.NET Core (CoreCLR) patch for emitting USDT probes

coreclr-usdt.patch

diff --git a/src/scripts/genXplatLttng.py b/src/scripts/genXplatLttng.py
index bacf034..3d40d77 100644
--- a/src/scripts/genXplatLttng.py
+++ b/src/scripts/genXplatLttng.py
@@ -407,8 +407,25 @@ def generateLttngTpProvider(providerName, eventNodes, allTemplates):
     for eventNode in eventNodes:
         eventName    = eventNode.getAttribute('symbol')
         templateName = eventNode.getAttribute('template')
+
+        template = allTemplates[templateName] if templateName else None
+        paramlist = template.signature.paramlist[:10] if template else []
+        strparamlist = str.join(", ", paramlist())
+        numparams = len(paramlist)
+
+        lTTngImpl.append("#define SDT_%s_%s_ENABLED() __builtin_expect (%s_%s_semaphore, 0)\n" %
+                         (providerName.upper(), eventName.upper(), providerName, eventName))
+        lTTngImpl.append(("__extension__ unsigned short %s_%s_semaphore __attribute__ ((unused)) " +
+                          "__attribute__ ((section (\".probes\")));\n") % (providerName, eventName))
+        lTTngImpl.append("#define SDT_%s_%s(%s) DTRACE_PROBE%s(%s, %s%s %s)\n\n" %
+                         (providerName.upper(), eventName.upper(), strparamlist,
+                          numParams if numParams != 0 else "", providerName, eventName,
+                          "," if numParams != 0 else "", strparamlist))
+
         #generate EventXplatEnabled
-        lTTngImpl.append("extern \"C\" BOOL  EventXplatEnabled%s(){ return tracepoint_enabled(%s, %s); }\n\n" % (eventName, providerName, eventName))
+        lTTngImpl.append("extern \"C\" BOOL  EventXplatEnabled%s() { " +
+                         "return tracepoint_enabled(%s, %s) || SDT_%s_%s_ENABLED(); }\n\n" %
+                         (eventName, providerName, eventName, providerName.upper(), eventName.upper()))
         #generate FireEtw functions
         fnptype = []
         linefnptype = []
@@ -416,12 +433,6 @@ def generateLttngTpProvider(providerName, eventNodes, allTemplates):
         fnptype.append(eventName)
         fnptype.append("(\n")
 
-        
-        if templateName:
-            template = allTemplates[templateName]
-        else:
-            template = None
-
         if template:
             fnSig   = template.signature
             for paramName in fnSig.paramlist:
@@ -451,6 +462,8 @@ def generateLttngTpProvider(providerName, eventNodes, allTemplates):
         lTTngImpl.extend(fnptype)
 
         #start of fn body
+        lTTngImpl.append("    if (SDT_%s_%s_ENABLED())\n" % (providerName.upper(), eventName.upper()))
+        lTTngImpl.append("        SDT_%s_%s(%s);\n\n" % (providerName.upper(), eventName.upper(), strparamlist))
         lTTngImpl.append("    if (!EventXplatEnabled%s())\n" % (eventName,))
         lTTngImpl.append("        return ERROR_SUCCESS;\n")
 
@@ -654,7 +667,7 @@ bool WriteToBuffer(const char *str, char *&buffer, int& offset, int& size, bool
         lTTngTpImpl       = open(lttngevntprovTp, 'w')
 
         lTTngHdr.write(stdprolog + "\n")
-        lTTngImpl.write(stdprolog + "\n")
+        lTTngImpl.write(stdprolog + "\n#define _SDT_HAS_SEMAPHORES 1\n#include <sys/sdt.h>\n")
         lTTngTpImpl.write(stdprolog + "\n")
 
         lTTngTpImpl.write("\n#define TRACEPOINT_CREATE_PROBES\n")