diff --git a/Android.mk b/Android.mk
index c544db9..bd8d09b 100644
--- a/Android.mk
+++ b/Android.mk
@@ -98,6 +98,7 @@
 LOCAL_STATIC_LIBRARIES := \
     libmincrypt \
     libminui \
+    libminzip \
     libcutils \
     libstdc++ \
     libc
diff --git a/install.cpp b/install.cpp
index 980830c..0bd7945 100644
--- a/install.cpp
+++ b/install.cpp
@@ -186,12 +186,22 @@
     ui->ShowProgress(VERIFICATION_PROGRESS_FRACTION, VERIFICATION_PROGRESS_TIME);
     LOGI("Update location: %s\n", path);
 
-    if (ensure_path_mounted(path) != 0) {
-        LOGE("Can't mount %s\n", path);
-        return INSTALL_CORRUPT;
+    // Map the update package into memory.
+    ui->Print("Opening update package...\n");
+
+    if (path) {
+        if (path[0] == '@') {
+            ensure_path_mounted(path+1);
+        } else {
+            ensure_path_mounted(path);
+        }
     }
 
-    ui->Print("Opening update package...\n");
+    MemMapping map;
+    if (sysMapFile(path, &map) != 0) {
+        LOGE("failed to map file\n");
+        return INSTALL_CORRUPT;
+    }
 
     int numKeys;
     Certificate* loadedKeys = load_keys(PUBLIC_KEYS_FILE, &numKeys);
@@ -204,27 +214,33 @@
     ui->Print("Verifying update package...\n");
 
     int err;
-    err = verify_file(path, loadedKeys, numKeys);
+    err = verify_file(map.addr, map.length, loadedKeys, numKeys);
     free(loadedKeys);
     LOGI("verify_file returned %d\n", err);
     if (err != VERIFY_SUCCESS) {
         LOGE("signature verification failed\n");
+        sysReleaseMap(&map);
         return INSTALL_CORRUPT;
     }
 
     /* Try to open the package.
      */
     ZipArchive zip;
-    err = mzOpenZipArchive(path, &zip);
+    err = mzOpenZipArchive(map.addr, map.length, &zip);
     if (err != 0) {
         LOGE("Can't open %s\n(%s)\n", path, err != -1 ? strerror(err) : "bad");
+        sysReleaseMap(&map);
         return INSTALL_CORRUPT;
     }
 
     /* Verify and install the contents of the package.
      */
     ui->Print("Installing update...\n");
-    return try_update_binary(path, &zip, wipe_cache);
+    int result = try_update_binary(path, &zip, wipe_cache);
+
+    sysReleaseMap(&map);
+
+    return result;
 }
 
 int
diff --git a/minzip/SysUtil.c b/minzip/SysUtil.c
index e6f6506..2cfa39a 100644
--- a/minzip/SysUtil.c
+++ b/minzip/SysUtil.c
@@ -8,11 +8,14 @@
 #include <unistd.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 #include <limits.h>
 #include <errno.h>
 #include <assert.h>
 
-#define LOG_TAG "minzip"
+#define LOG_TAG "sysutil"
 #include "Log.h"
 #include "SysUtil.h"
 
@@ -46,13 +49,13 @@
 }
 
 /*
- * Map a file (from fd's current offset) into a shared, read-only memory
+ * Map a file (from fd's current offset) into a private, read-only memory
  * segment.  The file offset must be a multiple of the page size.
  *
  * On success, returns 0 and fills out "pMap".  On failure, returns a nonzero
  * value and does not disturb "pMap".
  */
-int sysMapFileInShmem(int fd, MemMapping* pMap)
+static int sysMapFD(int fd, MemMapping* pMap)
 {
     off_t start;
     size_t length;
@@ -63,33 +66,146 @@
     if (getFileStartAndLength(fd, &start, &length) < 0)
         return -1;
 
-    memPtr = mmap(NULL, length, PROT_READ, MAP_FILE | MAP_SHARED, fd, start);
+    memPtr = mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, start);
     if (memPtr == MAP_FAILED) {
-        LOGW("mmap(%d, R, FILE|SHARED, %d, %d) failed: %s\n", (int) length,
+        LOGW("mmap(%d, R, PRIVATE, %d, %d) failed: %s\n", (int) length,
             fd, (int) start, strerror(errno));
         return -1;
     }
 
