recovery: save logs from the last few invocations of recovery

Extends the last_log mechanism to save logs from the last six
invocations of recovery, so that we're more likely to have useful logs
even if the device has repeatedly booted into recovery.

Change-Id: I08ae7a09553ada45f9e0733fe1e55e5a22efd9f9

1 files changed, 19 insertions, 1 deletions

diff --git a/recovery.cpp b/recovery.cpp
index a84d833..840e63c 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -59,10 +59,11 @@ static const struct option OPTIONS[] = {
   { NULL, 0, NULL, 0 },
 };
 
+#define LAST_LOG_FILE "/cache/recovery/last_log"
+
 static const char *COMMAND_FILE = "/cache/recovery/command";
 static const char *INTENT_FILE = "/cache/recovery/intent";
 static const char *LOG_FILE = "/cache/recovery/log";
-static const char *LAST_LOG_FILE = "/cache/recovery/last_log";
 static const char *LAST_INSTALL_FILE = "/cache/recovery/last_install";
 static const char *LOCALE_FILE = "/cache/recovery/last_locale";
 static const char *CACHE_ROOT = "/cache";
@@ -260,6 +261,21 @@ copy_log_file(const char* source, const char* destination, int append) {
     }
 }
 
+// Rename last_log -> last_log.1 -> last_log.2 -> ... -> last_log.$max
+// Overwrites any existing last_log.$max.
+static void
+rotate_last_logs(int max) {
+    char oldfn[256];
+    char newfn[256];
+
+    int i;
+    for (i = max-1; i >= 0; --i) {
+        snprintf(oldfn, sizeof(oldfn), (i==0) ? LAST_LOG_FILE : (LAST_LOG_FILE ".%d"), i);
+        snprintf(newfn, sizeof(newfn), LAST_LOG_FILE ".%d", i+1);
+        // ignore errors
+        rename(oldfn, newfn);
+    }
+}
 
 // clear the recovery command and prepare to boot a (hopefully working) system,
 // copy our log file to cache as well (for the system to read), and
@@ -843,6 +859,8 @@ main(int argc, char **argv) {
     printf("Starting recovery on %s", ctime(&start));
 
     load_volume_table();
+    ensure_path_mounted(LAST_LOG_FILE);
+    rotate_last_logs(5);
     get_args(&argc, &argv);
 
     int previous_runs = 0;