Support ENABLED sdt probe macro

[Stan Cox <scox at redhat dot com>]

SW10013
This is for utrace only; uprobes is related.

For test.d 'dtrace -h -s test.d' emits in test.h
__extension__ extern long test_semaphore __attribute__ ((unused)) 
__attribute__ ((section (".probes")));
and for 'dtrace -G test.d' adds the definition
The changes for sdt.h are simple for a change, it checks that value
before each probe setup.
session.h defines a map from filename to variable location
tapset-utrace.cxx will produce the following additional generated code:
add 'struct task_struct *tsk;' to stap_utrace_probe
 since there is not a means to determine the task from
 systemtap_module_exit
in _stp_utrace_probe_cb add for each probe if the filename matches.
(There is not a means to determine what probe brought us here so
incrementing only the concerned probe is a challenge)
      size_t sdt_semaphore = 1;
      __access_process_vm (tsk, 0x601230, &sdt_semaphore,
      sizeof (sdt_semaphore), 0);
      sdt_semaphore += 1;
in systemtap_module_exit add for each probe if the filename matches
     size_t sdt_semaphore;
     __access_process_vm (tsk, 0x601230, &sdt_semaphore,
     sizeof (sdt_semaphore, 0);
     sdt_semaphore -= 1;
     __access_process_vm (tsk, 0x601230, &sdt_semaphore,
     sizeof (sdt_semaphore), 1);
In tapsets.cxx record the mapping from filename to variable location
In translate.cxx include a new "access_process_vm.h"  (see itrace.c)




diff --git a/dtrace.in b/dtrace.in
index 168bfb1..38fb03b 100755
--- a/dtrace.in
+++ b/dtrace.in
@@ -19,2 +19,3 @@ from tempfile import mkstemp
 class provider:
+    semaphores_def = "\n"
     def typedef_append(self, typedefs,this_probe,arg,c):
@@ -30,2 +31,6 @@ class provider:
         return typedefs
+    def semaphore_def_append(self, this_probe):
+        self.semaphores_def += "__extension__ long %s_semaphore __attribute__ ((unused)) __attribute__ ((section (\".probes\")));\n" % (this_probe)
+    def semaphore_def_write(self, file):
+        file.write(self.semaphores_def)
     def generate(self, provider, header, add_typedefs):
@@ -35,2 +40,4 @@ class provider:
         self.h.write("/* Generated by the Systemtap dtrace wrapper */\n")
+        if (build_source):
+            self.h.write("\n#define STAP_HAS_SEMAPHORES 1\n\n")
         self.h.write("\n#include <sys/sdt.h>\n\n")
@@ -66,2 +73,3 @@ class provider:
                 c = 0
+                self.semaphore_def_append (this_probe)
                 while (i < len(args)):
@@ -93,3 +101,4 @@ class provider:
                 self.h.write ('/* %s (%s) */\n' % (this_probe_canon,args_string))
-                self.h.write ('#define %s_ENABLED() 1\n' % this_probe_canon)
+                self.h.write ('#define %s_ENABLED() %s_semaphore\n' % (this_probe_canon,this_probe))
+                self.h.write ("__extension__ extern long %s_semaphore __attribute__ ((unused)) __attribute__ ((section (\".probes\")));\n" % (this_probe))
                 self.h.write (define_str + ") \\\n")
@@ -176,2 +185,3 @@ if (build_header):
 elif (build_source):
+    providers = provider()
     (basename,ext) = os.path.splitext(s_filename)
@@ -181,2 +191,3 @@ elif (build_source):
     f.write("static __dtrace () {}\n")
+    providers.semaphore_def_write(f)
     f.close()

diff --git a/includes/sys/sdt.h b/includes/sys/sdt.h
index f179c2a..6f3aaab 100644
--- a/includes/sys/sdt.h
+++ b/includes/sys/sdt.h
@@ -254,2 +254,9 @@ extern long int syscall (long int __sysno, ...) __THROW;
 
+#ifdef STAP_HAS_SEMAPHORES
+#define STAP_SEMAPHORE(probe)			\
+  if ( probe ## _semaphore )
+#else
+#define STAP_SEMAPHORE(probe) ;
+#endif
+
 #include <sys/syscall.h>
@@ -257,4 +264,5 @@ extern long int syscall (long int __sysno, ...) __THROW;
 #define STAP_PROBE_(probe)			\
+STAP_SEMAPHORE(probe) \
 do {						\
-  STAP_PROBE_DATA(probe,STAP_SYSCALL,0);	\
+  STAP_PROBE_DATA(probe,STAP_GUARD,0);	\
   syscall (STAP_SYSCALL, #probe, STAP_GUARD);	\
@@ -263,2 +271,3 @@ do {						\
 #define STAP_PROBE1_(probe,label,parm1)				\
+STAP_SEMAPHORE(probe) \
 do {								\
@@ -269,2 +278,3 @@ do {								\
 #define STAP_PROBE2_(probe,label,parm1,parm2)				\
+STAP_SEMAPHORE(probe) \
 do {									\
@@ -278,2 +288,3 @@ do {									\
....

diff --git a/session.h b/session.h
index ea91442..f642b74 100644
--- a/session.h
+++ b/session.h
@@ -223,2 +223,6 @@ struct systemtap_session
 