-    pMap->baseAddr = pMap->addr = memPtr;
-    pMap->baseLength = pMap->length = length;
+    pMap->addr = memPtr;
+    pMap->length = length;
+    pMap->range_count = 1;
+    pMap->ranges = malloc(sizeof(MappedRange));
+    pMap->ranges[0].addr = memPtr;
+    pMap->ranges[0].length = length;
 
     return 0;
 }
 
+static int sysMapBlockFile(FILE* mapf, MemMapping* pMap)
+{
+    char block_dev[PATH_MAX+1];
+    size_t size;
+    unsigned int blksize;
+    unsigned int blocks;
+    unsigned int range_count;
+    unsigned int i;
+
+    if (fgets(block_dev, sizeof(block_dev), mapf) == NULL) {
+        LOGW("failed to read block device from header\n");
+        return -1;
+    }
+    for (i = 0; i < sizeof(block_dev); ++i) {
+        if (block_dev[i] == '\n') {
+            block_dev[i] = 0;
+            break;
+        }
+    }
+
+    if (fscanf(mapf, "%d %d\n%d\n", &size, &blksize, &range_count) != 3) {
+        LOGW("failed to parse block map header\n");
+        return -1;
+    }
+
+    blocks = ((size-1) / blksize) + 1;
+
+    pMap->range_count = range_count;
+    pMap->ranges = malloc(range_count * sizeof(MappedRange));
+    memset(pMap->ranges, 0, range_count * sizeof(MappedRange));
+
+    // Reserve enough contiguous address space for the whole file.
+    unsigned char* reserve;
+    reserve = mmap64(NULL, blocks * blksize, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
+    if (reserve == MAP_FAILED) {
+        LOGW("failed to reserve address space: %s\n", strerror(errno));
+        return -1;
+    }
+
+    pMap->ranges[range_count-1].addr = reserve;
+    pMap->ranges[range_count-1].length = blocks * blksize;
+
+    int fd = open(block_dev, O_RDONLY);
+    if (fd < 0) {
+        LOGW("failed to open block device %s: %s\n", block_dev, strerror(errno));
+        return -1;
+    }
+
+    unsigned char* next = reserve;
+    for (i = 0; i < range_count; ++i) {
+        int start, end;
+        if (fscanf(mapf, "%d %d\n", &start, &end) != 2) {
+            LOGW("failed to parse range %d in block map\n", i);
+            return -1;
+        }
+
+        void* addr = mmap64(next, (end-start)*blksize, PROT_READ, MAP_PRIVATE | MAP_FIXED, fd, ((off64_t)start)*blksize);
+        if (addr == MAP_FAILED) {
+            LOGW("failed to map block %d: %s\n", i, strerror(errno));
+            return -1;
+        }
+        pMap->ranges[i].addr = addr;
+        pMap->ranges[i].length = (end-start)*blksize;
+
+        next += pMap->ranges[i].length;
+    }
+
+    pMap->addr = reserve;
+    pMap->length = size;
+
+    return 0;
+}
+
+int sysMapFile(const char* fn, MemMapping* pMap)
+{
+    memset(pMap, 0, sizeof(*pMap));
+
+    if (fn && fn[0] == '@') {
+        // A map of blocks
+        FILE* mapf = fopen(fn+1, "r");
+        if (mapf == NULL) {
+            LOGV("Unable to open '%s': %s\n", fn+1, strerror(errno));
+            return -1;
+        }
+
+        if (sysMapBlockFile(mapf, pMap) != 0) {
+            LOGW("Map of '%s' failed\n", fn);
+            return -1;
+        }
+
+        fclose(mapf);
+    } else {
+        // This is a regular file.
+        int fd = open(fn, O_RDONLY, 0);
+        if (fd < 0) {
+            LOGE("Unable to open '%s': %s\n", fn, strerror(errno));
+            return -1;
+        }
+
+        if (sysMapFD(fd, pMap) != 0) {
+            LOGE("Map of '%s' failed\n", fn);
+            close(fd);
+            return -1;
+        }
+
+        close(fd);
+    }
+    return 0;
+}
+
 /*
  * Release a memory mapping.
  */
-void sysReleaseShmem(MemMapping* pMap)
+void sysReleaseMap(MemMapping* pMap)
 {
-    if (pMap->baseAddr == NULL && pMap->baseLength == 0)
-        return;
-
-    if (munmap(pMap->baseAddr, pMap->baseLength) < 0) {
-        LOGW("munmap(%p, %d) failed: %s\n",
-            pMap->baseAddr, (int)pMap->baseLength, strerror(errno));
-    } else {
-        LOGV("munmap(%p, %d) succeeded\n", pMap->baseAddr, pMap->baseLength);
-        pMap->baseAddr = NULL;
-        pMap->baseLength = 0;
+    int i;
+    for (i = 0; i < pMap->range_count; ++i) {
+        if (munmap(pMap->ranges[i].addr, pMap->ranges[i].length) < 0) {
+            LOGW("munmap(%p, %d) failed: %s\n",
+                 pMap->ranges[i].addr, (int)pMap->ranges[i].length, strerror(errno));
+        }
     }
+    free(pMap->ranges);
+    pMap->ranges = NULL;
+    pMap->range_count = 0;
 }
diff --git a/minzip/SysUtil.h b/minzip/SysUtil.h
index 55cd0e7..7adff1e 100644
--- a/minzip/SysUtil.h
+++ b/minzip/SysUtil.h
@@ -6,39 +6,47 @@
 #ifndef _MINZIP_SYSUTIL
 #define _MINZIP_SYSUTIL
 
