Write perfmap and jitdump files to /tmp by default [6.0 port] (#88486)

* Write perfmap and jitdump files to /tmp by default

* Simplify perfmap path generation

* Minor comment update

---------

Co-authored-by: David Mason <[email protected]>

src/coreclr/inc/clrconfigvalues.h

@@ -526,7 +526,7 @@ RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_ProfAPI_ValidateNGENInstrumentation, W("Pro
 
 #ifdef FEATURE_PERFMAP
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_PerfMapEnabled, W("PerfMapEnabled"), 0, "This flag is used on Linux to enable writing /tmp/perf-$pid.map. It is disabled by default")
-RETAIL_CONFIG_STRING_INFO(EXTERNAL_PerfMapJitDumpPath, W("PerfMapJitDumpPath"), "Specifies a path to write the perf jitdump file. Defaults to GetTempPathA()")
+RETAIL_CONFIG_STRING_INFO(EXTERNAL_PerfMapJitDumpPath, W("PerfMapJitDumpPath"), "Specifies a path to write the perf jitdump file. Defaults to /tmp")
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_PerfMapIgnoreSignal, W("PerfMapIgnoreSignal"), 0, "When perf map is enabled, this option will configure the specified signal to be accepted and ignored as a marker in the perf logs.  It is disabled by default")
 RETAIL_CONFIG_DWORD_INFO(EXTERNAL_PerfMapShowOptimizationTiers, W("PerfMapShowOptimizationTiers"), 1, "Shows optimization tiers in the perf map for methods, as part of the symbol name. Useful for seeing separate stack frames for different optimization tiers of each method.")
 RETAIL_CONFIG_STRING_INFO(EXTERNAL_NativeImagePerfMapFormat, W("NativeImagePerfMapFormat"), "Specifies the format of native image perfmap files generated by crossgen.  Valid options are RVA or OFFSET.")

src/coreclr/vm/perfinfo.cpp

@@ -10,19 +10,13 @@
 #include "perfinfo.h"
 #include "pal.h"
 
-PerfInfo::PerfInfo(int pid)
+PerfInfo::PerfInfo(int pid, const char* basePath)
   : m_Stream(nullptr)
 {
     LIMITED_METHOD_CONTRACT;
 
-    SString tempPath;
-    if (!WszGetTempPath(tempPath))
-    {
-        return;
-    }
-
     SString path;
-    path.Printf("%Sperfinfo-%d.map", tempPath.GetUnicode(), pid);
+    path.Printf("%s/perfinfo-%d.map", basePath, pid);
     OpenFile(path);
 }
 

src/coreclr/vm/perfinfo.h

@@ -20,7 +20,7 @@
 */
 class PerfInfo {
 public:
-    PerfInfo(int pid);
+    PerfInfo(int pid, const char* basePath);
     ~PerfInfo();
     void LogImage(PEFile* pFile, WCHAR* guid);
 

src/coreclr/vm/perfmap.cpp

@@ -22,6 +22,14 @@
 #define FMT_CODE_ADDR "%p"
 #endif
 
+#ifndef __ANDROID__
+#define TEMP_DIRECTORY_PATH "/tmp"
+#else
+// On Android, "/tmp/" doesn't exist; temporary files should go to
+// /data/local/tmp/
+#define TEMP_DIRECTORY_PATH "/data/local/tmp"
+#endif
+
 Volatile<bool> PerfMap::s_enabled = false;
 PerfMap * PerfMap::s_Current = nullptr;
 bool PerfMap::s_ShowOptimizationTiers = false;
@@ -40,53 +48,64 @@ void PerfMap::Initialize()
 {
     LIMITED_METHOD_CONTRACT;
 
+    const DWORD perfMapEnabled = CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled);
+    if (perfMapEnabled == DISABLED)
+    {
+        return;
+    }
+
+    // Build the path to the map file on disk.
+    char tempPathBuffer[MAX_LONGPATH+1];
+    const char* tempPath = InternalConstructPath(tempPathBuffer, sizeof(tempPathBuffer));
+
     // Only enable the map if requested.
-    if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled) == ALL || CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled) == PERFMAP)
+    if (perfMapEnabled == ALL || perfMapEnabled == PERFMAP)
     {
         // Get the current process id.
         int currentPid = GetCurrentProcessId();
 
