bc3703f21c
Using perf probe and libdw on kernel modules failed to find CFI data for symbols. The CFI data is stored in the .eh_frame section. The elfutils libdw is not able to extract the CFI data correctly, because the .eh_frame section requires "non-simple" relocations for kernel modules. The suggestion is to avoid these "non-simple" relocations by emitting the CFI data in the .debug_frame section. Let gcc emit respective directives by specifying the -fno-asynchronous-unwind-tables option. Using the .debug_frame section for CFI data, the .eh_frame section becomes unused and, thus, discard it for kernel and modules builds The vDSO requires the .eh_frame section and, hence, emit the CFI data in both, the .eh_frame and .debug_frame sections. See also discussion on elfutils/libdw bugzilla: https://sourceware.org/bugzilla/show_bug.cgi?id=22452 Suggested-by: Mark Wielaard <mark@klomp.org> Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
66 lines
1.8 KiB
Makefile
66 lines
1.8 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# List of files in the vdso, has to be asm only for now
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KCOV_INSTRUMENT := n
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obj-vdso64 = gettimeofday.o clock_getres.o clock_gettime.o note.o getcpu.o
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# Build rules
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targets := $(obj-vdso64) vdso64.so vdso64.so.dbg
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obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64))
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KBUILD_AFLAGS += -DBUILD_VDSO
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KBUILD_CFLAGS += -DBUILD_VDSO
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KBUILD_AFLAGS_64 := $(filter-out -m64,$(KBUILD_AFLAGS))
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KBUILD_AFLAGS_64 += -m64 -s
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KBUILD_CFLAGS_64 := $(filter-out -m64,$(KBUILD_CFLAGS))
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KBUILD_CFLAGS_64 += -m64 -fPIC -shared -fno-common -fno-builtin
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KBUILD_CFLAGS_64 += -nostdlib -Wl,-soname=linux-vdso64.so.1 \
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$(call cc-ldoption, -Wl$(comma)--hash-style=both)
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$(targets:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_64)
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$(targets:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_64)
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obj-y += vdso64_wrapper.o
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extra-y += vdso64.lds
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CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)
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# Disable gcov profiling and ubsan for VDSO code
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GCOV_PROFILE := n
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UBSAN_SANITIZE := n
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# Force dependency (incbin is bad)
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$(obj)/vdso64_wrapper.o : $(obj)/vdso64.so
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# link rule for the .so file, .lds has to be first
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$(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64)
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$(call if_changed,vdso64ld)
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# strip rule for the .so file
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$(obj)/%.so: OBJCOPYFLAGS := -S
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$(obj)/%.so: $(obj)/%.so.dbg FORCE
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$(call if_changed,objcopy)
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# assembly rules for the .S files
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$(obj-vdso64): %.o: %.S
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$(call if_changed_dep,vdso64as)
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# actual build commands
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quiet_cmd_vdso64ld = VDSO64L $@
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cmd_vdso64ld = $(CC) $(c_flags) -Wl,-T $^ -o $@
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quiet_cmd_vdso64as = VDSO64A $@
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cmd_vdso64as = $(CC) $(a_flags) -c -o $@ $<
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# install commands for the unstripped file
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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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vdso64.so: $(obj)/vdso64.so.dbg
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@mkdir -p $(MODLIB)/vdso
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$(call cmd,vdso_install)
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vdso_install: vdso64.so
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