-#include "inline_magic.h"
-
+#include <stdio.h>
 #include <sys/types.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct MappedRange {
+    void* addr;
+    size_t length;
+} MappedRange;
+
 /*
  * Use this to keep track of mapped segments.
  */
 typedef struct MemMapping {
-    void*   addr;           /* start of data */
-    size_t  length;         /* length of data */
+    unsigned char* addr;           /* start of data */
+    size_t         length;         /* length of data */
 
-    void*   baseAddr;       /* page-aligned base address */
-    size_t  baseLength;     /* length of mapping */
+    int            range_count;
+    MappedRange*   ranges;
 } MemMapping;
 
-/* copy a map */
-INLINE void sysCopyMap(MemMapping* dst, const MemMapping* src) {
-    *dst = *src;
-}
-
 /*
- * Map a file (from fd's current offset) into a shared,
- * read-only memory segment.
+ * Map a file into a private, read-only memory segment.  If 'fn'
+ * begins with an '@' character, it is a map of blocks to be mapped,
+ * otherwise it is treated as an ordinary file.
  *
  * On success, "pMap" is filled in, and zero is returned.
  */
-int sysMapFileInShmem(int fd, MemMapping* pMap);
+int sysMapFile(const char* fn, MemMapping* pMap);
 
 /*
  * Release the pages associated with a shared memory segment.
  *
  * This does not free "pMap"; it just releases the memory.
  */
-void sysReleaseShmem(MemMapping* pMap);
+void sysReleaseMap(MemMapping* pMap);
+
+#ifdef __cplusplus
+}
+#endif
 
 #endif /*_MINZIP_SYSUTIL*/
diff --git a/minzip/Zip.c b/minzip/Zip.c
index 439e5d9..6752bce 100644
--- a/minzip/Zip.c
+++ b/minzip/Zip.c
@@ -184,7 +184,7 @@
  *
  * Returns "true" on success.
  */
-static bool parseZipArchive(ZipArchive* pArchive, const MemMapping* pMap)
+static bool parseZipArchive(ZipArchive* pArchive)
 {
     bool result = false;
     const unsigned char* ptr;
@@ -196,7 +196,7 @@
      * signature for the first file (LOCSIG) or, if the archive doesn't
      * have any files in it, the end-of-central-directory signature (ENDSIG).
      */
-    val = get4LE(pMap->addr);
+    val = get4LE(pArchive->addr);
     if (val == ENDSIG) {
         LOGI("Found Zip archive, but it looks empty\n");
         goto bail;
@@ -209,14 +209,14 @@
      * Find the EOCD.  We'll find it immediately unless they have a file
      * comment.
      */
-    ptr = pMap->addr + pMap->length - ENDHDR;
+    ptr = pArchive->addr + pArchive->length - ENDHDR;
 
