bootm: Support string substitution in bootargs
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>
diff --git a/common/bootm.c b/common/bootm.c
index 020449d..8298693 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 @@
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 @@
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 @@
/* 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 @@
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;