update

decompressor_lz4.c

@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/* Minimal LZ4 decompressor for EROFS FreeBSD */
+#include <sys/param.h>
+#include <sys/endian.h>
+#include <sys/systm.h>
+
+#include "compress.h"
+
+#define EROFS_LZ4_TOKEN_LITERAL_SHIFT 4
+#define EROFS_LZ4_TOKEN_MATCH_MASK 0x0f
+#define EROFS_LZ4_MAX_RUN 15
+#define EROFS_LZ4_EXT_SENTINEL 255
+#define EROFS_LZ4_MIN_MATCH 4
+#define EROFS_LZ4_OFFSET_BYTES 2
+
+static int
+lz4_finish(const uint8_t *ip, const uint8_t *iend, int partial)
+{
+	if (partial)
+		return (0);
+	while (ip < iend) {
+		if (*ip++ != 0)
+			return (EINTEGRITY);
+	}
+	return (0);
+}
+
+int
+z_erofs_lz4_decompress(const struct z_erofs_decompress_req *rq)
+{
+	const uint8_t *ip, *iend;
+	uint8_t *op, *oend;
+	unsigned int token;
+	size_t length, copylen;
+	size_t offset;
+
+	ip = rq->in;
+	iend = ip + rq->inputsize;
+	op = rq->out;
+	oend = op + rq->outputsize;
+	if (iend < ip || oend < op)
+		return (EINTEGRITY);
+
+	while (ip < iend) {
+		token = *ip++;
+		length = token >> EROFS_LZ4_TOKEN_LITERAL_SHIFT;
+		if (length == EROFS_LZ4_MAX_RUN) {
+			unsigned int value;
+			do {
+				if (ip >= iend)
+					return (EINTEGRITY);
+				value = *ip++;
+				if (length > SIZE_MAX - value)
+					return (EINTEGRITY);
+				length += value;
+			} while (value == EROFS_LZ4_EXT_SENTINEL);
+		}
+		if (length > (size_t)(iend - ip))
+			return (EINTEGRITY);
+		if (!rq->partial_decoding && length > (size_t)(oend - op))
+			return (EINTEGRITY);
+		copylen = MIN(length, (size_t)(oend - op));
+		memcpy(op, ip, copylen);
+		ip += length;
+		op += copylen;
+		if (op == oend)
+			return (lz4_finish(ip, iend, rq->partial_decoding));
+		if (ip >= iend)
+			break;
+		if (ip + EROFS_LZ4_OFFSET_BYTES > iend)
+			return (EINTEGRITY);
+		offset = le16dec(ip);
+		ip += EROFS_LZ4_OFFSET_BYTES;
+		if (offset == 0 || offset >
+		    (size_t)(op - (uint8_t *)rq->out))
+			return (EINTEGRITY);
+		length = token & EROFS_LZ4_TOKEN_MATCH_MASK;
+		if (length == EROFS_LZ4_MAX_RUN) {
+			unsigned int value;
+			do {
+				if (ip >= iend)
+					return (EINTEGRITY);
+				value = *ip++;
+				if (length > SIZE_MAX - value)
+					return (EINTEGRITY);
+				length += value;
+			} while (value == EROFS_LZ4_EXT_SENTINEL);
+		}
+		if (length > SIZE_MAX - EROFS_LZ4_MIN_MATCH)
+			return (EINTEGRITY);
+		length += EROFS_LZ4_MIN_MATCH;
+		if (!rq->partial_decoding && length > (size_t)(oend - op))
+			return (EINTEGRITY);
+		copylen = MIN(length, (size_t)(oend - op));
+		while (copylen-- != 0) {
+			*op = *(op - offset);
+			++op;
+		}
+		if (op == oend)
+			return (lz4_finish(ip, iend, rq->partial_decoding));
+	}
+	return (op == oend ?
+	    lz4_finish(ip, iend, rq->partial_decoding) : EINTEGRITY);
+}