kernel: add bootargs support

Add support for passing args to main(). The
content of bootargs is taken from get_bootargs()
which should be implemented for each loader and
then its split into args and passed to main.

(cherry picked from commit 49fc106)

Original-Signed-off-by: Jakub Michalski <jmichalski@internships.antmicro.com>
Original-Signed-off-by: Filip Kokosinski <fkokosinski@antmicro.com>
GitOrigin-RevId: 49fc106
Cr-Build-Id: 8737098476786990081
Cr-Build-Url: https://cr-buildbucket.appspot.com/build/8737098476786990081
Copybot-Job-Name: zephyr-main-copybot-downstream
Change-Id: I7557853aa0f84f845c0d9e88aabb431cc0bea9be
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/5842088
Tested-by: Keith Short <keithshort@chromium.org>
Commit-Queue: Keith Short <keithshort@chromium.org>
Reviewed-by: Keith Short <keithshort@chromium.org>
Reviewed-by: Tristan Honscheid <honscheid@google.com>

kernel/Kconfig

@@ -998,6 +998,31 @@ config STATIC_INIT_GNU
  Note the option CMAKE_LINKER_GENERATOR does not yet support this feature
  or CPP.
 
+config BOOTARGS
+ bool "Support bootargs"
+ help
+ Enables bootargs support and passing them to main().
+
+config DYNAMIC_BOOTARGS
+ bool "Support dynamic bootargs"
+ depends on BOOTARGS
+ help
+ Enables dynamic bootargs support.
+
+config BOOTARGS_STRING
+ string "static bootargs string"
+ depends on BOOTARGS && !DYNAMIC_BOOTARGS
+ help
+ Static bootargs string. It includes argv[0], so if its expected that it
+ contains executable name it should be put at the beginning of this string.
+
+config BOOTARGS_ARGS_BUFFER_SIZE
+ int "Size of buffer containing main arguments in bytes"
+ default 1024
+ depends on BOOTARGS
+ help
+ Configures size of buffer containing all arguments passed to main.
+
 endmenu
 
 rsource "Kconfig.device"

kernel/init.c

@@ -11,6 +11,9 @@
  * This module contains routines that are used to initialize the kernel.
  */
 
+#include <ctype.h>
+#include <stdbool.h>
+#include <string.h>
 #include <offsets_short.h>
 #include <zephyr/kernel.h>
 #include <zephyr/sys/printk.h>
@@ -24,13 +27,11 @@
 #include <zephyr/linker/linker-defs.h>
 #include <ksched.h>
 #include <kthread.h>
-#include <string.h>
 #include <zephyr/sys/dlist.h>
 #include <kernel_internal.h>
 #include <zephyr/drivers/entropy.h>
 #include <zephyr/logging/log_ctrl.h>
 #include <zephyr/tracing/tracing.h>
-#include <stdbool.h>
 #include <zephyr/debug/gcov.h>
 #include <kswap.h>
 #include <zephyr/timing/timing.h>
@@ -42,7 +43,7 @@
  * TODO(b/272518464): Work around coreboot GCC preprocessor bug.
  * #line marks the *next* line, so it is off by one.
  */
-#line 46
+#line 47
 
 LOG_MODULE_REGISTER(os, CONFIG_KERNEL_LOG_LEVEL);
 
@@ -410,6 +411,93 @@ static inline int z_vrfy_device_init(const struct device *dev)
 
 extern void boot_banner(void);
 
+#ifdef CONFIG_BOOTARGS
+extern const char *get_bootargs(void);
+static char **prepare_main_args(int *argc)
+{
+#ifdef CONFIG_DYNAMIC_BOOTARGS
+ const char *bootargs = get_bootargs();
+#else
+ const char bootargs[] = CONFIG_BOOTARGS_STRING;
+#endif
+
+ /* beginning of the buffer contains argument's strings, end of it contains argvs */
+ static char args_buf[CONFIG_BOOTARGS_ARGS_BUFFER_SIZE];
+ char *strings_end = (char *)args_buf;
+ char **argv_begin = (char **)WB_DN(
+ args_buf + CONFIG_BOOTARGS_ARGS_BUFFER_SIZE - sizeof(char *));
+ int i = 0;
+
+ *argc = 0;
+ *argv_begin = NULL;
+
+#ifdef CONFIG_DYNAMIC_BOOTARGS
+ if (!bootargs) {
+ return argv_begin;
+ }
+#endif
+
+ while (1) {
+ while (isspace(bootargs[i])) {
+ i++;
+ }
+
+ if (bootargs[i] == '\0') {
+ return argv_begin;
+ }
+
+ if (strings_end + sizeof(char *) >= (char *)argv_begin) {
+ LOG_WRN("not enough space in args buffer to accommodate all bootargs"
+ " - bootargs truncated");
+ return argv_begin;
+ }
+
+ argv_begin--;
+ memmove(argv_begin, argv_begin + 1, *argc * sizeof(char *));
+ argv_begin[*argc] = strings_end;
+
+ bool quoted = false;
+
+ if (bootargs[i] == '\"' || bootargs[i] == '\'') {
+ char delimiter = bootargs[i];
+
+ for (int j = i + 1; bootargs[j] != '\0'; j++) {
+ if (bootargs[j] == delimiter) {
+ quoted = true;
+ break;
+ }
+ }
+ }
+
+ if (quoted) {
+ char delimiter = bootargs[i];
+
+ i++; /* strip quotes */
+ while (bootargs[i] != delimiter
+ && strings_end < (char *)argv_begin) {
+ *strings_end++ = bootargs[i++];
+ }
+ i++; /* strip quotes */
+ } else {
+ while (!isspace(bootargs[i])
+ && bootargs[i] != '\0'
+ && strings_end < (char *)argv_begin) {
+ *strings_end++ = bootargs[i++];
+ }
+ }
+
+ if (strings_end < (char *)argv_begin) {
+ *strings_end++ = '\0';
+ } else {
+ LOG_WRN("not enough space in args buffer to accommodate all bootargs"
+ " - bootargs truncated");
+ argv_begin[*argc] = NULL;
+ return argv_begin;
+ }
+ (*argc)++;
+ }
+}
+#endif
 
 /**
  * @brief Mainline for kernel's background thread
@@ -463,9 +551,17 @@ static void bg_thread_main(void *unused1, void *unused2, void *unused3)
  z_mem_manage_boot_finish();
 #endif /* CONFIG_MMU */
 
+#ifdef CONFIG_BOOTARGS
+ extern int main(int, char **);
+
+ int argc = 0;
+ char **argv = prepare_main_args(&argc);
+ (void)main(argc, argv);
+#else
  extern int main(void);
 
  (void)main();
+#endif /* CONFIG_BOOTARGS */
 
  /* Mark non-essential since main() has no more work to do */
  z_thread_essential_clear(&z_main_thread);