fix.patch

From 100d5e81de0f34ebba38472e373dece4c3449ea4 Mon Sep 17 00:00:00 2001
From: "Yichun Zhang (agentzh)" <yichun@openresty.com>
Date: Tue, 3 Mar 2020 15:15:30 -0800
Subject: [PATCH] Bug: proc_mem_rss() broken on older kernels lacking
 MM_SHMEMPAGES.

This is a regression introduced in commit de253786000.
---
 buildrun.cxx                           |  3 +++
 runtime/linux/autoconf-mm-shmempages.c |  5 +++++
 tapset/linux/proc_mem.stp              | 11 ++++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)
 create mode 100644 runtime/linux/autoconf-mm-shmempages.c

diff --git a/buildrun.cxx b/buildrun.cxx
index 0870af946..040132277 100644
--- a/buildrun.cxx
+++ b/buildrun.cxx
@@ -440,6 +440,9 @@ compile_pass (systemtap_session& s)
   output_autoconf(s, o, cs, "autoconf-cpu-clock.c", "STAPCONF_CPU_CLOCK", NULL);
   output_autoconf(s, o, cs, "autoconf-local-clock.c", "STAPCONF_LOCAL_CLOCK", NULL);
   
+  // used by tapset/linux/proc_mem.stp
+  output_autoconf(s, o, cs, "autoconf-mm-shmempages.c", "STAPCONF_MM_SHMEMPAGES", NULL);
+
   // used by runtime/uprobe-inode.c
   output_either_exportconf(s, o2, "uprobe_register", "register_uprobe",
 			   "STAPCONF_UPROBE_REGISTER_EXPORTED");
diff --git a/runtime/linux/autoconf-mm-shmempages.c b/runtime/linux/autoconf-mm-shmempages.c
new file mode 100644
index 000000000..2ce742be7
--- /dev/null
+++ b/runtime/linux/autoconf-mm-shmempages.c
@@ -0,0 +1,5 @@
+#include <linux/sched.h>
+
+void foo (void) {
+    (void) MM_SHMEMPAGES;
+}
diff --git a/tapset/linux/proc_mem.stp b/tapset/linux/proc_mem.stp
index 1208a2287..87f349bf8 100644
--- a/tapset/linux/proc_mem.stp
+++ b/tapset/linux/proc_mem.stp
@@ -73,9 +73,14 @@ enum {
 
 %(systemtap_v > "4.2" %?
 @__private30 function _MM_SHMEMPAGES:long()
-{
-	return @const("MM_SHMEMPAGES")
-}
+%{ /* pure */
+    STAP_RETVALUE =
+#ifdef STAPCONF_MM_SHMEMPAGES
+	MM_SHMEMPAGES;
+#else
+	0;
+#endif
+%}
 %)
 
 @__private30 function _stp_get_mm_counter:long(mm_ptr:long, member:long)
-- 
2.17.2