diff options
Diffstat (limited to 'arch/x86_64/lib/getuser.S')
| -rw-r--r-- | arch/x86_64/lib/getuser.S | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/arch/x86_64/lib/getuser.S b/arch/x86_64/lib/getuser.S new file mode 100644 index 000000000000..f94ea8a44051 --- /dev/null +++ b/arch/x86_64/lib/getuser.S @@ -0,0 +1,101 @@ +/* + * __get_user functions. + * + * (C) Copyright 1998 Linus Torvalds + * (C) Copyright 2005 Andi Kleen + * + * These functions have a non-standard call interface + * to make them more efficient, especially as they + * return an error value in addition to the "real" + * return value. + */ + +/* + * __get_user_X + * + * Inputs: %rcx contains the address. + * The register is modified, but all changes are undone + * before returning because the C code doesn't know about it. + * + * Outputs: %rax is error code (0 or -EFAULT) + * %rdx contains zero-extended value + * + * %r8 is destroyed. + * + * These functions should not modify any other registers, + * as they get called from within inline assembly. + */ + +#include <linux/linkage.h> +#include <asm/page.h> +#include <asm/errno.h> +#include <asm/offset.h> +#include <asm/thread_info.h> + + .text + .p2align 4 +.globl __get_user_1 +__get_user_1: + GET_THREAD_INFO(%r8) + cmpq threadinfo_addr_limit(%r8),%rcx + jae bad_get_user +1: movzb (%rcx),%edx + xorl %eax,%eax + ret + + .p2align 4 +.globl __get_user_2 +__get_user_2: + GET_THREAD_INFO(%r8) + addq $1,%rcx + jc 20f + cmpq threadinfo_addr_limit(%r8),%rcx + jae 20f + decq %rcx +2: movzwl (%rcx),%edx + xorl %eax,%eax + ret +20: decq %rcx + jmp bad_get_user + + .p2align 4 +.globl __get_user_4 +__get_user_4: + GET_THREAD_INFO(%r8) + addq $3,%rcx + jc 30f + cmpq threadinfo_addr_limit(%r8),%rcx + jae 30f + subq $3,%rcx +3: movl (%rcx),%edx + xorl %eax,%eax + ret +30: subq $3,%rcx + jmp bad_get_user + + .p2align 4 +.globl __get_user_8 +__get_user_8: + GET_THREAD_INFO(%r8) + addq $7,%rcx + jc bad_get_user + cmpq threadinfo_addr_limit(%r8),%rcx + jae bad_get_user + subq $7,%rcx +4: movq (%rcx),%rdx + xorl %eax,%eax + ret +40: subq $7,%rcx + jmp bad_get_user + +bad_get_user: + xorl %edx,%edx + movq $(-EFAULT),%rax + ret + +.section __ex_table,"a" + .quad 1b,bad_get_user + .quad 2b,bad_get_user + .quad 3b,bad_get_user + .quad 4b,bad_get_user +.previous |