1 /* 2 * User address space access functions. 3 * 4 * Copyright 1997 Andi Kleen <ak@muc.de> 5 * Copyright 1997 Linus Torvalds 6 * Copyright 2002 Andi Kleen <ak@suse.de> 7 */ 8 #include <linux/module.h> 9 #include <asm/uaccess.h> 10 11 /* 12 * Zero Userspace 13 */ 14 15 unsigned long __clear_user(void __user *addr, unsigned long size) 16 { 17 long __d0; 18 might_fault(); 19 /* no memory constraint because it doesn't change any memory gcc knows 20 about */ 21 asm volatile( 22 " testq %[size8],%[size8]\n" 23 " jz 4f\n" 24 "0: movq %[zero],(%[dst])\n" 25 " addq %[eight],%[dst]\n" 26 " decl %%ecx ; jnz 0b\n" 27 "4: movq %[size1],%%rcx\n" 28 " testl %%ecx,%%ecx\n" 29 " jz 2f\n" 30 "1: movb %b[zero],(%[dst])\n" 31 " incq %[dst]\n" 32 " decl %%ecx ; jnz 1b\n" 33 "2:\n" 34 ".section .fixup,\"ax\"\n" 35 "3: lea 0(%[size1],%[size8],8),%[size8]\n" 36 " jmp 2b\n" 37 ".previous\n" 38 _ASM_EXTABLE(0b,3b) 39 _ASM_EXTABLE(1b,2b) 40 : [size8] "=&c"(size), [dst] "=&D" (__d0) 41 : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr), 42 [zero] "r" (0UL), [eight] "r" (8UL)); 43 return size; 44 } 45 EXPORT_SYMBOL(__clear_user); 46 47 unsigned long clear_user(void __user *to, unsigned long n) 48 { 49 if (access_ok(VERIFY_WRITE, to, n)) 50 return __clear_user(to, n); 51 return n; 52 } 53 EXPORT_SYMBOL(clear_user); 54 55 unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len) 56 { 57 if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) { 58 return copy_user_generic((__force void *)to, (__force void *)from, len); 59 } 60 return len; 61 } 62 EXPORT_SYMBOL(copy_in_user); 63 64 /* 65 * Try to copy last bytes and clear the rest if needed. 66 * Since protection fault in copy_from/to_user is not a normal situation, 67 * it is not necessary to optimize tail handling. 68 */ 69 unsigned long 70 copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest) 71 { 72 char c; 73 unsigned zero_len; 74 75 for (; len; --len) { 76 if (__get_user_nocheck(c, from++, sizeof(char))) 77 break; 78 if (__put_user_nocheck(c, to++, sizeof(char))) 79 break; 80 } 81 82 for (c = 0, zero_len = len; zerorest && zero_len; --zero_len) 83 if (__put_user_nocheck(c, to++, sizeof(char))) 84 break; 85 return len; 86 } 87