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[209.132.180.67]) by mx.google.com with ESMTP id j15-v6si7241441pll.372.2018.10.04.22.46.00; Thu, 04 Oct 2018 22:46:16 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727956AbeJEMms (ORCPT + 99 others); Fri, 5 Oct 2018 08:42:48 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:56640 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727713AbeJEMmr (ORCPT ); Fri, 5 Oct 2018 08:42:47 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07609329|-1;CH=green;FP=0|0|0|0|0|-1|-1|-1;HT=e02c03290;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=19;RT=19;SR=0;TI=SMTPD_---.Czd0A3A_1538718317; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.Czd0A3A_1538718317) by smtp.aliyun-inc.com(10.147.42.16); Fri, 05 Oct 2018 13:45:17 +0800 From: Guo Ren To: akpm@linux-foundation.org, arnd@arndb.de, daniel.lezcano@linaro.org, davem@davemloft.net, gregkh@linuxfoundation.org, jason@lakedaemon.net, marc.zyngier@arm.com, mark.rutland@arm.com, mchehab+samsung@kernel.org, peterz@infradead.org, robh@kernel.org, robh+dt@kernel.org, tglx@linutronix.de Cc: green.hu@gmail.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, devicetree@vger.kernel.org, c-sky_gcc_upstream@c-sky.com, Guo Ren Subject: [PATCH V7 14/20] csky: User access Date: Fri, 5 Oct 2018 13:41:56 +0800 Message-Id: <089c7cbc917e2e148a70c765b9f518300457a40a.1538715563.git.ren_guo@c-sky.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch adds "user access from kernel" codes. Signed-off-by: Guo Ren --- arch/csky/include/asm/uaccess.h | 416 ++++++++++++++++++++++++++++++++++++++++ arch/csky/lib/usercopy.c | 262 +++++++++++++++++++++++++ 2 files changed, 678 insertions(+) create mode 100644 arch/csky/include/asm/uaccess.h create mode 100644 arch/csky/lib/usercopy.c diff --git a/arch/csky/include/asm/uaccess.h b/arch/csky/include/asm/uaccess.h new file mode 100644 index 0000000..acaf0e210 --- /dev/null +++ b/arch/csky/include/asm/uaccess.h @@ -0,0 +1,416 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. + +#ifndef __ASM_CSKY_UACCESS_H +#define __ASM_CSKY_UACCESS_H + +/* + * User space memory access functions + */ +#include +#include +#include +#include +#include +#include +#include +#include + +#define VERIFY_READ 0 +#define VERIFY_WRITE 1 + +static inline int access_ok(int type, const void *addr, unsigned long size) +{ + unsigned long limit = current_thread_info()->addr_limit.seg; + + return (((unsigned long)addr < limit) && + ((unsigned long)(addr + size) < limit)); +} + +static inline int verify_area(int type, const void *addr, unsigned long size) +{ + return access_ok(type, addr, size) ? 