Introduce minimum allowed major driver and nif versions on load

7 files changed, 69 insertions, 8 deletions

diff --git a/erts/doc/src/erl_driver.xml b/erts/doc/src/erl_driver.xml
index 8da1836da7..ad37813ac0 100644
--- a/erts/doc/src/erl_driver.xml
+++ b/erts/doc/src/erl_driver.xml
@@ -315,10 +315,13 @@
           <c>ERL_DRV_EXTENDED_MINOR_VERSION</c> will be incremented when
           new features are added. The runtime system uses the minor version
           of the driver to determine what features to use.
-          The runtime system will refuse to load a driver if the major
+          The runtime system will normally refuse to load a driver if the major
           versions differ, or if the major versions are equal and the
           minor version used by the driver is greater than the one used
-          by the runtime system.</p>
+          by the runtime system. Old drivers with lower major versions
+	  will however be allowed after a bump of the major version during
+	  a transition period of two major releases. Such old drivers might
+	  however fail if deprecated features are used.</p>
 	<p>The emulator will refuse to load a driver that does not use
 	  the extended driver interface,
 	  to allow for 64-bit capable drivers,
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index 8b19725c02..6b1f4cccf8 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -316,6 +316,32 @@ ok
       <p>The library initialization callbacks <c>load</c>, <c>reload</c> and
       <c>upgrade</c> are all thread-safe even for shared state data.</p>
       </item>
+
+      <tag><marker id="version_management"/>Version Management</tag>
+      <item><p>
+      When a NIF library is built, information about NIF API version
+      is compiled into the library. When a NIF library is loaded the
+      runtime system verifies that the library is of a compatible version.
+      <c>erl_nif.h</c> defines <c>ERL_NIF_MAJOR_VERSION</c>, and
+      <c>ERL_NIF_MINOR_VERSION</c>. <c>ERL_NIF_MAJOR_VERSION</c> will be
+      incremented when NIF library incompatible changes are made to the
+      Erlang runtime system. Normally it will suffice to recompile the NIF
+      library when the <c>ERL_NIF_MAJOR_VERSION</c> has changed, but it
+      could, under rare circumstances, mean that NIF libraries have to
+      be slightly modified. If so, this will of course be documented.
+      <c>ERL_NIF_MINOR_VERSION</c> will be incremented when
+      new features are added. The runtime system uses the minor version
+      to determine what features to use.
+      </p><p>
+      The runtime system will normally refuse to load a NIF library if
+      the major versions differ, or if the major versions are equal and
+      the minor version used by the NIF library is greater than the one
+      used by the runtime system. Old NIF libraries with lower major
+      versions will however be allowed after a bump of the major version
+      during a transition period of two major releases. Such old NIF
+      libraries might however fail if deprecated features are used.
+      </p></item>
+
       <tag>Dirty NIFs</tag>
       <item><p><marker id="dirty_nifs"/><em>Note that the dirty NIF functionality
       is experimental</em> and that you have to enable support for dirty
diff --git a/erts/emulator/beam/erl_bif_ddll.c b/erts/emulator/beam/erl_bif_ddll.c
index 1728b200f7..56cd2ba04f 100644
--- a/erts/emulator/beam/erl_bif_ddll.c
+++ b/erts/emulator/beam/erl_bif_ddll.c
@@ -1548,8 +1548,10 @@ static int do_load_driver_entry(DE_Handle *dh, char *path, char *name)
 
     switch (dp->extended_marker) {
     case ERL_DRV_EXTENDED_MARKER:
-	if (ERL_DRV_EXTENDED_MAJOR_VERSION != dp->major_version
-	    || ERL_DRV_EXTENDED_MINOR_VERSION < dp->minor_version) {
+	if (dp->major_version < ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD
+	    || (ERL_DRV_EXTENDED_MAJOR_VERSION < dp->major_version
+		|| (ERL_DRV_EXTENDED_MAJOR_VERSION == dp->major_version
+		    && ERL_DRV_EXTENDED_MINOR_VERSION < dp->minor_version))) {
 	    /* Incompatible driver version */
 	    res = ERL_DE_LOAD_ERROR_INCORRECT_VERSION;
 	    goto error;
diff --git a/erts/emulator/beam/erl_driver.h b/erts/emulator/beam/erl_driver.h
index 5517c26ba4..3ecb379326 100644
--- a/erts/emulator/beam/erl_driver.h
+++ b/erts/emulator/beam/erl_driver.h
@@ -136,6 +136,22 @@ typedef struct {
 #define ERL_DRV_EXTENDED_MINOR_VERSION	0
 
