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Add magic value

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This commit is contained in:
jpirnay
2026-03-08 16:26:52 +01:00
parent a3a50c8c40
commit ed1a21fb7b
2 changed files with 21 additions and 9 deletions
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lib/Logging/Logging.cpp
+17 -5
View File
@@ -8,14 +8,25 @@
// Simple ring buffer log, useful for error reporting when we encounter a crash // Simple ring buffer log, useful for error reporting when we encounter a crash
RTC_NOINIT_ATTR char logMessages[MAX_LOG_LINES][MAX_ENTRY_LEN]; RTC_NOINIT_ATTR char logMessages[MAX_LOG_LINES][MAX_ENTRY_LEN];
RTC_NOINIT_ATTR size_t logHead = 0; RTC_NOINIT_ATTR size_t logHead = 0;
// Magic word written alongside logHead to detect uninitialized RTC memory.
// RTC_NOINIT_ATTR is not zeroed on cold boot, so logHead may appear in-range
// (0..MAX_LOG_LINES-1) by chance even though logMessages is garbage. The magic
// value is only set by clearLastLogs(), so its absence means the buffer was
// never properly initialized.
RTC_NOINIT_ATTR uint32_t rtcLogMagic;
static constexpr uint32_t fnv1a32(const char* s, uint32_t h = 2166136261u) {
return *s ? fnv1a32(s + 1, (h ^ static_cast<uint32_t>(*s)) * 16777619u) : h;
}
static constexpr uint32_t LOG_RTC_MAGIC = fnv1a32("crosspoint-reader");
void addToLogRingBuffer(const char* message) { void addToLogRingBuffer(const char* message) {
// Add the message to the ring buffer, overwriting old messages if necessary // Add the message to the ring buffer, overwriting old messages if necessary.
// If RTC_NOINIT_ATTR left logHead out of range on cold boot, all slots are // If the magic is wrong or logHead is out of range (RTC_NOINIT_ATTR garbage
// garbage too — clear the entire buffer so subsequent reads are safe. // on cold boot), clear the entire buffer so subsequent reads are safe.
if (logHead >= MAX_LOG_LINES) { if (rtcLogMagic != LOG_RTC_MAGIC || logHead >= MAX_LOG_LINES) {
memset(logMessages, 0, sizeof(logMessages)); memset(logMessages, 0, sizeof(logMessages));
logHead = 0; logHead = 0;
rtcLogMagic = LOG_RTC_MAGIC;
} }
strncpy(logMessages[logHead], message, MAX_ENTRY_LEN - 1); strncpy(logMessages[logHead], message, MAX_ENTRY_LEN - 1);
logMessages[logHead][MAX_ENTRY_LEN - 1] = '\0'; logMessages[logHead][MAX_ENTRY_LEN - 1] = '\0';
@@ -81,7 +92,7 @@ std::string getLastLogs() {
} }
bool sanitizeLogHead() { bool sanitizeLogHead() {
if (logHead >= MAX_LOG_LINES) { if (rtcLogMagic != LOG_RTC_MAGIC || logHead >= MAX_LOG_LINES) {
logHead = 0; logHead = 0;
return true; return true;
} }
@@ -93,4 +104,5 @@ void clearLastLogs() {
logMessages[i][0] = '\0'; logMessages[i][0] = '\0';
} }
logHead = 0; logHead = 0;
rtcLogMagic = LOG_RTC_MAGIC;
} }
lib/Logging/Logging.h
+4 -4
View File
@@ -57,10 +57,10 @@ void logPrintf(const char* level, const char* origin, const char* format, ...);
std::string getLastLogs(); std::string getLastLogs();
void clearLastLogs(); void clearLastLogs();
// Clamps logHead into range. Returns true if logHead was out of range (repaired), // Validates the RTC log state (magic word + logHead range). Returns true if
// which also means logMessages is untrusted garbage. Callers should call // corruption was detected (magic mismatch or logHead out of range), meaning
// clearLastLogs() when this returns true so getLastLogs() does not dump corrupt // logMessages is untrusted garbage. Callers should call clearLastLogs() when
// data into crash reports. // this returns true so getLastLogs() does not dump corrupt data into crash reports.
bool sanitizeLogHead(); bool sanitizeLogHead();
class MySerialImpl : public Print { class MySerialImpl : public Print {