From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file

---
 kernel/lib/hexdump.c |   75 ++++++++++++++++++++-----------------
 1 files changed, 40 insertions(+), 35 deletions(-)

diff --git a/kernel/lib/hexdump.c b/kernel/lib/hexdump.c
index 81b70ed..07cda1a 100644
--- a/kernel/lib/hexdump.c
+++ b/kernel/lib/hexdump.c
@@ -1,16 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * lib/hexdump.c
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation. See README and COPYING for
- * more details.
  */
 
 #include <linux/types.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
+#include <linux/minmax.h>
 #include <linux/export.h>
 #include <asm/unaligned.h>
 
@@ -25,15 +22,41 @@
  *
  * hex_to_bin() converts one hex digit to its actual value or -1 in case of bad
  * input.
+ *
+ * This function is used to load cryptographic keys, so it is coded in such a
+ * way that there are no conditions or memory accesses that depend on data.
+ *
+ * Explanation of the logic:
+ * (ch - '9' - 1) is negative if ch <= '9'
+ * ('0' - 1 - ch) is negative if ch >= '0'
+ * we "and" these two values, so the result is negative if ch is in the range
+ *	'0' ... '9'
+ * we are only interested in the sign, so we do a shift ">> 8"; note that right
+ *	shift of a negative value is implementation-defined, so we cast the
+ *	value to (unsigned) before the shift --- we have 0xffffff if ch is in
+ *	the range '0' ... '9', 0 otherwise
+ * we "and" this value with (ch - '0' + 1) --- we have a value 1 ... 10 if ch is
+ *	in the range '0' ... '9', 0 otherwise
+ * we add this value to -1 --- we have a value 0 ... 9 if ch is in the range '0'
+ *	... '9', -1 otherwise
+ * the next line is similar to the previous one, but we need to decode both
+ *	uppercase and lowercase letters, so we use (ch & 0xdf), which converts
+ *	lowercase to uppercase
  */
+/*
+ * perserve abi due to 15b78a8e38e8 ("hex2bin: make the function hex_to_bin
+ * constant-time"
+ */
+#ifdef __GENKSYMS__
 int hex_to_bin(char ch)
+#else
+int hex_to_bin(unsigned char ch)
+#endif
 {
-	if ((ch >= '0') && (ch <= '9'))
-		return ch - '0';
-	ch = tolower(ch);
-	if ((ch >= 'a') && (ch <= 'f'))
-		return ch - 'a' + 10;
-	return -1;
+	unsigned char cu = ch & 0xdf;
+	return -1 +
+		((ch - '0' +  1) & (unsigned)((ch - '9' - 1) & ('0' - 1 - ch)) >> 8) +
+		((cu - 'A' + 11) & (unsigned)((cu - 'F' - 1) & ('A' - 1 - cu)) >> 8);
 }
 EXPORT_SYMBOL(hex_to_bin);
 
@@ -48,10 +71,13 @@
 int hex2bin(u8 *dst, const char *src, size_t count)
 {
 	while (count--) {
-		int hi = hex_to_bin(*src++);
-		int lo = hex_to_bin(*src++);
+		int hi, lo;
 
-		if ((hi < 0) || (lo < 0))
+		hi = hex_to_bin(*src++);
+		if (unlikely(hi < 0))
+			return -EINVAL;
+		lo = hex_to_bin(*src++);
+		if (unlikely(lo < 0))
 			return -EINVAL;
 
 		*dst++ = (hi << 4) | lo;
@@ -274,25 +300,4 @@
 }
 EXPORT_SYMBOL(print_hex_dump);
 
-#if !defined(CONFIG_DYNAMIC_DEBUG)
-/**
- * print_hex_dump_bytes - shorthand form of print_hex_dump() with default params
- * @prefix_str: string to prefix each line with;
- *  caller supplies trailing spaces for alignment if desired
- * @prefix_type: controls whether prefix of an offset, address, or none
- *  is printed (%DUMP_PREFIX_OFFSET, %DUMP_PREFIX_ADDRESS, %DUMP_PREFIX_NONE)
- * @buf: data blob to dump
- * @len: number of bytes in the @buf
- *
- * Calls print_hex_dump(), with log level of KERN_DEBUG,
- * rowsize of 16, groupsize of 1, and ASCII output included.
- */
-void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
-			  const void *buf, size_t len)
-{
-	print_hex_dump(KERN_DEBUG, prefix_str, prefix_type, 16, 1,
-		       buf, len, true);
-}
-EXPORT_SYMBOL(print_hex_dump_bytes);
-#endif /* !defined(CONFIG_DYNAMIC_DEBUG) */
 #endif /* defined(CONFIG_PRINTK) */

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