0 : -EFAULT; +} + +#define __addr_ok(addr) (access_ok(VERIFY_READ, addr, 0)) + +extern int __put_user_bad(void); + +/* + * Tell gcc we read from memory instead of writing: this is because + * we do not write to any memory gcc knows about, so there are no + * aliasing issues. + */ + +/* + * These are the main single-value transfer routines. They automatically + * use the right size if we just have the right pointer type. + * + * This gets kind of ugly. We want to return _two_ values in "get_user()" + * and yet we don't want to do any pointers, because that is too much + * of a performance impact. Thus we have a few rather ugly macros here, + * and hide all the ugliness from the user. + * + * The "__xxx" versions of the user access functions are versions that + * do not verify the address space, that must have been done previously + * with a separate "access_ok()" call (this is used when we do multiple + * accesses to the same area of user memory). + * + * As we use the same address space for kernel and user data on + * Ckcore, we can just do these as direct assignments. (Of course, the + * exception handling means that it's no longer "just"...) + */ + +#define put_user(x, ptr) \ + __put_user_check((x), (ptr), sizeof(*(ptr))) + +#define __put_user(x, ptr) \ + __put_user_nocheck((x), (ptr), sizeof(*(ptr))) + +#define __ptr(x) ((unsigned long *)(x)) + +#define get_user(x, ptr) \ + __get_user_check((x), (ptr), sizeof(*(ptr))) + +#define __get_user(x, ptr) \ + __get_user_nocheck((x), (ptr), sizeof(*(ptr))) + +#define __put_user_nocheck(x, ptr, size) \ +({ \ + long __pu_err = 0; \ + typeof(*(ptr)) *__pu_addr = (ptr); \ + typeof(*(ptr)) __pu_val = (typeof(*(ptr)))(x); \ + if (__pu_addr) \ + __put_user_size(__pu_val, (__pu_addr), (size), \ + __pu_err); \ + __pu_err; \ +}) + +#define __put_user_check(x, ptr, size) \ +({ \ + long __pu_err = -EFAULT; \ + typeof(*(ptr)) *__pu_addr = (ptr); \ + typeof(*(ptr)) __pu_val = (typeof(*(ptr)))(x); \ + if (access_ok(VERIFY_WRITE, __pu_addr, size) && __pu_addr) \ + __put_user_size(__pu_val, __pu_addr, (size), __pu_err); \ + __pu_err; \ +}) + +#define __put_user_size(x, ptr, size, retval) \ +do { \ + retval = 0; \ + switch (size) { \ + case 1: \ + __put_user_asm_b(x, ptr, retval); \ + break; \ + case 2: \ + __put_user_asm_h(x, ptr, retval); \ + break; \ + case 4: \ + __put_user_asm_w(x, ptr, retval); \ + break; \ + case 8: \ + __put_user_asm_64(x, ptr, retval); \ + break; \ + default: \ + __put_user_bad(); \ + } \ +} while (0) + +/* + * We don't tell gcc that we are accessing memory, but this is OK + * because we do not write to any memory gcc knows about, so there + * are no aliasing issues. + * + * Note that PC at a fault is the address *after* the faulting + * instruction. + */ +#define __put_user_asm_b(x, ptr, err) \ +do { \ + int errcode; \ + asm volatile( \ + "1: stb %1, (%2,0) \n" \ + " br 3f \n" \ + "2: mov %0, %3 \n" \ + " br 3f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 1b,2b \n" \ + ".previous \n" \ + "3: \n" \ + : "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \ + : "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \ + : "memory"); \ +} while (0) + +#define __put_user_asm_h(x, ptr, err) \ +do { \ + int errcode; \ + asm volatile( \ + "1: sth %1, (%2,0) \n" \ + " br 3f \n" \ + "2: mov %0, %3 \n" \ + " br 3f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 1b,2b \n" \ + ".previous \n" \ + "3: \n" \ + : "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \ + : "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \ + : "memory"); \ +} while (0) + +#define __put_user_asm_w(x, ptr, err) \ +do { \ + int errcode; \ + asm volatile( \ + "1: stw %1, (%2,0) \n" \ + " br 3f \n" \ + "2: mov %0, %3 \n" \ + " br 3f \n" \ + ".section __ex_table,\"a\" \n" \ + ".align 2 \n" \ + ".long 1b, 2b \n" \ + ".previous \n" \ + "3: \n" \ + : "=r"(err), "=r"(x), "=r"(ptr), "=r"(errcode) \ + : "0"(err), "1"(x), "2"(ptr), "3"(-EFAULT) \ + : "memory"); \ +} while (0) + +#define __put_user_asm_64(x, ptr, err) \ +do { \ + int tmp; \ + int errcode; \ + typeof(*(ptr))src = (typeof(*(ptr)))x; \ + typeof(*(ptr))*psrc = &src; \ + \ + asm volatile( \ + " ldw %3, (%1, 0) \n" \ + "1: stw %3, (%2, 0) \n" \ + " ldw %3, (%1, 4) \n" \ + "2: stw %3, (%2, 4) \n" \ + " br 4f \n" \ + "3: mov %0, %4 \n" \ + " br 4f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 1b, 3b \n" \ + ".long 2b, 3b \n" \ + ".previous \n" \ + "4: \n" \ + : "=r"(err), "=r"(psrc), "=r"(ptr), \ + "=r"(tmp), "=r"(errcode) \ + : "0"(err), "1"(psrc), "2"(ptr), "3"(0), "4"(-EFAULT) \ + : "memory"); \ +} while (0) + +#define __get_user_nocheck(x, ptr, size) \ +({ \ + long __gu_err; \ + __get_user_size(x, (ptr), (size), __gu_err); \ + __gu_err; \ +}) + +#define __get_user_check(x, ptr, size) \ +({ \ + int __gu_err = -EFAULT; \ + const __typeof__(*(ptr)) __user *__gu_ptr = (ptr); \ + if (access_ok(VERIFY_READ, __gu_ptr, size) && __gu_ptr) \ + __get_user_size(x, __gu_ptr, size, __gu_err); \ + __gu_err; \ +}) + +#define __get_user_size(x, ptr, size, retval) \ +do { \ + switch (size) { \ + case 1: \ + __get_user_asm_common((x), ptr, "ldb", retval); \ + break; \ + case 2: \ + __get_user_asm_common((x), ptr, "ldh", retval); \ + break; \ + case 4: \ + __get_user_asm_common((x), ptr, "ldw", retval); \ + break; \ + default: \ + x = 0; \ + (retval) = __get_user_bad(); \ + } \ +} while (0) + +#define __get_user_asm_common(x, ptr, ins, err) \ +do { \ + int errcode; \ + asm volatile( \ + "1: " ins " %1, (%4,0) \n" \ + " br 3f \n" \ + /* Fix up codes */ \ + "2: mov %0, %2 \n" \ + " movi %1, 0 \n" \ + " br 3f \n" \ + ".section __ex_table,\"a\" \n" \ + ".align 2 \n" \ + ".long 1b, 2b \n" \ + ".previous \n" \ + "3: \n" \ + : "=r"(err), "=r"(x), "=r"(errcode) \ + : "0"(0), "r"(ptr), "2"(-EFAULT) \ + : "memory"); \ +} while (0) + +extern int __get_user_bad(void); + +#define __copy_user(to, from, n) \ +do { \ + int w0, w1, w2, w3; \ + asm volatile( \ + "0: cmpnei %1, 0 \n" \ + " bf 8f \n" \ + " mov %3, %1 \n" \ + " or %3, %2 \n" \ + " andi %3, 3 \n" \ + " cmpnei %3, 0 \n" \ + " bf 1f \n" \ + " br 5f \n" \ + "1: cmplti %0, 16 \n" /* 4W */ \ + " bt 3f \n" \ + " ldw %3, (%2, 0) \n" \ + " ldw %4, (%2, 4) \n" \ + " ldw %5, (%2, 8) \n" \ + " ldw %6, (%2, 12) \n" \ + "2: stw %3, (%1, 0) \n" \ + "9: stw %4, (%1, 4) \n" \ + "10: stw %5, (%1, 8) \n" \ + "11: stw %6, (%1, 12) \n" \ + " addi %2, 16 \n" \ + " addi %1, 16 \n" \ + " subi %0, 16 \n" \ + " br 1b \n" \ + "3: cmplti %0, 4 \n" /* 1W */ \ + " bt 5f \n" \ + " ldw %3, (%2, 0) \n" \ + "4: stw %3, (%1, 0) \n" \ + " addi %2, 4 \n" \ + " addi %1, 4 \n" \ + " subi %0, 4 \n" \ + " br 3b \n" \ + "5: cmpnei %0, 0 \n" /* 