[ovs-dev] [PATCH v2 01/16] datapath: Allow compiling older kernels with GCC 5.

Jarno Rajahalme jarno at ovn.org
Tue Jun 14 22:25:22 UTC 2016


Older kernels don't have <linux/compiler.gcc5.h>, which causes
compilation to fail on GCC 5.

Signed-off-by: Jarno Rajahalme <jarno at ovn.org>
---
 acinclude.m4                                       |  4 ++
 datapath/linux/Modules.mk                          |  1 +
 .../linux/compat/include/linux/compiler-gcc5.h     | 71 ++++++++++++++++++++++
 3 files changed, 76 insertions(+)
 create mode 100644 datapath/linux/compat/include/linux/compiler-gcc5.h

diff --git a/acinclude.m4 b/acinclude.m4
index 0a14856..b651f2f 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -575,6 +575,10 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
   OVS_GREP_IFELSE([$KSRC/include/linux/utsrelease.h], [el6],
                   [OVS_DEFINE([HAVE_RHEL6_PER_CPU])])
 
+  OVS_GREP_IFELSE([$KSRC/include/linux/compiler-gcc5.h],
+                  [<linux/compiler-gcc5.h>],
+                  [OVS_DEFINE([HAVE_COMPILER_GCC5_H])])
+
   if cmp -s datapath/linux/kcompat.h.new \
             datapath/linux/kcompat.h >/dev/null 2>&1; then
     rm datapath/linux/kcompat.h.new
diff --git a/datapath/linux/Modules.mk b/datapath/linux/Modules.mk
index 5d38766..8b65b71 100644
--- a/datapath/linux/Modules.mk
+++ b/datapath/linux/Modules.mk
@@ -33,6 +33,7 @@ openvswitch_headers += \
 	linux/compat/include/linux/bug.h \
 	linux/compat/include/linux/compiler.h \
 	linux/compat/include/linux/compiler-gcc.h \
+	linux/compat/include/linux/compiler-gcc5.h \
 	linux/compat/include/linux/cpumask.h \
 	linux/compat/include/linux/err.h \
 	linux/compat/include/linux/etherdevice.h \
diff --git a/datapath/linux/compat/include/linux/compiler-gcc5.h b/datapath/linux/compat/include/linux/compiler-gcc5.h
new file mode 100644
index 0000000..5583704
--- /dev/null
+++ b/datapath/linux/compat/include/linux/compiler-gcc5.h
@@ -0,0 +1,71 @@
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc5.h> directly, include <linux/compiler.h> instead."
+#endif
+
+#ifdef HAVE_COMPILER_GCC5_H
+#include_next <linux/compiler-gcc5.h>
+#else
+
+#define __used				__attribute__((__used__))
+#define __must_check			__attribute__((warn_unused_result))
+#define __compiler_offsetof(a, b)	__builtin_offsetof(a, b)
+
+/* Mark functions as cold. gcc will assume any path leading to a call
+   to them will be unlikely.  This means a lot of manual unlikely()s
+   are unnecessary now for any paths leading to the usual suspects
+   like BUG(), printk(), panic() etc. [but let's keep them for now for
+   older compilers]
+
+   Early snapshots of gcc 4.3 don't support this and we can't detect this
+   in the preprocessor, but we can live with this because they're unreleased.
+   Maketime probing would be overkill here.
+
+   gcc also has a __attribute__((__hot__)) to move hot functions into
+   a special section, but I don't see any sense in this right now in
+   the kernel context */
+#define __cold			__attribute__((__cold__))
+
+#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#ifndef __CHECKER__
+# define __compiletime_warning(message) __attribute__((warning(message)))
+# define __compiletime_error(message) __attribute__((error(message)))
+#endif /* __CHECKER__ */
+
+/*
+ * Mark a position in code as unreachable.  This can be used to
+ * suppress control flow warnings after asm blocks that transfer
+ * control elsewhere.
+ *
+ * Early snapshots of gcc 4.5 don't support this and we can't detect
+ * this in the preprocessor, but we can live with this because they're
+ * unreleased.  Really, we need to have autoconf for the kernel.
+ */
+#define unreachable() __builtin_unreachable()
+
+/* Mark a function definition as prohibited from being cloned. */
+#define __noclone	__attribute__((__noclone__))
+
+/*
+ * Tell the optimizer that something else uses this function or variable.
+ */
+#define __visible __attribute__((externally_visible))
+
+/*
+ * GCC 'asm goto' miscompiles certain code sequences:
+ *
+ *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
+ *
+ * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
+ *
+ * (asm goto is automatically volatile - the naming reflects this.)
+ */
+#define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
+
+#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
+#define __HAVE_BUILTIN_BSWAP32__
+#define __HAVE_BUILTIN_BSWAP64__
+#define __HAVE_BUILTIN_BSWAP16__
+#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
+
+#endif /* HAVE_COMPILER_GCC5_H */
-- 
2.1.4




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