From: Nick Desaulniers <ndesaulniers@google.com>
To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de
Cc: peterz@infradead.org, clang-built-linux@googlegroups.com,
Nick Desaulniers <ndesaulniers@google.com>,
Vaibhav Rustagi <vaibhavrustagi@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] x86/purgatory: use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS
Date: Mon, 22 Jul 2019 14:32:45 -0700 [thread overview]
Message-ID: <20190722213250.238685-2-ndesaulniers@google.com> (raw)
In-Reply-To: <20190722213250.238685-1-ndesaulniers@google.com>
KBUILD_CFLAGS is very carefully built up in the top level Makefile,
particularly when cross compiling or using different build tools.
Resetting KBUILD_CFLAGS via := assignment is an antipattern.
The comment above the reset mentions that -pg is problematic. Other
Makefiles like arch/x86/xen/vdso/Makefile use
`CFLAGS_REMOVE_file.o = -pg` when CONFIG_FUNCTION_TRACER is set. Prefer
that pattern to wiping out all of the important KBUILD_CFLAGS then
manually having to re-add them.
Fixes: 8fc5b4d4121c ("purgatory: core purgatory functionality")
Reported-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Rather than manually add -mno-sse, -mno-mmx, -mno-sse2, prefer to filter
-pg flags.
arch/x86/purgatory/Makefile | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 91ef244026d2..56bcabca283f 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -20,11 +20,13 @@ KCOV_INSTRUMENT := n
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
# in turn leaves some undefined symbols like __fentry__ in purgatory and not
-# sure how to relocate those. Like kexec-tools, use custom flags.
-
-KBUILD_CFLAGS := -fno-strict-aliasing -Wall -Wstrict-prototypes -fno-zero-initialized-in-bss -fno-builtin -ffreestanding -c -Os -mcmodel=large
-KBUILD_CFLAGS += -m$(BITS)
-KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
+# sure how to relocate those.
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_sha256.o = -pg
+CFLAGS_REMOVE_purgatory.o = -pg
+CFLAGS_REMOVE_string.o = -pg
+CFLAGS_REMOVE_kexec-purgatory.o = -pg
+endif
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
--
2.22.0.657.g960e92d24f-goog
next prev parent reply other threads:[~2019-07-22 21:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 21:32 [PATCH v2 1/2] x86/purgatory: do not use __builtin_memcpy and __builtin_memset Nick Desaulniers
2019-07-22 21:32 ` Nick Desaulniers [this message]
2019-07-22 22:10 ` [PATCH v2 2/2] x86/purgatory: use CFLAGS_REMOVE rather than reset KBUILD_CFLAGS Nick Desaulniers
2019-07-22 22:59 ` Vaibhav Rustagi
2019-07-23 21:28 ` Nick Desaulniers
[not found] ` <20190722213250.238685-3-ndesaulniers@google.com>
2019-07-22 21:41 ` [PATCH v2 0/2] Support kexec/kdump for clang built kernel Nick Desaulniers
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