[PATCH v2 09/19] build: embed the standalone crypto module into vmlinux

Jay Wang
2026-04-18T00:23:05Z

As mentioned in earlier patch, in order to load standalone crypto module
in early boot before filesystem is ready, the module needs to be embedded
into vmlinux image. This patch intends to make such embedded process a
seamless process that will automatically trigger as building vmlinux (i.e.,
during `make vmlinux`). So it adds make dependency rule such that vmlinux
will depend on the `fips140.ko` and its signature `.fips140.hmac`
generation rule. It also modifies vmlinux link rule to finally link them
with vmlinux.o.

The high level idea of embedding fips140.ko into vmlinux stems from
Vegard Nossum <vegard.nossum@oracle.com>.

Signed-off-by: Jay Wang <wanjay@amazon.com>
---
Makefile | 32 +++++++++++++++++++++++++++++---
arch/arm64/kernel/vmlinux.lds.S | 16 ++++++++++++++++
arch/x86/kernel/vmlinux.lds.S | 16 ++++++++++++++++
crypto/fips140/Kconfig | 29 +++++++++++++++++++++++++++++
crypto/fips140/Makefile | 4 +++-
crypto/fips140/fips140-loader.c | 9 +++++++++
scripts/Makefile.modfinal | 18 +++++++++++++++++-
scripts/Makefile.vmlinux | 6 +++++-
scripts/link-vmlinux.sh | 5 +++++
9 files changed, 129 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index f3c43f87d6786..bd0e4034927c6 100644
--- a/Makefile
+++ b/Makefile
@@ -1306,12 +1306,21 @@ quiet_cmd_ar_vmlinux.a = AR $@
$(AR) mPiT $$($(AR) t $@ | sed -n 1p) $@ $$($(AR) t $@ | grep -F -f $(srctree)/scripts/head-object-list.txt)

ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
+fips140_build = .
+ifeq ($(CONFIG_CRYPTO_FIPS140_EXTMOD_SOURCE),y)
+fips140_build = fips140_build
+endif

# Generate exported symbol list from fips140.o (no vmlinux.o dependency)
quiet_cmd_gen_fips140_exported =
cmd_gen_fips140_exported = $(NM) $< 2>/dev/null | \
sed -n 's/.*__export_symbol_//p' | sort | \
- awk '{print "0x00000000\t" $$1 "\tcrypto/fips140/fips140\tEXPORT_SYMBOL_GPL\t"}' > $@
+ awk '{print "0x00000000\t" $$1 "\tcrypto/fips140/fips140\tEXPORT_SYMBOL_GPL\t"}' > $@ \
+ $(fips140_cp_exported)
+
+ifeq ($(CONFIG_CRYPTO_FIPS140_EXTMOD_SOURCE),y)
+fips140_cp_exported = ; cp "$(fips140_build)/crypto/fips140/.fips140.exported" crypto/fips140/.fips140.exported
+endif

crypto/fips140/.fips140.exported: crypto/fips140/fips140.o FORCE
$(call if_changed,gen_fips140_exported)
@@ -1357,7 +1366,22 @@ PHONY += vmlinux
vmlinux: private _LDFLAGS_vmlinux := $(LDFLAGS_vmlinux)
vmlinux: export LDFLAGS_vmlinux = $(_LDFLAGS_vmlinux)
ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
-vmlinux: fips140-ready
+vmlinux: crypto/fips140/fips140-embedded.o crypto/fips140/fips140-digest.o
+crypto/fips140/fips140-embedded.o: fips140-ready
+ @echo " LD $@"
+ @$(LD) -r -b binary -o $@ $(fips140_build)/crypto/fips140/fips140.ko
+ @$(OBJCOPY) --rename-section .data=.fips140_module_data $@
+
+crypto/fips140/.fips140.hmac: crypto/fips140/fips140-embedded.o
+ @echo " HMAC $@"
+ @hmac_key=$$(awk -F'"' '/^CONFIG_CRYPTO_FIPS140_HMAC_KEY=/{print $$2}' .config); \
+ openssl dgst -sha256 -hmac "$$hmac_key" -binary -out $@ $(fips140_build)/crypto/fips140/fips140.ko
+
+crypto/fips140/fips140-digest.o: crypto/fips140/.fips140.hmac
+ @echo " LD $@"
+ @$(LD) -r -b binary -o $@ crypto/fips140/.fips140.hmac
+ @$(OBJCOPY) --rename-section .data=.fips140_digest $@
+
# Ensure fips140.ko is built before embedding
fips140-ready: crypto/fips140/fips140.o crypto/fips140/.fips140.order crypto/fips140/fips140.mod vmlinux.o | modules_prepare
$(Q)$(MAKE) KBUILD_MODULES= -f $(srctree)/scripts/Makefile.modpost
@@ -1365,7 +1389,9 @@ fips140-ready: crypto/fips140/fips140.o crypto/fips140/.fips140.order crypto/fip
ifneq ($(KBUILD_MODPOST_NOFINAL),1)
$(Q)$(MAKE) KBUILD_MODULES=y crypto-module-gen=1 -f $(srctree)/scripts/Makefile.modfinal
endif
- @:
+ifeq ($(CONFIG_CRYPTO_FIPS140_EXTMOD_SOURCE),y)
+ cp "$(fips140_build)/crypto/fips140/fips140.ko" crypto/fips140/fips140.ko;
+endif