+
+  // Location of semaphores to activate sdt probes
+  std::multimap<std::string, Dwarf_Addr> sdt_semaphore_addr;
+
   // NB: It is very important for all of the above (and below) fields

diff --git a/tapset-utrace.cxx b/tapset-utrace.cxx
index a07e08b..844326d 100644
--- a/tapset-utrace.cxx
+++ b/tapset-utrace.cxx
@@ -718,2 +718,3 @@ utrace_derived_probe_group::emit_probe_decl (systemtap_session& s,
   s.op->line() << " .engine_attached=0,";
+  s.op->line() << " .tsk=0,";
   s.op->line() << " },";
@@ -752,2 +753,3 @@ utrace_derived_probe_group::emit_module_decls (systemtap_session& s)
   s.op->newline() << "int engine_attached;";
+  s.op->newline() << "struct task_struct *tsk;";
   s.op->newline(-1) << "};";
@@ -863,2 +865,3 @@ utrace_derived_probe_group::emit_module_decls (systemtap_session& s)
       s.op->newline() << "p->engine_attached = 1;";
+      s.op->newline() << "p->tsk = tsk;";
       s.op->newline(-1) << "}";
@@ -874,2 +877,24 @@ utrace_derived_probe_group::emit_module_decls (systemtap_session& s)
   s.op->newline(-1) << "}";
+
+  vector<Dwarf_Addr>::iterator it;
+  if (! s.sdt_semaphore_addr.empty())
+    for (p_b_path_iterator it = probes_by_path.begin();
+	 it != probes_by_path.end(); it++)
+      {
+	s.op->newline() << "{";
+	s.op->indent(1);
+	s.op->newline() << "size_t sdt_semaphore = 1;";
+	multimap<std::string,Dwarf_Addr>::iterator its;
+	for (its = s.sdt_semaphore_addr.begin();
+	     its != s.sdt_semaphore_addr.end();
+	     its++)
+	  if (it->first == its->first)
+	    {
+	      // Ideally we would increment this but we don't know what probe
+	      // this corresponds to.
+	      s.op->newline() << "__access_process_vm (tsk, " << hex << "0x" << its->second << ", &sdt_semaphore, sizeof (sdt_semaphore), 1);" << dec;
+	    }
+	s.op->newline(-1) << "}";
+      }
+
   s.op->newline(-1) << "}";
@@ -1047,2 +1072,27 @@ utrace_derived_probe_group::emit_module_exit (systemtap_session& s)
   s.op->newline(-1) << "}";
+
+  int sem_idx = 0;
+  if (! s.sdt_semaphore_addr.empty())
+    for (p_b_path_iterator it = probes_by_path.begin();
+	 it != probes_by_path.end(); it++)
+      {
+	s.op->newline() << "{";
+	s.op->indent(1);
+	s.op->newline() << "size_t sdt_semaphore;";
+	multimap<std::string,Dwarf_Addr>::iterator its;
+	for (its = s.sdt_semaphore_addr.begin();
+	     its != s.sdt_semaphore_addr.end();
+	     its++)
+	  {
+	  if (it->first == its->first)
+	    {
+	      s.op->newline() << "__access_process_vm (stap_utrace_probes[" << sem_idx << "].tsk, " << hex << "0x" << its->second << ", &sdt_semaphore, sizeof (sdt_semaphore), 0);" << dec;
+	      s.op->newline() << "sdt_semaphore -= 1;";
+	      s.op->newline() << "__access_process_vm (stap_utrace_probes[" << sem_idx << "].tsk, " << hex << "0x" << its->second << ", &sdt_semaphore, sizeof (sdt_semaphore), 1);" << dec;
+	    }
+	  }
+	
+	s.op->newline(-1) << "}";
+	sem_idx += it->second.size() - 1;
+      }
 }

diff --git a/tapsets.cxx b/tapsets.cxx
index f91d15d..6bbf761 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -3352,2 +3352,3 @@ private:
   probe_point * base_loc;
+  literal_map_t const & params;
   vector<derived_probe *> & results;
@@ -3367,2 +3368,3 @@ private:
   void convert_probe(probe *base);
+  void record_semaphore();
   void convert_location(probe *base, probe_point *location);
@@ -3375,3 +3377,3 @@ sdt_query::sdt_query(probe * base_probe, probe_point * base_loc,
   base_query(dw, params), base_probe(base_probe),
-  base_loc(base_loc), results(results)
+  base_loc(base_loc), params(params), results(results)
 {
@@ -3396,2 +3398,4 @@ sdt_query::handle_query_module()
 
+      record_semaphore();
+
       probe *new_base = new probe(*base_probe);
@@ -3561,2 +3565,23 @@ sdt_query::get_next_probe()
 void
+sdt_query::record_semaphore ()
+{
+  int sym_count = dwfl_module_getsymtab(dw.module);
+  assert (sym_count >= 0);
+  for (int i = 0; i < sym_count; i++)
+    {
+      GElf_Sym sym;
+      GElf_Word shndxp;
+      char *sym_str = (char*)dwfl_module_getsym (dw.module, i, &sym, &shndxp);
+      if (strcmp(sym_str, string(probe_name + "_semaphore").c_str()) == 0)
+	{
+	  string process_name;
+	  derived_probe_builder::get_param(params, TOK_PROCESS, process_name);
+	  sess.sdt_semaphore_addr.insert(make_pair(find_executable(process_name), sym.st_value));
+	  break;
+	}
+    }
+}
+
+
+void
 sdt_query::convert_probe (probe *base)
@@ -3711,3 +3736,2 @@ sdt_query::convert_location (probe *base, probe_point *location)
 
-
 void
diff --git a/translate.cxx b/translate.cxx
index 4a6a10b..f99cf0c 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -5179,2 +5181,4 @@ translate_pass (systemtap_session& s)
       s.op->newline() << "#include \"loc2c-runtime.h\" ";
+      if (! s.sdt_semaphore_addr.empty())
+	s.op->newline() << "#include \"access_process_vm.h\" ";