-    while (ptr >= (const unsigned char*) pMap->addr) {
+    while (ptr >= (const unsigned char*) pArchive->addr) {
         if (*ptr == (ENDSIG & 0xff) && get4LE(ptr) == ENDSIG)
             break;
         ptr--;
     }
-    if (ptr < (const unsigned char*) pMap->addr) {
+    if (ptr < (const unsigned char*) pArchive->addr) {
         LOGI("Could not find end-of-central-directory in Zip\n");
         goto bail;
     }
@@ -230,9 +230,9 @@
     cdOffset = get4LE(ptr + ENDOFF);
 
     LOGVV("numEntries=%d cdOffset=%d\n", numEntries, cdOffset);
-    if (numEntries == 0 || cdOffset >= pMap->length) {
+    if (numEntries == 0 || cdOffset >= pArchive->length) {
         LOGW("Invalid entries=%d offset=%d (len=%zd)\n",
-            numEntries, cdOffset, pMap->length);
+            numEntries, cdOffset, pArchive->length);
         goto bail;
     }
 
@@ -245,14 +245,14 @@
     if (pArchive->pEntries == NULL || pArchive->pHash == NULL)
         goto bail;
 
-    ptr = pMap->addr + cdOffset;
+    ptr = pArchive->addr + cdOffset;
     for (i = 0; i < numEntries; i++) {
         ZipEntry* pEntry;
         unsigned int fileNameLen, extraLen, commentLen, localHdrOffset;
         const unsigned char* localHdr;
         const char *fileName;
 
-        if (ptr + CENHDR > (const unsigned char*)pMap->addr + pMap->length) {
+        if (ptr + CENHDR > (const unsigned char*)pArchive->addr + pArchive->length) {
             LOGW("Ran off the end (at %d)\n", i);
             goto bail;
         }
@@ -266,7 +266,7 @@
         extraLen = get2LE(ptr + CENEXT);
         commentLen = get2LE(ptr + CENCOM);
         fileName = (const char*)ptr + CENHDR;
-        if (fileName + fileNameLen > (const char*)pMap->addr + pMap->length) {
+        if (fileName + fileNameLen > (const char*)pArchive->addr + pArchive->length) {
             LOGW("Filename ran off the end (at %d)\n", i);
             goto bail;
         }
@@ -352,15 +352,15 @@
         }
         pEntry->externalFileAttributes = get4LE(ptr + CENATX);
 
-        // Perform pMap->addr + localHdrOffset, ensuring that it won't
+        // Perform pArchive->addr + localHdrOffset, ensuring that it won't
         // overflow. This is needed because localHdrOffset is untrusted.
-        if (!safe_add((uintptr_t *)&localHdr, (uintptr_t)pMap->addr,
+        if (!safe_add((uintptr_t *)&localHdr, (uintptr_t)pArchive->addr,
             (uintptr_t)localHdrOffset)) {
             LOGW("Integer overflow adding in parseZipArchive\n");
             goto bail;
         }
         if ((uintptr_t)localHdr + LOCHDR >
-            (uintptr_t)pMap->addr + pMap->length) {
+            (uintptr_t)pArchive->addr + pArchive->length) {
             LOGW("Bad offset to local header: %d (at %d)\n", localHdrOffset, i);
             goto bail;
         }
@@ -374,7 +374,7 @@
             LOGW("Integer overflow adding in parseZipArchive\n");
             goto bail;
         }
-        if ((size_t)pEntry->offset + pEntry->compLen > pMap->length) {
+        if ((size_t)pEntry->offset + pEntry->compLen > pArchive->length) {
             LOGW("Data ran off the end (at %d)\n", i);
             goto bail;
         }
@@ -427,50 +427,30 @@
  *
  * On success, we fill out the contents of "pArchive".
  */
-int mzOpenZipArchive(const char* fileName, ZipArchive* pArchive)
+int mzOpenZipArchive(unsigned char* addr, size_t length, ZipArchive* pArchive)
 {
-    MemMapping map;
     int err;
 