         // Create the map.
-        s_Current = new PerfMap(currentPid);
+        s_Current = new PerfMap(currentPid, tempPath);
 
         int signalNum = (int) CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapIgnoreSignal);
 
         if (signalNum > 0)
         {
             PAL_IgnoreProfileSignal(signalNum);
         }
+    }
 
-        if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapShowOptimizationTiers) != 0)
-        {
-            s_ShowOptimizationTiers = true;
-        }
-
-        s_enabled = true;
+    // only enable JitDumps if requested
+    if (perfMapEnabled == ALL || perfMapEnabled == JITDUMP)
+    {
+        PAL_PerfJitDump_Start(tempPath);
     }
 
-    if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled) == ALL || CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapEnabled) == JITDUMP)
+    if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapShowOptimizationTiers) != 0)
     {
-        char jitdumpPath[4096];
-
-        // CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapJitDumpPath) returns a LPWSTR
-        // Use GetEnvironmentVariableA because it is simpler.
-        // Keep comment here to make it searchable.
-        DWORD len = GetEnvironmentVariableA("COMPlus_PerfMapJitDumpPath", jitdumpPath, sizeof(jitdumpPath) - 1);
-
-        if (len == 0)
-        {
-            GetTempPathA(sizeof(jitdumpPath) - 1, jitdumpPath);
-        }
+        s_ShowOptimizationTiers = true;
+    }
+
+    s_enabled = true;
+}
 
-        PAL_PerfJitDump_Start(jitdumpPath);
+// InternalConstructPath is guaranteed to return a non-null path
+// the function  uses the input buffer only whe PerfMapJitDumpPath environment variable is set
+const char * PerfMap::InternalConstructPath(char *tmpBuf, int lenBuf)
+{
+    DWORD len = GetEnvironmentVariableA("DOTNET_PerfMapJitDumpPath", tmpBuf, lenBuf);
+    if (len == 0)
+    {
+        len = GetEnvironmentVariableA("COMPlus_PerfMapJitDumpPath", tmpBuf, lenBuf);
+    }
 
-        if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapShowOptimizationTiers) != 0)
-        {
-            s_ShowOptimizationTiers = true;
-        }
-
-        s_enabled = true;
+    if (len == 0 || // GetEnvironmentVariableA returns 0 if the variable is not found, 
+        len >= lenBuf) // or the length of the string not including the null terminator on success.
+    {
+        return TEMP_DIRECTORY_PATH;
     }
+
+    return tmpBuf;
 }
 
 // Destroy the map for the process - called from EEShutdownHelper.
@@ -103,27 +122,21 @@ void PerfMap::Destroy()
 }
 
 // Construct a new map for the process.
-PerfMap::PerfMap(int pid)
+PerfMap::PerfMap(int pid, const char* path)
 {
     LIMITED_METHOD_CONTRACT;
 
     // Initialize with no failures.
     m_ErrorEncountered = false;
 
     // Build the path to the map file on disk.
-    WCHAR tempPath[MAX_LONGPATH+1];
-    if(!GetTempPathW(MAX_LONGPATH, tempPath))
-    {
-        return;
-    }
-
-    SString path;
-    path.Printf("%Sperf-%d.map", &tempPath, pid);
+    SString pathFile;
+    pathFile.Printf("%s/perf-%d.map", path, pid);
 
     // Open the map file for writing.
-    OpenFile(path);
+    OpenFile(pathFile);
 
-    m_PerfInfo = new PerfInfo(pid);
+    m_PerfInfo = new PerfInfo(pid, path);
 }
 
 // Construct a new map without a specified file name.

src/coreclr/vm/perfmap.h

@@ -31,7 +31,10 @@ class PerfMap
     bool m_ErrorEncountered;
 
     // Construct a new map for the specified pid.
-    PerfMap(int pid);
+    PerfMap(int pid, const char* path);
+
+    // Default to /tmp or use DOTNET_PerfMapJitDumpPath if set
+    static const char* InternalConstructPath(char *tmpBuf, int lenBuf);
 
 protected:
     // Indicates whether optimization tiers should be shown for methods in perf maps