Write perfmap and jitdump files to /tmp by default

src/coreclr/inc/clrconfigvalues.h

@@ -481,7 +481,7 @@ 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_EX(EXTERNAL_PerfMapJitDumpPath, W("PerfMapJitDumpPath"), "Specifies a path to write the perf jitdump file. Defaults to /tmp", CLRConfig::LookupOptions::TrimWhiteSpaceFromStringValue)
 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.")
 #endif

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.GetUTF8(), 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(PEAssembly* pPEAssembly, CHAR* guid);
 

src/coreclr/vm/perfmap.cpp

@@ -19,6 +19,14 @@
 
 #define FMT_CODE_ADDR "%p"
 
+#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;
@@ -36,6 +44,16 @@ void PerfMap::Initialize()
     PerfMap::Enable(perfMapType, false);
 }
 
+const char * PerfMap::InternalConstructPath()
+{
+    CLRConfigNoCache value = CLRConfigNoCache::Get("PerfMapJitDumpPath");
+    if (value.IsSet())
+    {
+        return value.AsString();
+    }
+    return TEMP_DIRECTORY_PATH;
+}
+
 void PerfMap::Enable(PerfMapType type, bool sendExisting)
 {
     LIMITED_METHOD_CONTRACT;
@@ -48,6 +66,8 @@ void PerfMap::Enable(PerfMapType type, bool sendExisting)
     {
         CrstHolder ch(&(s_csPerfMap));
 
+        const char* basePath = InternalConstructPath();
+
         if (s_Current == nullptr && (type == PerfMapType::ALL || type == PerfMapType::PERFMAP))
         {
             s_Current = new PerfMap();
@@ -64,27 +84,13 @@ void PerfMap::Enable(PerfMapType type, bool sendExisting)
             }
 
             int currentPid = GetCurrentProcessId();
-            s_Current->OpenFileForPid(currentPid);
+            s_Current->OpenFileForPid(currentPid, basePath);
             s_enabled = true;
         }
 
         if (!PAL_PerfJitDump_IsStarted() && (type == PerfMapType::ALL || type == PerfMapType::JITDUMP))
-        {   
-            const char* jitdumpPath;
-            char jitdumpPathBuffer[4096];
-
-            CLRConfigNoCache value = CLRConfigNoCache::Get("PerfMapJitDumpPath");
-            if (value.IsSet())
-            {
-                jitdumpPath = value.AsString();
-            }
-            else
-            {
-                GetTempPathA(sizeof(jitdumpPathBuffer) - 1, jitdumpPathBuffer);
-                jitdumpPath = jitdumpPathBuffer;
-            }
-
-            PAL_PerfJitDump_Start(jitdumpPath);
+        {
+            PAL_PerfJitDump_Start(basePath);
 
             if (CLRConfig::GetConfigValue(CLRConfig::EXTERNAL_PerfMapShowOptimizationTiers) != 0)
             {
@@ -209,23 +215,15 @@ PerfMap::~PerfMap()
     m_PerfInfo = nullptr;
 }
 
-void PerfMap::OpenFileForPid(int pid)
+void PerfMap::OpenFileForPid(int pid, const char* basePath)
 {
-    // Build the path to the map file on disk.
-    WCHAR tempPath[MAX_LONGPATH+1];
-    if(!GetTempPathW(MAX_LONGPATH, tempPath))
-    {
-        return;
-    }
-
-    SString path;
-    path.Append(tempPath);
-    path.AppendPrintf("perf-%d.map", pid);
+    SString fullPath;
+    fullPath.Printf("%s/perf-%d.map", basePath, pid);
 
     // Open the map file for writing.
-    OpenFile(path);
+    OpenFile(fullPath);
 
-    m_PerfInfo = new PerfInfo(pid);
+    m_PerfInfo = new PerfInfo(pid, basePath);
 }
 
 // Open the specified destination map file.

src/coreclr/vm/perfmap.h

@@ -38,14 +38,18 @@ class PerfMap
     // Set to true if an error is encountered when writing to the file.
     bool m_ErrorEncountered;
 
-    // Construct a new map for the specified pid.
+    // Construct a new map
     PerfMap();
 
-    void OpenFileForPid(int pid);
+    // Open a perfmap map for the specified pid
+    void OpenFileForPid(int pid, const char* basePath);
 
     // Write a line to the map file.
     void WriteLine(SString & line);
 
+    // Default to /tmp or use DOTNET_PerfMapJitDumpPath if set
+    static const char* InternalConstructPath();
+
 protected:
     // Open the perf map file for write.
     void OpenFile(SString& path);