fs: add readlink() feature to per-process links

fs/vfs.c

@@ -192,7 +192,7 @@ static int vfs_link_resolve_internal(struct vfs_ioctx *ctx,
     if (lnk->flags & VN_PER_PROCESS) {
         _assert(lnk->target_func);
         // TODO: pass it as an argument instead of ioctx
-        target = lnk->target_func(thread_self, lnk);
+        target = lnk->target_func(thread_self, lnk, NULL, 0);
     } else {
         target = lnk->target;
     }

fs/vfs_ops.c

@@ -4,6 +4,7 @@
 #include "sys/char/chr.h"
 #include "fs/ofile.h"
 #include "fs/node.h"
+#include "sys/thread.h"
 #include "fs/vfs.h"
 #include "sys/string.h"
 #include "sys/assert.h"
@@ -570,6 +571,14 @@ ssize_t vfs_readlinkat(struct vfs_ioctx *ctx,
     }
 
     if (!node->op || !node->op->readlink) {
+        if ((node->flags & VN_PER_PROCESS) && node->target_func) {
+            if (node->target_func(thread_self, node, buf, lim) != NULL) {
+                return 0;
+            } else {
+                return -EINVAL;
+            }
+        }
+
         kerror("readlink() not implemented for node\n");
         return -EINVAL;
     }

include/fs/node.h

@@ -23,7 +23,7 @@ struct thread;
 struct vnode;
 struct fs;
 
-typedef struct vnode *(*vnode_link_getter_t) (struct thread *, struct vnode *);
+typedef struct vnode *(*vnode_link_getter_t) (struct thread *, struct vnode *, char *, size_t);
 
 enum vnode_type {
     VN_REG,

sys/char/tty.c

@@ -175,13 +175,25 @@ void tty_putc(struct chrdev *tty, int c) {
     }
 }
 
-static struct vnode *tty_link_getter(struct thread *ctx, struct vnode *link) {
+static struct vnode *tty_link_getter(struct thread *ctx, struct vnode *link, char *buf, size_t len) {
     struct process *proc;
 
     if (!(proc = ctx->proc)) {
         return NULL;
     }
 
+    if (buf) {
+        if (proc->ctty) {
+            if (strlen(proc->ctty->name) < len) {
+                strcpy(buf, proc->ctty->name);
+            } else {
+                return NULL;
+            }
+        } else {
+            buf[0] = 0;
+        }
+    }
+
     return proc->ctty;
 }
 

sys/thread.c

@@ -61,8 +61,17 @@ static int sysfs_proc_ioctx(void *ctx, char *buf, size_t lim) {
     return 0;
 }
 
-static struct vnode *sysfs_proc_self(struct thread *ctx, struct vnode *link) {
+static struct vnode *sysfs_proc_self(struct thread *ctx, struct vnode *link, char *buf, size_t lim) {
     _assert(ctx && ctx->proc);
+    struct vnode *res = ctx->proc->fs_entry;
+
+    if (buf && strlen(res->name) < lim) {
+        if (strlen(res->name) < lim) {
+            strcpy(buf, res->name);
+        } else {
+            return NULL;
+        }
+    }
     return ctx->proc->fs_entry;
 }