4.9-stable review patch. If anyone has any objections, please let me know.
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From: Kees Cook keescook@chromium.org
[ Upstream commit 92a4728608a8fd228c572bc8ff50dd98aa0ddf2a ]
Dirk Gouders reported that two consecutive "make" invocations on an already compiled tree will show alternating behaviors:
$ make CALL scripts/checksyscalls.sh DESCEND objtool CHK include/generated/compile.h DATAREL arch/x86/boot/compressed/vmlinux Kernel: arch/x86/boot/bzImage is ready (#48) Building modules, stage 2. MODPOST 165 modules
$ make CALL scripts/checksyscalls.sh DESCEND objtool CHK include/generated/compile.h LD arch/x86/boot/compressed/vmlinux ZOFFSET arch/x86/boot/zoffset.h AS arch/x86/boot/header.o LD arch/x86/boot/setup.elf OBJCOPY arch/x86/boot/setup.bin OBJCOPY arch/x86/boot/vmlinux.bin BUILD arch/x86/boot/bzImage Setup is 15644 bytes (padded to 15872 bytes). System is 6663 kB CRC 3eb90f40 Kernel: arch/x86/boot/bzImage is ready (#48) Building modules, stage 2. MODPOST 165 modules
He bisected it back to:
commit 98f78525371b ("x86/boot: Refuse to build with data relocations")
The root cause was the use of the "if_changed" kbuild function multiple times for the same target. It was designed to only be used once per target, otherwise it will effectively always trigger, flipping back and forth between the two commands getting recorded by "if_changed". Instead, this patch merges the two commands into a single function to get stable build artifacts (i.e. .vmlinux.cmd), and a single build behavior.
Bisected-and-Reported-by: Dirk Gouders dirk@gouders.net Fix-Suggested-by: Masahiro Yamada yamada.masahiro@socionext.com Signed-off-by: Kees Cook keescook@chromium.org Reviewed-by: Masahiro Yamada yamada.masahiro@socionext.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/20180724230827.GA37823@beast Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/boot/compressed/Makefile | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -101,9 +101,13 @@ define cmd_check_data_rel done endef
+# We need to run two commands under "if_changed", so merge them into a +# single invocation. +quiet_cmd_check-and-link-vmlinux = LD $@ + cmd_check-and-link-vmlinux = $(cmd_check_data_rel); $(cmd_ld) + $(obj)/vmlinux: $(vmlinux-objs-y) FORCE - $(call if_changed,check_data_rel) - $(call if_changed,ld) + $(call if_changed,check-and-link-vmlinux)
OBJCOPYFLAGS_vmlinux.bin := -R .comment -S $(obj)/vmlinux.bin: vmlinux FORCE