linuxkm: initial support for cross-compilation.

also, additional backward-compatibility measures around cp and clean recipe in linuxkm/Makefile. also, in sp_int.c, tweak DECL_DYN_SP_INT_ARRAY() to use an explicit XMEMSET() to clear n[], to avoid unshimmable implicit memset() from gcc on aarch64.
wolfSSL · Jul 23, 2024 · 6ee22de · 6ee22de
1 parent 8f908e7
commit 6ee22de
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Showing 4 changed files with 59 additions and 22 deletions.
diff --git a/Makefile.am b/Makefile.am
@@ -207,7 +207,8 @@ if BUILD_LINUXKM
     SUBDIRS_OPT += linuxkm
     DIST_SUBDIRS_OPT += linuxkm
 
-    export KERNEL_ROOT KERNEL_ARCH KERNEL_EXTRA_CFLAGS \
+    export build_triplet host_triplet CC AS LD \
+        KERNEL_ROOT KERNEL_ARCH KERNEL_EXTRA_CFLAGS \
         EXTRA_CFLAGS EXTRA_CPPFLAGS EXTRA_CCASFLAGS EXTRA_LDFLAGS \
 	AM_CPPFLAGS CPPFLAGS AM_CFLAGS CFLAGS \
         AM_CCASFLAGS CCASFLAGS \

diff --git a/linuxkm/Kbuild b/linuxkm/Kbuild
@@ -18,7 +18,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
 
-SHELL=/bin/bash
+SHELL=bash
 
 ifeq "$(WOLFSSL_OBJ_FILES)" ""
     $(error $$WOLFSSL_OBJ_FILES is unset.)
@@ -48,9 +48,17 @@ endif
 
 $(obj)/linuxkm/module_exports.o: $(WOLFSSL_OBJ_TARGETS)
 
+ifndef KERNEL_THREAD_STACK_SIZE
+    ifdef CROSS_COMPILE
+        KERNEL_THREAD_STACK_SIZE=16384
+    endif
+endif
+
 # this mechanism only works in kernel 5.x+ (fallback to hardcoded value)
-hostprogs := linuxkm/get_thread_size
-always-y := $(hostprogs)
+ifndef KERNEL_THREAD_STACK_SIZE
+    hostprogs := linuxkm/get_thread_size
+    always-y := $(hostprogs)
+endif
 
 HOST_EXTRACFLAGS += $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(KBUILD_CFLAGS) -static -fno-omit-frame-pointer
 
@@ -63,8 +71,10 @@ endif
 # this rule is needed to get build to succeed in 4.x (get_thread_size still doesn't get built)
 $(obj)/linuxkm/get_thread_size: $(src)/linuxkm/get_thread_size.c
 
-$(WOLFSSL_OBJ_TARGETS): | $(obj)/linuxkm/get_thread_size
-KERNEL_THREAD_STACK_SIZE=$(shell test -x $(obj)/linuxkm/get_thread_size && $(obj)/linuxkm/get_thread_size || echo 16384)
+ifndef KERNEL_THREAD_STACK_SIZE
+    $(WOLFSSL_OBJ_TARGETS): | $(obj)/linuxkm/get_thread_size
+    KERNEL_THREAD_STACK_SIZE=$(shell test -x $(obj)/linuxkm/get_thread_size && $(obj)/linuxkm/get_thread_size || echo 16384)
+endif
 MAX_STACK_FRAME_SIZE=$(shell echo $$(( $(KERNEL_THREAD_STACK_SIZE) / 4)))
 