-    LOGV("Opening archive '%s' %p\n", fileName, pArchive);
-
-    map.addr = NULL;
-    memset(pArchive, 0, sizeof(*pArchive));
-
-    pArchive->fd = open(fileName, O_RDONLY, 0);
-    if (pArchive->fd < 0) {
-        err = errno ? errno : -1;
-        LOGV("Unable to open '%s': %s\n", fileName, strerror(err));
-        goto bail;
-    }
-
-    if (sysMapFileInShmem(pArchive->fd, &map) != 0) {
-        err = -1;
-        LOGW("Map of '%s' failed\n", fileName);
-        goto bail;
-    }
-
-    if (map.length < ENDHDR) {
+    if (length < ENDHDR) {
         err = -1;
         LOGV("File '%s' too small to be zip (%zd)\n", fileName, map.length);
         goto bail;
     }
 
-    if (!parseZipArchive(pArchive, &map)) {
+    pArchive->addr = addr;
+    pArchive->length = length;
+
+    if (!parseZipArchive(pArchive)) {
         err = -1;
         LOGV("Parsing '%s' failed\n", fileName);
         goto bail;
     }
 
     err = 0;
-    sysCopyMap(&pArchive->map, &map);
-    map.addr = NULL;
 
 bail:
     if (err != 0)
         mzCloseZipArchive(pArchive);
-    if (map.addr != NULL)
-        sysReleaseShmem(&map);
     return err;
 }
 
@@ -483,16 +463,10 @@
 {
     LOGV("Closing archive %p\n", pArchive);
 
-    if (pArchive->fd >= 0)
-        close(pArchive->fd);
-    if (pArchive->map.addr != NULL)
-        sysReleaseShmem(&pArchive->map);
-
     free(pArchive->pEntries);
 
     mzHashTableFree(pArchive->pHash);
 
-    pArchive->fd = -1;
     pArchive->pHash = NULL;
     pArchive->pEntries = NULL;
 }
@@ -528,29 +502,7 @@
     const ZipEntry *pEntry, ProcessZipEntryContentsFunction processFunction,
     void *cookie)
 {
-    size_t bytesLeft = pEntry->compLen;
-    while (bytesLeft > 0) {
-        unsigned char buf[32 * 1024];
-        ssize_t n;
-        size_t count;
-        bool ret;
-
-        count = bytesLeft;
-        if (count > sizeof(buf)) {
-            count = sizeof(buf);
-        }
-        n = read(pArchive->fd, buf, count);
-        if (n < 0 || (size_t)n != count) {
-            LOGE("Can't read %zu bytes from zip file: %ld\n", count, n);
-            return false;
-        }
-        ret = processFunction(buf, n, cookie);
-        if (!ret) {
-            return false;
-        }
-        bytesLeft -= count;
-    }
-    return true;
+    return processFunction(pArchive->addr + pEntry->offset, pEntry->uncompLen, cookie);
 }
 
 static bool processDeflatedEntry(const ZipArchive *pArchive,
@@ -573,8 +525,8 @@
     zstream.zalloc = Z_NULL;
     zstream.zfree = Z_NULL;
     zstream.opaque = Z_NULL;
-    zstream.next_in = NULL;
-    zstream.avail_in = 0;
+    zstream.next_in = pArchive->addr + pEntry->offset;
+    zstream.avail_in = pEntry->compLen;
     zstream.next_out = (Bytef*) procBuf;
     zstream.avail_out = sizeof(procBuf);
     zstream.data_type = Z_UNKNOWN;
@@ -598,25 +550,6 @@
      * Loop while we have data.
      */
     do {
-        /* read as much as we can */
-        if (zstream.avail_in == 0) {
-            long getSize = (compRemaining > (long)sizeof(readBuf)) ?
-                        (long)sizeof(readBuf) : compRemaining;
-            LOGVV("+++ reading %ld bytes (%ld left)\n",
-                getSize, compRemaining);
-
-            int cc = read(pArchive->fd, readBuf, getSize);
-            if (cc != (int) getSize) {
-                LOGW("inflate read failed (%d vs %ld)\n", cc, getSize);
-                goto z_bail;
-            }
-
-            compRemaining -= getSize;
-
-            zstream.next_in = readBuf;
-            zstream.avail_in = getSize;
-        }
-
         /* uncompress the data */
         zerr = inflate(&zstream, Z_NO_FLUSH);
         if (zerr != Z_OK && zerr != Z_STREAM_END) {
@@ -676,12 +609,6 @@
     bool ret = false;
     off_t oldOff;
 
