sandbox: implement reset

Up to now the sandbox would shutdown upon a cold reset request. Instead it
should be reset.

In our coding we use static variables like LIST_HEAD(efi_obj_list). A reset
can occur at any time, e.g. via an UEFI binary calling the reset service.
The only safe way to return to an initial state is to relaunch the U-Boot
binary.

The reset implementation uses execv() to relaunch U-Boot.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/sandbox/cpu/os.c

@@ -822,3 +822,9 @@ void *os_find_text_base(void)
 
 	return base;
 }
+
+void os_relaunch(char *argv[])
+{
+	execv(argv[0], argv);
+	os_exit(1);
+}

arch/sandbox/cpu/start.c

@@ -5,6 +5,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <dm/root.h>
 #include <errno.h>
 #include <init.h>
 #include <os.h>
@@ -19,6 +20,8 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+static char **os_argv;
+
 /* Compare two options so that they can be sorted into alphabetical order */
 static int h_compare_opt(const void *p1, const void *p2)
 {
@@ -403,12 +406,35 @@ void state_show(struct sandbox_state *state)
 	printf("\n");
 }
 
+void sandbox_reset(void)
+{
+	/* Do this here while it still has an effect */
+	os_fd_restore();
+	if (state_uninit())
+		os_exit(2);
+
+	if (dm_uninit())
+		os_exit(2);
+
+	/* Restart U-Boot */
+	os_relaunch(os_argv);
+}
+
 int main(int argc, char *argv[])
 {
 	struct sandbox_state *state;
 	gd_t data;
 	int ret;
 
+	/*
+	 * Copy argv[] so that we can pass the arguments in the original
+	 * sequence when resetting the sandbox.
+	 */
+	os_argv = calloc(argc + 1, sizeof(char *));
+	if (!os_argv)
+		os_exit(1);
+	memcpy(os_argv, argv, sizeof(char *) * (argc + 1));
+
 	memset(&data, '\0', sizeof(data));
 	gd = &data;
 	gd->arch.text_base = os_find_text_base();

arch/sandbox/cpu/state.c

@@ -358,6 +358,7 @@ void state_reset_for_test(struct sandbox_state *state)
 	/* No reset yet, so mark it as such. Always allow power reset */
 	state->last_sysreset = SYSRESET_COUNT;
 	state->sysreset_allowed[SYSRESET_POWER_OFF] = true;
+	state->sysreset_allowed[SYSRESET_COLD] = true;
 	state->allow_memio = false;
 
 	memset(&state->wdt, '\0', sizeof(state->wdt));

arch/sandbox/include/asm/u-boot-sandbox.h

@@ -84,6 +84,16 @@ void sandbox_set_enable_pci_map(int enable);
  */
 int sandbox_read_fdt_from_file(void);
 
+/**
+ * sandbox_reset() - reset sandbox
+ *
+ * This functions implements the cold reboot of the sandbox. It relaunches the
+ * U-Boot binary with the same command line parameters as the original call.
+ * The PID of the process stays the same. All file descriptors that have not
+ * been opened with O_CLOEXEC stay open including stdin, stdout, stderr.
+ */
+void sandbox_reset(void);
+
 /* Exit sandbox (quit U-Boot) */
 void sandbox_exit(void);
 

drivers/sysreset/sysreset_sandbox.c

@@ -56,6 +56,9 @@ static int sandbox_sysreset_request(struct udevice *dev, enum sysreset_t type)
 	switch (type) {
 	case SYSRESET_COLD:
 		state->last_sysreset = type;
+		if (!state->sysreset_allowed[type])
+			return -EACCES;
+		sandbox_reset();
 		break;
 	case SYSRESET_POWER_OFF:
 		state->last_sysreset = type;

include/os.h

@@ -355,4 +355,19 @@ int os_read_file(const char *name, void **bufp, int *sizep);
  */
 void *os_find_text_base(void);
 
+/**
+ * os_relaunch() - restart the sandbox
+ *
+ * This functions is used to implement the cold reboot of the sand box.
+ * @argv[0] specifies the binary that is started while the calling process
+ * stops immediately. If the new binary cannot be started, the process is
+ * terminated and 1 is set as shell return code.
+ *
+ * The PID of the process stays the same. All file descriptors that have not
+ * been opened with O_CLOEXEC stay open including stdin, stdout, stderr.
+ *
+ * @argv:	NULL terminated list of command line parameters
+ */
+void os_relaunch(char *argv[]);
+
 #endif