cmd: sandbox: implement exception command

Implement the commands

* exception undefined - execute an illegal instruction
* exception sigsegv - cause a segment violation

Here is a possible output:

    => exception undefined
    Illegal instruction
    pc = 0x55eb8d0a7575, pc_reloc = 0x57575
    Resetting ...

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

cmd/Kconfig

@@ -1691,7 +1691,7 @@ config CMD_EFIDEBUG
 
 config CMD_EXCEPTION
 	bool "exception - raise exception"
-	depends on ARM || RISCV || X86
+	depends on ARM || RISCV || SANDBOX || X86
 	help
 	  Enable the 'exception' command which allows to raise an exception.
 

cmd/Makefile

@@ -193,6 +193,7 @@ obj-$(CONFIG_CMD_AVB) += avb.o
 
 obj-$(CONFIG_ARM) += arm/
 obj-$(CONFIG_RISCV) += riscv/
+obj-$(CONFIG_SANDBOX) += sandbox/
 obj-$(CONFIG_X86) += x86/
 
 obj-$(CONFIG_ARCH_MVEBU) += mvebu/

cmd/sandbox/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0+
+
+obj-$(CONFIG_CMD_EXCEPTION) += exception.o

cmd/sandbox/exception.c

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2020, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <command.h>
+
+static int do_sigsegv(struct cmd_tbl *cmdtp, int flag, int argc,
+		      char *const argv[])
+{
+	u8 *ptr = NULL;
+
+	*ptr = 0;
+	return CMD_RET_FAILURE;
+}
+
+static int do_undefined(struct cmd_tbl *cmdtp, int flag, int argc,
+			char *const argv[])
+{
+	asm volatile (".word 0xffff\n");
+	return CMD_RET_FAILURE;
+}
+
+static struct cmd_tbl cmd_sub[] = {
+	U_BOOT_CMD_MKENT(sigsegv, CONFIG_SYS_MAXARGS, 1, do_sigsegv,
+			 "", ""),
+	U_BOOT_CMD_MKENT(undefined, CONFIG_SYS_MAXARGS, 1, do_undefined,
+			 "", ""),
+};
+
+static char exception_help_text[] =
+	"<ex>\n"
+	"  The following exceptions are available:\n"
+	"  undefined  - undefined instruction\n"
+	"  sigsegv    - illegal memory access\n"
+	;
+
+#include <exception.h>