7 files changed, 56 insertions, 0 deletions

diff --git a/src/init/main.c b/src/init/main.c
index 119984e..41a6ac0 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -18,6 +18,8 @@ int main() {
 	debuglog("hello from init! ",
 	  sizeof("hello from init! ") - 1);
 
+	_syscall(SC_FORK, 0, 0, 0);
+
 	exit(    "bye from init! ",
 	  sizeof("bye from init! ") - 1);
 }
diff --git a/src/kernel/arch/generic.h b/src/kernel/arch/generic.h
index 3ab21b4..1427658 100644
--- a/src/kernel/arch/generic.h
+++ b/src/kernel/arch/generic.h
@@ -21,8 +21,10 @@ int syscall_handler(int, int, int, int);
 
 // all of those can allocate memory
 struct pagedir *pagedir_new();
+struct pagedir *pagedir_copy(const struct pagedir *orig);
 void pagedir_map(struct pagedir *dir, void *virt, void *phys,
                  bool user, bool writeable);
+
 void pagedir_switch(struct pagedir *);
 
 // return 0 on failure
diff --git a/src/kernel/arch/i386/pagedir.c b/src/kernel/arch/i386/pagedir.c
index 02361e6..61ad170 100644
--- a/src/kernel/arch/i386/pagedir.c
+++ b/src/kernel/arch/i386/pagedir.c
@@ -1,5 +1,6 @@
 #include <kernel/arch/generic.h>
 #include <kernel/mem.h>
+#include <kernel/util.h>
 #include <stdint.h>
 
 /* <heat> nitpick: I highly recommend you dont use bitfields for paging
@@ -92,6 +93,38 @@ void pagedir_switch(struct pagedir *dir) {
 	asm volatile("mov %0, %%cr3;" : : "r" (dir) : "memory");
 }
 
+// creates a new pagedir with exact copies of the user pages
+struct pagedir *pagedir_copy(const struct pagedir *orig) {
+	struct pagedir *clone = page_alloc(1);
+	struct pagetable_entry *orig_pt, *clone_pt;
+	void *orig_page, *clone_page;
+
+	for (int i = 0; i < 1024; i++) {
+		clone->e[i] = orig->e[i];
+		if (!orig->e[i].present) continue;
+		if (!orig->e[i].user)    continue; // not really needed
+
+		orig_pt = (void*)(orig->e[i].address << 11);
+		clone_pt = page_alloc(1);
+		clone->e[i].address = (uintptr_t) clone_pt >> 11;
+
+		for (int j = 0; j < 1024; j++) {
+			clone_pt[j] = orig_pt[j];
+			if (!orig_pt[j].present) continue;
+			if (!orig_pt[j].user)    continue;
+			// i could use .global?
+
+			orig_page = (void*)(orig_pt[j].address << 11);
+			clone_page = page_alloc(1);
+			clone_pt[j].address = (uintptr_t) clone_page >> 11;
+
+			memcpy(clone_page, orig_page, PAGE_SIZE);
+		}
+	}
+
+	return clone;
+}
+
 void *pagedir_virt2phys(struct pagedir *dir, const void *virt,
                         bool user, bool writeable)
 {
diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 9c7e390..b165878 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -1,6 +1,7 @@
 #include <kernel/arch/generic.h>
 #include <kernel/mem.h>
 #include <kernel/proc.h>
+#include <kernel/util.h>
 #include <stdint.h>
 
 struct process *process_current;
@@ -23,6 +24,14 @@ struct process *process_new() {
 	return proc;
 }
 
+struct process *process_clone(const struct process *orig) {
+	struct process *clone = page_alloc(1);
+	memcpy(clone, orig, sizeof(struct process));
+	clone->pages = pagedir_copy(orig->pages);
+
+	return clone;
+}
+
 void process_switch(struct process *proc) {
 	process_current = proc;
 	pagedir_switch(proc->pages);
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 7ab8da8..71880e6 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -10,4 +10,5 @@ struct process {
 extern struct process *process_current;
 
 struct process *process_new();
+struct process *process_clone(const struct process *orig);
 _Noreturn void process_switch(struct process *proc);
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index a6a2b17..eff670e 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -9,6 +9,12 @@ _Noreturn void sc_exit(const char *msg, size_t len) {
 	panic();
 }
 
+int sc_fork() {
+	struct process *orig = process_current;
+	process_current = process_clone(orig);
+	process_switch(process_current);
+}
+
 int sc_debuglog(const char *msg, size_t len) {
 	struct pagedir *pages = process_current->pages;
 	void *phys = pagedir_virt2phys(pages, msg, true, false);
@@ -27,6 +33,8 @@ int syscall_handler(int num, int a, int b, int c) {
 	switch (num) {
 		case SC_EXIT:
 			sc_exit((void*)a, b);
+		case SC_FORK:
+			return sc_fork();
 		case SC_DEBUGLOG:
 			return sc_debuglog((void*)a, b);
 		default:
diff --git a/src/kernel/syscalls.h b/src/kernel/syscalls.h
index a249046..ceb90c1 100644
--- a/src/kernel/syscalls.h
+++ b/src/kernel/syscalls.h
@@ -3,6 +3,7 @@
 // not caring about stable syscall numbers just yet
 enum {
 	SC_EXIT,
+	SC_FORK,
 	
 	SC_DEBUGLOG
 };