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efb734d8ed
Add a comment explaining why this is important, and add a CFLAGS_REMOVE clause to the Makefile to make sure it happens. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
93 lines
2.9 KiB
C
93 lines
2.9 KiB
C
/*
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* Copyright 2011 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*
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* Do memcpy(), but trap and return "n" when a load or store faults.
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*
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* Note: this idiom only works when memcpy() compiles to a leaf function.
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* Here leaf function not only means it does not have calls, but also
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* requires no stack operations (sp, stack frame pointer) and no
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* use of callee-saved registers, else "jrp lr" will be incorrect since
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* unwinding stack frame is bypassed. Since memcpy() is not complex so
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* these conditions are satisfied here, but we need to be careful when
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* modifying this file. This is not a clean solution but is the best
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* one so far.
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*
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* Also note that we are capturing "n" from the containing scope here.
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*/
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#define _ST(p, inst, v) \
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({ \
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asm("1: " #inst " %0, %1;" \
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".pushsection .coldtext.memcpy,\"ax\";" \
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"2: { move r0, %2; jrp lr };" \
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".section __ex_table,\"a\";" \
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".quad 1b, 2b;" \
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".popsection" \
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: "=m" (*(p)) : "r" (v), "r" (n)); \
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})
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#define _LD(p, inst) \
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({ \
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unsigned long __v; \
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asm("1: " #inst " %0, %1;" \
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".pushsection .coldtext.memcpy,\"ax\";" \
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"2: { move r0, %2; jrp lr };" \
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".section __ex_table,\"a\";" \
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".quad 1b, 2b;" \
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".popsection" \
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: "=r" (__v) : "m" (*(p)), "r" (n)); \
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__v; \
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})
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#define USERCOPY_FUNC __copy_to_user_inatomic
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#define ST1(p, v) _ST((p), st1, (v))
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#define ST2(p, v) _ST((p), st2, (v))
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#define ST4(p, v) _ST((p), st4, (v))
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#define ST8(p, v) _ST((p), st, (v))
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#define LD1 LD
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#define LD2 LD
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#define LD4 LD
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#define LD8 LD
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#include "memcpy_64.c"
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#define USERCOPY_FUNC __copy_from_user_inatomic
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#define ST1 ST
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#define ST2 ST
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#define ST4 ST
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#define ST8 ST
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#define LD1(p) _LD((p), ld1u)
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#define LD2(p) _LD((p), ld2u)
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#define LD4(p) _LD((p), ld4u)
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#define LD8(p) _LD((p), ld)
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#include "memcpy_64.c"
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#define USERCOPY_FUNC __copy_in_user_inatomic
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#define ST1(p, v) _ST((p), st1, (v))
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#define ST2(p, v) _ST((p), st2, (v))
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#define ST4(p, v) _ST((p), st4, (v))
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#define ST8(p, v) _ST((p), st, (v))
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#define LD1(p) _LD((p), ld1u)
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#define LD2(p) _LD((p), ld2u)
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#define LD4(p) _LD((p), ld4u)
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#define LD8(p) _LD((p), ld)
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#include "memcpy_64.c"
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unsigned long __copy_from_user_zeroing(void *to, const void __user *from,
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unsigned long n)
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{
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unsigned long rc = __copy_from_user_inatomic(to, from, n);
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if (unlikely(rc))
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memset(to + n - rc, 0, rc);
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return rc;
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}
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