kernel: enumerate internal kexts during boot

Makefile

@@ -10,6 +10,14 @@ include tools/make/gcc-cross-compile.mk
 BUILD_DIR := build
 CONFIG_DIR := .config
 
+####################################
+# If the user has selected some kernel extensions to include
+# in the kernel image, include the file that describes the
+# extension source files to build
+####################################
+
+-include $(CONFIG_DIR)/extensions.mk
+
 ####################################
 # Architecture-specific source files
 ####################################
@@ -20,7 +28,7 @@ include arch/$(SOCKS_ARCH)/config.mk
 # Platform-independent kernel source files
 ####################################
 
-KERNEL_SRC_DIRS := init kernel vm ds util obj sched dev test
+KERNEL_SRC_DIRS := init kernel vm ds util obj sched dev test kxld
 KERNEL_C_FILES := $(foreach dir,$(KERNEL_SRC_DIRS),$(wildcard $(dir)/*.c))
 KERNEL_CXX_FILES := $(foreach dir,$(KERNEL_SRC_DIRS),$(wildcard $(dir)/*.cpp))
 KERNEL_OBJ := $(addprefix $(BUILD_DIR)/,$(KERNEL_C_FILES:.c=.o) $(KERNEL_CXX_FILES:.cpp=.o))
@@ -42,13 +50,15 @@ OPTIMISATION_LEVEL := -O2
 CFLAGS := $(CFLAGS) -DBUILD_ID=\"$(BUILD_ID)\" $(OPTIMISATION_LEVEL) -g -fPIC -std=gnu17 \
 	-Iinclude -Iarch/$(SOCKS_ARCH)/include -Ilibc/include $(CWARNINGS)
 
+KERNEL_DEFINES := -DSOCKS_INTERNAL=1
+
 CXXFLAGS := $(CXXFLAGS) -DBUILD_ID=\"$(BUILD_ID)\" $(OPTIMISATION_LEVEL) -g -fPIC -std=gnu++17 \
 	-Iinclude -Iarch/$(SOCKS_ARCH)/include -Ilibc/include -Wno-language-extension-token $(CWARNINGS)
 
 ASMFLAGS := $(ASMFLAGS) -DBUILD_ID=\"$(BUILD_ID)\"
 LDFLAGS := $(LDFLAGS) -g -lgcc $(OPTIMISATION_LEVEL)
 
-ALL_KERNEL_OBJECT_FILES := $(KERNEL_OBJ) $(ARCH_OBJ) $(LIBC_OBJ)
+ALL_KERNEL_OBJECT_FILES := $(KERNEL_OBJ) $(ARCH_OBJ) $(LIBC_OBJ) $(INTERNAL_KEXT_OBJ)
 ALL_KERNEL_DEPS := $(ALL_KERNEL_OBJECT_FILES:.o=.d)
 
 all: $(BUILD_DIR)/$(KERNEL_EXEC) tools
@@ -70,12 +80,12 @@ $(BUILD_DIR)/%.o: %.S
 $(BUILD_DIR)/%.o: %.c
 	@printf "    \033[1;32mCC\033[0m     \033[35m$(KERNEL_EXEC)\033[0m/$<\n"
 	@mkdir -p $(@D)
-	@$(CC) $< -o $@ -c $(CFLAGS) $(ARCH_CFLAGS) -MMD
+	@$(CC) $< -o $@ -c $(CFLAGS) $(ARCH_CFLAGS) -MMD $(KERNEL_DEFINES)
 
 $(BUILD_DIR)/%.o: %.cpp
 	@printf "    \033[1;32mCXX\033[0m    \033[35m$(KERNEL_EXEC)\033[0m/$<\n"
 	@mkdir -p $(@D)
-	@$(CXX) $< -o $@ -c $(CXXFLAGS) $(ARCH_CXXFLAGS) -MMD
+	@$(CXX) $< -o $@ -c $(CXXFLAGS) $(ARCH_CXXFLAGS) -MMD $(KERNEL_DEFINES)
 
 clean:
 	@printf "    \033[1;93mRM\033[0m     Deleting build files.\n"

arch/x86_64/layout.ld

@@ -31,6 +31,19 @@ SECTIONS {
         *(.data)
    }
 
+   .rodata ALIGN(4K) : AT(ADDR(.rodata) - KERNEL_VMA)
+   {
+	_rodata = .;
+	*(.rodata*)
+   }
+
+   .kexts ALIGN(4K) : AT(ADDR(.kexts) - KERNEL_VMA)
+   {
+	__kexts_start = .;
+        *(.kextinfo)
+	__kexts_end = .;
+   }
+
    .data.percpu ALIGN(4K) : AT(ADDR(.data.percpu) - KERNEL_VMA)
    {
 	__percpu_start = .;

