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x86/boot: Check that there are no run-time relocations 

Add a linker script check that there are no run-time relocations, and
remove the old one that tries to check via looking for specially-named
sections in the object files.

Drop the tests for -fPIE compiler option and -pie linker option, as they
are available in all supported gcc and binutils versions (as well as
clang and lld).

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Reviewed-by: Sedat Dilek <sedat.dilek@gmail.com>
Link: https://lore.kernel.org/r/20200731230820.1742553-8-keescook@chromium.org
This commit is contained in:
Arvind Sankar 2020-07-31 16:07:51 -07:00 committed by Ingo Molnar
parent 3f086189cd
commit 527afc2122
2 changed files with 11 additions and 25 deletions
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28
arch/x86/boot/compressed/Makefile
View File

@ -29,7 +29,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst
KBUILD_CFLAGS := -m$(BITS) -O2
KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
cflags-$(CONFIG_X86_32) := -march=i386
cflags-$(CONFIG_X86_64) := -mcmodel=small
@ -52,7 +52,7 @@ UBSAN_SANITIZE :=n
KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
# Compressed kernel should be built as PIE since it may be loaded at any
# address by the bootloader.
LDFLAGS_vmlinux := $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
LDFLAGS_vmlinux := -pie $(call ld-option, --no-dynamic-linker)
LDFLAGS_vmlinux += -T
hostprogs := mkpiggy
@ -87,30 +87,8 @@ vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a
# The compressed kernel is built with -fPIC/-fPIE so that a boot loader
# can place it anywhere in memory and it will still run. However, since
# it is executed as-is without any ELF relocation processing performed
# (and has already had all relocation sections stripped from the binary),
# none of the code can use data relocations (e.g. static assignments of
# pointer values), since they will be meaningless at runtime. This check
# will refuse to link the vmlinux if any of these relocations are found.
quiet_cmd_check_data_rel = DATAREL $@
define cmd_check_data_rel
for obj in $(filter %.o,$^); do \
$(READELF) -S $$obj | grep -qF .rel.local && { \
echo "error: $$obj has data relocations!" >&2; \
exit 1; \
} || true; \
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) $(efi-obj-y) FORCE
$(call if_changed,check-and-link-vmlinux)
$(call if_changed,ld)
OBJCOPYFLAGS_vmlinux.bin := -R .comment -S
$(obj)/vmlinux.bin: vmlinux FORCE

8
arch/x86/boot/compressed/vmlinux.lds.S
View File

@ -42,6 +42,12 @@ SECTIONS
*(.rodata.*)
_erodata = . ;
}
.rel.dyn : {
*(.rel.*)
}
.rela.dyn : {
*(.rela.*)
}
.got : {
*(.got)
}
@ -85,3 +91,5 @@ ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT en
#else
ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0xc, "Unexpected GOT/PLT entries detected!")
#endif
ASSERT(SIZEOF(.rel.dyn) == 0 && SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations detected!")