Merge pull request #529 from nbdd0121/rust

kallsyms: use ULEB128 for big symbols

Author: ojeda

kernel/kallsyms.c

@@ -69,19 +69,20 @@ static unsigned int kallsyms_expand_symbol(unsigned int off,
 	data = &kallsyms_names[off];
 	len = *data;
 	data++;
+	off++;
+
+	/* If MSB is 1, it is a "big" symbol, so needs an additional byte. */
+	if ((len & 0x80) != 0) {
+		len = (len & 0x7F) | (*data << 7);
+		data++;
+		off++;
+	}
 
 	/*
 	 * Update the offset to return the offset for the next symbol on
 	 * the compressed stream.
 	 */
-	off += len + 1;
-
-	/* If zero, it is a "big" symbol, so a two byte length follows. */
-	if (len == 0) {
-		len = (data[0] << 8) | data[1];
-		data += 2;
-		off += len + 2;
-	}
+	off += len;
 
 	/*
 	 * For every byte on the compressed symbol data, copy the table

scripts/kallsyms.c

@@ -473,33 +473,31 @@ static void write_src(void)
 		if ((i & 0xFF) == 0)
 			markers[i >> 8] = off;
 
-		/*
-		 * There cannot be any symbol of length zero -- we use that
-		 * to mark a "big" symbol (and it doesn't make sense anyway).
-		 */
+		/* There cannot be any symbol of length zero. */
 		if (table[i]->len == 0) {
 			fprintf(stderr, "kallsyms failure: "
 				"unexpected zero symbol length\n");
 			exit(EXIT_FAILURE);
 		}
 
-		/* Only lengths that fit in up to two bytes are supported. */
-		if (table[i]->len > 0xFFFF) {
+		/* Only lengths that fit in up-to-two-byte ULEB128 are supported. */
+		if (table[i]->len > 0x3FFF) {
 			fprintf(stderr, "kallsyms failure: "
 				"unexpected huge symbol length\n");
 			exit(EXIT_FAILURE);
 		}
 
-		if (table[i]->len <= 0xFF) {
+		/* Encode length with ULEB128. */
+		if (table[i]->len <= 0x7F) {
 			/* Most symbols use a single byte for the length. */
 			printf("\t.byte 0x%02x", table[i]->len);
 			off += table[i]->len + 1;
 		} else {
-			/* "Big" symbols use a zero and then two bytes. */
-			printf("\t.byte 0x00, 0x%02x, 0x%02x",
-				(table[i]->len >> 8) & 0xFF,
-				table[i]->len & 0xFF);
-			off += table[i]->len + 3;
+			/* "Big" symbols use two bytes. */
+			printf("\t.byte 0x%02x, 0x%02x",
+				(table[i]->len & 0x7F) | 0x80,
+				(table[i]->len >> 7) & 0x7F);
+			off += table[i]->len + 2;
 		}
 		for (k = 0; k < table[i]->len; k++)
 			printf(", 0x%02x", table[i]->sym[k]);