change system file

hc

2024-10-09 244b2c5ca8b14627e4a17755e5922221e121c771

 kernel/lib/hexdump.c
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@@ -1,16 +1,13 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * lib/hexdump.c
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- *
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- * This program is free software; you can redistribute it and/or modify
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- * it under the terms of the GNU General Public License version 2 as
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- * published by the Free Software Foundation. See README and COPYING for
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- * more details.
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  */
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 #include <linux/types.h>
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 #include <linux/ctype.h>
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 #include <linux/errno.h>
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 #include <linux/kernel.h>
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+#include <linux/minmax.h>
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 #include <linux/export.h>
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 #include <asm/unaligned.h>
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@@ -25,15 +22,41 @@
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  *
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  * hex_to_bin() converts one hex digit to its actual value or -1 in case of bad
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  * input.
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+ *
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+ * This function is used to load cryptographic keys, so it is coded in such a
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+ * way that there are no conditions or memory accesses that depend on data.
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+ *
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+ * Explanation of the logic:
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+ * (ch - '9' - 1) is negative if ch <= '9'
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+ * ('0' - 1 - ch) is negative if ch >= '0'
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+ * we "and" these two values, so the result is negative if ch is in the range
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+ *	'0' ... '9'
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+ * we are only interested in the sign, so we do a shift ">> 8"; note that right
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+ *	shift of a negative value is implementation-defined, so we cast the
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+ *	value to (unsigned) before the shift --- we have 0xffffff if ch is in
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+ *	the range '0' ... '9', 0 otherwise
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+ * we "and" this value with (ch - '0' + 1) --- we have a value 1 ... 10 if ch is
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+ *	in the range '0' ... '9', 0 otherwise
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+ * we add this value to -1 --- we have a value 0 ... 9 if ch is in the range '0'
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+ *	... '9', -1 otherwise
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+ * the next line is similar to the previous one, but we need to decode both
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+ *	uppercase and lowercase letters, so we use (ch & 0xdf), which converts
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+ *	lowercase to uppercase
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  */
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+/*
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+ * perserve abi due to 15b78a8e38e8 ("hex2bin: make the function hex_to_bin
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+ * constant-time"
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+ */
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+#ifdef __GENKSYMS__
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 int hex_to_bin(char ch)
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+#else
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+int hex_to_bin(unsigned char ch)
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+#endif
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 {
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-	if ((ch >= '0') && (ch <= '9'))
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-		return ch - '0';
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-	ch = tolower(ch);
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-	if ((ch >= 'a') && (ch <= 'f'))
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-		return ch - 'a' + 10;
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-	return -1;
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+	unsigned char cu = ch & 0xdf;
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+	return -1 +
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+		((ch - '0' +  1) & (unsigned)((ch - '9' - 1) & ('0' - 1 - ch)) >> 8) +
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+		((cu - 'A' + 11) & (unsigned)((cu - 'F' - 1) & ('A' - 1 - cu)) >> 8);
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 }
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 EXPORT_SYMBOL(hex_to_bin);
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@@ -48,10 +71,13 @@
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 int hex2bin(u8 *dst, const char *src, size_t count)
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 {
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 	while (count--) {
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-		int hi = hex_to_bin(*src++);
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-		int lo = hex_to_bin(*src++);
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+		int hi, lo;
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-		if ((hi < 0) || (lo < 0))
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+		hi = hex_to_bin(*src++);
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+		if (unlikely(hi < 0))
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+			return -EINVAL;
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+		lo = hex_to_bin(*src++);
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+		if (unlikely(lo < 0))
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 			return -EINVAL;
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 		*dst++ = (hi << 4) | lo;
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@@ -274,25 +300,4 @@
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 }
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 EXPORT_SYMBOL(print_hex_dump);
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-#if !defined(CONFIG_DYNAMIC_DEBUG)
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-/**
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- * print_hex_dump_bytes - shorthand form of print_hex_dump() with default params
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- * @prefix_str: string to prefix each line with;
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- *  caller supplies trailing spaces for alignment if desired
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- * @prefix_type: controls whether prefix of an offset, address, or none
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- *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
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- * @buf: data blob to dump
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- * @len: number of bytes in the @buf
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- *
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- * Calls print_hex_dump(), with log level of KERN_DEBUG,
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- * rowsize of 16, groupsize of 1, and ASCII output included.
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- */
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-void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
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-			  const void *buf, size_t len)
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-{
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-	print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, 16, 1,
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-		       buf, len, true);
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-}
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-EXPORT_SYMBOL(print_hex_dump_bytes);
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-#endif /* !defined(CONFIG_DYNAMIC_DEBUG) */
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 #endif /* defined(CONFIG_PRINTK) */