-    /* save current offset */
-    oldOff = lseek(pArchive->fd, 0, SEEK_CUR);
-
-    /* Seek to the beginning of the entry's compressed data. */
-    lseek(pArchive->fd, pEntry->offset, SEEK_SET);
-
     switch (pEntry->compression) {
     case STORED:
         ret = processStoredEntry(pArchive, pEntry, processFunction, cookie);
@@ -695,8 +622,6 @@
         break;
     }
 
-    /* restore file offset */
-    lseek(pArchive->fd, oldOff, SEEK_SET);
     return ret;
 }
 
diff --git a/minzip/Zip.h b/minzip/Zip.h
index c942828..05a2e60 100644
--- a/minzip/Zip.h
+++ b/minzip/Zip.h
@@ -46,11 +46,11 @@
  * One Zip archive.  Treat as opaque.
  */
 typedef struct ZipArchive {
-    int         fd;
-    unsigned int numEntries;
-    ZipEntry*   pEntries;
-    HashTable*  pHash;          // maps file name to ZipEntry
-    MemMapping  map;
+    unsigned int   numEntries;
+    ZipEntry*      pEntries;
+    HashTable*     pHash;          // maps file name to ZipEntry
+    unsigned char* addr;
+    size_t         length;
 } ZipArchive;
 
 /*
@@ -68,7 +68,7 @@
  * On success, returns 0 and populates "pArchive".  Returns nonzero errno
  * value on failure.
  */
-int mzOpenZipArchive(const char* fileName, ZipArchive* pArchive);
+int mzOpenZipArchive(unsigned char* addr, size_t length, ZipArchive* pArchive);
 
 /*
  * Close archive, releasing resources associated with it.
diff --git a/roots.cpp b/roots.cpp
index 47cea0b..28004a7 100644
--- a/roots.cpp
+++ b/roots.cpp
@@ -238,10 +238,16 @@
 
         if (strcmp(v->mount_point, "/tmp") == 0 ||
             strcmp(v->mount_point, "/cache") == 0) {
-            if (ensure_path_mounted(v->mount_point) != 0) return -1;
+            if (ensure_path_mounted(v->mount_point) != 0) {
+                LOGE("failed to mount %s\n", v->mount_point);
+                return -1;
+            }
 
         } else {
-            if (ensure_path_unmounted(v->mount_point) != 0) return -1;
+            if (ensure_path_unmounted(v->mount_point) != 0) {
+                LOGE("failed to unmount %s\n", v->mount_point);
+                return -1;
+            }
         }
     }
     return 0;
diff --git a/updater/updater.c b/updater/updater.c
index c7009fe..4e1cc9c 100644
--- a/updater/updater.c
+++ b/updater/updater.c
@@ -22,6 +22,7 @@
 #include "updater.h"
 #include "install.h"
 #include "minzip/Zip.h"
+#include "minzip/SysUtil.h"
 
 // Generated by the makefile, this function defines the
 // RegisterDeviceExtensions() function, which calls all the
@@ -65,19 +66,24 @@
 
     // Extract the script from the package.
 
-    char* package_data = argv[3];
+    const char* package_filename = argv[3];
+    MemMapping map;
+    if (sysMapFile(package_filename, &map) != 0) {
+        printf("failed to map package %s\n", argv[3]);
+        return 3;
+    }
     ZipArchive za;
     int err;
-    err = mzOpenZipArchive(package_data, &za);
+    err = mzOpenZipArchive(map.addr, map.length, &za);
     if (err != 0) {
         printf("failed to open package %s: %s\n",
-                package_data, strerror(err));
+               argv[3], strerror(err));
         return 3;
     }
 
     const ZipEntry* script_entry = mzFindZipEntry(&za, SCRIPT_NAME);
     if (script_entry == NULL) {
-        printf("failed to find %s in %s\n", SCRIPT_NAME, package_data);
+        printf("failed to find %s in %s\n", SCRIPT_NAME, package_filename);
         return 4;
     }
 
@@ -152,6 +158,7 @@
     if (updater_info.package_zip) {
         mzCloseZipArchive(updater_info.package_zip);
     }
+    sysReleaseMap(&map);
     free(script);
 
     return 0;
diff --git a/verifier.cpp b/verifier.cpp
index 0930fbd..55d58ee 100644
--- a/verifier.cpp
+++ b/verifier.cpp
@@ -111,15 +111,10 @@
 // Return VERIFY_SUCCESS, VERIFY_FAILURE (if any error is encountered
 // or no key matches the signature).
 
