Merge tag 'llvmlinux-for-v3.15' of git://git.linuxfoundation.org/llvmlinux/kernel

Pull llvm patches from Behan Webster:
 "These are some initial updates to support compiling the kernel with
  clang.

  These patches have been through the proper reviews to the best of my
  ability, and have been soaking in linux-next for a few weeks.  These
  patches by themselves still do not completely allow clang to be used
  with the kernel code, but lay the foundation for other patches which
  are still under review.

  Several other of the LLVMLinux patches have been already added via
  maintainer trees"

* tag 'llvmlinux-for-v3.15' of git://git.linuxfoundation.org/llvmlinux/kernel:
  x86: LLVMLinux: Fix "incomplete type const struct x86cpu_device_id"
  x86 kbuild: LLVMLinux: More cc-options added for clang
  x86, acpi: LLVMLinux: Remove nested functions from Thinkpad ACPI
  LLVMLinux: Add support for clang to compiler.h and new compiler-clang.h
  LLVMLinux: Remove warning about returning an uninitialized variable
  kbuild: LLVMLinux: Fix LINUX_COMPILER definition script for compilation with clang
  Documentation: LLVMLinux: Update Documentation/dontdiff
  kbuild: LLVMLinux: Adapt warnings for compilation with clang
  kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang

9 files changed, 71 insertions, 5 deletions

diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index b89a739a3276..9de9813d0ec5 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -1,5 +1,6 @@
 *.a
 *.aux
+*.bc
 *.bin
 *.bz2
 *.cis
@@ -21,6 +22,7 @@
 *.i
 *.jpeg
 *.ko
+*.ll
 *.log
 *.lst
 *.lzma
@@ -35,6 +37,7 @@
 *.out
 *.patch
 *.pdf
+*.plist
 *.png
 *.pot
 *.ps
diff --git a/Makefile b/Makefile
index cf3e07516a04..10812e495e8d 100644
--- a/Makefile
+++ b/Makefile
@@ -248,6 +248,11 @@ HOSTCXX      = g++
 HOSTCFLAGS   = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer
 HOSTCXXFLAGS = -O2
 
+ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1)
+HOSTCFLAGS  += -Wno-unused-value -Wno-unused-parameter \
+                -Wno-missing-field-initializers -fno-delete-null-pointer-checks
+endif
+
 # Decide whether to build built-in, modular, or both.
 # Normally, just do built-in.
 
@@ -324,6 +329,14 @@ endif
 
 export quiet Q KBUILD_VERBOSE
 
+ifneq ($(CC),)
+ifeq ($(shell $(CC) -v 2>&1 | grep -c "clang version"), 1)
+COMPILER := clang
+else
+COMPILER := gcc
+endif
+export COMPILER
+endif
 
 # Look for make include files relative to root of kernel src
 MAKEFLAGS += --include-dir=$(srctree)
@@ -383,7 +396,7 @@ KBUILD_CFLAGS   := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
                    -fno-strict-aliasing -fno-common \
                    -Werror-implicit-function-declaration \
                    -Wno-format-security \
-                   -fno-delete-null-pointer-checks
+                   $(call cc-option,-fno-delete-null-pointer-checks,)
 KBUILD_AFLAGS_KERNEL :=
 KBUILD_CFLAGS_KERNEL :=
 KBUILD_AFLAGS   := -D__ASSEMBLY__
@@ -623,9 +636,24 @@ endif
 endif
 KBUILD_CFLAGS += $(stackp-flag)
 
+ifeq ($(COMPILER),clang)
+KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
+KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
+KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
+# Quiet clang warning: comparison of unsigned expression < 0 is always false
+KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
+# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
+# source of a reference will be _MergedGlobals and not on of the whitelisted names.
+# See modpost pattern 2
+KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,)
+else
+
 # This warning generated too much noise in a regular build.
 # Use make W=1 to enable this warning (see scripts/Makefile.build)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
+endif
 
 ifdef CONFIG_FRAME_POINTER
 KBUILD_CFLAGS   += -fno-omit-frame-pointer -fno-optimize-sibling-calls
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 3b9348a0c1a4..602f57e590b5 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -108,7 +108,7 @@ else
 