1B */ \ + " bf 8f \n" \ + " ldb %3, (%2, 0) \n" \ + "6: stb %3, (%1, 0) \n" \ + " addi %2, 1 \n" \ + " addi %1, 1 \n" \ + " subi %0, 1 \n" \ + " br 5b \n" \ + "7: br 8f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 2b, 7b \n" \ + ".long 9b, 7b \n" \ + ".long 10b, 7b \n" \ + ".long 11b, 7b \n" \ + ".long 4b, 7b \n" \ + ".long 6b, 7b \n" \ + ".previous \n" \ + "8: \n" \ + : "=r"(n), "=r"(to), "=r"(from), "=r"(w0), \ + "=r"(w1), "=r"(w2), "=r"(w3) \ + : "0"(n), "1"(to), "2"(from) \ + : "memory"); \ +} while (0) + +#define __copy_user_zeroing(to, from, n) \ +do { \ + int tmp; \ + int nsave; \ + asm volatile( \ + "0: cmpnei %1, 0 \n" \ + " bf 7f \n" \ + " mov %3, %1 \n" \ + " or %3, %2 \n" \ + " andi %3, 3 \n" \ + " cmpnei %3, 0 \n" \ + " bf 1f \n" \ + " br 5f \n" \ + "1: cmplti %0, 16 \n" \ + " bt 3f \n" \ + "2: ldw %3, (%2, 0) \n" \ + "10: ldw %4, (%2, 4) \n" \ + " stw %3, (%1, 0) \n" \ + " stw %4, (%1, 4) \n" \ + "11: ldw %3, (%2, 8) \n" \ + "12: ldw %4, (%2, 12) \n" \ + " stw %3, (%1, 8) \n" \ + " stw %4, (%1, 12) \n" \ + " addi %2, 16 \n" \ + " addi %1, 16 \n" \ + " subi %0, 16 \n" \ + " br 1b \n" \ + "3: cmplti %0, 4 \n" \ + " bt 5f \n" \ + "4: ldw %3, (%2, 0) \n" \ + " stw %3, (%1, 0) \n" \ + " addi %2, 4 \n" \ + " addi %1, 4 \n" \ + " subi %0, 4 \n" \ + " br 3b \n" \ + "5: cmpnei %0, 0 \n" \ + " bf 7f \n" \ + "6: ldb %3, (%2, 0) \n" \ + " stb %3, (%1, 0) \n" \ + " addi %2, 1 \n" \ + " addi %1, 1 \n" \ + " subi %0, 1 \n" \ + " br 5b \n" \ + "8: mov %3, %0 \n" \ + " movi %4, 0 \n" \ + "9: stb %4, (%1, 0) \n" \ + " addi %1, 1 \n" \ + " subi %3, 1 \n" \ + " cmpnei %3, 0 \n" \ + " bt 9b \n" \ + " br 7f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 2b, 8b \n" \ + ".long 10b, 8b \n" \ + ".long 11b, 8b \n" \ + ".long 12b, 8b \n" \ + ".long 4b, 8b \n" \ + ".long 6b, 8b \n" \ + ".previous \n" \ + "7: \n" \ + : "=r"(n), "=r"(to), "=r"(from), "=r"(nsave), \ + "=r"(tmp) \ + : "0"(n), "1"(to), "2"(from) \ + : "memory"); \ +} while (0) + +unsigned long raw_copy_from_user(void *to, const void *from, unsigned long n); +unsigned long raw_copy_to_user(void *to, const void *from, unsigned long n); + +unsigned long clear_user(void *to, unsigned long n); +unsigned long __clear_user(void __user *to, unsigned long n); + +long strncpy_from_user(char *dst, const char *src, long count); +long __strncpy_from_user(char *dst, const char *src, long count); + +/* + * Return the size of a string (including the ending 0) + * + * Return 0 on exception, a value greater than N if too long + */ +long strnlen_user(const char *src, long n); + +#define strlen_user(str) strnlen_user(str, 32767) + +struct exception_table_entry { + unsigned long insn; + unsigned long nextinsn; +}; + +extern int fixup_exception(struct pt_regs *regs); + +#endif /* __ASM_CSKY_UACCESS_H */ diff --git a/arch/csky/lib/usercopy.c b/arch/csky/lib/usercopy.c new file mode 100644 index 0000000..ac9170e --- /dev/null +++ b/arch/csky/lib/usercopy.c @@ -0,0 +1,262 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. + +#include +#include + +unsigned long raw_copy_from_user(void *to, const void *from, + unsigned long n) +{ + if (access_ok(VERIFY_READ, from, n)) + __copy_user_zeroing(to, from, n); + else + memset(to, 0, n); + return n; +} +EXPORT_SYMBOL(raw_copy_from_user); + +unsigned long raw_copy_to_user(void *to, const void *from, + unsigned long n) +{ + if (access_ok(VERIFY_WRITE, to, n)) + __copy_user(to, from, n); + return n; +} +EXPORT_SYMBOL(raw_copy_to_user); + + +/* + * copy a null terminated string from userspace. + */ +#define __do_strncpy_from_user(dst, src, count, res) \ +do { \ + int tmp; \ + long faultres; \ + asm volatile( \ + " cmpnei %3, 0 \n" \ + " bf 4f \n" \ + "1: cmpnei %1, 0 \n" \ + " bf 5f \n" \ + "2: ldb %4, (%3, 0) \n" \ + " stb %4, (%2, 0) \n" \ + " cmpnei %4, 0 \n" \ + " bf 3f \n" \ + " addi %3, 1 \n" \ + " addi %2, 1 \n" \ + " subi %1, 1 \n" \ + " br 1b \n" \ + "3: subu %0, %1 \n" \ + " br 5f \n" \ + "4: mov %0, %5 \n" \ + " br 5f \n" \ + ".section __ex_table, \"a\" \n" \ + ".align 2 \n" \ + ".long 2b, 4b \n" \ + ".previous \n" \ + "5: \n" \ + : "=r"(res), "=r"(count), "=r"(dst), \ + "=r"(src), "=r"(tmp), "=r"(faultres) \ + : "5"(-EFAULT), "0"(count), "1"(count), \ + "2"(dst), "3"(src) \ + : "memory", "cc"); \ +} while (0) + +/* + * __strncpy_from_user: - Copy a NUL terminated string from userspace, + * with less checking. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @src: Source address, in user space. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from userspace to kernel space. + * Caller must check the specified block with access_ok() before calling + * this function. + * + * On success, returns the length of the string (not including the trailing + * NUL). + * + * If access to userspace fails, returns -EFAULT (some data may have been + * copied). + * + * If @count is smaller than the length of the string, copies @count bytes + * and returns @count. + */ +long __strncpy_from_user(char *dst, const char *src, long count) +{ + long res; + + __do_strncpy_from_user(dst, src, count, res); + return res; +} +EXPORT_SYMBOL(__strncpy_from_user); + +/* + * strncpy_from_user: - Copy a NUL terminated string from userspace. + * @dst: Destination address, in kernel space. This buffer must be at + * least @count bytes long. + * @src: Source address, in user space. + * @count: Maximum number of bytes to copy, including the trailing NUL. + * + * Copies a NUL-terminated string from userspace to kernel space. + * + * On success, returns the length of the string (not including the trailing + * NUL). + * + * If access to userspace fails, returns -EFAULT (some data may have been + * copied). + * + * If @count is smaller than the length of the string, copies @count bytes + * and returns @count. + */ +long strncpy_from_user(char *dst, const char *src, long count) +{ + long res = -EFAULT; + + if (access_ok(VERIFY_READ, src, 1)) + __do_strncpy_from_user(dst, src, count, res); + return res; +} +EXPORT_SYMBOL(strncpy_from_user); + +/* + * strlen_user: - Get the size of a string in user space. + * @str: The string to measure. + * @n: The maximum valid length + * + * Get the size of a NUL-terminated string in user