cmd: Add command for calculating binary operations

This patch adds a command that enables the calculation of bit operations
(AND, OR, XOR) on binary data from the command line. Memory locations as
well as the contents of environment variables are eligible as sources
and destination of the binary data used in the operations.

The possible applications are manifold: Setting specific bits in
registers using the regular read-OR-write pattern, masking out bits in
bit values, implementation of simple OTP encryption using the XOR
operation, etc.

Signed-off-by: Mario Six <mario.six@gdsys.cc>

cmd/Kconfig

@@ -423,6 +423,12 @@ endmenu
 
 menu "Memory commands"
 
+config CMD_BINOP
+	bool "binop"
+	help
+	  Compute binary operations (xor, or, and) of byte arrays of arbitrary
+	  size from memory and store the result in memory or the environment.
+
 config CMD_CRC32
 	bool "crc32"
 	select HASH

cmd/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_SOURCE) += source.o
 obj-$(CONFIG_CMD_SOURCE) += source.o
 obj-$(CONFIG_CMD_BDI) += bdinfo.o
 obj-$(CONFIG_CMD_BEDBUG) += bedbug.o
+obj-$(CONFIG_CMD_BINOP) += binop.o
 obj-$(CONFIG_CMD_BLOCK_CACHE) += blkcache.o
 obj-$(CONFIG_CMD_BMP) += bmp.o
 obj-$(CONFIG_CMD_BOOTEFI) += bootefi.o

cmd/binop.c

@@ -0,0 +1,176 @@
+/*
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <linux/ctype.h>
+
+enum {
+	OP_ID_XOR,
+	OP_ID_AND,
+	OP_ID_OR,
+};
+
+void write_to_env_var(char *varname, u8 *result, ulong len)
+{
+	char *str_output;
+	char *str_ptr;
+	int i;
+
+	str_output = malloc(len * 2 + 1);
+	str_ptr = str_output;
+
+	for (i = 0; i < len; i++) {
+		sprintf(str_ptr, "%02x", result[i]);
+		str_ptr += 2;
+	}
+	*str_ptr = '\0';
+	setenv(varname, str_output);
+
+	free(str_output);
+}
+
+void decode_hexstring(char *hexstr, u8 *result)
+{
+	int i;
+	int acc = 0;
+
+	for (i = 0; i < strlen(hexstr); ++i) {
+		char d = hexstr[i];
+		int value;
+
+		if (isdigit(d))
+			value = (d - '0');
+		else
+			value = (islower(d) ? toupper(d) : d) - 'A' + 10;
+
+		if (i % 2 == 0) {
+			acc = value * 16;
+		} else {
+			result[i / 2] = acc + value;
+			acc = 0;
+		}
+	}
+}
+
+void read_from_env_var(char *varname, u8 *result)
+{
+	char *str_value;
+
+	str_value = getenv(varname);
+	if (str_value)
+		decode_hexstring(str_value, result);
+	else
+		decode_hexstring(varname, result);
+}
+
+void read_from_mem(ulong addr, u8 *result, ulong len)
+{
+	u8 *src;
+
+	src = map_sysmem(addr, len);
+	memcpy(result, src, len);
+	unmap_sysmem(src);
+}
+
+void write_to_mem(char *varname, u8 *result, ulong len)
+{
+	ulong addr;
+	u8 *buf;
+
+	addr = simple_strtoul(varname, NULL, 16);
+	buf = map_sysmem(addr, len);
+	memcpy(buf, result, len);
+	unmap_sysmem(buf);
+}
+
+static int do_binop(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	ulong len;
+	u8 *result, *src1, *src2;
+	char *oparg, *lenarg, *src1arg, *src2arg, *destarg;
+	int i, op;
+
+	if (argc < 5)
+		return CMD_RET_USAGE;
+
+	oparg = argv[1];
+	lenarg = argv[2];
+	src1arg = argv[3];
+	src2arg = argv[4];
+
+	if (!strcmp(oparg, "xor"))
+		op = OP_ID_XOR;
+	else if (!strcmp(oparg, "or"))
+		op = OP_ID_OR;
+	else if (!strcmp(oparg, "and"))
+		op = OP_ID_AND;
+	else
+		return CMD_RET_USAGE;
+
+	len = simple_strtoul(lenarg, NULL, 10);
+
+	src1 = malloc(len);
+	src2 = malloc(len);
+
+	if (*src1arg == '*')
+		read_from_mem(simple_strtoul(src1arg + 1, NULL, 16), src1, len);
+	else
+		read_from_env_var(src1arg, src1);
+
+	if (*src2arg == '*')
+		read_from_mem(simple_strtoul(src2arg + 1, NULL, 16), src2, len);
+	else
+		read_from_env_var(src2arg, src2);
+
+	result = malloc(len);
+
+	switch (op) {
+	case OP_ID_XOR:
+		for (i = 0; i < len; i++)
+			result[i] = src1[i] ^ src2[i];
+		break;
+	case OP_ID_OR:
+		for (i = 0; i < len; i++)
+			result[i] = src1[i] | src2[i];
+		break;
+	case OP_ID_AND:
+		for (i = 0; i < len; i++)
+			result[i] = src1[i] & src2[i];
+		break;
+	}
+
+	if (argc == 5) {
+		for (i = 0; i < len; i++) {
+			printf("%02x ", result[i]);
+			if (i % 16 == 15)
+				puts("\n");
+		}
+		puts("\n");
+
+		goto exit;
+	}
+
+	destarg = argv[5];
+
+	if (*destarg == '*')
+		write_to_mem(destarg + 1, result, len); /* Skip asterisk */
+	else
+		write_to_env_var(destarg, result, len);
+exit:
+	free(result);
+	free(src2);
+	free(src1);
+
+	return 0;
+}
+
+U_BOOT_CMD(
+	binop,	6,	1,	do_binop,
+	"compute binary operation",
+	"op count [*]src1 [*]src2 [[*]dest]\n"
+		"    - compute binary operation of data at/in src1 and\n      src2 (either *memaddr, env var name or hex string)\n      and store result in/at dest, where op is one of\n      xor, or, and."
+);