From d1a9c5cd45d88a3f62748751566459bd6072ff33 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Sat, 21 Mar 2026 10:46:15 +0000
Subject: [PATCH] lib: fs: implement private and shared file mappings

---
 lib/libfs/include/fs/inode.h |  3 ++
 lib/libfs/interface/map.c    | 76 +++++++++++++++++++++++++++---------
 lib/libfs/mapping.h          |  7 +++-
 3 files changed, 66 insertions(+), 20 deletions(-)

diff --git a/lib/libfs/include/fs/inode.h b/lib/libfs/include/fs/inode.h
index da0d2b3..36b4648 100644
--- a/lib/libfs/include/fs/inode.h
+++ b/lib/libfs/include/fs/inode.h
@@ -2,12 +2,14 @@
 #define FS_INODE_H_
 
 #include <fs/status.h>
+#include <mango/types.h>
 #include <stddef.h>
 
 struct fs_inode;
 struct fs_dentry;
 struct fs_superblock;
 struct fs_file_ops;
+struct file_mapping;
 
 enum fs_inode_mode {
 	FS_INODE_REG = 0x01u,
@@ -27,6 +29,7 @@ struct fs_inode {
 	const struct fs_inode_ops *i_ops;
 	const struct fs_file_ops *i_fops;
 	size_t i_size;
+	struct file_mapping *i_shared_mapping;
 };
 
 extern enum fs_status fs_inode_lookup(
diff --git a/lib/libfs/interface/map.c b/lib/libfs/interface/map.c
index c855f57..a0632b8 100644
--- a/lib/libfs/interface/map.c
+++ b/lib/libfs/interface/map.c
@@ -11,29 +11,25 @@
 #include <stdio.h>
 #include <sys/mman.h>
 
-extern kern_status_t fs_msg_map(
-	xpc_context_t *xpc,
-	const xpc_endpoint_t *sender,
+static int create_file_mapping(
+	struct fs_context *ctx,
 	int prot,
 	int flags,
-	int *out_err,
-	kern_handle_t *out_vmo,
-	void *arg)
+	struct fs_file *f,
+	struct file_mapping **out)
 {
-	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;
+	if ((flags & MAP_SHARED) && f->f_inode->i_shared_mapping) {
+		*out = f->f_inode->i_shared_mapping;
+		return SUCCESS;
 	}
 
 	struct file_mapping *mapping = fs_context_alloc(ctx, sizeof *mapping);
 	if (!mapping) {
-		*out_err = ENOMEM;
-		return KERN_OK;
+		return ENOMEM;
 	}
 
-	kern_logf("mapping file %s", f->f_dent->d_name);
+	memset(mapping, 0x0, sizeof *mapping);
+
 	vm_prot_t vm_prot = VM_PROT_USER;
 	if (prot & PROT_READ) {
 		vm_prot |= VM_PROT_READ;
@@ -59,14 +55,56 @@ extern kern_status_t fs_msg_map(
 
 	if (status != KERN_OK) {
 		fs_context_free(ctx, mapping);
-		*out_err = __errno_from_kern_status(status);
-		return KERN_OK;
+		return __errno_from_kern_status(status);
 	}
 
 	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);
+	mapping->m_vmo = vmo;
+
+	if (flags & MAP_SHARED) {
+		mapping->m_type = FILE_MAPPING_SHARED;
+		f->f_inode->i_shared_mapping = mapping;
+	} else {
+		mapping->m_type = FILE_MAPPING_PRIVATE;
+		queue_push_back(&f->f_mappings, &mapping->m_entry);
+	}
+
+	*out = mapping;
+
+	return SUCCESS;
+}
+
+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 = NULL;
+	int err = create_file_mapping(ctx, prot, flags, f, &mapping);
+	if (err != SUCCESS) {
+		*out_err = err;
+		return KERN_OK;
+	}
+
+	kern_tracef(
+		"mapping file %s (%s) using vmo %zx",
+		f->f_dent->d_name,
+		(flags & MAP_SHARED) ? "shared" : "private",
+		mapping->m_vmo);
+
+	kern_handle_t vmo;
+	kern_handle_duplicate(mapping->m_vmo, &vmo);
 
 	*out_err = SUCCESS;
 	*out_vmo = vmo;
diff --git a/lib/libfs/mapping.h b/lib/libfs/mapping.h
index 30f3c0d..572ae26 100644
--- a/lib/libfs/mapping.h
+++ b/lib/libfs/mapping.h
@@ -7,10 +7,15 @@
 
 struct fs_file;
 
+enum file_mapping_type {
+	FILE_MAPPING_PRIVATE,
+	FILE_MAPPING_SHARED,
+};
+
 struct file_mapping {
+	enum file_mapping_type m_type;
 	struct fs_file *m_file;
 	kern_handle_t m_vmo;
-	off_t m_file_offset;
 	struct queue_entry m_entry;
 };