__fetchint64

5bb26da5 · Silas Boyd-Wickizer · a9b40e7e · 5bb26da5 · 5bb26da5
--- a/kernel/syscall.cc
+++ b/kernel/syscall.cc
@@ -11,6 +11,7 @@
 #include "kmtrace.hh"

 extern "C" int __fetchstr(char* dst, const char* usrc, unsigned size);
+extern "C" int __fetchint64(uptr addr, u64* ip);

 int
 fetchstr(char* dst, const char* usrc, unsigned size)
@@ -20,22 +21,12 @@ fetchstr(char* dst, const char* usrc, unsigned size)
  return __fetchstr(dst, usrc, size);
 }

-// User code makes a system call with INT T_SYSCALL.
-// System call number in %eax.
-// Arguments on the stack, from the user call to the C
-// library system call function. The saved user %esp points
-// to a saved program counter, and then the first argument.
-
-// Fetch the int at addr from process p.
 int
 fetchint64(uptr addr, u64 *ip)
 {
-  if(pagefault(myproc()->vmap, addr, 0) < 0)
-    return -1;
-  if(pagefault(myproc()->vmap, addr+sizeof(*ip)-1, 0) < 0)
-    return -1;
-  *ip = *(u64*)(addr);
-  return 0;
+  if(mycpu()->ncli != 0)
+    panic("fetchstr: cli'd");
+  return __fetchint64(addr, ip);
 }

 // Fetch the nul-terminated string at addr from process p.

--- a/kernel/uaccess.S
+++ b/kernel/uaccess.S
@@ -2,6 +2,20 @@
 #include "asmdefines.h"

 .code64
+.globl __fetchint64
+.align 8
+// rdi user src
+// rsi kernel dst
+// We aren't allowed to touch rbx,rsp,rbp,r12-r15
+__fetchint64:
+        mov     %gs:0x8, %r11
+        movl    $1, PROC_UACCESS(%r11)
+        mov     (%rdi), %r10
+        mov     %r10, (%rsi)
+        mov     $0, %rax
+        jmp __fetch_end
+        
+.code64
 .globl __fetchstr
 .align 8
 // rdi kernel dst
@@ -20,13 +34,13 @@ __fetchstr:
        movb    %r10b, (%rdi)
        // Check for NULL
        cmp     $0, %r10b
-        je      done
+        je      2f
        inc     %rdi
        inc     %rsi
        loop    1b
        // Error
        movq    $-1, %rax
-done:
+2:      // Done
        jmp __fetch_end

 .code64