-int verify_file(const char* path, const Certificate* pKeys, unsigned int numKeys) {
+int verify_file(unsigned char* addr, size_t length,
+                const Certificate* pKeys, unsigned int numKeys) {
     ui->SetProgress(0.0);
 
-    FILE* f = fopen(path, "rb");
-    if (f == NULL) {
-        LOGE("failed to open %s (%s)\n", path, strerror(errno));
-        return VERIFY_FAILURE;
-    }
-
     // An archive with a whole-file signature will end in six bytes:
     //
     //   (2-byte signature start) $ff $ff (2-byte comment size)
@@ -131,22 +126,15 @@
 
 #define FOOTER_SIZE 6
 
-    if (fseek(f, -FOOTER_SIZE, SEEK_END) != 0) {
-        LOGE("failed to seek in %s (%s)\n", path, strerror(errno));
-        fclose(f);
+    if (length < FOOTER_SIZE) {
+        LOGE("not big enough to contain footer\n");
         return VERIFY_FAILURE;
     }
 
-    unsigned char footer[FOOTER_SIZE];
-    if (fread(footer, 1, FOOTER_SIZE, f) != FOOTER_SIZE) {
-        LOGE("failed to read footer from %s (%s)\n", path, strerror(errno));
-        fclose(f);
-        return VERIFY_FAILURE;
-    }
+    unsigned char* footer = addr + length - FOOTER_SIZE;
 
     if (footer[2] != 0xff || footer[3] != 0xff) {
         LOGE("footer is wrong\n");
-        fclose(f);
         return VERIFY_FAILURE;
     }
 
@@ -157,7 +145,6 @@
 
     if (signature_start <= FOOTER_SIZE) {
         LOGE("Signature start is in the footer");
-        fclose(f);
         return VERIFY_FAILURE;
     }
 
@@ -167,9 +154,8 @@
     // comment length.
     size_t eocd_size = comment_size + EOCD_HEADER_SIZE;
 
-    if (fseek(f, -eocd_size, SEEK_END) != 0) {
-        LOGE("failed to seek in %s (%s)\n", path, strerror(errno));
-        fclose(f);
+    if (length < eocd_size) {
+        LOGE("not big enough to contain EOCD\n");
         return VERIFY_FAILURE;
     }
 
@@ -177,26 +163,15 @@
     // This is everything except the signature data and length, which
     // includes all of the EOCD except for the comment length field (2
     // bytes) and the comment data.
-    size_t signed_len = ftell(f) + EOCD_HEADER_SIZE - 2;
+    size_t signed_len = length - eocd_size + EOCD_HEADER_SIZE - 2;
 
-    unsigned char* eocd = (unsigned char*)malloc(eocd_size);
-    if (eocd == NULL) {
-        LOGE("malloc for EOCD record failed\n");
-        fclose(f);
-        return VERIFY_FAILURE;
-    }
-    if (fread(eocd, 1, eocd_size, f) != eocd_size) {
-        LOGE("failed to read eocd from %s (%s)\n", path, strerror(errno));
-        fclose(f);
-        return VERIFY_FAILURE;
-    }
+    unsigned char* eocd = addr + length - eocd_size;
 
     // If this is really is the EOCD record, it will begin with the
     // magic number $50 $4b $05 $06.
     if (eocd[0] != 0x50 || eocd[1] != 0x4b ||
         eocd[2] != 0x05 || eocd[3] != 0x06) {
         LOGE("signature length doesn't match EOCD marker\n");
-        fclose(f);
         return VERIFY_FAILURE;
     }
 