         # this works around some issues with generating unwind tables in older gccs
         # newer gccs do it by default
-        KBUILD_CFLAGS += -maccumulate-outgoing-args
+        KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
 endif
 
 # Make sure compiler does not have buggy stack-protector support.
diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h
index d8d4c898c1bb..70bef78912b7 100644
--- a/include/asm-generic/cmpxchg-local.h
+++ b/include/asm-generic/cmpxchg-local.h
@@ -4,7 +4,8 @@
 #include <linux/types.h>
 #include <linux/irqflags.h>
 
-extern unsigned long wrong_size_cmpxchg(volatile void *ptr);
+extern unsigned long wrong_size_cmpxchg(volatile void *ptr)
+        __noreturn;
 
 /*
  * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
new file mode 100644
index 000000000000..d1e49d52b640
--- /dev/null
+++ b/include/linux/compiler-clang.h
@@ -0,0 +1,12 @@
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
+#endif
+
+/* Some compiler specific definitions are overwritten here
+ * for Clang compiler
+ */
+
+#ifdef uninitialized_var
+#undef uninitialized_var
+#define uninitialized_var(x) x = *(&(x))
+#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 2472740d7ab2..ee7239ea1583 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -63,6 +63,13 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 # include <linux/compiler-intel.h>
 #endif
 
+/* Clang compiler defines __GNUC__. So we will overwrite implementations
+ * coming from above header files here
+ */
+#ifdef __clang__
+#include <linux/compiler-clang.h>
+#endif
+
 /*
  * Generic compiler-dependent macros required for kernel
  * build go below this comment. Actual compiler/compiler version
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 9a165a213d93..44eeef0da186 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -556,6 +556,11 @@ struct amba_id {
  * See documentation of "x86_match_cpu" for details.
  */
 
+/*
+ * MODULE_DEVICE_TABLE expects this struct to be called x86cpu_device_id.
+ * Although gcc seems to ignore this error, clang fails without this define.
+ */
+#define x86cpu_device_id x86_cpu_id
 struct x86_cpu_id {
         __u16 vendor;
         __u16 family;
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9f0ee22b914f..003bc263105a 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -65,12 +65,22 @@ warning-  := $(empty)
 warning-1 := -Wextra -Wunused -Wno-unused-parameter
 warning-1 += -Wmissing-declarations
 warning-1 += -Wmissing-format-attribute
-warning-1 += -Wmissing-prototypes
+warning-1 += $(call cc-option, -Wmissing-prototypes)
 warning-1 += -Wold-style-definition
 warning-1 += $(call cc-option, -Wmissing-include-dirs)
 warning-1 += $(call cc-option, -Wunused-but-set-variable)
 warning-1 += $(call cc-disable-warning, missing-field-initializers)
 
+# Clang
+warning-1 += $(call cc-disable-warning, initializer-overrides)
+warning-1 += $(call cc-disable-warning, unused-value)
+warning-1 += $(call cc-disable-warning, format)
+warning-1 += $(call cc-disable-warning, unknown-warning-option)
+warning-1 += $(call cc-disable-warning, sign-compare)
+warning-1 += $(call cc-disable-warning, format-zero-length)
+warning-1 += $(call cc-disable-warning, uninitialized)
+warning-1 += $(call cc-option, -fcatch-undefined-behavior)
+
 warning-2 := -Waggregate-return
 warning-2 += -Wcast-align
 warning-2 += -Wdisabled-optimization
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index f221ddf69080..cfb8440cc0b2 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -76,7 +76,7 @@ UTS_TRUNCATE="cut -b -$UTS_LEN"
   echo \#define LINUX_COMPILE_BY \"`echo $LINUX_COMPILE_BY | $UTS_TRUNCATE`\"
   echo \#define LINUX_COMPILE_HOST \"`echo $LINUX_COMPILE_HOST | $UTS_TRUNCATE`\"
 
-  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | tail -n 1`\"
+  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | grep ' version '`\"
 ) > .tmpcompile
 
 # Only replace the real compile.h if the new one is different,