PEL: Add function to generate unique PEL IDs

Create generatePELID() to return a unique 4B PEL ID every time it is
called. It will start at a base value, and then increment by 1 each
time.  It uses a file to save the next value to use.

This will be used by the PEL handling code to create unique values
for the error log ID field in the Private Header section.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I841a8dcc5dc48e2b663004be3dccfb114ba366f2

1 files changed, 97 insertions, 0 deletions

diff --git a/extensions/openpower-pels/log_id.cpp b/extensions/openpower-pels/log_id.cpp
new file mode 100644
index 0000000..cbe1247
--- /dev/null
+++ b/extensions/openpower-pels/log_id.cpp
@@ -0,0 +1,97 @@
+#include "log_id.hpp"
+
+#include "paths.hpp"
+
+#include <chrono>
+#include <filesystem>
+#include <fstream>
+#include <phosphor-logging/log.hpp>
+
+namespace openpower
+{
+namespace pels
+{
+
+namespace fs = std::filesystem;
+using namespace phosphor::logging;
+
+constexpr uint32_t startingLogID = 1;
+constexpr uint32_t bmcLogIDPrefix = 0x50000000;
+
+namespace detail
+{
+
+uint32_t addLogIDPrefix(uint32_t id)
+{
+    // If redundant BMCs are ever a thing, may need a different prefix.
+    return (id & 0x00FFFFFF) | bmcLogIDPrefix;
+}
+
+uint32_t getTimeBasedLogID()
+{
+    using namespace std::chrono;
+
+    // Use 3 bytes of the nanosecond count since the epoch.
+    uint32_t id =
+        duration_cast<nanoseconds>(system_clock::now().time_since_epoch())
+            .count();
+
+    return addLogIDPrefix(id);
+}
+
+} // namespace detail
+
+uint32_t generatePELID()
+{
+    // Note: there isn't a need to be thread safe.
+
+    static std::string idFilename;
+    if (idFilename.empty())
+    {
+        idFilename = getPELIDFile();
+    }
+
+    uint32_t id = 0;
+
+    if (!fs::exists(idFilename))
+    {
+        auto path = fs::path(idFilename).parent_path();
+        if (!fs::exists(path))
+        {
+            fs::create_directories(path);
+        }
+
+        id = startingLogID;
+    }
+    else
+    {
+        std::ifstream idFile{idFilename};
+        idFile >> id;
+        if (idFile.fail())
+        {
+            // Just make up an ID
+            log<level::ERR>("Unable to read PEL ID File!");
+            return detail::getTimeBasedLogID();
+        }
+    }
+
+    // Wrapping shouldn't be a problem, but check anyway
+    if (id == 0x00FFFFFF)
+    {
+        id = startingLogID;
+    }
+
+    std::ofstream idFile{idFilename};
+    idFile << (id + 1);
+    if (idFile.fail())
+    {
+        // Just make up an ID so we don't reuse one next time
+        log<level::ERR>("Unable to write PEL ID File!");
+        return detail::getTimeBasedLogID();
+    }
+
+    return detail::addLogIDPrefix(id);
+}
+
+} // namespace pels
+} // namespace openpower