logd: refactor mLast setting into a GetOldest function
This code was duplicated throughout LogBuffer.cpp, so refactor it into
a single location and clean up some comments along the way.
This may fix a subtle bug: if `logcat -c` is used from a
non-privileged UID, the current code may set mLast to the oldest seen
log message *from that UID* and not not the oldest log message for
that log id. That may prevent pruning from the start of that log,
resulting in old log entries that are impossible to delete.
Bug: 144382260
Test: logging works, and above scenario is not seen
Change-Id: I1749293ce6ea1697dd8a9258cfd7eab29dbeac6e
diff --git a/logd/LogBuffer.cpp b/logd/LogBuffer.cpp
index 1f8ad05..36273de 100644
--- a/logd/LogBuffer.cpp
+++ b/logd/LogBuffer.cpp
@@ -46,9 +46,6 @@
void LogBuffer::init() {
log_id_for_each(i) {
- mLastSet[i] = false;
- mLast[i] = mLogElements.begin();
-
if (setSize(i, __android_logger_get_buffer_size(i))) {
setSize(i, LOG_BUFFER_MIN_SIZE);
}
@@ -131,6 +128,20 @@
}
}
+LogBufferElementCollection::iterator LogBuffer::GetOldest(log_id_t log_id) {
+ auto it = mLogElements.begin();
+ if (mOldest[log_id]) {
+ it = *mOldest[log_id];
+ }
+ while (it != mLogElements.end() && (*it)->getLogId() != log_id) {
+ it++;
+ }
+ if (it != mLogElements.end()) {
+ mOldest[log_id] = it;
+ }
+ return it;
+}
+
enum match_type { DIFFERENT, SAME, SAME_LIBLOG };
static enum match_type identical(LogBufferElement* elem,
@@ -450,9 +461,7 @@
bool setLast[LOG_ID_MAX];
bool doSetLast = false;
- log_id_for_each(i) {
- doSetLast |= setLast[i] = mLastSet[i] && (it == mLast[i]);
- }
+ log_id_for_each(i) { doSetLast |= setLast[i] = mOldest[i] && it == *mOldest[i]; }
#ifdef DEBUG_CHECK_FOR_STALE_ENTRIES
LogBufferElementCollection::iterator bad = it;
int key = ((id == LOG_ID_EVENTS) || (id == LOG_ID_SECURITY))
@@ -463,11 +472,11 @@
if (doSetLast) {
log_id_for_each(i) {
if (setLast[i]) {
- if (__predict_false(it == mLogElements.end())) { // impossible
- mLastSet[i] = false;
- mLast[i] = mLogElements.begin();
+ if (__predict_false(it == mLogElements.end())) {
+ mOldest[i] = std::nullopt;
} else {
- mLast[i] = it; // push down the road as next-best-watermark
+ mOldest[i] = it; // Store the next iterator even if it does not correspond to
+ // the same log_id, as a starting point for GetOldest().
}
}
}
@@ -486,11 +495,6 @@
b.first);
}
}
- if (mLastSet[i] && (bad == mLast[i])) {
- android::prdebug("stale mLast[%d]\n", i);
- mLastSet[i] = false;
- mLast[i] = mLogElements.begin();
- }
}
#endif
if (coalesce) {
@@ -668,7 +672,7 @@
if (__predict_false(caller_uid != AID_ROOT)) { // unlikely
// Only here if clear all request from non system source, so chatty
// filter logistics is not required.
- it = mLastSet[id] ? mLast[id] : mLogElements.begin();
+ it = GetOldest(id);
while (it != mLogElements.end()) {
LogBufferElement* element = *it;
@@ -678,11 +682,6 @@
continue;
}
- if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
- mLast[id] = it;
- mLastSet[id] = true;
- }
-
if (oldest && oldest->mStart <= element->getSequence()) {
busy = true;
kickMe(oldest, id, pruneRows);
@@ -734,8 +733,8 @@
}
bool kick = false;
- bool leading = true;
- it = mLastSet[id] ? mLast[id] : mLogElements.begin();
+ bool leading = true; // true if starting from the oldest log entry, false if starting from
+ // a specific chatty entry.
// Perform at least one mandatory garbage collection cycle in following
// - clear leading chatty tags
// - coalesce chatty tags
@@ -763,6 +762,9 @@
}
}
}
+ if (leading) {
+ it = GetOldest(id);
+ }
static const timespec too_old = { EXPIRE_HOUR_THRESHOLD * 60 * 60, 0 };
LogBufferElementCollection::iterator lastt;
lastt = mLogElements.end();
@@ -783,11 +785,6 @@
}
// below this point element->getLogId() == id
- if (leading && (!mLastSet[id] || ((*mLast[id])->getLogId() != id))) {
- mLast[id] = it;
- mLastSet[id] = true;
- }
-
uint16_t dropped = element->getDropped();
// remove any leading drops
@@ -909,7 +906,7 @@
bool whitelist = false;
bool hasWhitelist = (id != LOG_ID_SECURITY) && mPrune.nice() && !clearAll;
- it = mLastSet[id] ? mLast[id] : mLogElements.begin();
+ it = GetOldest(id);
while ((pruneRows > 0) && (it != mLogElements.end())) {
LogBufferElement* element = *it;
@@ -918,11 +915,6 @@
continue;
}
- if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
- mLast[id] = it;
- mLastSet[id] = true;
- }
-
if (oldest && oldest->mStart <= element->getSequence()) {
busy = true;
if (!whitelist) kickMe(oldest, id, pruneRows);
@@ -942,7 +934,7 @@
// Do not save the whitelist if we are reader range limited
if (whitelist && (pruneRows > 0)) {
- it = mLastSet[id] ? mLast[id] : mLogElements.begin();
+ it = GetOldest(id);
while ((it != mLogElements.end()) && (pruneRows > 0)) {
LogBufferElement* element = *it;
@@ -951,11 +943,6 @@
continue;
}
- if (!mLastSet[id] || ((*mLast[id])->getLogId() != id)) {
- mLast[id] = it;
- mLastSet[id] = true;
- }
-
if (oldest && oldest->mStart <= element->getSequence()) {
busy = true;
kickMe(oldest, id, pruneRows);