linux-kernel - [PATCH 2/3] MIPS: boot/compressed: Build without LTO

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Date:   Mon, 13 Dec 2021 22:49:13 +0000
From:   Paul Cercueil <paul@...pouillou.net>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     list@...ndingux.net, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH 2/3] MIPS: boot/compressed: Build without LTO

We need a valid ELF object for dummy.o, so that objcopy can insert the
vmlinuz payload.

Therefore, we must build the decompresser program without LTO, otherwise
dummy.o will be LLVM bytecode instead of a ELF object file.

Building the decompresser with LTO wouldn't make much sense anyway,
unlike building the vmlinuz itself with LTO.

Signed-off-by: Paul Cercueil <paul@...pouillou.net>
---
 arch/mips/boot/compressed/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
index 4c9ecfbb0ef4..2d01c50fb0b1 100644
--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -27,6 +27,9 @@ ifdef CONFIG_CPU_LOONGSON64
 KBUILD_CFLAGS := $(filter-out -march=loongson3a, $(KBUILD_CFLAGS)) -march=mips64r2
 endif
 
+# Disable LTO
+KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
+
 KBUILD_CFLAGS := $(KBUILD_CFLAGS) -mno-abicalls -D__KERNEL__ -D__DISABLE_EXPORTS \
 	-DBOOT_HEAP_SIZE=$(BOOT_HEAP_SIZE) -D"VMLINUX_LOAD_ADDRESS_ULL=$(VMLINUX_LOAD_ADDRESS)ull"
 
-- 
2.33.0