From eefc036a0a9ff0d34c98778632693451c84baf56 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Thu, 18 Jul 2024 21:05:25 -0400
Subject: kernel: Add copyin() and copyout()

Add copyin() and copyout() for copying from userspace to kernel space
and vice versa.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/kern/kern_subr.c | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 sys/kern/kern_subr.c

(limited to 'sys/kern')

diff --git a/sys/kern/kern_subr.c b/sys/kern/kern_subr.c
new file mode 100644
index 0000000..a4476f9
--- /dev/null
+++ b/sys/kern/kern_subr.c
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/proc.h>
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/exec.h>
+#include <sys/systm.h>
+#include <string.h>
+
+
+/*
+ * Check if a user address is valid.
+ *
+ * @uaddr: User address to check.
+ *
+ * Returns true if valid, otherwise false.
+ */
+static bool
+check_uaddr(const void *uaddr)
+{
+    vaddr_t stack_start, stack_end;
+    struct exec_prog exec;
+    struct proc *td;
+    uintptr_t addr;
+
+    td = this_td();
+    exec = td->exec;
+    addr = (uintptr_t)uaddr;
+
+    stack_start = td->stack_base;
+    stack_end = td->stack_base + PROC_STACK_SIZE;
+
+    if (addr >= exec.start && addr <= exec.end)
+        return true;
+    if (addr >= stack_start && addr <= stack_end)
+        return true;
+
+    return false;
+}
+
+/*
+ * Copy from userspace to the kernel.
+ *
+ * @uaddr: Userspace address.
+ * @kaddr: Kernelspace address.
+ * @len: Length of data.
+ */
+int
+copyin(const void *uaddr, void *kaddr, size_t len)
+{
+    char *tmp = (char *)uaddr;
+
+    if (!check_uaddr(tmp) || !check_uaddr(tmp + len)) {
+        return -EFAULT;
+    }
+
+    memcpy(kaddr, uaddr, len);
+    return 0;
+}
+
+/*
+ * Copy from the kernel to userspace.
+ *
+ * @kaddr: Kernelspace address.
+ * @uaddr: Userspace address.
+ * @len: Length of data.
+ */
+int
+copyout(const void *kaddr, void *uaddr, size_t len)
+{
+    char *tmp = uaddr;
+
+    if (!check_uaddr(tmp) || !check_uaddr(tmp + len)) {
+        return -EFAULT;
+    }
+
+    memcpy(uaddr, kaddr, len);
+    return 0;
+}
+
+/*
+ * Copy in a string from userspace
+ *
+ * Unlike the typical copyin(), this routine will
+ * copy until we've hit NUL ('\0')
+ *
+ * @uaddr: Userspace address.
+ * @kaddr: Kernelspace address.
+ * @len: Length of string.
+ *
+ * XXX: Please note that if `len' is less than the actual
+ *      string length, the returned value will not be
+ *      NUL terminated.
+ */
+int
+copyinstr(const void *uaddr, char *kaddr, size_t len)
+{
+    char *dest = (char *)kaddr;
+    const char *src = (char *)uaddr;
+
+    if (!check_uaddr(src)) {
+        return -EFAULT;
+    }
+
+    for (size_t i = 0; i < len; ++i) {
+        if (!check_uaddr(src + i)) {
+            return -EFAULT;
+        }
+
+        dest[i] = src[i];
+
+        if (src[i] == '\0') {
+            break;
+        }
+    }
+
+    return 0;
+}
-- 
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