From fe303aec69078d753d95171e6265943a4aabdd9a Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Sat, 9 Sep 2023 00:30:43 -0300
Subject: [PATCH] devfs: maxseek

---
 kernel-src/fs/devfs.c             |  9 ++++++++
 kernel-src/include/kernel/devfs.h |  1 +
 kernel-src/include/kernel/vfs.h   |  2 ++
 kernel-src/sys/syscalls/seek.c    | 35 ++++++++++++++++++++-----------
 4 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/kernel-src/fs/devfs.c b/kernel-src/fs/devfs.c
index b26ad2e8..ba998ce8 100644
--- a/kernel-src/fs/devfs.c
+++ b/kernel-src/fs/devfs.c
@@ -201,6 +201,14 @@ int devfs_ioctl(vnode_t *node, unsigned long request, void *arg, int *ret) {
 	return devnode->devops->ioctl ? devnode->devops->ioctl(devnode->attr.rdevminor, request, arg, ret) : ENOTTY;
 }
 
+int devfs_maxseek(vnode_t *node, size_t *max) {
+	devnode_t *devnode = (devnode_t *)node;
+	if (devnode->master)
+		devnode = devnode->master;
+
+	return devnode->devops->maxseek ? devnode->devops->maxseek(devnode->attr.rdevminor, max) : ENOTTY;
+}
+
 int devfs_inactive(vnode_t *node) {
 	VOP_LOCK(node);
 	devnode_t *devnode = (devnode_t *)node;
@@ -325,6 +333,7 @@ static vops_t vnops = {
 	.getdents = devfs_getdents,
 	.isatty = devfs_isatty,
 	.ioctl = devfs_ioctl,
+	.maxseek = devfs_maxseek,
 	.resize = devfs_enodev
 };
 
diff --git a/kernel-src/include/kernel/devfs.h b/kernel-src/include/kernel/devfs.h
index 88c36e0d..f1c393f9 100644
--- a/kernel-src/include/kernel/devfs.h
+++ b/kernel-src/include/kernel/devfs.h
@@ -24,6 +24,7 @@ typedef struct {
 	int (*munmap)(int minor, void *addr, uintmax_t offset, int flags);
 	int (*isatty)(int minor);
 	int (*ioctl)(int minor, unsigned long request, void *arg, int *result);
+	int (*maxseek)(int minor, size_t *max);
 } devops_t;
 
 typedef struct devnode_t {
diff --git a/kernel-src/include/kernel/vfs.h b/kernel-src/include/kernel/vfs.h
index 0c65a0eb..15a75903 100644
--- a/kernel-src/include/kernel/vfs.h
+++ b/kernel-src/include/kernel/vfs.h
@@ -96,6 +96,7 @@ typedef struct vops_t {
 	int (*getdents)(vnode_t *node, dent_t *buffer, size_t count, uintmax_t offset, size_t *readcount);
 	int (*isatty)(vnode_t *node);
 	int (*ioctl)(vnode_t *node, unsigned long request, void *arg, int *result);
+	int (*maxseek)(vnode_t *node, size_t *max);
 	int (*resize)(vnode_t *node, size_t newsize, cred_t *cred);
 } vops_t;
 
@@ -142,6 +143,7 @@ typedef struct vops_t {
 #define VOP_POLL(v, d, p) (v)->ops->poll(v, d, p)
 #define VOP_ISATTY(v) ((v)->ops->isatty ? (v)->ops->isatty(v) : ENOTTY)
 #define VOP_IOCTL(v, r, a, rp) ((v)->ops->ioctl ? (v)->ops->ioctl(v, r, a, rp) : ENOTTY)
+#define VOP_MAXSEEK(v, rp) ((v)->ops->maxseek ? (v)->ops->maxseek(v, rp) : ENOTTY)
 #define VOP_RESIZE(v, s, c) (v)->ops->resize(v, s, c)
 #define VOP_HOLD(v) __atomic_add_fetch(&(v)->refcount, 1, __ATOMIC_SEQ_CST)
 #define VOP_RELEASE(v) {\
diff --git a/kernel-src/sys/syscalls/seek.c b/kernel-src/sys/syscalls/seek.c
index 0cf6b737..71a5edef 100644
--- a/kernel-src/sys/syscalls/seek.c
+++ b/kernel-src/sys/syscalls/seek.c
@@ -9,7 +9,8 @@
 
 syscallret_t syscall_seek(context_t *context, int fd, off_t offset, int whence) {
 	syscallret_t ret = {
-		.ret = -1
+		.ret = -1,
+		.errno = 0
 	};
 
 	if (whence > 2) {
@@ -28,15 +29,30 @@ syscallret_t syscall_seek(context_t *context, int fd, off_t offset, int whence)
 		goto cleanup;
 	}
 
-	// TODO device check seek
-
+	size_t size = -1;
 	uintmax_t curroffset = file->offset;
 	uintmax_t newoffset = 0;
 
+	// determine size
+
+	if (file->vnode->type == V_TYPE_CHDEV) {
+		ret.errno = VOP_MAXSEEK(file->vnode, &size);
+		if (ret.errno) {
+			ret.errno = ESPIPE;
+			goto cleanup;
+		}
+	} else {
+		vattr_t attr;
+		ret.errno = VOP_GETATTR(file->vnode, &attr, &_cpu()->thread->proc->cred);
+		if (ret.errno)
+			goto cleanup;
+		size = attr.size;
+	}
+
 	switch (whence) {
 		case SEEK_SET:
-		newoffset = offset;
-		break;
+			newoffset = offset;
+			break;
 		case SEEK_CUR:
 			newoffset = curroffset + offset;
 			if (offset > 0 && newoffset < curroffset) {
@@ -48,14 +64,9 @@ syscallret_t syscall_seek(context_t *context, int fd, off_t offset, int whence)
 				goto cleanup;
 			}
 			break;
-		case SEEK_END: {
-			vattr_t attr;
-			ret.errno = VOP_GETATTR(file->vnode, &attr, &_cpu()->thread->proc->cred);
-			if (ret.errno) 
-				goto cleanup;
-			newoffset = attr.size;
+		case SEEK_END:
+			newoffset = size;
 			break;
-		}
 	}
 
 	file->offset = newoffset;