The following commit has been merged into the x86/build branch of tip: Commit-ID: 9e2276fa6eb39817dcc4cda415f0199fb7016b37 Gitweb: https://git.kernel.org/tip/9e2276fa6eb39817dcc4cda415f0199fb7016b37 Author: Bruce Ashfield <bruce.ashfield@xxxxxxxxx> AuthorDate: Thu, 26 Sep 2019 10:32:26 +01:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Tue, 01 Oct 2019 11:19:40 +02:00 arch/x86/boot: Use prefix map to avoid embedded paths It was observed that the kernel embeds the absolute build path in the x86 boot image when the __FILE__ macro is expanded. > From https://bugzilla.yoctoproject.org/show_bug.cgi?id=13458: If you turn on the buildpaths QA test, or try a reproducible build, you discover that the kernel image contains build paths. $ strings bzImage-5.0.19-yocto-standard |grep tmp/ out of pgt_buf in /data/poky-tmp/reproducible/tmp/work-shared/qemux86-64/kernel-source/arch/x86/boot/compressed/kaslr_64.c!? But what's this in the top-level Makefile: $ git grep prefix-map Makefile:KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) So the __FILE__ shouldn't be using the full path. However arch/x86/boot/compressed/Makefile has this: KBUILD_CFLAGS := -m$(BITS) -O2 So that clears KBUILD_FLAGS, removing the -fmacro-prefix-map option. Use -fmacro-prefix-map to have relative paths in the boot image too. [ bp: Massage commit message and put the KBUILD_CFLAGS addition in ..boot/Makefile after the KBUILD_AFLAGS assignment because gas doesn't support -fmacro-prefix-map. ] Signed-off-by: Bruce Ashfield <bruce.ashfield@xxxxxxxxx> Signed-off-by: Ross Burton <ross.burton@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: George Rimar <grimar@xxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> Cc: Nathan Chancellor <natechancellor@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20190926093226.8568-1-ross.burton@xxxxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=204333 --- arch/x86/boot/Makefile | 1 + arch/x86/boot/compressed/Makefile | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index e2839b5..3e9f554 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -67,6 +67,7 @@ clean-files += cpustr.h KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ +KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) GCOV_PROFILE := n UBSAN_SANITIZE := n diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 6b84afd..b246f18 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -38,6 +38,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += -Wno-pointer-sign +KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ GCOV_PROFILE := n
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