cmd: add exception command

The 'exception' command allows to test exception handling.

This implementation supports ARM, x86, RISC-V and the following exceptions:
* 'breakpoint' - prefetch abort exception (ARM 32bit only)
* 'unaligned'  - data abort exception (ARM only)
* 'undefined'  - undefined instruction exception

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

MAINTAINERS

@@ -86,6 +86,7 @@ M:	Albert Aribaud <albert.u.boot@aribaud.net>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-arm.git
 F:	arch/arm/
+F:	cmd/arm/
 
 ARM ALTERA SOCFPGA
 M:	Marek Vasut <marex@denx.de>
@@ -677,6 +678,7 @@ M:	Rick Chen <rick@andestech.com>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-riscv.git
 F:	arch/riscv/
+F:	cmd/riscv/
 F:	tools/prelink-riscv.c
 
 ROCKUSB
@@ -788,6 +790,7 @@ M:	Bin Meng <bmeng.cn@gmail.com>
 S:	Maintained
 T:	git git://git.denx.de/u-boot-x86.git
 F:	arch/x86/
+F:	cmd/x86/
 
 XTENSA
 M:	Max Filippov <jcmvbkbc@gmail.com>

cmd/Kconfig

@@ -1433,6 +1433,12 @@ config CMD_EFIDEBUG
 	  particularly for managing boot parameters as  well as examining
 	  various EFI status for debugging.
 
+config CMD_EXCEPTION
+	bool "exception - raise exception"
+	depends on ARM || RISCV || X86
+	help
+	  Enable the 'exception' command which allows to raise an exception.
+
 config CMD_LED
 	bool "led"
 	depends on LED

cmd/Makefile

@@ -173,6 +173,8 @@ obj-$(CONFIG_CMD_BLOB) += blob.o
 # Android Verified Boot 2.0
 obj-$(CONFIG_CMD_AVB) += avb.o
 
+obj-$(CONFIG_ARM) += arm/
+obj-$(CONFIG_RISCV) += riscv/
 obj-$(CONFIG_X86) += x86/
 
 obj-$(CONFIG_ARCH_MVEBU) += mvebu/

cmd/arm/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
+
+ifdef CONFIG_ARM64
+obj-$(CONFIG_CMD_EXCEPTION) += exception64.o
+else
+obj-$(CONFIG_CMD_EXCEPTION) += exception.o
+endif

cmd/arm/exception.c

@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <command.h>
+
+static int do_unaligned(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	/*
+	 * The LDRD instruction requires the data source to be four byte aligned
+	 * even if strict alignment fault checking is disabled in the system
+	 * control register.
+	 */
+	asm volatile (
+		"MOV r5, sp\n"
+		"ADD r5, #1\n"
+		"LDRD r6, r7, [r5]\n");
+	return CMD_RET_FAILURE;
+}
+
+static int do_breakpoint(cmd_tbl_t *cmdtp, int flag, int argc,
+			 char * const argv[])
+{
+	asm volatile ("BKPT #123\n");
+	return CMD_RET_FAILURE;
+}
+
+static int do_undefined(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	/*
+	 * 0xe7f...f.	is undefined in ARM mode
+	 * 0xde..	is undefined in Thumb mode
+	 */
+	asm volatile (".word 0xe7f7defb\n");
+	return CMD_RET_FAILURE;
+}
+
+static cmd_tbl_t cmd_sub[] = {
+	U_BOOT_CMD_MKENT(breakpoint, CONFIG_SYS_MAXARGS, 1, do_breakpoint,
+			 "", ""),
+	U_BOOT_CMD_MKENT(unaligned, CONFIG_SYS_MAXARGS, 1, do_unaligned,
+			 "", ""),
+	U_BOOT_CMD_MKENT(undefined, CONFIG_SYS_MAXARGS, 1, do_undefined,
+			 "", ""),
+};
+
+static char exception_help_text[] =
+	"<ex>\n"
+	"  The following exceptions are available:\n"
+	"  breakpoint - prefetch abort\n"
+	"  unaligned  - data abort\n"
+	"  undefined  - undefined instruction\n"
+	;
+
+#include <exception.h>

cmd/arm/exception64.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <command.h>
+
+static int do_undefined(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	/*
+	 * 0xe7f...f.	is undefined in ARM mode
+	 * 0xde..	is undefined in Thumb mode
+	 */
+	asm volatile (".word 0xe7f7defb\n");
+	return CMD_RET_FAILURE;
+}
+
+static cmd_tbl_t cmd_sub[] = {
+	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"
+	;
+
+#include <exception.h>

cmd/riscv/Makefile

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

cmd/riscv/exception.c

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <command.h>
+
+static int do_undefined(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	asm volatile (".word 0xffffffff\n");
+	return CMD_RET_FAILURE;
+}
+
+static cmd_tbl_t cmd_sub[] = {
+	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"
+	;
+
+#include <exception.h>

cmd/x86/Makefile

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0+
 
 obj-y += mtrr.o
+obj-$(CONFIG_CMD_EXCEPTION) += exception.o
 obj-$(CONFIG_HAVE_FSP) += fsp.o

cmd/x86/exception.c

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+#include <common.h>
+#include <command.h>
+
+static int do_undefined(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	asm volatile (".word 0xffff\n");
+	return CMD_RET_FAILURE;
+}
+
+static cmd_tbl_t cmd_sub[] = {
+	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"
+	;
+
+#include <exception.h>

include/exception.h

@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * The 'exception' command can be used for testing exception handling.
+ *
+ * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
+ */
+
+static int do_exception(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	cmd_tbl_t *cp;
+
+	if (argc != 2)
+		return CMD_RET_USAGE;
+
+	/* drop sub-command parameter */
+	argc--;
+	argv++;
+
+	cp = find_cmd_tbl(argv[0], cmd_sub, ARRAY_SIZE(cmd_sub));
+
+	if (cp)
+		return cp->cmd(cmdtp, flag, argc, argv);
+
+	return CMD_RET_USAGE;
+}
+
+static int exception_complete(int argc, char * const argv[], char last_char,
+			      int maxv, char *cmdv[])
+{
+	int len = 0;
+	int i = 0;
+	cmd_tbl_t *cmdtp;
+
+	switch (argc) {
+	case 1:
+		break;
+	case 2:
+		len = strlen(argv[1]);
+		break;
+	default:
+		return 0;
+	}
+	for (cmdtp = cmd_sub; cmdtp != cmd_sub + ARRAY_SIZE(cmd_sub); cmdtp++) {
+		if (i >= maxv - 1)
+			return i;
+		if (!strncmp(argv[1], cmdtp->name, len))
+			cmdv[i++] = cmdtp->name;
+	}
+	cmdv[i] = NULL;
+	return i;
+}
+
+U_BOOT_CMD_COMPLETE(
+	exception, 2, 0, do_exception,
+	"Forces an exception to occur",
+	exception_help_text, exception_complete
+);