PR10524: reduce massive-uprobe script modules' .data consumption

The general approach is to rip out task_finder_tgt's from all over the
place (including the unwindsym vmcbs, and the stap_uprobe_specs), and
instead have a small handful of them: one for all unwindsyms, and one
per abstract probed process (PID or NAME).  These are in turn shared
by all new stap_unwind_specs by index.

Before:  probe process("./stap").function("*")

-rw-r--r--. 1 fche users 11775283 2009-09-08 20:26 /var/tmp/fche/systemtap/cache/96/stap_96c0479d674db55ec98d8a8750a790e7_7989596.ko
   text    data     bss     dec     hex filename
 445158 8351944 4306472 13103574 c7f1d6 /var/tmp/fche/systemtap/cache/96/stap_96c0479d674db55ec98d8a8750a790e7_7989596.ko

After: (Note how data shrank, though text gained a bit in const-init-data.)

-rw-r--r--. 1 fche users  4021569 2009-09-08 20:27 /var/tmp/fche/systemtap/cache/e4/stap_e46e88634efd850b1586e81c231c239a_8058419.ko
   text    data     bss     dec     hex filename
1896511    2192 4324808 6223511  5ef697 /var/tmp/fche/systemtap/cache/e4/stap_e46e88634efd850b1586e81c231c239a_8058419.ko

* tapsets.cxx (uprobe_derived_probe_group): Rewrite emit_module_decls,
  and adjust emit_module_init.
* runtime/sym.c (_stp_sym_init): Initialize unwindsyms-shared vmcb.
* runtime/sym.h (_stp_module): Remove *vmcb field.
* translate.cxx (emit_module_init, dump_unwindsyms): Adapt.
* translate.h (assert_0_indent): Flush output before possibly assert-failing.

1 files changed, 40 insertions, 15 deletions

diff --git a/runtime/sym.c b/runtime/sym.c
index 856ccbcc..0baa1a5e 100644
--- a/runtime/sym.c
+++ b/runtime/sym.c
@@ -16,21 +16,6 @@
 #include "string.c"
 #include "task_finder_vma.c"
 
-/** @file sym.c
- * @addtogroup sym Symbolic Functions
- * Symbolic Lookup Functions
- * @{
- */
-
-static void _stp_sym_init(void)
-{
-	static int initialized = 0;
-	if (! initialized) {
-		__stp_tf_vma_initialize();
-		initialized = 1;
-	}
-}
-
 /* Callback that needs to be registered (in
    session.unwindsyms_modules) for every user task path for which we
    might need symbols or unwind info. */
@@ -409,4 +394,44 @@ static void _stp_symbol_snprint(char *str, size_t len, unsigned long address,
 }
 
 /** @} */
+
+
+/** @file sym.c
+ * @addtogroup sym Symbolic Functions
+ * Symbolic Lookup Functions
+ * @{
+ */
+static void _stp_sym_init(void)
+{
+        // NB: it's too "early" to make this conditional on STP_NEED_VMA_TRACKER,
+        // since we're #included at the top of the generated module, before any
+        // tapset-induced #define's.
+#if defined(CONFIG_UTRACE)
+	static int initialized = 0;
+        static struct stap_task_finder_target vmcb = {
+                // NB: no .pid, no .procname filters here.
+                // This means that we get a system-wide mmap monitoring
+                // widget while the script is running.  (The system-wideness may
+                // be restricted by stap -c or -x.)  But this seems to
+                // be necessary if we want to to stack tracebacks through arbitrary
+                // shared libraries.  XXX: There may be an optimization opportunity
+                // for executables (for which the main task-finder callback should be
+                // sufficient).
+                .mmap_callback = &_stp_tf_mmap_cb,
+                .munmap_callback = &_stp_tf_munmap_cb,
+        };
+	if (! initialized) {
+                int rc;
+		__stp_tf_vma_initialize();
+                rc = stap_register_task_finder_target (& vmcb);
+#ifdef DEBUG_TASK_FINDER_VMA
+                _stp_dbug(__FUNCTION__, __LINE__, "registered vmcb");
+#endif
+                (void) rc; // XXX
+		initialized = 1;
+	}
+#endif
+}
+
+
 #endif /* _STP_SYM_C_ */