diff --git a/applypatch/applypatch.cpp b/applypatch/applypatch.cpp
index 9fbfc99..c8594c2 100644
--- a/applypatch/applypatch.cpp
+++ b/applypatch/applypatch.cpp
@@ -34,8 +34,8 @@
 #include "applypatch/applypatch.h"
 #include "mtdutils/mtdutils.h"
 #include "edify/expr.h"
+#include "ota_io.h"
 #include "print_sha1.h"
-#include "otafault/ota_io.h"
 
 static int LoadPartitionContents(const char* filename, FileContents* file);
 static ssize_t FileSink(const unsigned char* data, ssize_t len, void* token);
diff --git a/otafault/Android.mk b/otafault/Android.mk
index d441a77..33308c7 100644
--- a/otafault/Android.mk
+++ b/otafault/Android.mk
@@ -1,10 +1,10 @@
-# Copyright 2015 The ANdroid Open Source Project
+# Copyright 2015 The Android Open Source Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
-# 	   http://www.apache.org/licenses/LICENSE-2.0
+#      http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ -14,29 +14,20 @@
 
 LOCAL_PATH := $(call my-dir)
 
-empty :=
-space := $(empty) $(empty)
-comma := ,
-
-ifneq ($(TARGET_INJECT_FAULTS),)
-TARGET_INJECT_FAULTS := $(subst $(comma),$(space),$(strip $(TARGET_INJECT_FAULTS)))
-endif
-
 include $(CLEAR_VARS)
 
-LOCAL_SRC_FILES := ota_io.cpp
+otafault_static_libs := \
+    libminzip \
+    libz \
+    libselinux \
+
+LOCAL_SRC_FILES := config.cpp ota_io.cpp
 LOCAL_MODULE_TAGS := eng
 LOCAL_MODULE := libotafault
 LOCAL_CLANG := true
-
-ifneq ($(TARGET_INJECT_FAULTS),)
-$(foreach ft,$(TARGET_INJECT_FAULTS),\
-	$(eval LOCAL_CFLAGS += -DTARGET_$(ft)_FAULT=$(TARGET_$(ft)_FAULT_FILE)))
-LOCAL_CFLAGS += -Wno-unused-parameter
-LOCAL_CFLAGS += -DTARGET_INJECT_FAULTS
-endif
-
-LOCAL_STATIC_LIBRARIES := libc
+LOCAL_C_INCLUDES := bootable/recovery
+LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
+LOCAL_WHOLE_STATIC_LIBRARIES := $(otafault_static_libs)
 
 include $(BUILD_STATIC_LIBRARY)
 
@@ -44,17 +35,11 @@
 # ===============================
 include $(CLEAR_VARS)
 
-LOCAL_SRC_FILES := ota_io.cpp test.cpp
+LOCAL_SRC_FILES := config.cpp ota_io.cpp test.cpp
 LOCAL_MODULE_TAGS := tests
 LOCAL_MODULE := otafault_test
-LOCAL_STATIC_LIBRARIES := libc
+LOCAL_STATIC_LIBRARIES := $(otafault_static_libs)
+LOCAL_C_INCLUDES := bootable/recovery
 LOCAL_FORCE_STATIC_EXECUTABLE := true
-LOCAL_CFLAGS += -Wno-unused-parameter -Wno-writable-strings
-
-ifneq ($(TARGET_INJECT_FAULTS),)
-$(foreach ft,$(TARGET_INJECT_FAULTS),\
-	$(eval LOCAL_CFLAGS += -DTARGET_$(ft)_FAULT=$(TARGET_$(ft)_FAULT_FILE)))
-LOCAL_CFLAGS += -DTARGET_INJECT_FAULTS
-endif
 
