linux/arch/x86/purgatory/Makefile
Hans de Goede e4160b2e4b x86/purgatory: Fail the build if purgatory.ro has missing symbols
Linking purgatory.ro with -r enables "incremental linking"; this means
no checks for unresolved symbols are done while linking purgatory.ro.

A change to the sha256 code has caused the purgatory in 5.4-rc1 to have
a missing symbol on memzero_explicit(), yet things still happily build.

Add an extra check for unresolved symbols by calling ld without -r
before running bin2c to generate kexec-purgatory.c.

This causes a build of 5.4-rc1 with this patch added to fail as it should:

    CHK     arch/x86/purgatory/purgatory.ro
  ld: arch/x86/purgatory/purgatory.ro: in function `sha256_transform':
  sha256.c:(.text+0x1c0c): undefined reference to `memzero_explicit'
  make[2]: *** [arch/x86/purgatory/Makefile:72:
      arch/x86/purgatory/kexec-purgatory.c] Error 1
  make[1]: *** [scripts/Makefile.build:509: arch/x86/purgatory] Error 2
  make: *** [Makefile:1650: arch/x86] Error 2

Also remove --no-undefined from LDFLAGS_purgatory.ro as that has no
effect.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200317130841.290418-2-hdegoede@redhat.com
2020-03-17 15:59:12 +01:00

80 lines
2.4 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0
OBJECT_FILES_NON_STANDARD := y
purgatory-y := purgatory.o stack.o setup-x86_$(BITS).o sha256.o entry64.o string.o
targets += $(purgatory-y)
PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y))
$(obj)/string.o: $(srctree)/arch/x86/boot/compressed/string.c FORCE
$(call if_changed_rule,cc_o_c)
$(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE
$(call if_changed_rule,cc_o_c)
CFLAGS_sha256.o := -D__DISABLE_EXPORTS
# When linking purgatory.ro with -r unresolved symbols are not checked,
# also link a purgatory.chk binary without -r to check for unresolved symbols.
PURGATORY_LDFLAGS := -e purgatory_start -nostdlib -z nodefaultlib
LDFLAGS_purgatory.ro := -r $(PURGATORY_LDFLAGS)
LDFLAGS_purgatory.chk := $(PURGATORY_LDFLAGS)
targets += purgatory.ro purgatory.chk
# Sanitizer, etc. runtimes are unavailable and cannot be linked here.
GCOV_PROFILE := n
KASAN_SANITIZE := n
UBSAN_SANITIZE := n
KCOV_INSTRUMENT := n
# These are adjustments to the compiler flags used for objects that
# make up the standalone purgatory.ro
PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
# Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
# in turn leaves some undefined symbols like __fentry__ in purgatory and not
# sure how to relocate those.
ifdef CONFIG_FUNCTION_TRACER
PURGATORY_CFLAGS_REMOVE += $(CC_FLAGS_FTRACE)
endif
ifdef CONFIG_STACKPROTECTOR
PURGATORY_CFLAGS_REMOVE += -fstack-protector
endif
ifdef CONFIG_STACKPROTECTOR_STRONG
PURGATORY_CFLAGS_REMOVE += -fstack-protector-strong
endif
ifdef CONFIG_RETPOLINE
PURGATORY_CFLAGS_REMOVE += $(RETPOLINE_CFLAGS)
endif
CFLAGS_REMOVE_purgatory.o += $(PURGATORY_CFLAGS_REMOVE)
CFLAGS_purgatory.o += $(PURGATORY_CFLAGS)
CFLAGS_REMOVE_sha256.o += $(PURGATORY_CFLAGS_REMOVE)
CFLAGS_sha256.o += $(PURGATORY_CFLAGS)
CFLAGS_REMOVE_string.o += $(PURGATORY_CFLAGS_REMOVE)
CFLAGS_string.o += $(PURGATORY_CFLAGS)
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
$(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
$(call if_changed,ld)
targets += kexec-purgatory.c
quiet_cmd_bin2c = BIN2C $@
cmd_bin2c = $(objtree)/scripts/bin2c kexec_purgatory < $< > $@
$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro $(obj)/purgatory.chk FORCE
$(call if_changed,bin2c)
obj-$(CONFIG_KEXEC_FILE) += kexec-purgatory.o