1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * The 'exception' command can be used for testing exception handling.
4 *
5 * Copyright (c) 2018, Heinrich Schuchardt <xypron.glpk@gmx.de>
6 */
7
8#include <common.h>
9#include <command.h>
10#include <linux/bitops.h>
11
12static int do_undefined(struct cmd_tbl *cmdtp, int flag, int argc,
13			char *const argv[])
14{
15	/*
16	 * Instructions starting with the upper 16 bits all 0 are permanently
17	 * undefined. The lower 16 bits can be used for some kind of immediate.
18	 * --- ARMv8 ARM (ARM DDI 0487G.a C6.2.339: "UDF")
19	 */
20	asm volatile (".word 0x00001234\n");
21
22	return CMD_RET_FAILURE;
23}
24
25/*
26 * The ID_AA64MMFR2_EL1 register name is only know to binutils for ARMv8.2
27 * and later architecture revisions. However the register is valid regardless
28 * of binutils architecture support or the core the code is running on, so
29 * just use the generic encoding.
30 */
31#define ID_AA64MMFR2_EL1 "S3_0_C0_C7_2"
32
33static int do_unaligned(struct cmd_tbl *cmdtp, int flag, int argc,
34			char *const argv[])
35{
36	uint64_t reg;
37
38	/*
39	 * The unaligned LDAR access below is only guaranteed to generate an
40	 * alignment fault on cores not implementing FEAT_LSE2. To avoid false
41	 * negatives, check this condition before we exectute LDAR.
42	 */
43	asm ("mrs %0, "ID_AA64MMFR2_EL1"\n" : "=r" (reg));
44	if (reg & GENMASK(35, 32)) {
45		printf("unaligned access check only supported on pre-v8.4 cores\n");
46		return CMD_RET_FAILURE;
47	}
48
49	/*
50	 * The load acquire instruction requires the data source to be
51	 * naturally aligned, and will fault even if strict alignment fault
52	 * checking is disabled (but only without FEAT_LSE2).
53	 * --- ARMv8 ARM (ARM DDI 0487G.a B2.5.2: "Alignment of data accesses")
54	 */
55	asm volatile (
56		"mov	x1, sp\n\t"
57		"orr	x1, x1, #3\n\t"
58		"ldar	x0, [x1]\n"
59		::: "x0", "x1" );
60
61	return CMD_RET_FAILURE;
62}
63
64static int do_breakpoint(struct cmd_tbl *cmdtp, int flag, int argc,
65			 char *const argv[])
66{
67	asm volatile ("brk	#123\n");
68
69	return CMD_RET_FAILURE;
70}
71
72static struct cmd_tbl cmd_sub[] = {
73	U_BOOT_CMD_MKENT(breakpoint, CONFIG_SYS_MAXARGS, 1, do_breakpoint,
74			 "", ""),
75	U_BOOT_CMD_MKENT(unaligned, CONFIG_SYS_MAXARGS, 1, do_unaligned,
76			 "", ""),
77	U_BOOT_CMD_MKENT(undefined, CONFIG_SYS_MAXARGS, 1, do_undefined,
78			 "", ""),
79};
80
81static char exception_help_text[] =
82	"<ex>\n"
83	"  The following exceptions are available:\n"
84	"  breakpoint - breakpoint instruction exception\n"
85	"  unaligned  - unaligned LDAR data abort\n"
86	"  undefined  - undefined instruction exception\n"
87	;
88
89#include <exception.h>
90