#  SPDX-License-Identifier: BSD-3-Clause
#
#  Build glue for the Rust ELF loader.
#
#  The loader core is a `no_std` Rust staticlib; `glue/shim.c` is the only C
#  that talks to Unikraft's headers. Unikraft links the archive through
#  `ALIBS-y`, which `buildrule_olib` already wraps in --start-group.

$(eval $(call addlib,appelfloader))

APPELFLOADER_CFLAGS-$(CONFIG_APPELFLOADER_DEBUG) += -DUK_DEBUG

APPELFLOADER_SRCS-y += $(APPELFLOADER_BASE)/glue/shim.c

APPELFLOADER_SRCS-$(CONFIG_APPELFLOADER_VDSO) += $(APPELFLOADER_BUILD)/vdso-image.c
APPELFLOADER_SRCS-$(CONFIG_APPELFLOADER_VDSO) += $(APPELFLOADER_BASE)/vdso/vsyscall.c

################################################################################
# The Rust loader core
################################################################################
#
# Bare-metal targets, not *-unknown-linux-*: the unikernel has no OS below it,
# and Unikraft compiles kernel code without FP/SIMD (-mgeneral-regs-only on
# arm64, -mno-sse on x86_64). The `softfloat`/`none` targets match that ABI, so
# the archive can be linked with the rest of the kernel without the compiler
# spilling a NEON register into an interrupt-time code path.
#
APPELFLOADER_RUST_DIR    := $(APPELFLOADER_BASE)/rust

# Cargo's target directory. Overridable (and inherited from the environment,
# hence `?=`) so a caller can point it at a cache that outlives the Unikraft
# build tree -- the loader is the same archive for a given source revision,
# target and feature set, and rebuilding it on every kernel build is pure
# waste. bsdkrun's build.sh mounts a host directory here.
APPELFLOADER_RUST_CACHE ?= $(APPELFLOADER_BUILD)/rust

ifeq ($(CONFIG_ARCH_ARM_64),y)
APPELFLOADER_RUST_TARGET := aarch64-unknown-none-softfloat
else ifeq ($(CONFIG_ARCH_X86_64),y)
APPELFLOADER_RUST_TARGET := x86_64-unknown-none
else
$(error app-elfloader-rs supports arm64 and x86_64 only)
endif

# What cargo produces, in the (possibly shared) cache...
APPELFLOADER_RUST_BUILT := \
	$(APPELFLOADER_RUST_CACHE)/$(APPELFLOADER_RUST_TARGET)/release/libelfloader_rs.a

# ...and the copy this build links, inside the build tree.
APPELFLOADER_RUST_LIB := $(APPELFLOADER_BUILD)/libelfloader_rs.a

# Kconfig symbols the Rust side needs at *compile* time, because they decide
# which C the archive is allowed to reference. CONFIG_APPELFLOADER_ELF_BINFMT
# guards the `uk_binfmt_loader_args` accessors in glue/shim.c, so `binfmt.rs`
# has to be compiled out with them.
APPELFLOADER_RUST_FEATURES-$(CONFIG_APPELFLOADER_ELF_BINFMT) += binfmt

APPELFLOADER_RUST_FEATURE_FLAGS := $(if $(APPELFLOADER_RUST_FEATURES-y), \
	--features $(subst $(space),$(comma),$(strip $(APPELFLOADER_RUST_FEATURES-y))))

# $(UK_CONFIG) is a prerequisite because the *feature set* is derived from
# Kconfig: without it, toggling CONFIG_APPELFLOADER_ELF_BINFMT leaves the
# previously built archive in place and the link fails on the binfmt entry
# points that glue/shim.c has just started referencing.
APPELFLOADER_RUST_SRCS := \
	$(wildcard $(APPELFLOADER_RUST_DIR)/src/*.rs) \
	$(APPELFLOADER_RUST_DIR)/Cargo.toml \
	$(APPELFLOADER_RUST_DIR)/rust-toolchain.toml \
	$(UK_CONFIG)

# CARGO can be overridden for a pinned toolchain (`make CARGO="cargo +1.83"`).
CARGO ?= cargo

ifeq ($(shell command -v $(CARGO) 2>/dev/null),)
$(error app-elfloader-rs needs cargo. Install it with: \
  curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y \
  and make sure ~/.cargo/bin is on PATH)
endif

