# Linux kernel-native Makefile ("Kbuild") for libwolfssl.ko
#
# Copyright (C) 2006-2024 wolfSSL Inc.
#
# This file is part of wolfSSL.
#
# wolfSSL is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# wolfSSL is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA

SHELL=bash

ifeq "$(WOLFSSL_OBJ_FILES)" ""
    $(error $$WOLFSSL_OBJ_FILES is unset.)
endif

ifeq "$(WOLFSSL_CFLAGS)" ""
    $(error $$WOLFSSL_CFLAGS is unset.)
endif

WOLFSSL_CFLAGS += -ffreestanding -Wframe-larger-than=$(MAX_STACK_FRAME_SIZE) -isystem $(shell $(CC) -print-file-name=include)

ifeq "$(KERNEL_ARCH)" "x86"
    WOLFSSL_CFLAGS += -mpreferred-stack-boundary=4
else ifeq "$(KERNEL_ARCH)" "aarch64"
    WOLFSSL_CFLAGS += -mno-outline-atomics
else ifeq "$(KERNEL_ARCH)" "arm64"
    WOLFSSL_CFLAGS += -mno-outline-atomics
endif

obj-m := libwolfssl.o

WOLFSSL_OBJ_TARGETS := $(patsubst %, $(obj)/%, $(WOLFSSL_OBJ_FILES))

ifeq "$(ENABLED_LINUXKM_PIE)" "yes"
    WOLFCRYPT_PIE_FILES := $(patsubst %, $(obj)/%, $(WOLFCRYPT_PIE_FILES))
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)
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

# "-mindirect-branch=keep -mfunction-return=keep" to avoid "undefined reference
#  to `__x86_return_thunk'" on CONFIG_RETHUNK kernels (5.19.0-rc7)
ifeq "$(KERNEL_ARCH)" "x86"
  HOST_EXTRACFLAGS += -mindirect-branch=keep -mfunction-return=keep
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

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

WOLFSSL_CFLAGS_NO_VECTOR_INSNS := $(CFLAGS_SIMD_DISABLE) $(CFLAGS_FPU_DISABLE)
ifeq "$(ENABLED_ASM)" "yes"
    WOLFSSL_CFLAGS_YES_VECTOR_INSNS := $(CFLAGS_SIMD_ENABLE) $(CFLAGS_FPU_DISABLE) $(CFLAGS_AUTO_VECTORIZE_DISABLE)
else
    WOLFSSL_CFLAGS_YES_VECTOR_INSNS := $(WOLFSSL_CFLAGS_NO_VECTOR_INSNS)
endif

ccflags-y := $(WOLFSSL_CFLAGS) $(WOLFSSL_CFLAGS_NO_VECTOR_INSNS)

$(obj)/libwolfssl.mod.o: ccflags-y :=
$(obj)/wolfcrypt/test/test.o: ccflags-y += -DNO_MAIN_DRIVER -DWOLFSSL_NO_OPTIONS_H

$(obj)/wolfcrypt/src/aes.o: ccflags-y = $(WOLFSSL_CFLAGS) $(WOLFSSL_CFLAGS_YES_VECTOR_INSNS)

ifeq "$(ENABLED_LINUXKM_PIE)" "yes"
    PIE_FLAGS := -fPIE -fno-stack-protector -fno-toplevel-reorder
    PIE_SUPPORT_FLAGS := -DUSE_WOLFSSL_LINUXKM_PIE_REDIRECT_TABLE
    ifeq "$(KERNEL_ARCH)" "x86"
        PIE_FLAGS += -mcmodel=small -mindirect-branch=keep -mfunction-return=keep
    endif
    ifeq "$(KERNEL_ARCH)" "mips"
        PIE_FLAGS += -mabicalls
    endif
    $(WOLFCRYPT_PIE_FILES): ccflags-y += $(PIE_SUPPORT_FLAGS) $(PIE_FLAGS)
    $(WOLFCRYPT_PIE_FILES): ccflags-remove-y += -pg
    # disabling retpoline generation leads to profuse warnings without this:
    $(WOLFCRYPT_PIE_FILES): OBJECT_FILES_NON_STANDARD := y
    $(obj)/linuxkm/module_hooks.o: ccflags-y += $(PIE_SUPPORT_FLAGS)
endif

