linux-kernel - [PATCH 4.19 160/306] powerpc/xmon: Relax frame size for clang

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Message-Id: <20191127203127.204172470@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:30:10 +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>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 160/306] powerpc/xmon: Relax frame size for clang

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

[ Upstream commit 9c87156cce5a63735d1218f0096a65c50a7a32aa ]

When building with clang (8 trunk, 7.0 release) the frame size limit is
hit:

 arch/powerpc/xmon/xmon.c:452:12: warning: stack frame size of 2576
 bytes in function 'xmon_core' [-Wframe-larger-than=]

Some investigation by Naveen indicates this is due to clang saving the
addresses to printf format strings on the stack.

While this issue is investigated, bump up the frame size limit for xmon
when building with clang.

Link: https://github.com/ClangBuiltLinux/linux/issues/252
Signed-off-by: Joel Stanley <joel@....id.au>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/powerpc/xmon/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index 9d7d8e6d705c4..9ba44e190e5e4 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -13,6 +13,12 @@ UBSAN_SANITIZE := n
 ORIG_CFLAGS := $(KBUILD_CFLAGS)
 KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
 
+ifdef CONFIG_CC_IS_CLANG
+# clang stores addresses on the stack causing the frame size to blow
+# out. See https://github.com/ClangBuiltLinux/linux/issues/252
+KBUILD_CFLAGS += -Wframe-larger-than=4096
+endif
+
 ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
 
 obj-y			+= xmon.o nonstdio.o spr_access.o
-- 
2.20.1