diff --git a/include/fbos/compiler.h b/include/fbos/compiler.h
index b88bb0b..c26c05c 100644
--- a/include/fbos/compiler.h
+++ b/include/fbos/compiler.h
@@ -19,16 +19,18 @@
 #endif /* __KERNEL__ */
 
 /*
- * Multiple aliases for 32/64-bit integers which have their definition on the
+ * Multiple aliases for integer types which have their definition on the
  * standard library.
  */
 
+typedef short int16_t;
 typedef int int32_t;
 typedef long ssize_t;
 typedef long int64_t;
 
-typedef unsigned long size_t;
+typedef unsigned short uint16_t;
 typedef unsigned int uint32_t;
+typedef unsigned long size_t;
 typedef unsigned long uint64_t;
 typedef unsigned long uintptr_t;
 
diff --git a/include/fbos/init.h b/include/fbos/init.h
index c4d0a85..978eebe 100644
--- a/include/fbos/init.h
+++ b/include/fbos/init.h
@@ -3,11 +3,9 @@
 
 #include <fbos/compiler.h>
 
-extern struct task_struct init_task;
-
 // Extract the executables from the initrd that is located at `base_addr` and
 // has the given `size`.
-void extract_initrd(const char *const base_addr, uint64_t size);
+void extract_initrd(const unsigned char *const base_addr, uint64_t size);
 
 // The entry point for the kernel.
 void start_kernel(void *dtb);
diff --git a/include/fbos/sched.h b/include/fbos/sched.h
index 5cfc2ba..ff56f32 100644
--- a/include/fbos/sched.h
+++ b/include/fbos/sched.h
@@ -1,6 +1,8 @@
 #ifndef __FBOS_SCHED_H_
 #define __FBOS_SCHED_H_
 
+#include <fbos/compiler.h>
+
 enum task_id {
 	TASK_UNKNOWN = -1,
 	TASK_INIT = 0,
@@ -11,6 +13,10 @@ enum task_id {
 
 struct task_struct {
 	void *stack;
+	const void *addr;
+	uint64_t entry_offset;
 };
 
+extern struct task_struct tasks[4];
+
 #endif // __FBOS_SCHED_H_
diff --git a/kernel/head.S b/kernel/head.S
index de7852b..9018a8e 100644
--- a/kernel/head.S
+++ b/kernel/head.S
@@ -43,8 +43,8 @@ _start:
 	csrw sscratch, 0
 
 	// Point tp and sp to the init task.
-	la tp, init_task
-	la sp, init_task + THREAD_SIZE
+	la tp, tasks
+	la sp, tasks + THREAD_SIZE
 
 	// The `start_kernel` function requires an argument to be passed, which is
 	// the pointer to the `fdt` blob. The bootloader puts this on the `a1`
diff --git a/kernel/initrd.c b/kernel/initrd.c
index c05e77d..4706fe8 100644
--- a/kernel/initrd.c
+++ b/kernel/initrd.c
@@ -63,16 +63,48 @@ __kernel int get_task_id_from_name(const char *const name)
 	return TASK_UNKNOWN;
 }
 
-__kernel void extract_elf(int task_id, const char *const addr, size_t size)
+__kernel void ensure_elf_format(const unsigned char *const addr)
+{
+	if (addr[0] != 0x7F || memcmp(&addr[1], "ELF", 3) != 0) {
+		die("Bad ELF format\n");
+	}
+	if (addr[4] != 2) {
+		die("64-bit format is mandatory\n");
+	}
+	if (addr[5] != 1) {
+		die("Little-endian only\n");
+	}
+}
+
+struct exec_header {
+	uint64_t e_entry;
+	uint64_t e_phoff;
+	uint16_t e_phnum;
+	uint16_t e_phentsize;
+};
+
+// TODO
+__kernel void extract_elf(int task_id, const unsigned char *const addr, size_t size)
 {
 	__unused(task_id);
-	__unused(addr);
 	__unused(size);
 
