[PATCH 11/11] bootm: Support string substitution in bootargs
Simon Glass
sjg at chromium.org
Mon Oct 19 15:56:02 CEST 2020
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=%U" to be used in bootargs, with the %U substitution
providing the UUID of the root device.
For example, to substitute the GUID of the kernel partition:
setenv bootargs "console=/dev/ttyS0 rootdev=%U/PARTNROFF=1 kern_guid=%U"
part uuid mmc 2:2 uuid
setenv bootargs_U $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 at chromium.org>
---
README | 16 +++++++
arch/Kconfig | 1 +
common/Kconfig.boot | 20 ++++++++
common/bootm.c | 72 +++++++++++++++++++++++++++--
include/bootm.h | 14 ++++--
test/bootm.c | 110 ++++++++++++++++++++++++++++++++++++++++++--
6 files changed, 221 insertions(+), 12 deletions(-)
diff --git a/README b/README
index 91c5a1a8fa3..263e31ab7f6 100644
--- a/README
+++ b/README
@@ -3229,6 +3229,22 @@ List of environment variables (most likely not complete):
bootargs - Boot arguments when booting an RTOS image
+ bootargs_subst - Substitution parameters for bootargs. These are applied after
+ the commandline has been built. The format is:
+
+ <key>=<value>[!<key>=<value>...]
+
+ where
+ <key> is a string to replace
+ <value> is the value to replace it with (either a simple
+ string or an environment variable starting with $
+
+ One use for this is to insert the root-disk UUID into the
+ command line where bootargs contains "root=%U"
+
+ part uuid mmc 2:2 uuid
+ setenv cmdline_repl %U=$uuid
+
bootfile - Name of the image to load with TFTP
bootm_low - Memory range available for image processing in the bootm
diff --git a/arch/Kconfig b/arch/Kconfig
index 6caf2338bcf..421ea9a9b51 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -141,6 +141,7 @@ 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 4191bfb34df..c5668cf2931 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -848,6 +848,26 @@ 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. Set the
+ 'bootargs_subst' envvar to control this. The format is:
+
+ <key>=<value>[!<key>=<value>...]
+
+ where
+ <key> is a string to replace
+ <value> is the value to replace it with (either a simple
+ string or an environment variable starting with $
+
+ One use for this is to insert the root-disk UUID into the
+ command line where bootargs contains "root=%U"
+
+ part uuid mmc 2:2 uuid
+ setenv cmdline_repl %U=$uuid
+
config USE_BOOTCOMMAND
bool "Enable a default value for bootcmd"
help
diff --git a/common/bootm.c b/common/bootm.c
index 5484c2be900..0a89a72a660 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -540,6 +540,68 @@ static int fixup_silent_linux(char *buf, int maxlen)
return 0;
}
+/**
+ * process_subst() - Handle substitution of %x fields in the environment
+ *
+ * For every "%x" found, it is replaced with the value of envvar "bootargs_x"
+ * where x is a case-sensitive alphanumeric character. If that environment
+ * variable does not exist, no substitution is made and the %x remains, to
+ * allow for plain % characters in the string.
+ *
+ * @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)
+{
+ const char *in;
+ char *cmdline, *out;
+ bool percent;
+ int size;
+
+ /* Move to end of buffer */
+ size = strlen(buf) + 1;
+ cmdline = buf + maxlen - size;
+ if (buf + size > cmdline)
+ return -ENOSPC;
+ memmove(cmdline, buf, size);
+
+ /* Replace %c with value of envvar 'bootargs_%c' */
+ percent = false;
+ for (in = cmdline, out = buf; *in; in++) {
+ /* If we catch up with the input string, we're out of space */
+ if (out >= in)
+ return -ENOSPC;
+ if (percent) {
+ char var[12];
+ const char *val;
+
+ snprintf(var, sizeof(var), "bootargs_%c", *in);
+ val = env_get(var);
+ if (val) {
+ for (; *val; val++) {
+ if (out >= in)
+ return -ENOSPC;
+ *out++ = *val;
+ }
+ percent = false;
+ continue;
+ } else {
+ /* No value, put the % back */
+ *out++ = '%';
+ }
+ } else if (*in == '%') {
+ percent = true;
+ continue;
+ }
+ *out++ = *in;
+ percent = false;
+ }
+ *out++ = '\0';
+
+ return 0;
+}
+
int bootm_process_cmdline(char *buf, int maxlen, int flags)
{
int ret;
@@ -552,6 +614,11 @@ 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;
}
@@ -567,7 +634,7 @@ 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");
@@ -700,8 +767,7 @@ 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 8d95fb2a90a..7f88ec718b8 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 d0b29441d65..8a83be9719f 100644
--- a/test/bootm.c
+++ b/test/bootm.c
@@ -116,22 +116,122 @@ 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];
+
+ strcpy(buf, "some%Athing");
+ ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("some%Athing", buf);
+
+ /* Replace with shorter string */
+ ut_assertok(env_set("bootargs_A", "a"));
+ strcpy(buf, "some%Athing");
+ ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("someathing", buf);
+
+ /* Replace with same-length string */
+ ut_assertok(env_set("bootargs_A", "ab"));
+ strcpy(buf, "some%Athing");
+ ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("someabthing", buf);
+
+ /* Replace with longer string */
+ ut_assertok(env_set("bootargs_A", "abc"));
+ strcpy(buf, "some%Athing");
+ ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("someabcthing", buf);
+
+ /* Check it is case sensitive */
+ strcpy(buf, "some%athing");
+ ut_assertok(bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("some%athing", buf);
+
+ /* Check too long - need 12 bytes for each string */
+ strcpy(buf, "some%Athing");
+ ut_asserteq(-ENOSPC,
+ bootm_process_cmdline(buf, 12 * 2 - 1, BOOTM_CL_SUBST));
+
+ /* Check just enough space */
+ strcpy(buf, "some%Athing");
+ ut_assertok(bootm_process_cmdline(buf, 12 * 2, BOOTM_CL_SUBST));
+ ut_asserteq_str("someabcthing", buf);
+
+ /*
+ * Check the substition string being too long. This results in a string
+ * of 12 (13 bytes). Allow one more byte margin.
+ */
+ ut_assertok(env_set("bootargs_A", "1234567890"));
+ strcpy(buf, "a%Ac");
+ ut_asserteq(-ENOSPC,
+ bootm_process_cmdline(buf, 13, BOOTM_CL_SUBST));
+
+ strcpy(buf, "a%Ac");
+ ut_asserteq(0, bootm_process_cmdline(buf, 14, BOOTM_CL_SUBST));
+
+ /* Check multiple substitutions */
+ ut_assertok(env_set("bootargs_A", "abc"));
+ strcpy(buf, "some%Athing%Belse");
+ ut_asserteq(0, bootm_process_cmdline(buf, BUF_SIZE, BOOTM_CL_SUBST));
+ ut_asserteq_str("someabcthing%Belse", buf);
+
+ /* Check multiple substitutions */
+ ut_assertok(env_set("bootargs_B", "123"));
+ strcpy(buf, "some%Athing%Belse");
+ 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%Athing"));
+ ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SUBST));
+ ut_asserteq_str("some%Athing", 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("bootargs", "some%Athing"));
+ ut_assertok(bootm_process_cmdline_env(BOOTM_CL_SILENT));
+ ut_asserteq_str("some%Athing 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%Athing " CONSOLE_STR));
+ ut_assertok(env_set("bootargs_A", "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[])
{
--
2.29.0.rc1.297.gfa9743e501-goog
More information about the U-Boot
mailing list