From 2e42d32407165f437549abddd319f8feab0051d6 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 5 Oct 2025 19:13:44 -0400
Subject: kern: os: Add copyinstr()

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 src/sys/include/os/systm.h | 12 ++++++++++++
 src/sys/os/os_systm.c      | 26 ++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/src/sys/include/os/systm.h b/src/sys/include/os/systm.h
index 33de08a..24f21db 100644
--- a/src/sys/include/os/systm.h
+++ b/src/sys/include/os/systm.h
@@ -32,6 +32,18 @@
 
 #include <sys/types.h>
 
+/*
+ * Copy userland string to kernel space safely
+ *
+ * @uaddr: Userspace source address to copy from
+ * @kaddr: Kernel address dest address to copy to
+ * @len: Length of buffer
+ *
+ * Returns 0 on success, otherwise a less than zero value
+ * on failure.
+ */
+int copyinstr(const void *uaddr, char *kaddr, size_t len);
+
 /*
  * Copy userland data to kernel space safely
  *
diff --git a/src/sys/os/os_systm.c b/src/sys/os/os_systm.c
index f7fd8f1..69fab30 100644
--- a/src/sys/os/os_systm.c
+++ b/src/sys/os/os_systm.c
@@ -91,3 +91,29 @@ copyout(const void *kaddr, void *uaddr, size_t len)
     memcpy(uaddr, kaddr, len);
     return 0;
 }
+
+int
+copyinstr(const void *uaddr, char *kaddr, size_t len)
+{
+    char *dest = (char *)kaddr;
+    const char *src = (char *)uaddr;
+    char dmmy;
+
+    if (copyin(uaddr, &dmmy, 1) != 0) {
+        return -EFAULT;
+    }
+
+    for (size_t i = 0; i < len; ++i) {
+        if (copyin(uaddr + i, &dmmy, 1) != 0) {
+            return -EFAULT;
+        }
+
+        dest[i] = src[i];
+
+        if (src[i] == '\0') {
+            break;
+        }
+    }
+
+    return 0;
+}
-- 
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