-	// TODO
+	ensure_elf_format(addr);
+
+	/* struct exec_header header = { */
+	/* 	.e_entry = (unsigned long long)addr[0x18], */
+	/* 	.e_phoff = (uint64_t)addr[0x20], */
+	/* 	.e_phentsize = (uint16_t)addr[0x36], */
+	/* 	.e_phnum = (uint16_t)addr[0x38], */
+	/* }; */
+
+#ifdef __KERNEL__
+	tasks[task_id].addr = (const void *)addr;
+	tasks[task_id].entry_offset = (uint64_t)addr[0x18];
+#endif
 }
 
-__kernel void extract_initrd(const char *const initrd_addr, uint64_t size)
+__kernel void extract_initrd(const unsigned char *const initrd_addr, uint64_t size)
 {
 	char buffer[BUFFER_SIZE];
 	uint64_t name_size, file_size, padding, base = 0;
diff --git a/kernel/main.c b/kernel/main.c
index 7eb2ef6..089614f 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -4,9 +4,14 @@
 #include <fbos/sched.h>
 #include <fbos/dt.h>
 
-unsigned long init_stack[THREAD_SIZE / sizeof(unsigned long)];
+unsigned long init_stack[4][THREAD_SIZE / sizeof(unsigned long)];
 
-struct task_struct init_task = { .stack = init_stack };
+struct task_struct tasks[4] = {
+	[0] = { .stack = init_stack[0] },
+	[1] = { .stack = init_stack[1] },
+	[2] = { .stack = init_stack[2] },
+	[3] = { .stack = init_stack[3] },
+};
 
 /*
  * This is the main entry point of the kernel after head.S is done. This
@@ -21,7 +26,11 @@ __noreturn __kernel void start_kernel(void *dtb)
 
 	struct initrd_addr addr = find_dt_initrd_addr(dtb);
 
-	extract_initrd((char *)addr.start, addr.end - addr.start);
+	extract_initrd((unsigned char *)addr.start, addr.end - addr.start);
+
+	// TODO: this is the jump address for the first task.
+	const char *ddr = (const char *)tasks[1].addr + tasks[1].entry_offset;
+	__unused(ddr);
 
 	// TODO: reenable stuff
 
diff --git a/test/test_initrd.c b/test/test_initrd.c
index 3662eaa..73429b8 100644
--- a/test/test_initrd.c
+++ b/test/test_initrd.c
@@ -3,6 +3,17 @@
 #include <assert.h>
 
 #include <fbos/init.h>
+#include <fbos/sched.h>
+#include <fbos/mm.h>
+
+unsigned long init_stack[4][THREAD_SIZE / sizeof(unsigned long)];
+
+struct task_struct tasks[4] = {
+	[0] = { .stack = init_stack[0] },
+	[1] = { .stack = init_stack[1] },
+	[2] = { .stack = init_stack[2] },
+	[3] = { .stack = init_stack[3] },
+};
 
 int main(void)
 {
@@ -13,7 +24,7 @@ int main(void)
 	long fsize = ftell(fh);
 	rewind(fh);
 
-	char *contents = malloc((unsigned long)fsize + 1);
+	unsigned char *contents = malloc((unsigned long)fsize + 1);
 	fread(contents, (unsigned long)fsize, 1, fh);
 	fclose(fh);
 
diff --git a/usr/src/bar.S b/usr/src/bar.S
index 09c68e3..ee86b3e 100644
--- a/usr/src/bar.S
+++ b/usr/src/bar.S
@@ -2,8 +2,8 @@
 .text
 
 _start:
-	li a0, 1
-	la a1, bar
+	li a7, 1
+	la a0, bar
 	ecall
 .Loop:
 	j .Loop
diff --git a/usr/src/foo.S b/usr/src/foo.S
index 57e82a1..c26b550 100644
--- a/usr/src/foo.S
+++ b/usr/src/foo.S
@@ -2,8 +2,8 @@
 .text
 
 _start:
-	li a0, 1
-	la a1, foo
+	li a7, 1
+	la a0, foo
 	ecall
 .Loop:
 	j .Loop
diff --git a/usr/src/foobar.S b/usr/src/foobar.S
index 49c9e1d..e3fecb8 100644
--- a/usr/src/foobar.S
+++ b/usr/src/foobar.S
@@ -2,8 +2,8 @@
 .text
 
 _start:
-	li a0, 1
-	la a1, foobar
+	li a7, 1
+	la a0, foobar
 	ecall
 .Loop:
 	j .Loop