env_set("var", NULL));
+	strcpy(buf, "some${var}thing");
+	ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("something", buf);
+
+	/* Replace with shorter string */
+	ut_assertok(env_set("var", "bb"));
+	strcpy(buf, "some${var}thing");
+	ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("somebbthing", buf);
+
+	/* Replace with same-length string */
+	ut_assertok(env_set("var", "abc"));
+	strcpy(buf, "some${var}thing");
+	ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("someabcthing", buf);
+
+	/* Replace with longer string */
+	ut_assertok(env_set("var", "abcde"));
+	strcpy(buf, "some${var}thing");
+	ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("someabcdething", buf);
+
+	/* Check it is case sensitive */
+	ut_assertok(env_set("VAR", NULL));
+	strcpy(buf, "some${VAR}thing");
+	ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("something", buf);
+
+	/* Check too long - need 12 bytes for each string */
+	strcpy(buf, "some${var}thing");
+	ut_asserteq(-ENOSPC,
+		    bootm_process_cmdline(buf, 12 * 2 - 1, BOOTM_CL_SUBST));
+
+	/* Check just enough space */
+	strcpy(buf, "some${var}thing");
+	ut_assertok(bootm_process_cmdline(buf, 16 * 2, BOOTM_CL_SUBST));
+	ut_asserteq_str("someabcdething", buf);
+
+	/*
+	 * Check the substition string being too long. This results in a string
+	 * of 12 (13 bytes). We need enough space for that plus the original
+	 * "a${var}c" string of 9 bytes. So 12 + 9 = 21 bytes.
+	 */
+	ut_assertok(env_set("var", "1234567890"));
+	strcpy(buf, "a${var}c");
+	ut_asserteq(-ENOSPC, bootm_process_cmdline(buf, 21, BOOTM_CL_SUBST));
+
+	strcpy(buf, "a${var}c");
+	ut_asserteq(0, bootm_process_cmdline(buf, 22, BOOTM_CL_SUBST));
+
+	/* Check multiple substitutions */
+	ut_assertok(env_set("var", "abc"));
+	strcpy(buf, "some${var}thing${bvar}else");
+	ut_asserteq(0, bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("someabcthingelse", buf);
+
+	/* Check multiple substitutions */
+	ut_assertok(env_set("bvar", "123"));
+	strcpy(buf, "some${var}thing${bvar}else");
+	ut_asserteq(0, bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+	ut_asserteq_str("someabcthing123else", buf);
+
+	return 0;
+}
+BOOTM_TEST(bootm_test_subst, 0);
+
 /* Test silent processing in the bootargs variable */
 static int bootm_test_silent_var(struct unit_test_state *uts)
 {
 	env_set("bootargs", NULL);
-	env_set("silent_linux", NULL);
-	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SUBST));
 	ut_assertnull(env_get("bootargs"));
 
-	env_set("bootargs", CONSOLE_STR);
-	env_set("silent_linux", "yes");
+	ut_assertok(env_set("bootargs", "some${var}thing"));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SUBST));
+	ut_asserteq_str("something", env_get("bootargs"));
+
+	return 0;
+}
+BOOTM_TEST(bootm_test_silent_var, 0);
+
+/* Test substitution processing in the bootargs variable */
+static int bootm_test_subst_var(struct unit_test_state *uts)
+{
+	env_set("bootargs", NULL);
 	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
 	ut_asserteq_str("console=", env_get("bootargs"));
 
+	ut_assertok(env_set("var", "abc"));
+	ut_assertok(env_set("bootargs", "some${var}thing"));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
+	ut_asserteq_str("some${var}thing console=", env_get("bootargs"));
+
 	return 0;
 }
-BOOTM_TEST(bootm_test_silent_var, 0);
+BOOTM_TEST(bootm_test_subst_var, 0);
+
+/* Test substitution and silent console processing in the bootargs variable */
+static int bootm_test_subst_both(struct unit_test_state *uts)
+{
+	ut_assertok(env_set("silent_linux", "yes"));
+	env_set("bootargs", NULL);
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_ALL));
+	ut_asserteq_str("console=", env_get("bootargs"));
+
+	ut_assertok(env_set("bootargs", "some${var}thing " CONSOLE_STR));
+	ut_assertok(env_set("var", "1234567890"));
+	ut_assertok(bootm_process_cmdline_env(BOOTM_CL_ALL));
+	ut_asserteq_str("some1234567890thing console=", env_get("bootargs"));
+
+	return 0;
+}
+BOOTM_TEST(bootm_test_subst_both, 0);
 
 int do_ut_bootm(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
 {