 libwolfssl-y := $(WOLFSSL_OBJ_FILES) linuxkm/module_hooks.o linuxkm/module_exports.o
@@ -181,8 +191,8 @@ endif
 # exclude symbols that don't match wc_* or wolf*.
 $(obj)/linuxkm/module_exports.c: $(src)/module_exports.c.template $(WOLFSSL_OBJ_TARGETS)
 	@cp $< $@
-	@readelf --symbols --wide $(WOLFSSL_OBJ_TARGETS) |				\
-		awk '/^ *[0-9]+: / {							\
+	@$(READELF) --symbols --wide $(WOLFSSL_OBJ_TARGETS) |				\
+		$(AWK) '/^ *[0-9]+: / {							\
 		  if ($$8 !~ /^(wc_|wolf|WOLF|TLSX_)/){next;}				\
 		  if (($$4 == "FUNC") && ($$5 == "GLOBAL") && ($$6 == "DEFAULT")) {	\
 		    print "EXPORT_SYMBOL_NS_GPL(" $$8 ", WOLFSSL);";    		\

diff --git a/linuxkm/Makefile b/linuxkm/Makefile
@@ -18,7 +18,7 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
 
-SHELL=/bin/bash
+SHELL=bash
 
 all: libwolfssl.ko libwolfssl.ko.signed
 
@@ -58,20 +58,41 @@ endif
 
 export WOLFSSL_CFLAGS WOLFSSL_ASFLAGS WOLFSSL_OBJ_FILES WOLFCRYPT_PIE_FILES
 
+ifneq "$(host_triplet)" "$(build_triplet)"
+    CROSS_COMPILE := 'CROSS_COMPILE=$(host_triplet)-'
+endif
+
+OVERRIDE_PATHS :=
+
+ifdef CC
+    ifneq "$(CC)" "cc"
+        OVERRIDE_PATHS := $(OVERRIDE_PATHS) 'CC=$(CC)'
+    endif
+endif
+ifdef AS
+    ifneq "$(AS)" "as"
+        OVERRIDE_PATHS := $(OVERRIDE_PATHS) 'AS=$(AS)'
+    endif
+endif
+ifdef LD
+    ifneq "$(LD)" "ld"
+        OVERRIDE_PATHS := $(OVERRIDE_PATHS) 'LD=$(LD)'
+    endif
+endif
+
 libwolfssl.ko:
-	@if test -z "$(KERNEL_ROOT)"; then echo '$$KERNEL_ROOT is unset' >&2; exit 1; fi
-	@if test -z "$(AM_CFLAGS)$(CFLAGS)"; then echo '$$AM_CFLAGS and $$CFLAGS are both unset.' >&2; exit 1; fi
-	@if test -z "$(src_libwolfssl_la_OBJECTS)"; then echo '$$src_libwolfssl_la_OBJECTS is unset.' >&2; exit 1; fi
-	@if test ! -h $(SRC_TOP)/Kbuild; then ln -s $(MODULE_TOP)/Kbuild $(SRC_TOP)/Kbuild; fi
+	@if test -z '$(KERNEL_ROOT)'; then echo '$$KERNEL_ROOT is unset' >&2; exit 1; fi
+	@if test -z '$(AM_CFLAGS)$(CFLAGS)'; then echo '$$AM_CFLAGS and $$CFLAGS are both unset.' >&2; exit 1; fi
+	@if test -z '$(src_libwolfssl_la_OBJECTS)'; then echo '$$src_libwolfssl_la_OBJECTS is unset.' >&2; exit 1; fi
         # after commit 9a0ebe5011 (6.10), sources must be in $(obj).  work around this by making links to all needed sources:
-	@mkdir -p linuxkm
-	@cp --no-dereference --symbolic-link --no-clobber '$(MODULE_TOP)'/*.[ch] '$(MODULE_TOP)'/linuxkm/
-	@cp --no-dereference --symbolic-link --no-clobber --recursive '$(SRC_TOP)'/wolfcrypt '$(MODULE_TOP)'/
-	@cp --no-dereference --symbolic-link --no-clobber --recursive '$(SRC_TOP)'/src '$(MODULE_TOP)'/
+	@mkdir -p '$(MODULE_TOP)/linuxkm'
+	@test '$(MODULE_TOP)/module_hooks.c' -ef '$(MODULE_TOP)/linuxkm/module_hooks.c' || cp --no-dereference --symbolic-link --no-clobber '$(MODULE_TOP)'/*.[ch] '$(MODULE_TOP)/linuxkm/'
+	@test '$(SRC_TOP)/wolfcrypt/src/wc_port.c' -ef '$(MODULE_TOP)/wolfcrypt/src/wc_port.c' || cp --no-dereference --symbolic-link --no-clobber --recursive '$(SRC_TOP)/wolfcrypt' '$(MODULE_TOP)/'
+	@test '$(SRC_TOP)/src/wolfio.c' -ef '$(MODULE_TOP)/src/wolfio.c' || cp --no-dereference --symbolic-link --no-clobber --recursive '$(SRC_TOP)/src' '$(MODULE_TOP)/'
 ifeq "$(ENABLED_LINUXKM_PIE)" "yes"
-	+$(MAKE) -C $(KERNEL_ROOT) M=$(MODULE_TOP) $(KBUILD_EXTRA_FLAGS) CC_FLAGS_FTRACE=
+	+$(MAKE) ARCH='$(KERNEL_ARCH)' $(OVERRIDE_PATHS) $(CROSS_COMPILE) -C '$(KERNEL_ROOT)' M='$(MODULE_TOP)' $(KBUILD_EXTRA_FLAGS) CC_FLAGS_FTRACE=
 else
-	+$(MAKE) -C $(KERNEL_ROOT) M=$(MODULE_TOP) $(KBUILD_EXTRA_FLAGS)
+	+$(MAKE) ARCH='$(KERNEL_ARCH)' $(OVERRIDE_PATHS) $(CROSS_COMPILE) -C '$(KERNEL_ROOT)' M='$(MODULE_TOP)' $(KBUILD_EXTRA_FLAGS)
 endif
 