include/socks/kext.h

@@ -0,0 +1,81 @@
+#ifndef SOCKS_KEXT_H_
+#define SOCKS_KEXT_H_
+
+#include <socks/status.h>
+#include <socks/compiler.h>
+
+#define KERNEL_KEXT_ID "net.doorstuck.socks-kernel"
+#define KEXT_IDENT_MAX 80
+
+#define __KEXT_INFO_VARNAME_2(a, b) a ## b
+#define __KEXT_INFO_VARNAME_1(a, b) __KEXT_INFO_VARNAME_2(a, b)
+
+#ifdef SOCKS_INTERNAL
+#define __KEXT_INFO_LINKAGE static
+#define __KEXT_INFO_VARNAME() __KEXT_INFO_VARNAME_1(__kext_info, __LINE__)
+#define __KEXT_INFO_DEPNAME() __KEXT_INFO_VARNAME_1(__kext_deps, __LINE__)
+#define __KEXT_INFO_FLAGS KEXT_INTERNAL
+#else
+#define __KEXT_INFO_LINKAGE
+#define __KEXT_INFO_VARNAME() __kext_info
+#define __KEXT_INFO_DEPNAME() __kext_deps
+#define __KEXT_INFO_FLAGS KEXT_NONE
+#endif
+
+#ifdef __cplusplus
+#define DEFINE_KEXT(ident, online, offline, ...)                                        \
+	static const char *__KEXT_INFO_DEPNAME()[] = {          \
+		__VA_ARGS__                                                             \
+	};                                                                              \
+	static struct kext_info __section(".kextinfo") __used __KEXT_INFO_VARNAME() = { \
+		__KEXT_INFO_FLAGS,                                                      \
+		ident,                                                                  \
+		online,                                                                 \
+		offline,                                                                \
+		__KEXT_INFO_DEPNAME(),	                                                \
+	}
+#else
+#define DEFINE_KEXT(ident, online, offline, ...)                              \
+	static const char *__kext_deps[] = {          \
+		__VA_ARGS__                                                   \
+	};                                                                    \
+	static struct kext_info __section(".kextinfo") __used __kext_info = { \
+		.k_flags = __KEXT_INFO_FLAGS,                                 \
+		.k_ident = ident,                                             \
+		.k_online = online,                                           \
+		.k_offline = offline,                                         \
+		.k_dependencies = __kext_deps,                                \
+	}
+#endif
+
+struct kext;
+
+enum kext_flags {
+	KEXT_NONE = 0x00u,
+	KEXT_INTERNAL = 0x01u,
+	KEXT_ONLINE = 0x02u,
+};
+
+struct kext_info {
+	enum kext_flags k_flags;
+	char k_ident[KEXT_IDENT_MAX];
+	kern_status_t(*k_online)(struct kext *);
+	kern_status_t(*k_offline)(struct kext *);
+	const char **k_dependencies;
+};
+
+struct kext {
+	enum kext_flags k_flags;
+	char k_ident[KEXT_IDENT_MAX];
+
+	kern_status_t(*k_online)(struct kext *);
+	kern_status_t(*k_offline)(struct kext *);
+
+	unsigned int k_nr_dependencies;
+	struct kext **k_dependencies;
+};
+
+extern kern_status_t scan_internal_kexts(void);
+extern kern_status_t bring_internal_kexts_online(void);
+
+#endif

init/main.c

@@ -2,6 +2,7 @@
 #include <socks/init.h>
 #include <socks/test.h>
 #include <socks/printk.h>
+#include <socks/kext.h>
 #include <socks/object.h>
 #include <socks/sched.h>
 #include <socks/machine/init.h>
@@ -20,6 +21,8 @@ void kernel_init(uintptr_t arg)
 {
 	ml_init(arg);
 
+	scan_internal_kexts();
+
 	printk("kernel_init() running on processor %u", this_cpu());
 
 	run_all_tests();

kexts/hello-world/hello-world.c

@@ -6,3 +6,7 @@ kern_status_t online(struct kext *self)
 	printk("Hello, world!");
 	return KERN_OK;
 }
+
+DEFINE_KEXT("net.doorstuck.socks.hello-world",
+	    online, NULL,
+	    "net.doorstuck.socks-kernel");

kxld/internal.c

@@ -0,0 +1,36 @@
+#include <socks/kext.h>
+#include <socks/printk.h>
+#include <socks/vm.h>
+#include <socks/libc/stdio.h>
+
+static vm_cache_t kext_cache = { .c_obj_size = sizeof(struct kext) };
+static struct kext *self = NULL;
+
+extern char __kexts_start[];
+extern char __kexts_end[];
+
+kern_status_t scan_internal_kexts(void)
+{
+	vm_cache_init(&kext_cache);
+
+	self = vm_cache_alloc(&kext_cache, 0);
+	snprintf(self->k_ident, sizeof self->k_ident, "%s", KERNEL_KEXT_ID);
+	self->k_flags = KEXT_INTERNAL | KEXT_ONLINE;
+
+	self->k_nr_dependencies = 0;
+	self->k_dependencies = NULL;
+
+	struct kext_info *cur = (struct kext_info *)__kexts_start;
+	struct kext_info *end = (struct kext_info *)__kexts_end;
+	while (cur < end) {
+		printk("kext: found internal kext '%s'", cur->k_ident);
+		cur++;
+	}
+
+	return KERN_OK;
+}
+
+kern_status_t bring_internal_kexts_online(void)
+{
+	return KERN_OK;
+}