linux-kernel - [PATCH] Revert "Revert "powerpc/xmon: Relax frame size for clang""

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Message-ID: <20230828-ppc_rerevert-v1-1-74f55b818907@google.com>
Date:   Mon, 28 Aug 2023 10:35:26 -0700
From:   ndesaulniers@...gle.com
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Nathan Chancellor <nathan@...nel.org>,
        Tom Rix <trix@...hat.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        kernel test robot <lkp@...el.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH] Revert "Revert "powerpc/xmon: Relax frame size for clang""

This reverts commit 7f3c5d099b6f8452dc4dcfe4179ea48e6a13d0eb.

Turns out that this is reproducible still under specific compiler
versions (mea culpa: I did not test every supported version of clang),
and even a few randconfigs bots found.

We'll have to revisit this again in the future, for now back this out.

Reported-by: Nathan Chancellor <nathan@...nel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/252#issuecomment-1690371256
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/llvm/202308260344.Vc4Giuk7-lkp@intel.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 arch/powerpc/xmon/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index 7705aa74a24d..d334de392e6c 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -10,6 +10,12 @@ KCSAN_SANITIZE := n
 # Disable ftrace for the entire directory
 ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
 
+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 xmon_bpts.o

---
base-commit: 2ee82481c392eec06a7ef28df61b7f0d8e45be2e
change-id: 20230828-ppc_rerevert-647427f04ce1

Best regards,
-- 
Nick Desaulniers <ndesaulniers@...gle.com>