kernel: basic page allocator, `process_free`

4 files changed, 28 insertions, 0 deletions

diff --git a/src/kernel/arch/generic.h b/src/kernel/arch/generic.h
index 01a3826..84be937 100644
--- a/src/kernel/arch/generic.h
+++ b/src/kernel/arch/generic.h
@@ -27,6 +27,8 @@ _Noreturn void sysexit(struct registers);
 // all of those can allocate memory
 struct pagedir *pagedir_new(void);
 struct pagedir *pagedir_copy(const struct pagedir *orig);
+
+void pagedir_free(struct pagedir *);
 void pagedir_map(struct pagedir *dir, void __user *virt, void *phys,
                  bool user, bool writeable);
 
diff --git a/src/kernel/arch/i386/boot.c b/src/kernel/arch/i386/boot.c
index c25a848..a2b4f01 100644
--- a/src/kernel/arch/i386/boot.c
+++ b/src/kernel/arch/i386/boot.c
@@ -32,5 +32,7 @@ void kmain_early(struct multiboot_info *multiboot) {
 		info.init.size = module->end - module->start;
 	}
 
+	info.memtop = (void*) (multiboot->mem_upper * 1024);
+
 	kmain(info);
 }
diff --git a/src/kernel/arch/i386/multiboot.s b/src/kernel/arch/i386/multiboot.s
index 10702c6..62bc9fd 100644
--- a/src/kernel/arch/i386/multiboot.s
+++ b/src/kernel/arch/i386/multiboot.s
@@ -1,6 +1,7 @@
 .set MAGIC, 0x1BADB002
 
 /* 1<<0  - align modules on page boundaries.
+   1<<1  - fill the mem_ fields in multiboot_info
    1<<16 - enable manual addressing */
 .set FLAGS,        1<<0 | 1<<16
 .set CHECKSUM, -(MAGIC + FLAGS)
diff --git a/src/kernel/arch/i386/pagedir.c b/src/kernel/arch/i386/pagedir.c
index 88f6ebb..e3c2fa5 100644
--- a/src/kernel/arch/i386/pagedir.c
+++ b/src/kernel/arch/i386/pagedir.c
@@ -46,6 +46,29 @@ struct pagedir *pagedir_new(void) {
 	return dir;
 }
 
+void pagedir_free(struct pagedir *dir) {
+	// assumes all user pages are unique and can be freed
+	struct pagetable_entry *pt;
+	void *page;
+
+	for (int i = 0; i < 1024; i++) {
+		if (!dir->e[i].present) continue;
+		if (!dir->e[i].user)    continue;
+
+		pt = (void*)(dir->e[i].address << 11);
+
+		for (int j = 0; j < 1024; j++) {
+			if (!pt[j].present) continue;
+			if (!pt[j].user)    continue;
+
+			page = (void*)(pt[j].address << 11);
+			page_free(page, 1);
+		}
+		page_free(pt, 1);
+	}
+	page_free(dir, 1);
+}
+
 void pagedir_map(struct pagedir *dir, void __user *virt, void *phys,
                  bool user, bool writeable)
 {