 libwolfssl.ko.signed: libwolfssl.ko
@@ -114,6 +135,9 @@ install modules_install:
 # note, must supply $(MODULE_TOP) as the src value for clean so that Kbuild is included, else
 # the top Makefile (which is not for the kernel build) would be included here.
 clean:
+	$(RM) -rf '$(MODULE_TOP)/linuxkm'
+	$(RM) -rf '$(MODULE_TOP)/wolfcrypt'
+	$(RM) -rf '$(MODULE_TOP)/src'
 	+$(MAKE) -C $(KERNEL_ROOT) M=$(MODULE_TOP) src=$(MODULE_TOP) clean
 
 .PHONY: check

diff --git a/wolfcrypt/src/sp_int.c b/wolfcrypt/src/sp_int.c
@@ -210,9 +210,10 @@ This library provides single precision (SP) integer math functions.
 
 
 /* Declare a variable that will be assigned a value on XMALLOC. */
-#define DECL_DYN_SP_INT_ARRAY(n, s, c)  \
-    sp_int* n##d = NULL;            \
-    sp_int* (n)[c] = { NULL, }
+#define DECL_DYN_SP_INT_ARRAY(n, s, c)               \
+    sp_int* n##d = NULL;                             \
+    sp_int* (n)[c];                                  \
+    void *n ## _dummy_var = XMEMSET(n, 0, sizeof(n))
 
 /* DECL_SP_INT_ARRAY: Declare array of 'sp_int'. */
 #if (defined(WOLFSSL_SMALL_STACK) || defined(SP_ALLOC)) && \
@@ -240,6 +241,7 @@ This library provides single precision (SP) integer math functions.
  */
 #define ALLOC_DYN_SP_INT_ARRAY(n, s, c, err, h)                                \
 do {                                                                           \
+    (void)n ## _dummy_var;                                                     \
     if (((err) == MP_OKAY) && ((s) > SP_INT_DIGITS)) {                         \
         (err) = MP_VAL;                                                        \
     }                                                                          \