# Generate fips140.o from crypto-module.a files
crypto/fips140/fips140.o: crypto-module.a FORCE
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 2d1e75263f033..8d7905b9207ef 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -201,6 +201,22 @@ SECTIONS
/* everything from this point to __init_begin will be marked RO NX */
RO_DATA(PAGE_SIZE)

+#ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
+ /* FIPS 140 embedded module data */
+ .fips140_embedded : {
+ . = ALIGN(8);
+ _binary_fips140_ko_start = .;
+ KEEP(*(.fips140_module_data))
+ _binary_fips140_ko_end = .;
+ }
+ .fips140_digest : {
+ . = ALIGN(8);
+ _binary_fips140_hmac_start = .;
+ KEEP(*(.fips140_digest))
+ _binary_fips140_hmac_end = .;
+ }
+#endif
+
HYPERVISOR_RODATA_SECTIONS

.got : { *(.got) }
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 4711a35e706cd..392d209082427 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -171,6 +171,22 @@ SECTIONS
RO_DATA(PAGE_SIZE)
X86_ALIGN_RODATA_END

+#ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
+ /* FIPS 140 embedded module data */
+ .fips140_embedded : AT(ADDR(.fips140_embedded) - LOAD_OFFSET) {
+ . = ALIGN(8);
+ _binary_fips140_ko_start = .;
+ KEEP(*(.fips140_module_data))
+ _binary_fips140_ko_end = .;
+ }
+ .fips140_digest : AT(ADDR(.fips140_digest) - LOAD_OFFSET) {
+ . = ALIGN(8);
+ _binary_fips140_hmac_start = .;
+ KEEP(*(.fips140_digest))
+ _binary_fips140_hmac_end = .;
+ }
+#endif
+
/* Data */
.data : AT(ADDR(.data) - LOAD_OFFSET) {
/* Start of data section */
diff --git a/crypto/fips140/Kconfig b/crypto/fips140/Kconfig
index 0665e94b9fe05..68b877f0dbab7 100644
--- a/crypto/fips140/Kconfig
+++ b/crypto/fips140/Kconfig
@@ -12,4 +12,33 @@ config CRYPTO_FIPS140_EXTMOD
can be enabled to restrict crypto algorithm usage to only
those provided by this module.

+ If unsure, say N.
+config CRYPTO_FIPS140_HMAC_KEY
+ string "FIPS 140-3 external module HMAC key"
+ depends on CRYPTO_FIPS140_EXTMOD
+ default "The quick brown fox jumps over the lazy dog while the sphinx of black quartz judges my vow"
+ help
+ This is the HMAC key used to build and verify the integrity of
+ the FIPS module.
+
+ Must be at least 80 characters.
+config CRYPTO_FIPS140_EXTMOD_SOURCE
+ bool "Use external FIPS module source"
+ depends on CRYPTO_FIPS140_EXTMOD
+ default n
+ help
+ Use pre-built FIPS modules from an external build directory instead
+ of freshly built modules from the current kernel build.
+
+ If N, the kernel uses freshly generated crypto modules from the
+ current build directory:
+ - crypto/fips140/fips140.ko
+ - crypto/aes.ko
+ - crypto/sha256.ko
+
+ If Y, pre-built modules from fips140_build/ are used:
+ - fips140_build/crypto/fips140/fips140.ko
+ - fips140_build/crypto/aes.ko
+ - fips140_build/crypto/sha256.ko
+
If unsure, say N.
diff --git a/crypto/fips140/Makefile b/crypto/fips140/Makefile
index 6a3dcc224e828..db61f1113d686 100644
--- a/crypto/fips140/Makefile
+++ b/crypto/fips140/Makefile
@@ -2,7 +2,9 @@
crypto-objs-y += \
fips140-module.o

+obj-y += fips140-loader.o
+
CFLAGS_fips140-fn-redirect.o += -I$(obj)
CFLAGS_fips140-module.o += -DFIPS140_CORE