 include $(BUILD_EXECUTABLE)
diff --git a/otafault/config.cpp b/otafault/config.cpp
new file mode 100644
index 0000000..aa4b4d5
--- /dev/null
+++ b/otafault/config.cpp
@@ -0,0 +1,70 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <map>
+#include <string>
+
+#include <stdio.h>
+#include <unistd.h>
+
+#include "minzip/Zip.h"
+#include "config.h"
+#include "ota_io.h"
+
+#define OTAIO_MAX_FNAME_SIZE 128
+
+static ZipArchive* archive;
+static std::map<const char*, bool> should_inject_cache;
+
+static const char* get_type_path(const char* io_type) {
+    char* path = (char*)calloc(strlen(io_type) + strlen(OTAIO_BASE_DIR) + 2, sizeof(char));
+    sprintf(path, "%s/%s", OTAIO_BASE_DIR, io_type);
+    return path;
+}
+
+void ota_io_init(ZipArchive* za) {
+    archive = za;
+    ota_set_fault_files();
+}
+
+bool should_fault_inject(const char* io_type) {
+    // archive will be NULL if we used an entry point other
+    // than updater/updater.cpp:main
+    if (archive == NULL) {
+        return false;
+    }
+    if (should_inject_cache.find(io_type) != should_inject_cache.end()) {
+        return should_inject_cache[io_type];
+    }
+    const char* type_path = get_type_path(io_type);
+    const ZipEntry* entry = mzFindZipEntry(archive, type_path);
+    should_inject_cache[type_path] = entry != nullptr;
+    free((void*)type_path);
+    return entry != NULL;
+}
+
+bool should_hit_cache() {
+    return should_fault_inject(OTAIO_CACHE);
+}
+
+std::string fault_fname(const char* io_type) {
+    const char* type_path = get_type_path(io_type);
+    char* fname = (char*) calloc(OTAIO_MAX_FNAME_SIZE, sizeof(char));
+    const ZipEntry* entry = mzFindZipEntry(archive, type_path);
+    mzReadZipEntry(archive, entry, fname, OTAIO_MAX_FNAME_SIZE);
+    free((void*)type_path);
+    return std::string(fname);
+}
diff --git a/otafault/config.h b/otafault/config.h
new file mode 100644
index 0000000..4430be3
--- /dev/null
+++ b/otafault/config.h
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Read configuration files in the OTA package to determine which files, if any, will trigger errors.
+ *
+ * OTA packages can be modified to trigger errors by adding a top-level
+ * directory called .libotafault, which may optionally contain up to three
+ * files called READ, WRITE, and FSYNC. Each one of these optional files
+ * contains the name of a single file on the device disk which will cause
+ * an IO error on the first call of the appropriate I/O action to that file.
+ *
+ * Example:
+ * ota.zip
+ *   <normal package contents>
+ *   .libotafault
+ *     WRITE
+ *
+ * If the contents of the file WRITE were /system/build.prop, the first write
+ * action to /system/build.prop would fail with EIO. Note that READ and
+ * FSYNC files are absent, so these actions will not cause an error.
+ */
+
+#ifndef _UPDATER_OTA_IO_CFG_H_
+#define _UPDATER_OTA_IO_CFG_H_
+
+#include <string>
+
+#include <stdbool.h>
+
+#include "minzip/Zip.h"
+
+#define OTAIO_BASE_DIR ".libotafault"
+#define OTAIO_READ "READ"
+#define OTAIO_WRITE "WRITE"
+#define OTAIO_FSYNC "FSYNC"
+#define OTAIO_CACHE "CACHE"
+
+/*
+ * Initialize libotafault by providing a reference to the OTA package.
+ */
+void ota_io_init(ZipArchive* za);
+
+/*
+ * Return true if a config file is present for the given IO type.
+ */
+bool should_fault_inject(const char* io_type);
+
+/*
+ * Return true if an EIO should occur on the next hit to /cache/saved.file
+ * instead of the next hit to the specified file.
+ */
+bool should_hit_cache();
+
+/*
+ * Return the name of the file that should cause an error for the
+ * given IO type.
+ */
+std::string fault_fname(const char* io_type);
+
+#endif
diff --git a/otafault/ota_io.cpp b/otafault/ota_io.cpp
index 2d08fde..94be815 100644
--- a/otafault/ota_io.cpp
+++ b/otafault/ota_io.cpp
@@ -14,9 +14,7 @@
  * limitations under the License.
  */
 
