From 945fc68c62692467ddb8b7d714bcf0bf01c783c2 Mon Sep 17 00:00:00 2001
From: Doug Zongker <dougz@google.com>
Date: Thu, 10 Jul 2014 10:50:39 -0700
Subject: do sdcard sideloading through the fuse filesystem

Make a fuse filesystem that sits on top of the selected package file
on the sdcard, so we can verify that the file contents don't change
while being read and avoid copying the file to /tmp (that is, RAM)
before verifying and installing it.

Change-Id: Ifd982aa68bfe469eda5f839042648654bf7386a1
---
 fuse_sdcard_provider.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 fuse_sdcard_provider.c

(limited to 'fuse_sdcard_provider.c')

diff --git a/fuse_sdcard_provider.c b/fuse_sdcard_provider.c
new file mode 100644
index 000000000..19fb52df0
--- /dev/null
+++ b/fuse_sdcard_provider.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright (C) 2014 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 <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <pthread.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "fuse_sideload.h"
+
+struct file_data {
+    int fd;  // the underlying sdcard file
+
+    uint64_t file_size;
+    uint32_t block_size;
+};
+
+static int read_block_file(void* cookie, uint32_t block, uint8_t* buffer, uint32_t fetch_size) {
+    struct file_data* fd = (struct file_data*)cookie;
+
+    if (lseek(fd->fd, block * fd->block_size, SEEK_SET) < 0) {
+        printf("seek on sdcard failed: %s\n", strerror(errno));
+        return -EIO;
+    }
+
+    while (fetch_size > 0) {
+        ssize_t r = read(fd->fd, buffer, fetch_size);
+        if (r < 0) {
+            if (r != -EINTR) {
+                printf("read on sdcard failed: %s\n", strerror(errno));
+                return -EIO;
+            }
+            r = 0;
+        }
+        fetch_size -= r;
+        buffer += r;
+    }
+
+    return 0;
+}
+
+static void close_file(void* cookie) {
+    struct file_data* fd = (struct file_data*)cookie;
+    close(fd->fd);
+}
+
+struct token {
+    pthread_t th;
+    const char* path;
+    int result;
+};
+
+static void* run_sdcard_fuse(void* cookie) {
+    struct token* t = (struct token*)cookie;
+
+    struct stat sb;
+    if (stat(t->path, &sb) < 0) {
+        fprintf(stderr, "failed to stat %s: %s\n", t->path, strerror(errno));
+        t->result = -1;
+        return NULL;
+    }
+
+    struct file_data fd;
+    struct provider_vtab vtab;
+
+    fd.fd = open(t->path, O_RDONLY);
+    if (fd.fd < 0) {
+        fprintf(stderr, "failed to open %s: %s\n", t->path, strerror(errno));
+        t->result = -1;
+        return NULL;
+    }
+    fd.file_size = sb.st_size;
+    fd.block_size = 65536;
+
+    vtab.read_block = read_block_file;
+    vtab.close = close_file;
+
+    t->result = run_fuse_sideload(&vtab, &fd, fd.file_size, fd.block_size);
+    return NULL;
+}
+
+// How long (in seconds) we wait for the fuse-provided package file to
+// appear, before timing out.
+#define SDCARD_INSTALL_TIMEOUT 10
+
+void* start_sdcard_fuse(const char* path) {
+    struct token* t = malloc(sizeof(struct token));
+
+    t->path = path;
+    pthread_create(&(t->th), NULL, run_sdcard_fuse, t);
+
+    struct stat st;
+    int i;
+    for (i = 0; i < SDCARD_INSTALL_TIMEOUT; ++i) {
+        if (stat(FUSE_SIDELOAD_HOST_PATHNAME, &st) != 0) {
+            if (errno == ENOENT && i < SDCARD_INSTALL_TIMEOUT-1) {
+                sleep(1);
+                continue;
+            } else {
+                return NULL;
+            }
+        }
+    }
+
+    // The installation process expects to find the sdcard unmounted.
+    // Unmount it with MNT_DETACH so that our open file continues to
+    // work but new references see it as unmounted.
+    umount2("/sdcard", MNT_DETACH);
+
+    return t;
+}
+
+void finish_sdcard_fuse(void* cookie) {
+    if (cookie == NULL) return;
+    struct token* t = (struct token*)cookie;
+
+    // Calling stat() on this magic filename signals the fuse
+    // filesystem to shut down.
+    struct stat st;
+    stat(FUSE_SIDELOAD_HOST_EXIT_PATHNAME, &st);
+
+    pthread_join(t->th, NULL);
+    free(t);
+}
-- 
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