$(obj)/wolfcrypt/benchmark/benchmark.o: ccflags-y = $(WOLFSSL_CFLAGS) $(CFLAGS_FPU_ENABLE) $(CFLAGS_SIMD_ENABLE) $(PIE_SUPPORT_FLAGS) -DNO_MAIN_FUNCTION -DWOLFSSL_NO_OPTIONS_H
$(obj)/wolfcrypt/benchmark/benchmark.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_ENABLE_SIMD_DISABLE)

asflags-y := $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPUSIMD_DISABLE)

# vectorized implementations that are kernel-safe are listed here.
# these are known kernel-compatible, but need the vector instructions enabled in the assembler,
# and most of them still irritate objtool.
$(obj)/wolfcrypt/src/aes_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/aes_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/aes_gcm_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/aes_gcm_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/aes_xts_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/aes_xts_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/sp_x86_64_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/sp_x86_64_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/sha256_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/sha256_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/sha512_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/sha512_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/sha3_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/sha3_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/chacha_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/chacha_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/poly1305_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)
$(obj)/wolfcrypt/src/poly1305_asm.o: OBJECT_FILES_NON_STANDARD := y
$(obj)/wolfcrypt/src/wc_kyber_asm.o: asflags-y = $(WOLFSSL_ASFLAGS) $(ASFLAGS_FPU_DISABLE_SIMD_ENABLE)

ifeq "$(ENABLED_LINUXKM_PIE)" "yes"

rename-pie-text-and-data-sections: $(WOLFSSL_OBJ_TARGETS)

ifndef NM
    NM := nm
endif

ifndef READELF
    READELF := readelf
endif

ifndef OBJCOPY
    OBJCOPY := objcopy
endif

.PHONY: rename-pie-text-and-data-sections
rename-pie-text-and-data-sections:
ifneq "$(quiet)" "silent_"
	@echo -n '  Checking wolfCrypt for unresolved symbols and forbidden relocations... '
endif
	@cd "$(obj)" || exit $$?; \
	$(LD) -relocatable -o wolfcrypt_test_link.o $(WOLFCRYPT_PIE_FILES) || exit $$?; \
	undefined=$$($(NM) --undefined-only wolfcrypt_test_link.o) || exit $$?; \
	GOT_relocs=$$($(READELF) --relocs --wide wolfcrypt_test_link.o | egrep '^[^ ]+ +[^ ]+ +[^ ]*GOT[^ ]* ') || [ $$? = 1 ] || exit 2; \
	rm wolfcrypt_test_link.o; \
	if [ -n "$$undefined" ]; then \
	    echo "wolfCrypt container has unresolved symbols:" 1>&2; \
	    echo "$$undefined" 1>&2; \
	    exit 1; \
	fi; \
	if [ -n "$$GOT_relocs" ]; then \
	    echo "wolfCrypt container has GOT relocations (non-local function address used as operand?):" 1>&2; \
	    echo "$$GOT_relocs" 1>&2; \
	    exit 1; \
	fi
ifneq "$(quiet)" "silent_"
	@echo 'OK.'
endif
	@cd "$(obj)" || exit $$?; \
	for file in $(WOLFCRYPT_PIE_FILES); do \
	    $(OBJCOPY) --rename-section .text=.text.wolfcrypt --rename-section .data=.data.wolfcrypt --rename-section .rodata=.rodata.wolfcrypt "$$file" || exit $$?; \
	done
ifneq "$(quiet)" "silent_"
	@echo '  wolfCrypt .{text,data,rodata} sections containerized to .{text,data,rodata}.wolfcrypt'
endif

$(obj)/linuxkm/module_exports.c: rename-pie-text-and-data-sections

endif


# auto-generate the exported symbol list, leveraging the WOLFSSL_API visibility tags.
# 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]+: / {							\
		  if ($$8 !~ /^(wc_|wolf|WOLF|TLSX_)/){next;}				\
		  if (($$4 == "FUNC") && ($$5 == "GLOBAL") && ($$6 == "DEFAULT")) {	\
		    print "EXPORT_SYMBOL_NS_GPL(" $$8 ", WOLFSSL);";    		\
		  }									\
		}' >> $@
	@echo -e '#ifndef NO_CRYPT_TEST\nEXPORT_SYMBOL_NS_GPL(wolfcrypt_test, WOLFSSL);\n#endif' >> $@

clean-files := linuxkm src wolfcrypt