-#if defined (TARGET_INJECT_FAULTS)
 #include <map>
-#endif
 
 #include <errno.h>
 #include <fcntl.h>
@@ -24,186 +22,156 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "config.h"
 #include "ota_io.h"
 
-#if defined (TARGET_INJECT_FAULTS)
-static std::map<int, const char*> FilenameCache;
-static std::string FaultFileName =
-#if defined (TARGET_READ_FAULT)
-        TARGET_READ_FAULT;
-#elif defined (TARGET_WRITE_FAULT)
-        TARGET_WRITE_FAULT;
-#elif defined (TARGET_FSYNC_FAULT)
-        TARGET_FSYNC_FAULT;
-#endif // defined (TARGET_READ_FAULT)
-#endif // defined (TARGET_INJECT_FAULTS)
+static std::map<intptr_t, const char*> filename_cache;
+static std::string read_fault_file_name = "";
+static std::string write_fault_file_name = "";
+static std::string fsync_fault_file_name = "";
+
+static bool get_hit_file(const char* cached_path, std::string ffn) {
+    return should_hit_cache()
+        ? !strncmp(cached_path, OTAIO_CACHE_FNAME, strlen(cached_path))
+        : !strncmp(cached_path, ffn.c_str(), strlen(cached_path));
+}
+
+void ota_set_fault_files() {
+    if (should_fault_inject(OTAIO_READ)) {
+        read_fault_file_name = fault_fname(OTAIO_READ);
+    }
+    if (should_fault_inject(OTAIO_WRITE)) {
+        write_fault_file_name = fault_fname(OTAIO_WRITE);
+    }
+    if (should_fault_inject(OTAIO_FSYNC)) {
+        fsync_fault_file_name = fault_fname(OTAIO_FSYNC);
+    }
+}
 
 bool have_eio_error = false;
 
 int ota_open(const char* path, int oflags) {
-#if defined (TARGET_INJECT_FAULTS)
     // Let the caller handle errors; we do not care if open succeeds or fails
     int fd = open(path, oflags);
-    FilenameCache[fd] = path;
+    filename_cache[fd] = path;
     return fd;
-#else
-    return open(path, oflags);
-#endif
 }
 
 int ota_open(const char* path, int oflags, mode_t mode) {
-#if defined (TARGET_INJECT_FAULTS)
     int fd = open(path, oflags, mode);
-    FilenameCache[fd] = path;
-    return fd;
-#else
-    return open(path, oflags, mode);
-#endif
-}
+    filename_cache[fd] = path;
+    return fd; }
 
 FILE* ota_fopen(const char* path, const char* mode) {
-#if defined (TARGET_INJECT_FAULTS)
     FILE* fh = fopen(path, mode);
-    FilenameCache[(intptr_t)fh] = path;
+    filename_cache[(intptr_t)fh] = path;
     return fh;
-#else
-    return fopen(path, mode);
-#endif
 }
 
 int ota_close(int fd) {
-#if defined (TARGET_INJECT_FAULTS)
-    // descriptors can be reused, so make sure not to leave them in the cahce
-    FilenameCache.erase(fd);
-#endif
+    // descriptors can be reused, so make sure not to leave them in the cache
+    filename_cache.erase(fd);
     return close(fd);
 }
 
 int ota_fclose(FILE* fh) {
-#if defined (TARGET_INJECT_FAULTS)
-    FilenameCache.erase((intptr_t)fh);
-#endif
+    filename_cache.erase((intptr_t)fh);
     return fclose(fh);
 }
 
