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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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6f121e548f
Currently, vdso.so files are prepared and analyzed by a combination of objcopy, nm, some linker script tricks, and some simple ELF parsers in the kernel. Replace all of that with plain C code that runs at build time. All five vdso images now generate .c files that are compiled and linked in to the kernel image. This should cause only one userspace-visible change: the loaded vDSO images are stripped more heavily than they used to be. Everything outside the loadable segment is dropped. In particular, this causes the section table and section name strings to be missing. This should be fine: real dynamic loaders don't load or inspect these tables anyway. The result is roughly equivalent to eu-strip's --strip-sections option. The purpose of this change is to enable the vvar and hpet mappings to be moved to the page following the vDSO load segment. Currently, it is possible for the section table to extend into the page after the load segment, so, if we map it, it risks overlapping the vvar or hpet page. This happens whenever the load segment is just under a multiple of PAGE_SIZE. The only real subtlety here is that the old code had a C file with inline assembler that did 'call VDSO32_vsyscall' and a linker script that defined 'VDSO32_vsyscall = __kernel_vsyscall'. This most likely worked by accident: the linker script entry defines a symbol associated with an address as opposed to an alias for the real dynamic symbol __kernel_vsyscall. That caused ld to relocate the reference at link time instead of leaving an interposable dynamic relocation. Since the VDSO32_vsyscall hack is no longer needed, I now use 'call __kernel_vsyscall', and I added -Bsymbolic to make it work. vdso2c will generate an error and abort the build if the resulting image contains any dynamic relocations, so we won't silently generate bad vdso images. (Dynamic relocations are a problem because nothing will even attempt to relocate the vdso.) Signed-off-by: Andy Lutomirski <luto@amacapital.net> Link: http://lkml.kernel.org/r/2c4fcf45524162a34d87fdda1eb046b2a5cecee7.1399317206.git.luto@amacapital.net Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
190 lines
5.5 KiB
Makefile
190 lines
5.5 KiB
Makefile
#
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# Building vDSO images for x86.
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#
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KBUILD_CFLAGS += $(DISABLE_LTO)
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VDSO64-$(CONFIG_X86_64) := y
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VDSOX32-$(CONFIG_X86_X32_ABI) := y
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VDSO32-$(CONFIG_X86_32) := y
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VDSO32-$(CONFIG_COMPAT) := y
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vdso-install-$(VDSO64-y) += vdso.so
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vdso-install-$(VDSOX32-y) += vdsox32.so
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vdso-install-$(VDSO32-y) += $(vdso32-images)
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# files to link into the vdso
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vobjs-y := vdso-note.o vclock_gettime.o vgetcpu.o
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vobjs-$(VDSOX32-y) += $(vobjx32s-compat)
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# Filter out x32 objects.
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vobj64s := $(filter-out $(vobjx32s-compat),$(vobjs-y))
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# files to link into kernel
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obj-y += vma.o
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# vDSO images to build
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vdso_img-$(VDSO64-y) += 64
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vdso_img-$(VDSOX32-y) += x32
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vdso_img-$(VDSO32-y) += 32-int80
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vdso_img-$(CONFIG_COMPAT) += 32-syscall
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vdso_img-$(VDSO32-y) += 32-sysenter
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obj-$(VDSO32-y) += vdso32-setup.o
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vobjs := $(foreach F,$(vobj64s),$(obj)/$F)
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$(obj)/vdso.o: $(obj)/vdso.so
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targets += vdso.lds $(vobjs-y)
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# Build the vDSO image C files and link them in.
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vdso_img_objs := $(vdso_img-y:%=vdso-image-%.o)
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vdso_img_cfiles := $(vdso_img-y:%=vdso-image-%.c)
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vdso_img_sodbg := $(vdso_img-y:%=vdso%.so.dbg)
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obj-y += $(vdso_img_objs)
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targets += $(vdso_img_cfiles)
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targets += $(vdso_img_sodbg)
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.SECONDARY: $(vdso_img-y:%=$(obj)/vdso-image-%.c)
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export CPPFLAGS_vdso.lds += -P -C
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VDSO_LDFLAGS_vdso.lds = -m64 -Wl,-soname=linux-vdso.so.1 \
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-Wl,--no-undefined \
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-Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 \
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$(DISABLE_LTO)
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$(obj)/vdso64.so.dbg: $(src)/vdso.lds $(vobjs) FORCE
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$(call if_changed,vdso)
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hostprogs-y += vdso2c
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quiet_cmd_vdso2c = VDSO2C $@
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define cmd_vdso2c
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$(obj)/vdso2c $< $@
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endef
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$(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso2c FORCE
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$(call if_changed,vdso2c)
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#
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# Don't omit frame pointers for ease of userspace debugging, but do
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# optimize sibling calls.
