lib: fs: implement memory-mapped file i/o

lib/libfs/interface/map.c

@@ -0,0 +1,74 @@
+#include "../file.h"
+#include "../mapping.h"
+
+#include <errno.h>
+#include <fs/context.h>
+#include <fs/file.h>
+#include <fs/status.h>
+#include <mango/handle.h>
+#include <mango/log.h>
+#include <mango/vm.h>
+#include <stdio.h>
+#include <sys/mman.h>
+
+extern kern_status_t fs_msg_map(
+	xpc_context_t *xpc,
+	const xpc_endpoint_t *sender,
+	int prot,
+	int flags,
+	int *out_err,
+	kern_handle_t *out_vmo,
+	void *arg)
+{
+	struct fs_context *ctx = arg;
+	struct fs_file *f = fs_context_get_file(ctx, sender->e_port);
+	if (!f) {
+		*out_err = EBADF;
+		return KERN_OK;
+	}
+
+	struct file_mapping *mapping = fs_context_alloc(ctx, sizeof *mapping);
+	if (!mapping) {
+		*out_err = ENOMEM;
+		return KERN_OK;
+	}
+
+	kern_logf("mapping file %s", f->f_dent->d_name);
+	vm_prot_t vm_prot = VM_PROT_USER;
+	if (prot & PROT_READ) {
+		vm_prot |= VM_PROT_READ;
+	}
+
+	if (prot & PROT_WRITE) {
+		vm_prot |= VM_PROT_WRITE;
+	}
+
+	if (prot & PROT_EXEC) {
+		vm_prot |= VM_PROT_EXEC;
+	}
+
+	kern_handle_t vmo = KERN_HANDLE_INVALID;
+	kern_status_t status = vm_controller_create_object(
+		fs_context_get_vm_controller(ctx),
+		f->f_dent->d_name,
+		strlen(f->f_dent->d_name),
+		(equeue_key_t)mapping,
+		f->f_inode->i_size,
+		vm_prot,
+		&vmo);
+
+	if (status != KERN_OK) {
+		fs_context_free(ctx, mapping);
+		*out_err = __errno_from_kern_status(status);
+		return KERN_OK;
+	}
+
+	mapping->m_file = f;
+	mapping->m_file_offset = 0;
+	kern_handle_duplicate(vmo, &mapping->m_vmo);
+	queue_push_back(&f->f_mappings, &mapping->m_entry);
+
+	*out_err = SUCCESS;
+	*out_vmo = vmo;
+	return KERN_OK;
+}