-clean-files:= .fips140.order .fips140.symvers .fips140-fn-redirect.h .fips140.exported
\ No newline at end of file
+clean-files:= .fips140.order .fips140.symvers .fips140-fn-redirect.h .fips140.exported .fips140.hmac
\ No newline at end of file
diff --git a/crypto/fips140/fips140-loader.c b/crypto/fips140/fips140-loader.c
index 369ab3ceede9c..d2eb14f406d6e 100644
--- a/crypto/fips140/fips140-loader.c
+++ b/crypto/fips140/fips140-loader.c
@@ -14,10 +14,17 @@

extern const u8 _binary_fips140_ko_start[];
extern const u8 _binary_fips140_ko_end[];
+extern const u8 _binary_fips140_hmac_start[];
+extern const u8 _binary_fips140_hmac_end[];
+
const u8 *_binary_crypto_ko_start;
EXPORT_SYMBOL_GPL(_binary_crypto_ko_start);
const u8 *_binary_crypto_ko_end;
EXPORT_SYMBOL_GPL(_binary_crypto_ko_end);
+const u8 *_binary_crypto_hmac_start;
+EXPORT_SYMBOL_GPL(_binary_crypto_hmac_start);
+const u8 *_binary_crypto_hmac_end;
+EXPORT_SYMBOL_GPL(_binary_crypto_hmac_end);

/* Function to load crypto module from memory */
extern int load_crypto_module_mem(const char *mem, size_t size);
@@ -26,6 +33,8 @@ static void load_prepare(void)
{
_binary_crypto_ko_start = _binary_fips140_ko_start;
_binary_crypto_ko_end = _binary_fips140_ko_end;
+ _binary_crypto_hmac_start = _binary_fips140_hmac_start;
+ _binary_crypto_hmac_end = _binary_fips140_hmac_end;
}

static int fips_loader_init(void)
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index 2e087355988ba..f9b9c798db1a7 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -69,12 +69,28 @@ ifeq ($(crypto-module-gen),1)
+$(call if_changed,ld_ko_o)
else
%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
- +$(call if_changed_except,ld_ko_o,$(objtree)/vmlinux)
+ +$(call if_changed_except,ld_ko_o_and_cp_extmod,$(objtree)/vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+$(if $(newer-prereqs),$(call cmd,btf_ko))
endif
+$(call cmd,check_tracepoint)
endif
+
+fips140_build = .
+ifeq ($(CONFIG_CRYPTO_FIPS140_EXTMOD_SOURCE),y)
+fips140_build = fips140_build
+endif
+
+quiet_cmd_ld_ko_o_and_cp_extmod = LD [M] $@
+ cmd_ld_ko_o_and_cp_extmod = \
+ $(LD) -r $(KBUILD_LDFLAGS) \
+ $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE) \
+ -T $(objtree)/scripts/module.lds -o $@ $(filter %.o, $^); \
+ if [ "$(CONFIG_CRYPTO_FIPS140_EXTMOD_SOURCE)" = "y" ] && \
+ [ -f "$(fips140_build)/$@" ]; then \
+ echo " CP [M] $@"; \
+ cp "$(fips140_build)/$@" "$@"; \
+ fi
else
%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
+$(call if_changed_except,ld_ko_o,$(objtree)/vmlinux)
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index fcae1e432d9ad..93b382e08892d 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -67,8 +67,12 @@ cmd_link_vmlinux = \
$< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)" "$@"; \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)

+ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
+fips140-deps := crypto/fips140/fips140-embedded.o crypto/fips140/fips140-digest.o
+endif
+
targets += vmlinux.unstripped .vmlinux.export.o
-vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) FORCE
+vmlinux.unstripped: scripts/link-vmlinux.sh vmlinux.o .vmlinux.export.o $(KBUILD_LDS) $(fips140-deps) FORCE
+$(call if_changed_dep,link_vmlinux)
ifdef CONFIG_DEBUG_INFO_BTF
vmlinux.unstripped: $(RESOLVE_BTFIDS) $(srctree)/scripts/gen-btf.sh
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index ee83d54a7cd0f..e5f0eef865f78 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -75,6 +75,11 @@ vmlinux_link()
fi

objs="${objs} .vmlinux.export.o"
+
+ if is_enabled CONFIG_CRYPTO_FIPS140_EXTMOD; then
+ objs="${objs} crypto/fips140/fips140-embedded.o crypto/fips140/fips140-digest.o"
+ fi
+
objs="${objs} init/version-timestamp.o"

if [ "${SRCARCH}" = "um" ]; then
--
2.47.3