| 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/export.h> |
| 9 | #include <linux/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 | stac(); |
| 22 | asm volatile( |
| 23 | " testq %[size8],%[size8]\n" |
| 24 | " jz 4f\n" |
| 25 | "0: movq %[zero],(%[dst])\n" |
| 26 | " addq %[eight],%[dst]\n" |
| 27 | " decl %%ecx ; jnz 0b\n" |
| 28 | "4: movq %[size1],%%rcx\n" |
| 29 | " testl %%ecx,%%ecx\n" |
| 30 | " jz 2f\n" |
| 31 | "1: movb %b[zero],(%[dst])\n" |
| 32 | " incq %[dst]\n" |
| 33 | " decl %%ecx ; jnz 1b\n" |
| 34 | "2:\n" |
| 35 | ".section .fixup,\"ax\"\n" |
| 36 | "3: lea 0(%[size1],%[size8],8),%[size8]\n" |
| 37 | " jmp 2b\n" |
| 38 | ".previous\n" |
| 39 | _ASM_EXTABLE(0b,3b) |
| 40 | _ASM_EXTABLE(1b,2b) |
| 41 | : [size8] "=&c"(size), [dst] "=&D" (__d0) |
| 42 | : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr), |
| 43 | [zero] "r" (0UL), [eight] "r" (8UL)); |
| 44 | clac(); |
| 45 | return size; |
| 46 | } |
| 47 | EXPORT_SYMBOL(__clear_user); |
| 48 | |
| 49 | unsigned long clear_user(void __user *to, unsigned long n) |
| 50 | { |
| 51 | if (access_ok(VERIFY_WRITE, to, n)) |
| 52 | return __clear_user(to, n); |
| 53 | return n; |
| 54 | } |
| 55 | EXPORT_SYMBOL(clear_user); |
| 56 | |
| 57 | unsigned long copy_in_user(void __user *to, const void __user *from, unsigned len) |
| 58 | { |
| 59 | if (access_ok(VERIFY_WRITE, to, len) && access_ok(VERIFY_READ, from, len)) { |
| 60 | return copy_user_generic((__force void *)to, (__force void *)from, len); |
| 61 | } |
| 62 | return len; |
| 63 | } |
| 64 | EXPORT_SYMBOL(copy_in_user); |
| 65 | |
| 66 | /* |
| 67 | * Try to copy last bytes and clear the rest if needed. |
| 68 | * Since protection fault in copy_from/to_user is not a normal situation, |
| 69 | * it is not necessary to optimize tail handling. |
| 70 | */ |
| 71 | __visible unsigned long |
| 72 | copy_user_handle_tail(char *to, char *from, unsigned len) |
| 73 | { |
| 74 | for (; len; --len, to++) { |
| 75 | char c; |
| 76 | |
| 77 | if (__get_user_nocheck(c, from++, sizeof(char))) |
| 78 | break; |
| 79 | if (__put_user_nocheck(c, to, sizeof(char))) |
| 80 | break; |
| 81 | } |
| 82 | clac(); |
| 83 | |
| 84 | /* If the destination is a kernel buffer, we always clear the end */ |
| 85 | if (!__addr_ok(to)) |
| 86 | memset(to, 0, len); |
| 87 | return len; |
| 88 | } |