# --offline is safe because the crate has no dependencies; it keeps the build
# from reaching for a registry it does not need. --locked makes that explicit.
#
# The archive is only copied into the build tree when it actually differs, so
# an unchanged loader does not give the 130 MB unikernel a newer prerequisite
# and force a relink. cargo's own up-to-date check makes the build itself a
# no-op in that case, so the whole rule costs well under a second.
#
# The copy uses `verbose_cmd_inner`, not `verbose_cmd`: the latter expands to a
# string starting with `@`, which make only strips at the start of a recipe
# line. Anywhere else -- such as inside this `if` -- the shell is handed a
# literal `@printf` and the rule dies with "command not found".
$(APPELFLOADER_RUST_LIB): $(APPELFLOADER_RUST_SRCS)
	$(call verbose_cmd,CARGO,appelfloader: $(notdir $(APPELFLOADER_RUST_BUILT)), \
		$(CARGO) build \
			--manifest-path $(APPELFLOADER_RUST_DIR)/Cargo.toml \
			--target $(APPELFLOADER_RUST_TARGET) \
			--target-dir $(APPELFLOADER_RUST_CACHE) \
			$(APPELFLOADER_RUST_FEATURE_FLAGS) \
			--release --locked --offline)
	$(Q)if ! cmp -s $(APPELFLOADER_RUST_BUILT) $@ 2>/dev/null; then \
		$(call verbose_cmd_inner,CACHE,appelfloader: $(notdir $@), \
			cp $(APPELFLOADER_RUST_BUILT) $@); \
	fi

APPELFLOADER_ALIBS-y += $(APPELFLOADER_RUST_LIB)

# The cache is deliberately not in CLEAN: it is shared across builds, and
# `make clean` should not throw away work that is still valid.
APPELFLOADER_CLEAN += $(APPELFLOADER_RUST_LIB)

# Run the loader's own tests on the build host. Not wired into `all`: it builds
# for the host triple, which is a different compilation from the one above.
.PHONY: appelfloader-test
appelfloader-test:
	$(CARGO) test --manifest-path $(APPELFLOADER_RUST_DIR)/Cargo.toml

################################################################################
# vDSO (unchanged from the C loader: a build-time asset, not loader logic)
################################################################################
$(APPELFLOADER_BUILD)/vdso.o: $(APPELFLOADER_BASE)/vdso/vdso.c
	$(call build_cmd,CC,appelfloader,$(notdir $@), \
		$(CC) $< -c -o $@ -fPIC -O2 -nostdlib)

$(APPELFLOADER_BUILD)/vdso.patched.o: $(APPELFLOADER_BUILD)/vdso.o $(APPELFLOADER_BASE)/vdso/vdso_mapping.conf
	$(call build_cmd,ADDSYM,appelfloader,$(notdir $@), \
		OBJCOPY_CMD=$(OBJCOPY) APPELFLOADER_BASE=$(APPELFLOADER_BASE) VDSO_MAGIC_NUMBER=0x369C217100000000 $(APPELFLOADER_BASE)/vdso/add_symbol.sh $(APPELFLOADER_BASE)/vdso/vdso_mapping.conf $< $@)

$(APPELFLOADER_BUILD)/libvdso.so: $(APPELFLOADER_BUILD)/vdso.patched.o $(APPELFLOADER_BASE)/vdso/vdso.lds
	$(call build_cmd,LD,appelfloader,$(notdir $@), \
		$(LD) $< -o $@ -nostdlib -Wl$(comma)--hash-style=both -Wl$(comma)-soname=unikraft-vdso.so.1 -Wl$(comma)-shared -Wl$(comma)-T$(comma)$(APPELFLOADER_BASE)/vdso/vdso.lds)

$(APPELFLOADER_BUILD)/vdso-image.c: $(APPELFLOADER_BUILD)/libvdso.so $(APPELFLOADER_BASE)/vdso/vdso_mapping.conf
	$(call build_cmd,PYTHON,appelfloader,$(notdir $@), \
		$(PYTHON) $(APPELFLOADER_BASE)/vdso/bin2c.py $(APPELFLOADER_BASE)/vdso/vdso_mapping.conf $< $@)

APPELFLOADER_CLEAN += $(APPELFLOADER_BUILD)/vdso.o
APPELFLOADER_CLEAN += $(APPELFLOADER_BUILD)/vdso.patched.o
APPELFLOADER_CLEAN += $(APPELFLOADER_BUILD)/libvdso.so
APPELFLOADER_CLEAN += $(APPELFLOADER_BUILD)/vdso-image.c

################################################################################
# /etc autogeneration (unchanged, still C)
################################################################################
APPELFLOADER_SRCS-$(CONFIG_APPELFLOADER_AUTOGEN) += $(APPELFLOADER_BASE)/autogen/conffile.c
ifneq ($(filter y,$(CONFIG_APPELFLOADER_AUTOGEN_ETCRESOLVCONF) \
		  $(CONFIG_APPELFLOADER_AUTOGEN_ETCHOSTS) \
		  $(CONFIG_APPELFLOADER_AUTOGEN_ETCHOSTNAME) \
	),)
APPELFLOADER_SRCS-$(CONFIG_APPELFLOADER_AUTOGEN) += $(APPELFLOADER_BASE)/autogen/etc.c
endif