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#
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CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
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$(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
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-fno-omit-frame-pointer -foptimize-sibling-calls
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$(vobjs): KBUILD_CFLAGS += $(CFL)
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#
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# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
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#
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CFLAGS_REMOVE_vdso-note.o = -pg
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CFLAGS_REMOVE_vclock_gettime.o = -pg
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CFLAGS_REMOVE_vgetcpu.o = -pg
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CFLAGS_REMOVE_vvar.o = -pg
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#
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# X32 processes use x32 vDSO to access 64bit kernel data.
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#
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# Build x32 vDSO image:
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# 1. Compile x32 vDSO as 64bit.
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# 2. Convert object files to x32.
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# 3. Build x32 VDSO image with x32 objects, which contains 64bit codes
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# so that it can reach 64bit address space with 64bit pointers.
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#
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CPPFLAGS_vdsox32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdsox32.lds = -Wl,-m,elf32_x86_64 \
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-Wl,-soname=linux-vdso.so.1 \
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-Wl,-z,max-page-size=4096 \
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-Wl,-z,common-page-size=4096
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vobjx32s-y := $(vobj64s:.o=-x32.o)
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vobjx32s := $(foreach F,$(vobjx32s-y),$(obj)/$F)
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# Convert 64bit object file to x32 for x32 vDSO.
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quiet_cmd_x32 = X32 $@
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cmd_x32 = $(OBJCOPY) -O elf32-x86-64 $< $@
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$(obj)/%-x32.o: $(obj)/%.o FORCE
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$(call if_changed,x32)
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targets += vdsox32.lds $(vobjx32s-y)
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$(obj)/vdsox32.so.dbg: $(src)/vdsox32.lds $(vobjx32s) FORCE
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$(call if_changed,vdso)
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#
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# Build multiple 32-bit vDSO images to choose from at boot time.
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#
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vdso32.so-$(VDSO32-y) += int80
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vdso32.so-$(CONFIG_COMPAT) += syscall
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vdso32.so-$(VDSO32-y) += sysenter
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vdso32-images = $(vdso32.so-y:%=vdso32-%.so)
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CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
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VDSO_LDFLAGS_vdso32.lds = -m32 -Wl,-m,elf_i386 -Wl,-soname=linux-gate.so.1
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# This makes sure the $(obj) subdirectory exists even though vdso32/
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# is not a kbuild sub-make subdirectory.
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override obj-dirs = $(dir $(obj)) $(obj)/vdso32/
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targets += vdso32/vdso32.lds
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targets += vdso32/note.o vdso32/vclock_gettime.o $(vdso32.so-y:%=vdso32/%.o)
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targets += vdso32/vclock_gettime.o
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$(obj)/vdso32.o: $(vdso32-images:%=$(obj)/%)
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KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
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$(vdso32-images:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
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$(vdso32-images:%=$(obj)/%.dbg): asflags-$(CONFIG_X86_64) += -m32
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KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
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KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
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KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
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KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
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KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
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KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
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$(vdso32-images:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
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$(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \
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$(obj)/vdso32/vdso32.lds \
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$(obj)/vdso32/vclock_gettime.o \
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$(obj)/vdso32/note.o \
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$(obj)/vdso32/%.o
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$(call if_changed,vdso)
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#
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# The DSO images are built using a special linker script.
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#
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quiet_cmd_vdso = VDSO $@
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cmd_vdso = $(CC) -nostdlib -o $@ \
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$(VDSO_LDFLAGS) $(VDSO_LDFLAGS_$(filter %.lds,$(^F))) \
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-Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \
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sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@'
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VDSO_LDFLAGS = -fPIC -shared $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) \
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-Wl,-Bsymbolic $(LTO_CFLAGS)
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GCOV_PROFILE := n
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#
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# Install the unstripped copy of vdso*.so listed in $(vdso-install-y).
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#
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quiet_cmd_vdso_install = INSTALL $@
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cmd_vdso_install = cp $(obj)/$@.dbg $(MODLIB)/vdso/$@
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$(vdso-install-y): %.so: $(obj)/%.so.dbg FORCE
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@mkdir -p $(MODLIB)/vdso
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$(call cmd,vdso_install)
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PHONY += vdso_install $(vdso-install-y)
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vdso_install: $(vdso-install-y)
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clean-files := vdso32-syscall* vdso32-sysenter* vdso32-int80*
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