@@ -209,7 +184,6 @@
             // which could be exploitable.  Fail verification if
             // this sequence occurs anywhere after the real one.
             LOGE("EOCD marker occurs after start of EOCD\n");
-            fclose(f);
             return VERIFY_FAILURE;
         }
     }
@@ -229,35 +203,23 @@
     SHA256_CTX sha256_ctx;
     SHA_init(&sha1_ctx);
     SHA256_init(&sha256_ctx);
-    unsigned char* buffer = (unsigned char*)malloc(BUFFER_SIZE);
-    if (buffer == NULL) {
-        LOGE("failed to alloc memory for sha1 buffer\n");
-        fclose(f);
-        return VERIFY_FAILURE;
-    }
 
     double frac = -1.0;
     size_t so_far = 0;
-    fseek(f, 0, SEEK_SET);
     while (so_far < signed_len) {
-        size_t size = BUFFER_SIZE;
-        if (signed_len - so_far < size) size = signed_len - so_far;
-        if (fread(buffer, 1, size, f) != size) {
-            LOGE("failed to read data from %s (%s)\n", path, strerror(errno));
-            fclose(f);
-            return VERIFY_FAILURE;
-        }
-        if (need_sha1) SHA_update(&sha1_ctx, buffer, size);
-        if (need_sha256) SHA256_update(&sha256_ctx, buffer, size);
+        size_t size = signed_len - so_far;
+        if (size > BUFFER_SIZE) size = BUFFER_SIZE;
+
+        if (need_sha1) SHA_update(&sha1_ctx, addr + so_far, size);
+        if (need_sha256) SHA256_update(&sha256_ctx, addr + so_far, size);
         so_far += size;
+
         double f = so_far / (double)signed_len;
         if (f > frac + 0.02 || size == so_far) {
             ui->SetProgress(f);
             frac = f;
         }
     }
-    fclose(f);
-    free(buffer);
 
     const uint8_t* sha1 = SHA_final(&sha1_ctx);
     const uint8_t* sha256 = SHA256_final(&sha256_ctx);
@@ -269,10 +231,8 @@
     if (!read_pkcs7(eocd + eocd_size - signature_start, signature_size, &sig_der,
             &sig_der_length)) {
         LOGE("Could not find signature DER block\n");
-        free(eocd);
         return VERIFY_FAILURE;
     }
-    free(eocd);
 
     /*
      * Check to make sure at least one of the keys matches the signature. Since
diff --git a/verifier.h b/verifier.h
index 023d3bf..15f8d98 100644
--- a/verifier.h
+++ b/verifier.h
@@ -37,10 +37,13 @@
     ECPublicKey* ec;
 } Certificate;
 
-/* Look in the file for a signature footer, and verify that it
- * matches one of the given keys.  Return one of the constants below.
+/* addr and length define a an update package file that has been
+ * loaded (or mmap'ed, or whatever) into memory.  Verify that the file
+ * is signed and the signature matches one of the given keys.  Return
+ * one of the constants below.
  */
-int verify_file(const char* path, const Certificate *pKeys, unsigned int numKeys);
+int verify_file(unsigned char* addr, size_t length,
+                const Certificate *pKeys, unsigned int numKeys);
 
 Certificate* load_keys(const char* filename, int* numKeys);
 
diff --git a/verifier_test.cpp b/verifier_test.cpp
index 88fcad4..10a5dda 100644
--- a/verifier_test.cpp
+++ b/verifier_test.cpp
@@ -17,12 +17,16 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 
 #include "common.h"
 #include "verifier.h"
 #include "ui.h"
 #include "mincrypt/sha.h"
 #include "mincrypt/sha256.h"
+#include "minzip/SysUtil.h"
 
 // This is build/target/product/security/testkey.x509.pem after being
 // dumped out by dumpkey.jar.
@@ -227,7 +231,13 @@
 
     ui = new FakeUI();
 
-    int result = verify_file(argv[argn], certs, num_keys);
+    MemMapping map;
+    if (sysMapFile(argv[argn], &map) != 0) {
+        fprintf(stderr, "failed to mmap %s: %s\n", argv[argn], strerror(errno));
+        return 4;
+    }
+
+    int result = verify_file(map.addr, map.length, certs, num_keys);
     if (result == VERIFY_SUCCESS) {
         printf("VERIFIED\n");
         return 0;