move most of the memory stuff to kernel/mem/

4 files changed, 159 insertions, 0 deletions

diff --git a/src/kernel/mem/alloc.c b/src/kernel/mem/alloc.c
new file mode 100644
index 0000000..42a2f3b
--- /dev/null
+++ b/src/kernel/mem/alloc.c
@@ -0,0 +1,38 @@
+#include <kernel/arch/generic.h>
+#include <kernel/mem/alloc.h>
+#include <kernel/util.h>
+#include <stdint.h>
+
+static void *highest_page;
+
+void mem_init(struct kmain_info *info) {
+	// finds the highest used page, and starts allocating pages above it
+	void *highest = &_bss_end;
+
+	if (highest < info->init.at + info->init.size)
+		highest = info->init.at + info->init.size;
+
+	// align up to PAGE_SIZE
+	highest_page = (void*)(((uintptr_t)highest + PAGE_MASK) & ~PAGE_MASK);
+}
+
+void *page_alloc(size_t pages) {
+	void *bottom = highest_page;
+	highest_page += pages * PAGE_SIZE;
+	return bottom;
+}
+
+// frees `pages` consecutive pages starting from *first
+void page_free(void *first, size_t pages) {
+	// not implemented
+}
+
+
+void *kmalloc(size_t len) {
+	// extremely inefficient, but this is only temporary anyways
+	return page_alloc(len / PAGE_SIZE + 1);
+}
+
+void kfree(void *ptr) {
+	// unimplemented
+}
diff --git a/src/kernel/mem/alloc.h b/src/kernel/mem/alloc.h
new file mode 100644
index 0000000..571b289
--- /dev/null
+++ b/src/kernel/mem/alloc.h
@@ -0,0 +1,15 @@
+#pragma once
+#include <kernel/arch/generic.h>
+#include <kernel/main.h>
+#include <stddef.h>
+
+void mem_init(struct kmain_info *);
+
+// allocates `pages` consecutive pages
+void *page_alloc(size_t pages);
+
+// frees `pages` consecutive pages starting from *first
+void page_free(void *first, size_t pages);
+
+void *kmalloc(size_t len);
+void kfree(void *ptr);
diff --git a/src/kernel/mem/virt.c b/src/kernel/mem/virt.c
new file mode 100644
index 0000000..2990668
--- /dev/null
+++ b/src/kernel/mem/virt.c
@@ -0,0 +1,78 @@
+#include <kernel/arch/generic.h>
+#include <kernel/mem/virt.h>
+#include <kernel/util.h>
+
+void virt_iter_new(
+		struct virt_iter *iter, user_ptr virt, size_t length,
+		struct pagedir *pages, bool user, bool writeable)
+{
+	iter->frag       = 0;
+	iter->frag_len   = 0;
+	iter->prior      = 0;
+	iter->error      = false;
+	iter->_virt      = virt;
+	iter->_remaining = length;
+	iter->_pages     = pages;
+	iter->_user      = user;
+	iter->_writeable = writeable;
+}
+
+bool virt_iter_next(struct virt_iter *iter) {
+	/* note: While i'm pretty sure that this should always work, this
+	 * was only tested in cases where the pages were consecutive both in
+	 * virtual and physical memory, which might not always be the case.
+	 * TODO test this */
+
+	user_ptr virt = iter->_virt;
+	size_t partial = iter->_remaining;
+	iter->prior   += iter->frag_len;
+	if (partial <= 0) return false;
+
+	// don't read past the page
+	if ((virt & PAGE_MASK) + partial > PAGE_SIZE)
+		partial = PAGE_SIZE - (virt & PAGE_MASK);
+
+	iter->frag = pagedir_virt2phys(iter->_pages,
+			iter->_virt, iter->_user, iter->_writeable);
+
+	if (iter->frag == 0) {
+		iter->error = true;
+		return false;
+	}
+
+	iter->frag_len    = partial;
+	iter->_remaining -= partial;
+	iter->_virt      += partial;
+	return true;
+}
+
+bool virt_user_cpy(
+		struct pagedir *dest_pages,       user_ptr dest,
+		struct pagedir  *src_pages, const user_ptr src, size_t length)
+{
+	struct virt_iter dest_iter, src_iter;
+	size_t min;
+
+	virt_iter_new(&dest_iter, dest, length, dest_pages, true, true);
+	virt_iter_new( &src_iter, src, length,  src_pages, true, false);
+	dest_iter.frag_len = 0;
+	src_iter.frag_len  = 0;
+
+	for (;;) {
+		if (dest_iter.frag_len <= 0)
+			if (!virt_iter_next(&dest_iter)) break;
+		if ( src_iter.frag_len <= 0)
+			if (!virt_iter_next( &src_iter)) break;
+
+		min = src_iter.frag_len < dest_iter.frag_len
+		    ? src_iter.frag_len : dest_iter.frag_len;
+		memcpy(dest_iter.frag, src_iter.frag, min);
+
+		dest_iter.frag_len -= min;
+		dest_iter.frag     += min;
+		src_iter.frag_len  -= min;
+		src_iter.frag      += min;
+	}
+
+	return !(dest_iter.error || src_iter.error);
+}
diff --git a/src/kernel/mem/virt.h b/src/kernel/mem/virt.h
new file mode 100644
index 0000000..98a7a16
--- /dev/null
+++ b/src/kernel/mem/virt.h
@@ -0,0 +1,28 @@
+/* contains utilities for interacting with virtual memory */
+#pragma once
+#include <kernel/types.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+struct virt_iter {
+	void *frag;
+	size_t frag_len;
+	size_t prior; // sum of all prior frag_lens
+	bool error;
+
+	user_ptr _virt;
+	size_t _remaining;
+	struct pagedir *_pages;
+	bool _user;
+	bool _writeable;
+};
+
+void virt_iter_new(
+		struct virt_iter *iter, user_ptr virt, size_t length,
+		struct pagedir *pages, bool user, bool writeable);
+
+bool virt_iter_next(struct virt_iter *);
+
+bool virt_user_cpy(
+		struct pagedir *dest_pages,       user_ptr dest,
+		struct pagedir  *src_pages, const user_ptr src, size_t length);