From 0c710141bbb9bd62617d981a3dbaed1b8775fded Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Tue, 10 Mar 2015 16:28:38 +0100
Subject: Add simple shared memory facility to IPC (no syscall yet)

---
 src/kernel/dev/vesa.c      | 18 ++---------
 src/kernel/include/ipc.h   |  4 +++
 src/kernel/include/pager.h |  5 ++-
 src/kernel/include/vfs.h   | 10 +++---
 src/kernel/user/ipc.c      | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 src/kernel/user/nullfs.c   |  4 +--
 src/kernel/user/pager.c    |  6 +++-
 src/kernel/user/process.c  |  2 +-
 8 files changed, 101 insertions(+), 26 deletions(-)

diff --git a/src/kernel/dev/vesa.c b/src/kernel/dev/vesa.c
index 2a7b876..645a649 100644
--- a/src/kernel/dev/vesa.c
+++ b/src/kernel/dev/vesa.c
@@ -215,8 +215,6 @@ typedef struct {
 //  ---- VESA code
 
 bool vesa_open(fs_node_ptr n, int mode);
-size_t vesa_read(fs_handle_t *f, size_t offset, size_t len, char* buf);
-size_t vesa_write(fs_handle_t *f, size_t offset, size_t len, const char* buf);
 void vesa_close(fs_handle_t *f);
 int vesa_ioctl(fs_node_ptr n, int command, void* data);
 bool vesa_stat(fs_node_ptr n, stat_t *st);
@@ -227,8 +225,8 @@ bool vesa_set_mode(vesa_driver_t *d, int n);
 
 fs_node_ops_t vesa_fs_ops = {
 	.open = vesa_open,
-	.read = vesa_read,
-	.write = vesa_write,
+	.read = fs_read_from_pager,
+	.write = fs_write_to_pager,
 	.close = vesa_close,
 	.ioctl = vesa_ioctl,
 	.stat = vesa_stat,
@@ -363,18 +361,6 @@ bool vesa_open(fs_node_ptr n, int mode) {
 	return true;
 }
 
-size_t vesa_read(fs_handle_t *f, size_t offset, size_t len, char* buf) {
-	vesa_driver_t *d = (vesa_driver_t*)f->node->data;
-
-	return pager_read(d->pager, offset, len, buf);
-}
-
-size_t vesa_write(fs_handle_t *f, size_t offset, size_t len, const char* buf) {
-	vesa_driver_t *d = (vesa_driver_t*)f->node->data;
-
-	return pager_write(d->pager, offset, len, buf);
-}
-
 void vesa_close(fs_handle_t *f) {
 	// nothing to do
 }
diff --git a/src/kernel/include/ipc.h b/src/kernel/include/ipc.h
index 05d14a8..4f8573c 100644
--- a/src/kernel/include/ipc.h
+++ b/src/kernel/include/ipc.h
@@ -14,6 +14,10 @@ typedef struct {
 
 fs_handle_pair_t make_channel(bool blocking);
 
+//  ---- shared memory regions
+
+fs_handle_t* make_shm(size_t size);
+
 //  ---- Tokens for sharing file descriptors between processes
 
 #define TOKEN_LIFETIME 1500000		// in usecs
diff --git a/src/kernel/include/pager.h b/src/kernel/include/pager.h
index 03e5da4..a53c7d3 100644
--- a/src/kernel/include/pager.h
+++ b/src/kernel/include/pager.h
@@ -32,6 +32,9 @@ typedef struct pager {
 	pager_ops_t *ops;
 
 	union {
+		struct {
+			bool allow_resize;
+		} swap_pager;
 		struct {
 			fs_node_t* node;
 			vfs_pager_ops_t *ops;
@@ -49,7 +52,7 @@ typedef struct pager {
 	user_region_t *maps;
 } pager_t;
 
-pager_t* new_swap_pager(size_t size);
+pager_t* new_swap_pager(size_t size, bool allow_resize);
 pager_t* new_vfs_pager(size_t size, fs_node_t* vfs_node, vfs_pager_ops_t *vfs_ops);
 pager_t* new_device_pager(size_t size, void* phys_offset);
 
diff --git a/src/kernel/include/vfs.h b/src/kernel/include/vfs.h
index c22ec9a..888c0bc 100644
--- a/src/kernel/include/vfs.h
+++ b/src/kernel/include/vfs.h
@@ -81,11 +81,11 @@ typedef struct fs_handle {
 
 typedef struct fs_node_ops {
 	bool (*open)(fs_node_ptr n, int mode);
-	size_t (*read)(fs_handle_t *f, size_t offset, size_t len, char* buf);
-	size_t (*write)(fs_handle_t *f, size_t offset, size_t len, const char* buf);
-	bool (*readdir)(fs_handle_t *f, size_t ent_no, dirent_t *d);
-	int (*poll)(fs_handle_t *f, void** out_wait_obj);
-	void (*close)(fs_handle_t *f);
+	size_t (*read)(fs_handle_t *h, size_t offset, size_t len, char* buf);
+	size_t (*write)(fs_handle_t *h, size_t offset, size_t len, const char* buf);
+	bool (*readdir)(fs_handle_t *h, size_t ent_no, dirent_t *d);
+	int (*poll)(fs_handle_t *h, void** out_wait_obj);
+	void (*close)(fs_handle_t *h);
 
 	bool (*stat)(fs_node_ptr n, stat_t *st);
 	int (*ioctl)(fs_node_ptr n, int command, void* data);
diff --git a/src/kernel/user/ipc.c b/src/kernel/user/ipc.c
index a8362ea..e565082 100644
--- a/src/kernel/user/ipc.c
+++ b/src/kernel/user/ipc.c
@@ -227,6 +227,84 @@ void channel_dispose(fs_node_t *n) {
 	free(c);
 }
 
