fix: sublevel version overflow in LINUX_VERSION_CODE

[lttng-modules.git] / lttng-kernel-version.h

diff --git a/lttng-kernel-version.h b/lttng-kernel-version.h
index 9e02cc6dd4deec73b6ca4f31db2bcd561f786b0f..e7fffe606a288bdf1dd4203abd01162ef94fbbc9 100644 (file)
--- a/lttng-kernel-version.h
+++ b/lttng-kernel-version.h
@@ -25,9 +25,49 @@
 
 #include <linux/version.h>
 
+/*
+ * The following defines are extracted from the toplevel Linux Makefile and
+ * passed on the command line -with '-D'.
+ */
+
+#ifndef LTTNG_LINUX_MAJOR
+#define LTTNG_LINUX_MAJOR 0
+#endif
+
+#ifndef LTTNG_LINUX_MINOR
+#define LTTNG_LINUX_MINOR 0
+#endif
+
+#ifndef LTTNG_LINUX_PATCH
+#define LTTNG_LINUX_PATCH 0
+#endif
+
+/*
+ * Some stable releases have overflowed the 8bits allocated to the sublevel in
+ * the version code. To determine if the current kernel is affected, use the
+ * sublevel version from the Makefile. This is currently true for the 4.4.256
+ * and 4.9.256 stable releases.
+ *
+ * When the sublevel has overflowed, use the values from the Makefile instead
+ * of LINUX_VERSION_CODE from the kernel headers and allocate 16bits.
+ * Otherwise, keep using the version code from the headers to minimise the
+ * behavior change and avoid regressions.
+ */
+#if (LTTNG_LINUX_PATCH >= 256)
+
+#define LTTNG_KERNEL_VERSION(a, b, c) \
+       (((a) << 24) + ((b) << 16) + (c))
+
+#define LTTNG_LINUX_VERSION_CODE \
+       LTTNG_KERNEL_VERSION(LTTNG_LINUX_MAJOR, LTTNG_LINUX_MINOR, LTTNG_LINUX_PATCH)
+
+#else
+
 #define LTTNG_KERNEL_VERSION(a, b, c) KERNEL_VERSION(a, b, c)
 #define LTTNG_LINUX_VERSION_CODE LINUX_VERSION_CODE
 
+#endif
+
 #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(2,6,33))
 #include <generated/utsrelease.h>
 #else /* #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(2,6,33)) */