linux-kernel - [PATCH v2] reapply: powerpc/xmon: Relax frame size for clang

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Message-ID: <20230828-ppc_rerevert-v2-1-46b71a3656c6@google.com>
Date:   Mon, 28 Aug 2023 13:39:06 -0700
From:   Nick Desaulniers <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 v2] reapply: powerpc/xmon: Relax frame size for clang

This is a manual revert of commit
7f3c5d099b6f8452dc4dcfe4179ea48e6a13d0eb, but using
ccflags-$(CONFIG_CC_IS_CLANG) which is shorter.

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/
Suggested-by: Nathan Chancellor <nathan@...nel.org>
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
Changes in v2:
- Use ccflags-$(CONFIG_CC_IS_CLANG) as per Nathan.
- Move that to be below the initial setting of ccflags-y as per Nathan.
- Add Nathan's Suggested-by and Reviewed-by tags.
- Update commit message slightly, including oneline.
- Link to v1: https://lore.kernel.org/r/20230828-ppc_rerevert-v1-1-74f55b818907@google.com
---
 arch/powerpc/xmon/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index 7705aa74a24d..682c7c0a6f77 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -12,6 +12,10 @@ ccflags-remove-$(CONFIG_FUNCTION_TRACER) += $(CC_FLAGS_FTRACE)
 
 ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC)
 
+# Clang stores addresses on the stack causing the frame size to blow
+# out. See https://github.com/ClangBuiltLinux/linux/issues/252
+ccflags-$(CONFIG_CC_IS_CLANG) += -Wframe-larger-than=4096
+
 obj-y			+= xmon.o nonstdio.o spr_access.o xmon_bpts.o
 
 ifdef CONFIG_XMON_DISASSEMBLY

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

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