 size_t ota_fread(void* ptr, size_t size, size_t nitems, FILE* stream) {
-#if defined (TARGET_READ_FAULT)
-    if (FilenameCache.find((intptr_t)stream) != FilenameCache.end()
-            && FilenameCache[(intptr_t)stream] == FaultFileName) {
-        FaultFileName = "";
-        errno = EIO;
-        have_eio_error = true;
-        return 0;
-    } else {
-        size_t status = fread(ptr, size, nitems, stream);
-        // If I/O error occurs, set the retry-update flag.
-        if (status != nitems && errno == EIO) {
+    if (should_fault_inject(OTAIO_READ)) {
+        auto cached = filename_cache.find((intptr_t)stream);
+        const char* cached_path = cached->second;
+        if (cached != filename_cache.end() &&
+                get_hit_file(cached_path, read_fault_file_name)) {
+            read_fault_file_name = "";
+            errno = EIO;
             have_eio_error = true;
+            return 0;
         }
-        return status;
     }
-#else
     size_t status = fread(ptr, size, nitems, stream);
     // If I/O error occurs, set the retry-update flag.
     if (status != nitems && errno == EIO) {
         have_eio_error = true;
     }
     return status;
-#endif
 }
 
 ssize_t ota_read(int fd, void* buf, size_t nbyte) {
-#if defined (TARGET_READ_FAULT)
-    if (FilenameCache.find(fd) != FilenameCache.end()
-            && FilenameCache[fd] == FaultFileName) {
-        FaultFileName = "";
-        errno = EIO;
-        have_eio_error = true;
-        return -1;
-    } else {
-        ssize_t status = read(fd, buf, nbyte);
-        if (status == -1 && errno == EIO) {
+    if (should_fault_inject(OTAIO_READ)) {
+        auto cached = filename_cache.find(fd);
+        const char* cached_path = cached->second;
+        if (cached != filename_cache.end()
+                && get_hit_file(cached_path, read_fault_file_name)) {
+            read_fault_file_name = "";
+            errno = EIO;
             have_eio_error = true;
+            return -1;
         }
-        return status;
     }
-#else
     ssize_t status = read(fd, buf, nbyte);
     if (status == -1 && errno == EIO) {
         have_eio_error = true;
     }
     return status;
-#endif
 }
 
 size_t ota_fwrite(const void* ptr, size_t size, size_t count, FILE* stream) {
-#if defined (TARGET_WRITE_FAULT)
-    if (FilenameCache.find((intptr_t)stream) != FilenameCache.end()
-            && FilenameCache[(intptr_t)stream] == FaultFileName) {
-        FaultFileName = "";
-        errno = EIO;
-        have_eio_error = true;
-        return 0;
-    } else {
-        size_t status = fwrite(ptr, size, count, stream);
-        if (status != count && errno == EIO) {
+    if (should_fault_inject(OTAIO_WRITE)) {
+        auto cached = filename_cache.find((intptr_t)stream);
+        const char* cached_path = cached->second;
+        if (cached != filename_cache.end() &&
+                get_hit_file(cached_path, write_fault_file_name)) {
+            write_fault_file_name = "";
+            errno = EIO;
             have_eio_error = true;
+            return 0;
         }
-        return status;
     }
-#else
     size_t status = fwrite(ptr, size, count, stream);
     if (status != count && errno == EIO) {
         have_eio_error = true;
     }
     return status;
-#endif
 }
 
 ssize_t ota_write(int fd, const void* buf, size_t nbyte) {
-#if defined (TARGET_WRITE_FAULT)
-    if (FilenameCache.find(fd) != FilenameCache.end()
-            && FilenameCache[fd] == FaultFileName) {
-        FaultFileName = "";
-        errno = EIO;
-        have_eio_error = true;
-        return -1;
-    } else {
-        ssize_t status = write(fd, buf, nbyte);
-        if (status == -1 && errno == EIO) {
+    if (should_fault_inject(OTAIO_WRITE)) {
+        auto cached = filename_cache.find(fd);
+        const char* cached_path = cached->second;
+        if (cached != filename_cache.end() &&
+                get_hit_file(cached_path, write_fault_file_name)) {
+            write_fault_file_name = "";
+            errno = EIO;
             have_eio_error = true;
+            return -1;
         }
-        return status;
     }
-#else
     ssize_t status = write(fd, buf, nbyte);
     if (status == -1 && errno == EIO) {
         have_eio_error = true;
     }
     return status;
-#endif
 }
 