space. + * + * Returns the size of the string INCLUDING the terminating NUL. + * On exception, returns 0. + * If the string is too long, returns a value greater than @n. + */ +long strnlen_user(const char *s, long n) +{ + unsigned long res, tmp; + + if (s == NULL) + return 0; + + asm volatile( + " cmpnei %1, 0 \n" + " bf 3f \n" + "1: cmpnei %0, 0 \n" + " bf 3f \n" + "2: ldb %3, (%1, 0) \n" + " cmpnei %3, 0 \n" + " bf 3f \n" + " subi %0, 1 \n" + " addi %1, 1 \n" + " br 1b \n" + "3: subu %2, %0 \n" + " addi %2, 1 \n" + " br 5f \n" + "4: movi %0, 0 \n" + " br 5f \n" + ".section __ex_table, \"a\" \n" + ".align 2 \n" + ".long 2b, 4b \n" + ".previous \n" + "5: \n" + : "=r"(n), "=r"(s), "=r"(res), "=r"(tmp) + : "0"(n), "1"(s), "2"(n) + : "memory", "cc"); + + return res; +} +EXPORT_SYMBOL(strnlen_user); + +#define __do_clear_user(addr, size) \ +do { \ + int __d0, zvalue, tmp; \ + \ + asm volatile( \ + "0: cmpnei %1, 0 \n" \ + " bf 7f \n" \ + " mov %3, %1 \n" \ + " andi %3, 3 \n" \ + " cmpnei %3, 0 \n" \ + " bf 1f \n" \ + " br 5f \n" \ + "1: cmplti %0, 32 \n" /* 4W */ \ + " bt 3f \n" \ + "8: stw %2, (%1, 0) \n" \ + "10: stw %2, (%1, 4) \n" \ + "11: stw %2, (%1, 8) \n" \ + "12: stw %2, (%1, 12) \n" \ + "13: stw %2, (%1, 16) \n" \ + "14: stw %2, (%1, 20) \n" \ + "15: stw %2, (%1, 24) \n" \ + "16: stw %2, (%1, 28) \n" \ + " addi %1, 32 \n" \ + " subi %0, 32 \n" \ + " br 1b \n" \ + "3: cmplti %0, 4 \n" /* 1W */ \ + " bt 5f \n" \ + "4: stw %2, (%1, 0) \n" \ + " addi %1, 4 \n" \ + " subi %0, 4 \n" \ + " br 3b \n" \ + "5: cmpnei %0, 0 \n" /* 1B */ \ + "9: bf 7f \n" \ + "6: stb %2, (%1, 0) \n" \ + " addi %1, 1 \n" \ + " subi %0, 1 \n" \ + " br 5b \n" \ + ".section __ex_table,\"a\" \n" \ + ".align 2 \n" \ + ".long 8b, 9b \n" \ + ".long 10b, 9b \n" \ + ".long 11b, 9b \n" \ + ".long 12b, 9b \n" \ + ".long 13b, 9b \n" \ + ".long 14b, 9b \n" \ + ".long 15b, 9b \n" \ + ".long 16b, 9b \n" \ + ".long 4b, 9b \n" \ + ".long 6b, 9b \n" \ + ".previous \n" \ + "7: \n" \ + : "=r"(size), "=r" (__d0), \ + "=r"(zvalue), "=r"(tmp) \ + : "0"(size), "1"(addr), "2"(0) \ + : "memory", "cc"); \ +} while (0) + +/* + * clear_user: - Zero a block of memory in user space. + * @to: Destination address, in user space. + * @n: Number of bytes to zero. + * + * Zero a block of memory in user space. + * + * Returns number of bytes that could not be cleared. + * On success, this will be zero. + */ +unsigned long +clear_user(void __user *to, unsigned long n) +{ + if (access_ok(VERIFY_WRITE, to, n)) + __do_clear_user(to, n); + return n; +} +EXPORT_SYMBOL(clear_user); + +/* + * __clear_user: - Zero a block of memory in user space, with less checking. + * @to: Destination address, in user space. + * @n: Number of bytes to zero. + * + * Zero a block of memory in user space. Caller must check + * the specified block with access_ok() before calling this function. + * + * Returns number of bytes that could not be cleared. + * On success, this will be zero. + */ +unsigned long +__clear_user(void __user *to, unsigned long n) +{ + __do_clear_user(to, n); + return n; +} +EXPORT_SYMBOL(__clear_user); -- 2.7.4