 /*
+ * The emulator will refuse to load a driver with a major version
+ * lower than ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD. The load
+ * may however fail if user have not removed use of deprecated
+ * symbols.
+ *
+ * The ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD have to allow
+ * loading of drivers built at least two major OTP releases
+ * ago.
+ *
+ * Bump of major version to 3 happened in OTP 17. That is, in
+ * OTP 19 we can increase ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD
+ * to 3.
+ */
+#define ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD 2
+
+/*
  * The emulator will refuse to load a driver with different major
  * version than the one used by the emulator.
  */
diff --git a/erts/emulator/beam/erl_nif.c b/erts/emulator/beam/erl_nif.c
index 40860e141c..063dba056e 100644
--- a/erts/emulator/beam/erl_nif.c
+++ b/erts/emulator/beam/erl_nif.c
@@ -2049,8 +2049,10 @@ BIF_RETTYPE load_nif_2(BIF_ALIST_2)
 	      (entry = erts_sys_ddll_call_nif_init(init_func)) == NULL)) {
 	ret = load_nif_error(BIF_P, bad_lib, "Library init-call unsuccessful");
     }
-    else if (entry->major != ERL_NIF_MAJOR_VERSION
-	     || entry->minor > ERL_NIF_MINOR_VERSION
+    else if (entry->major < ERL_NIF_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD
+	     || (ERL_NIF_MAJOR_VERSION < entry->major
+		 || (ERL_NIF_MAJOR_VERSION == entry->major
+		     && ERL_NIF_MINOR_VERSION < entry->minor))
 	     || (entry->major==2 && entry->minor == 5)) { /* experimental maps */
 	
 	ret = load_nif_error(BIF_P, bad_lib, "Library version (%d.%d) not compatible (with %d.%d).",
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index c12ba4d554..5b93c2398e 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -46,6 +46,18 @@
 #define ERL_NIF_MAJOR_VERSION 2
 #define ERL_NIF_MINOR_VERSION 6
 
+/*
+ * The emulator will refuse to load a nif-lib with a major version
+ * lower than ERL_NIF_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD. The load
+ * may however fail if user have not removed use of deprecated
+ * symbols.
+ *
+ * The ERL_NIF_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD have to allow
+ * loading of nif-libs built at least two major OTP releases
+ * ago.
+ */
+#define ERL_NIF_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD 2
+
 #include <stdlib.h>
 
 #ifdef SIZEOF_CHAR
diff --git a/erts/emulator/test/driver_SUITE_data/smaller_major_vsn_drv.c b/erts/emulator/test/driver_SUITE_data/smaller_major_vsn_drv.c
index a1299fe807..6b9d4745ba 100644
--- a/erts/emulator/test/driver_SUITE_data/smaller_major_vsn_drv.c
+++ b/erts/emulator/test/driver_SUITE_data/smaller_major_vsn_drv.c
@@ -20,12 +20,12 @@
  * Author: Rickard Green
  *
  * Description: Implementation of a driver with a smaller major
- *              driver version than the current system.
+ *              driver version than allowed on load.
  */
 
 #define VSN_MISMATCH_DRV_NAME_STR		"smaller_major_vsn_drv"
 #define VSN_MISMATCH_DRV_NAME			smaller_major_vsn_drv
-#define VSN_MISMATCH_DRV_MAJOR_VSN_DIFF		(-1)
+#define VSN_MISMATCH_DRV_MAJOR_VSN_DIFF		(ERL_DRV_MIN_REQUIRED_MAJOR_VERSION_ON_LOAD - ERL_DRV_EXTENDED_MAJOR_VERSION - 1)
 #define VSN_MISMATCH_DRV_MINOR_VSN_DIFF		0
  
 #include "vsn_mismatch_drv_impl.c"