clear BCB in misc partition before rebooting

Something is leaving behind wipe commands in the BCB area of the /misc
partition.  We don't know what is doing that.  It should always be
safe to zero out that area from uncrypt, though (because if uncrypt is
running then it's got the command we want in the recovery command file
rather than the BCB).

Bug: 16715412
Change-Id: Iad01124287f13b80ff71d6371db6371f43c43211

1 files changed, 43 insertions, 3 deletions

diff --git a/uncrypt/uncrypt.c b/uncrypt/uncrypt.c
index bce53db..77bfdc2 100644
--- a/uncrypt/uncrypt.c
+++ b/uncrypt/uncrypt.c
@@ -56,6 +56,8 @@
 #define RECOVERY_COMMAND_FILE_TMP "/cache/recovery/command.tmp"
 #define CACHE_BLOCK_MAP "/cache/recovery/block.map"
 
+static struct fstab* fstab = NULL;
+
 static int write_at_offset(unsigned char* buffer, size_t size,
                            int wfd, off64_t offset)
 {
@@ -101,8 +103,10 @@ void add_block_to_ranges(int** ranges, int* range_alloc, int* range_used, int ne
     }
 }
 
-const char* find_block_device(const char* path, int* encryptable, int* encrypted)
+static struct fstab* read_fstab()
 {
+    fstab = NULL;
+
     // The fstab path is always "/fstab.${ro.hardware}".
     char fstab_path[PATH_MAX+1] = "/fstab.";
     if (!property_get("ro.hardware", fstab_path+strlen(fstab_path), "")) {
@@ -110,12 +114,17 @@ const char* find_block_device(const char* path, int* encryptable, int* encrypted
         return NULL;
     }
 
-    struct fstab* fstab = fs_mgr_read_fstab(fstab_path);
+    fstab = fs_mgr_read_fstab(fstab_path);
     if (!fstab) {
         fprintf(stderr, "failed to read %s\n", fstab_path);
         return NULL;
     }
 
+    return fstab;
+}
+
+const char* find_block_device(const char* path, int* encryptable, int* encrypted)
+{
     // Look for a volume whose mount point is the prefix of path and
     // return its block device.  Set encrypted if it's currently
     // encrypted.
@@ -302,6 +311,33 @@ int produce_block_map(const char* path, const char* map_file, const char* blk_de
     return 0;
 }
 
+void wipe_misc() {
+    int i;
+    for (i = 0; i < fstab->num_entries; ++i) {
+        struct fstab_rec* v = &fstab->recs[i];
+        if (!v->mount_point) continue;
+        if (strcmp(v->mount_point, "/misc") == 0) {
+            int fd = open(v->blk_device, O_RDWR);
+            uint8_t zeroes[1088];   // sizeof(bootloader_message) from recovery
+            memset(zeroes, 0, sizeof(zeroes));
+
+            size_t written = 0;
+            size_t size = sizeof(zeroes);
+            while (written < size) {
+                ssize_t w = write(fd, zeroes, size-written);
+                if (w < 0 && errno != EINTR) {
+                    fprintf(stderr, "zero write failed: %s\n", strerror(errno));
+                    return;
+                } else {
+                    written += w;
+                }
+            }
+
+            close(fd);
+        }
+    }
+}
+
 void reboot_to_recovery() {
     property_set("sys.powerctl", "reboot,recovery");
     sleep(10);
@@ -347,6 +383,9 @@ int main(int argc, char** argv)
 
     int encryptable;
     int encrypted;
+    if (read_fstab() == NULL) {
+        return 1;
+    }
     const char* blk_dev = find_block_device(path, &encryptable, &encrypted);
     if (blk_dev == NULL) {
         fprintf(stderr, "failed to find block device for %s\n", path);
@@ -376,7 +415,8 @@ int main(int argc, char** argv)
         }
     }
 
+    wipe_misc();
     rename(RECOVERY_COMMAND_FILE_TMP, RECOVERY_COMMAND_FILE);
-    reboot_to_recovery();
+    if (do_reboot) reboot_to_recovery();
     return 0;
 }