 int ota_fsync(int fd) {
-#if defined (TARGET_FSYNC_FAULT)
-    if (FilenameCache.find(fd) != FilenameCache.end()
-            && FilenameCache[fd] == FaultFileName) {
-        FaultFileName = "";
-        errno = EIO;
-        have_eio_error = true;
-        return -1;
-    } else {
-        int status = fsync(fd);
-        if (status == -1 && errno == EIO) {
+    if (should_fault_inject(OTAIO_FSYNC)) {
+        auto cached = filename_cache.find(fd);
+        const char* cached_path = cached->second;
+        if (cached != filename_cache.end() &&
+                get_hit_file(cached_path, fsync_fault_file_name)) {
+            fsync_fault_file_name = "";
+            errno = EIO;
             have_eio_error = true;
+            return -1;
         }
-        return status;
     }
-#else
     int status = fsync(fd);
     if (status == -1 && errno == EIO) {
         have_eio_error = true;
     }
     return status;
-#endif
 }
+
diff --git a/otafault/ota_io.h b/otafault/ota_io.h
index 641a5ae..84187a7 100644
--- a/otafault/ota_io.h
+++ b/otafault/ota_io.h
@@ -26,6 +26,10 @@
 #include <stdio.h>
 #include <sys/stat.h>
 
+#define OTAIO_CACHE_FNAME "/cache/saved.file"
+
+void ota_set_fault_files();
+
 int ota_open(const char* path, int oflags);
 
 int ota_open(const char* path, int oflags, mode_t mode);
diff --git a/otafault/test.cpp b/otafault/test.cpp
index a0f7315..6514782 100644
--- a/otafault/test.cpp
+++ b/otafault/test.cpp
@@ -17,16 +17,18 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
+#include <unistd.h>
 
 #include "ota_io.h"
 
-int main(int argc, char **argv) {
+int main(int /* argc */, char** /* argv */) {
     int fd = open("testdata/test.file", O_RDWR);
     char buf[8];
-    char *out = "321";
+    const char* out = "321";
     int readv = ota_read(fd, buf, 4);
     printf("Read returned %d\n", readv);
     int writev = ota_write(fd, out, 4);
     printf("Write returned %d\n", writev);
+    close(fd);
     return 0;
 }
diff --git a/updater/blockimg.cpp b/updater/blockimg.cpp
index 44de4e0..56378d4 100644
--- a/updater/blockimg.cpp
+++ b/updater/blockimg.cpp
@@ -45,7 +45,7 @@
 #include "install.h"
 #include "openssl/sha.h"
 #include "minzip/Hash.h"
-#include "otafault/ota_io.h"
+#include "ota_io.h"
 #include "print_sha1.h"
 #include "unique_fd.h"
 #include "updater.h"
diff --git a/updater/install.cpp b/updater/install.cpp
index 413e147..bc4cca9 100644
--- a/updater/install.cpp
+++ b/updater/install.cpp
@@ -51,7 +51,7 @@
 #include "minzip/DirUtil.h"
 #include "mtdutils/mounts.h"
 #include "mtdutils/mtdutils.h"
-#include "otafault/ota_io.h"
+#include "ota_io.h"
 #include "updater.h"
 #include "install.h"
 #include "tune2fs.h"
diff --git a/updater/updater.cpp b/updater/updater.cpp
index f82097d..d2a7ac9 100644
--- a/updater/updater.cpp
+++ b/updater/updater.cpp
@@ -27,6 +27,7 @@
 #include "blockimg.h"
 #include "minzip/Zip.h"
 #include "minzip/SysUtil.h"
+#include "config.h"
 
 // Generated by the makefile, this function defines the
 // RegisterDeviceExtensions() function, which calls all the
@@ -86,6 +87,7 @@
                argv[3], strerror(err));
         return 3;
     }
+    ota_io_init(&za);
 
     const ZipEntry* script_entry = mzFindZipEntry(&za, SCRIPT_NAME);
     if (script_entry == NULL) {