umemcpy: a kernel function that copies data from user to kernel

umemcpy is as safe as argptr.

umemcpy: a kernel function that copies data from user to kernel
976918db · Silas Boyd-Wickizer · 18399524 · 976918db · 976918db
--- a/kernel.h
+++ b/kernel.h
@@ -273,6 +273,7 @@ int             argptr(int, char**, int);
 int             argstr(int, char**);
 int             fetchint64(uptr, u64*);
 int             fetchstr(uptr, char**);
+int             umemcpy(void *, const void *, u64);
 void            syscall(void);

 // string.c

--- a/syscall.c
+++ b/syscall.c
@@ -109,6 +109,18 @@ argstr(int n, char **pp)
  return fetchstr(addr, pp);
 }

+int
+umemcpy(void *dst, const void *umen, u64 size)
+{
+  uptr src = (uptr)umen;
+
+  for(uptr va = PGROUNDDOWN(src); va < src+size; va = va+PGSIZE)
+    if(pagefault(myproc()->vmap, va, 0) < 0)
+      return -1;
+  memmove(dst, umen, size);
+  return 0;
+}
+
 extern long sys_chdir(void);
 extern long sys_close(void);
 extern long sys_dup(void);