From bce74491c3008e27dd6e8f79a83b4faa77a08f7e Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Thu, 24 Dec 2020 02:11:41 +0900 Subject: [PATCH] powerpc/vdso: fix unnecessary rebuilds of vgettimeofday.o vgettimeofday.o is unnecessarily rebuilt. Adding it to 'targets' is not enough to fix the issue. Kbuild is correctly rebuilding it because the command line is changed. PowerPC builds each vdso directory twice; first in vdso_prepare to generate vdso{32,64}-offsets.h, second as part of the ordinary build process to embed vdso{32,64}.so.dbg into the kernel. The problem shows up when CONFIG_PPC_WERROR=y due to the following line in arch/powerpc/Kbuild: subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror In the preparation stage, Kbuild directly visits the vdso directories, hence it does not inherit subdir-ccflags-y. In the second descend, Kbuild adds -Werror, which results in the command line flipping with/without -Werror. It implies a potential danger; if a more critical flag that would impact the resulted vdso, the offsets recorded in the headers might be different from real offsets in the embedded vdso images. Removing the unneeded second descend solves the problem. Reported-by: Michael Ellerman Signed-off-by: Masahiro Yamada Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/linuxppc-dev/87tuslxhry.fsf@mpe.ellerman.id.au/ Link: https://lore.kernel.org/r/20201223171142.707053-1-masahiroy@kernel.org --- arch/powerpc/kernel/Makefile | 4 ++-- arch/powerpc/kernel/vdso32/Makefile | 5 +---- arch/powerpc/kernel/{vdso32 => }/vdso32_wrapper.S | 0 arch/powerpc/kernel/vdso64/Makefile | 6 +----- arch/powerpc/kernel/{vdso64 => }/vdso64_wrapper.S | 0 5 files changed, 4 insertions(+), 11 deletions(-) rename arch/powerpc/kernel/{vdso32 => }/vdso32_wrapper.S (100%) rename arch/powerpc/kernel/{vdso64 => }/vdso64_wrapper.S (100%) diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index fe2ef598e2ea..79ee7750937d 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -51,7 +51,7 @@ obj-y += ptrace/ obj-$(CONFIG_PPC64) += setup_64.o \ paca.o nvram_64.o note.o syscall_64.o obj-$(CONFIG_COMPAT) += sys_ppc32.o signal_32.o -obj-$(CONFIG_VDSO32) += vdso32/ +obj-$(CONFIG_VDSO32) += vdso32_wrapper.o obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o obj-$(CONFIG_PPC_DAWR) += dawr.o @@ -60,7 +60,7 @@ obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_power.o obj-$(CONFIG_PPC_BOOK3S_64) += mce.o mce_power.o obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o idle_book3e.o obj-$(CONFIG_PPC_BARRIER_NOSPEC) += security.o -obj-$(CONFIG_PPC64) += vdso64/ +obj-$(CONFIG_PPC64) += vdso64_wrapper.o obj-$(CONFIG_ALTIVEC) += vecemu.o obj-$(CONFIG_PPC_BOOK3S_IDLE) += idle_book3s.o procfs-y := proc_powerpc.o diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile index 9cb6f524854b..7d9a6fee0e3d 100644 --- a/arch/powerpc/kernel/vdso32/Makefile +++ b/arch/powerpc/kernel/vdso32/Makefile @@ -30,7 +30,7 @@ CC32FLAGS += -m32 KBUILD_CFLAGS := $(filter-out -mcmodel=medium -mabi=elfv1 -mabi=elfv2 -mcall-aixdesc,$(KBUILD_CFLAGS)) endif -targets := $(obj-vdso32) vdso32.so.dbg +targets := $(obj-vdso32) vdso32.so.dbg vgettimeofday.o obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32)) GCOV_PROFILE := n @@ -46,9 +46,6 @@ obj-y += vdso32_wrapper.o targets += vdso32.lds CPPFLAGS_vdso32.lds += -P -C -Upowerpc -# Force dependency (incbin is bad) -$(obj)/vdso32_wrapper.o : $(obj)/vdso32.so.dbg - # link rule for the .so file, .lds has to be first $(obj)/vdso32.so.dbg: $(src)/vdso32.lds $(obj-vdso32) $(obj)/vgettimeofday.o FORCE $(call if_changed,vdso32ld_and_check) diff --git a/arch/powerpc/kernel/vdso32/vdso32_wrapper.S b/arch/powerpc/kernel/vdso32_wrapper.S similarity index 100% rename from arch/powerpc/kernel/vdso32/vdso32_wrapper.S rename to arch/powerpc/kernel/vdso32_wrapper.S diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile index bf363ff37152..a06fb9b461fc 100644 --- a/arch/powerpc/kernel/vdso64/Makefile +++ b/arch/powerpc/kernel/vdso64/Makefile @@ -17,7 +17,7 @@ endif # Build rules -targets := $(obj-vdso64) vdso64.so.dbg +targets := $(obj-vdso64) vdso64.so.dbg vgettimeofday.o obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64)) GCOV_PROFILE := n @@ -29,15 +29,11 @@ ccflags-y := -shared -fno-common -fno-builtin -nostdlib \ -Wl,-soname=linux-vdso64.so.1 -Wl,--hash-style=both asflags-y := -D__VDSO64__ -s -obj-y += vdso64_wrapper.o targets += vdso64.lds CPPFLAGS_vdso64.lds += -P -C -U$(ARCH) $(obj)/vgettimeofday.o: %.o: %.c FORCE -# Force dependency (incbin is bad) -$(obj)/vdso64_wrapper.o : $(obj)/vdso64.so.dbg - # link rule for the .so file, .lds has to be first $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE $(call if_changed,vdso64ld_and_check) diff --git a/arch/powerpc/kernel/vdso64/vdso64_wrapper.S b/arch/powerpc/kernel/vdso64_wrapper.S similarity index 100% rename from arch/powerpc/kernel/vdso64/vdso64_wrapper.S rename to arch/powerpc/kernel/vdso64_wrapper.S