mirror of https://gitee.com/openkylin/linux.git
76 lines
1.7 KiB
C
76 lines
1.7 KiB
C
/*
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* User address space access functions.
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*
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* Copyright 1997 Andi Kleen <ak@muc.de>
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* Copyright 1997 Linus Torvalds
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* Copyright 2002 Andi Kleen <ak@suse.de>
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*/
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#include <linux/export.h>
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#include <linux/uaccess.h>
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/*
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* Zero Userspace
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*/
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unsigned long __clear_user(void __user *addr, unsigned long size)
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{
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long __d0;
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might_fault();
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/* no memory constraint because it doesn't change any memory gcc knows
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about */
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stac();
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asm volatile(
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" testq %[size8],%[size8]\n"
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" jz 4f\n"
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"0: movq %[zero],(%[dst])\n"
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" addq %[eight],%[dst]\n"
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" decl %%ecx ; jnz 0b\n"
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"4: movq %[size1],%%rcx\n"
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" testl %%ecx,%%ecx\n"
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" jz 2f\n"
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"1: movb %b[zero],(%[dst])\n"
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" incq %[dst]\n"
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" decl %%ecx ; jnz 1b\n"
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"2:\n"
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".section .fixup,\"ax\"\n"
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"3: lea 0(%[size1],%[size8],8),%[size8]\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(0b,3b)
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_ASM_EXTABLE(1b,2b)
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: [size8] "=&c"(size), [dst] "=&D" (__d0)
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: [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr),
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[zero] "r" (0UL), [eight] "r" (8UL));
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clac();
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return size;
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}
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EXPORT_SYMBOL(__clear_user);
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unsigned long clear_user(void __user *to, unsigned long n)
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{
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if (access_ok(VERIFY_WRITE, to, n))
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return __clear_user(to, n);
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return n;
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}
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EXPORT_SYMBOL(clear_user);
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/*
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* Try to copy last bytes and clear the rest if needed.
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* Since protection fault in copy_from/to_user is not a normal situation,
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* it is not necessary to optimize tail handling.
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*/
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__visible unsigned long
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copy_user_handle_tail(char *to, char *from, unsigned len)
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{
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for (; len; --len, to++) {
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char c;
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if (__get_user_nocheck(c, from++, sizeof(char)))
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break;
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if (__put_user_nocheck(c, to, sizeof(char)))
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break;
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}
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clac();
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return len;
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}
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