add new stap -F (flight recorder) option that just passes through to staprun -L

5 files changed, 20 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index b7647c30..824f3ded 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,10 @@
 * What's new
 
+- The stap "-F" flag activates "flight recorder" mode, which consists of
+  translating the given script as usual, but implicitly launching it into
+  the background with staprun's existing "-L" (launch) option.  A user
+  can later reattach to the module with "staprun -A MODULENAME".
+
 - Additional context variables are available on user-space syscall probes.
   - $argN ($arg1, $arg2, ... $arg6) in process(PATH_OR_PID).syscall
     gives you the argument of the system call.
diff --git a/buildrun.cxx b/buildrun.cxx
index ada00027..8ec731df 100644
--- a/buildrun.cxx
+++ b/buildrun.cxx
@@ -287,6 +287,9 @@ run_pass (systemtap_session& s)
   if (s.need_uprobes)
     staprun_cmd += "-u ";
 
+  if (s.load_only)
+    staprun_cmd += "-L ";
+
   staprun_cmd += s.tmpdir + "/" + s.module_name + ".ko";
 
   if (s.verbose>1) clog << "Running " << staprun_cmd << endl;
diff --git a/main.cxx b/main.cxx
index 563e4b01..ce4572c1 100644
--- a/main.cxx
+++ b/main.cxx
@@ -108,6 +108,7 @@ usage (systemtap_session& s, int exitcode)
     << "   -c CMD     start the probes, run CMD, and exit when it finishes"
     << endl
     << "   -x PID     sets target() to PID" << endl
+    << "   -F         load module and start probes, then detach" << endl
     << "   -d OBJECT  add unwind/symbol data for OBJECT file";
   if (s.unwindsym_modules.size() == 0)
     clog << endl;
@@ -363,6 +364,7 @@ main (int argc, char * const argv [])
   s.consult_symtab = false;
   s.ignore_vmlinux = false;
   s.ignore_dwarf = false;
+  s.load_only = false;
 
   const char* s_p = getenv ("SYSTEMTAP_TAPSET");
   if (s_p != NULL)
@@ -426,7 +428,7 @@ main (int argc, char * const argv [])
         { "ignore-dwarf", 0, &long_opt, LONG_OPT_IGNORE_DWARF },
         { NULL, 0, NULL, 0 }
       };
-      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:m:kgPc:x:D:bs:uqwl:d:L:",
+      int grc = getopt_long (argc, argv, "hVMvtp:I:e:o:R:r:m:kgPc:x:D:bs:uqwl:d:L:F",
                                                           long_options, NULL);
       if (grc < 0)
         break;
@@ -611,6 +613,10 @@ main (int argc, char * const argv [])
           have_script = true;
           break;
 
+        case 'F':
+          s.load_only = true;
+	  break;
+
         case 0:
           switch (long_opt)
             {
diff --git a/session.h b/session.h
index 22575e8d..b8bd971a 100644
--- a/session.h
+++ b/session.h
@@ -104,6 +104,7 @@ struct systemtap_session
   bool prologue_searching;
   bool tapset_compile_coverage;
   bool need_uprobes;
+  bool load_only; // flight recorder mode
 
   // Cache data
   bool use_cache;
diff --git a/stap.1.in b/stap.1.in
index 22336cd5..0546d022 100644
--- a/stap.1.in
+++ b/stap.1.in
@@ -185,6 +185,10 @@ and aliases.
 .BI \-L " PROBE"
 Similar to "-l", but list probe points and local variables.
 .TP
+.BI \-F
+Load module and start probes, then detach from the module leaving the
+probes running.
+.TP
 .B \-\-kelf
 For names and addresses of functions to probe,
 consult the symbol tables in the kernel and modules.