linux-kernel - [PATCH 4.14 070/105] powerpc: Disable -Wbuiltin-requires-header when setjmp is used

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Date:   Fri, 11 Jan 2019 15:14:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Joel Stanley <joel@....id.au>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH 4.14 070/105] powerpc: Disable -Wbuiltin-requires-header when setjmp is used

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joel Stanley <joel@....id.au>

commit aea447141c7e7824b81b49acd1bc785506fba46e upstream.

The powerpc kernel uses setjmp which causes a warning when building
with clang:

  In file included from arch/powerpc/xmon/xmon.c:51:
  ./arch/powerpc/include/asm/setjmp.h:15:13: error: declaration of
  built-in function 'setjmp' requires inclusion of the header <setjmp.h>
        [-Werror,-Wbuiltin-requires-header]
  extern long setjmp(long *);
              ^
  ./arch/powerpc/include/asm/setjmp.h:16:13: error: declaration of
  built-in function 'longjmp' requires inclusion of the header <setjmp.h>
        [-Werror,-Wbuiltin-requires-header]
  extern void longjmp(long *, long);
              ^

This *is* the header and we're not using the built-in setjump but
rather the one in arch/powerpc/kernel/misc.S. As the compiler warning
does not make sense, it for the files where setjmp is used.

Signed-off-by: Joel Stanley <joel@....id.au>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
[mpe: Move subdir-ccflags in xmon/Makefile to not clobber -Werror]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/kernel/Makefile |    3 +++
 arch/powerpc/xmon/Makefile   |    5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -5,6 +5,9 @@
 
 CFLAGS_ptrace.o		+= -DUTS_MACHINE='"$(UTS_MACHINE)"'
 
+# Disable clang warning for using setjmp without setjmp.h header
+CFLAGS_crash.o		+= $(call cc-disable-warning, builtin-requires-header)
+
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
 ifeq ($(CONFIG_PPC64),y)
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -1,7 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 # Makefile for xmon
 
-subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
+# Disable clang warning for using setjmp without setjmp.h header
+subdir-ccflags-y := $(call cc-disable-warning, builtin-requires-header)
+
+subdir-ccflags-$(CONFIG_PPC_WERROR) += -Werror
 
 GCOV_PROFILE := n
 UBSAN_SANITIZE := n