+//  ---- ------ ------
+//  ---- Shared memory
+//  ---- ------ ------
+
+bool shm_open(fs_node_ptr n, int mode);
+void shm_close(fs_handle_t *h);
+bool shm_stat(fs_node_ptr n, stat_t *st);
+void shm_dispose(fs_node_t *n);
+
+fs_node_ops_t shm_ops = {
+	.open = shm_open,
+	.read = fs_read_from_pager,
+	.write = fs_write_to_pager,
+	.readdir = 0,
+	.poll = 0,
+	.close = shm_close,
+	.stat = shm_stat,
+	.ioctl = 0,
+	.walk = 0,
+	.delete = 0,
+	.move = 0,
+	.create = 0,
+	.dispose = shm_dispose,
+};
+
+fs_handle_t* make_shm(size_t size) {
+	fs_node_t *n = 0;
+	fs_handle_t *h = 0;
+
+	n = (fs_node_t*)malloc(sizeof(fs_node_t));
+	if (n == 0) goto error;
+	memset(n, 0, sizeof(fs_node_t));
+
+	h = (fs_handle_t*)malloc(sizeof(fs_handle_t));
+	if (h == 0) goto error;
+
+	n->pager = new_swap_pager(size, false);
+	if (n->pager == 0) goto error;
+
+	n->refs = 1;
+	n->lock = MUTEX_UNLOCKED;
+	n->ops = &shm_ops;
+	n->data = 0;
+
+	h->fs = 0;
+	h->node = n;
+	h->refs = 1;
+	h->mode = FM_READ | FM_WRITE | FM_MMAP;
+
+	return h;
+
+error:
+	if (n && n->pager) delete_pager(n->pager);
+	if (n) free(n);
+	if (h) free(h);
+	return 0;
+}
+
+bool shm_open(fs_node_ptr n, int mode) {
+	int ok_modes = FM_READ | FM_WRITE | FM_MMAP;
+	if (mode & ~ok_modes) return false;
+
+	return true;
+}
+
+void shm_close(fs_handle_t *h) {
+	// nothing to do
+}
+
+bool shm_stat(fs_node_ptr n, stat_t *st) {
+	// TODO
+	return false;
+}
+
+void shm_dispose(fs_node_t *n) {
+	delete_pager(n->pager);
+}
+
 //  ---- ------
 //  ---- Tokens
 //  ---- ------
diff --git a/src/kernel/user/nullfs.c b/src/kernel/user/nullfs.c
index d4f345f..636d7fa 100644
--- a/src/kernel/user/nullfs.c
+++ b/src/kernel/user/nullfs.c
@@ -204,7 +204,7 @@ bool nullfs_add_ram_file(fs_t *fs, const char* name, const char* data, size_t in
 	nullfs_file_t *f = (nullfs_file_t*)malloc(sizeof(nullfs_file_t));
 	if (f == 0) return false;
 	
-	p = new_swap_pager(init_sz);
+	p = new_swap_pager(init_sz, true);
 	if (p == 0) goto error;
 
 	f->ok_modes = ok_modes & (FM_MMAP | FM_TRUNC | FM_READ | FM_WRITE);
@@ -339,7 +339,7 @@ bool nullfs_d_create(fs_node_ptr n, const char* file, int type) {
 		nullfs_file_t *f = (nullfs_file_t*)malloc(sizeof(nullfs_file_t));
 		if (f == 0) goto f_error;
 
-		p = new_swap_pager(0);
+		p = new_swap_pager(0, true);
 		if (p == 0) goto f_error;
 
 		f->ok_modes = FM_READ | FM_WRITE | FM_TRUNC | FM_APPEND;
diff --git a/src/kernel/user/pager.c b/src/kernel/user/pager.c
index 79f293b..b9233b0 100644
--- a/src/kernel/user/pager.c
+++ b/src/kernel/user/pager.c
@@ -26,7 +26,7 @@ pager_ops_t swap_pager_ops = {
 	.resize = swap_pager_resize,
 };
 
-pager_t *new_swap_pager(size_t size) {
+pager_t *new_swap_pager(size_t size, bool allow_resize) {
 	pager_t *p = (pager_t*)malloc(sizeof(pager_t));
 	if (p == 0) return 0;
 
@@ -38,6 +38,8 @@ pager_t *new_swap_pager(size_t size) {
 	p->lock = MUTEX_UNLOCKED;
 	p->maps = 0;
 
+	p->swap_pager.allow_resize = allow_resize;
+
 	return p;
 
 error:
@@ -86,6 +88,8 @@ void swap_page_release(pager_t *p, size_t offset, size_t len) {
 }
 
 bool swap_pager_resize(pager_t *p, size_t new_size) {
+	if (!p->swap_pager.allow_resize) return false;
+
 	// later : remove unused pages in swap file
 
 	return true;
diff --git a/src/kernel/user/process.c b/src/kernel/user/process.c
index 4d79327..85530ca 100644
--- a/src/kernel/user/process.c
+++ b/src/kernel/user/process.c
@@ -500,7 +500,7 @@ bool mmap(process_t *proc, void* addr, size_t size, int mode) {
 	r->size = size;
 
 	r->own_pager = true;
-	r->pager = new_swap_pager(size);
+	r->pager = new_swap_pager(size, false);
 	if (r->pager == 0) goto error;
 	r->offset = 0;
 
-- 
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