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linux/arch/cris/arch-v10/lib/usercopy.c

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/*
* User address space access functions.
* The non-inlined parts of asm-cris/uaccess.h are here.
*
* Copyright (C) 2000, Axis Communications AB.
*
* Written by Hans-Peter Nilsson.
* Pieces used from memcpy, originally by Kenny Ranerup long time ago.
*/
#include <linux/uaccess.h>
/* Asm:s have been tweaked (within the domain of correctness) to give
satisfactory results for "gcc version 2.96 20000427 (experimental)".
Check regularly...
Note that the PC saved at a bus-fault is the address *after* the
faulting instruction, which means the branch-target for instructions in
delay-slots for taken branches. Note also that the postincrement in
the instruction is performed regardless of bus-fault; the register is
seen updated in fault handlers.
Oh, and on the code formatting issue, to whomever feels like "fixing
it" to Conformity: I'm too "lazy", but why don't you go ahead and "fix"
string.c too. I just don't think too many people will hack this file
for the code format to be an issue. */
/* Copy to userspace. This is based on the memcpy used for
kernel-to-kernel copying; see "string.c". */
unsigned long __copy_user(void __user *pdst, const void *psrc, unsigned long pn)
{
/* We want the parameters put in special registers.
Make sure the compiler is able to make something useful of this.
As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
FIXME: Comment for old gcc version. Check.
If gcc was alright, it really would need no temporaries, and no
stack space to save stuff on. */
register char *dst __asm__ ("r13") = pdst;
register const char *src __asm__ ("r11") = psrc;
register int n __asm__ ("r12") = pn;
register int retn __asm__ ("r10") = 0;
/* When src is aligned but not dst, this makes a few extra needless
cycles. I believe it would take as many to check that the
re-alignment was unnecessary. */
if (((unsigned long) dst & 3) != 0
/* Don't align if we wouldn't copy more than a few bytes; so we
don't have to check further for overflows. */
&& n >= 3)
{
if ((unsigned long) dst & 1)
{
__asm_copy_to_user_1 (dst, src, retn);
n--;
}
if ((unsigned long) dst & 2)
{
__asm_copy_to_user_2 (dst, src, retn);
n -= 2;
}
}
/* Decide which copying method to use. */
if (n >= 44*2) /* Break even between movem and
move16 is at 38.7*2, but modulo 44. */
{
/* For large copies we use 'movem'. */
/* It is not optimal to tell the compiler about clobbering any
registers; that will move the saving/restoring of those registers
to the function prologue/epilogue, and make non-movem sizes
suboptimal.
This method is not foolproof; it assumes that the "asm reg"
declarations at the beginning of the function really are used
here (beware: they may be moved to temporary registers).
This way, we do not have to save/move the registers around into
temporaries; we can safely use them straight away.
If you want to check that the allocation was right; then
check the equalities in the first comment. It should say
"r13=r13, r11=r11, r12=r12". */
__asm__ volatile ("\
.ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
.err \n\
.endif \n\
\n\
;; Save the registers we'll use in the movem process \n\
;; on the stack. \n\
subq 11*4,$sp \n\
movem $r10,[$sp] \n\
\n\
;; Now we've got this: \n\
;; r11 - src \n\
;; r13 - dst \n\
;; r12 - n \n\
\n\
;; Update n for the first loop \n\
subq 44,$r12 \n\
\n\
; Since the noted PC of a faulting instruction in a delay-slot of a taken \n\
; branch, is that of the branch target, we actually point at the from-movem \n\
; for this case. There is no ambiguity here; if there was a fault in that \n\
; instruction (meaning a kernel oops), the faulted PC would be the address \n\
; after *that* movem. \n\
\n\
0: \n\
movem [$r11+],$r10 \n\
subq 44,$r12 \n\
bge 0b \n\
movem $r10,[$r13+] \n\
1: \n\
addq 44,$r12 ;; compensate for last loop underflowing n \n\
\n\
;; Restore registers from stack \n\
movem [$sp+],$r10 \n\
2: \n\
.section .fixup,\"ax\" \n\
\n\
; To provide a correct count in r10 of bytes that failed to be copied, \n\
; we jump back into the loop if the loop-branch was taken. There is no \n\
; performance penalty for sany use; the program will segfault soon enough.\n\
\n\
3: \n\
move.d [$sp],$r10 \n\
addq 44,$r10 \n\
move.d $r10,[$sp] \n\
jump 0b \n\
4: \n\
movem [$sp+],$r10 \n\
addq 44,$r10 \n\
addq 44,$r12 \n\
jump 2b \n\
\n\
.previous \n\
.section __ex_table,\"a\" \n\
.dword 0b,3b \n\
.dword 1b,4b \n\
.previous"
/* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
/* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
}
/* Either we directly start copying, using dword copying in a loop, or
we copy as much as possible with 'movem' and then the last block (<44
bytes) is copied here. This will work since 'movem' will have
updated SRC, DST and N. */
while (n >= 16)
{
__asm_copy_to_user_16 (dst, src, retn);
n -= 16;
}
/* Having a separate by-four loops cuts down on cache footprint.
FIXME: Test with and without; increasing switch to be 0..15. */
while (n >= 4)
{
__asm_copy_to_user_4 (dst, src, retn);
n -= 4;
}
switch (n)
{
case 0:
break;
case 1:
__asm_copy_to_user_1 (dst, src, retn);
break;
case 2:
__asm_copy_to_user_2 (dst, src, retn);
break;
case 3:
__asm_copy_to_user_3 (dst, src, retn);
break;
}
return retn;
}
EXPORT_SYMBOL(__copy_user);
/* Copy from user to kernel, zeroing the bytes that were inaccessible in
userland. The return-value is the number of bytes that were
inaccessible. */
unsigned long __copy_user_zeroing(void *pdst, const void __user *psrc,
unsigned long pn)
{
/* We want the parameters put in special registers.
Make sure the compiler is able to make something useful of this.
As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
FIXME: Comment for old gcc version. Check.
If gcc was alright, it really would need no temporaries, and no
stack space to save stuff on. */
register char *dst __asm__ ("r13") = pdst;
register const char *src __asm__ ("r11") = psrc;
register int n __asm__ ("r12") = pn;
register int retn __asm__ ("r10") = 0;
/* The best reason to align src is that we then know that a read-fault
was for aligned bytes; there's no 1..3 remaining good bytes to
pickle. */
if (((unsigned long) src & 3) != 0)
{
if (((unsigned long) src & 1) && n != 0)
{
__asm_copy_from_user_1 (dst, src, retn);
n--;
}
if (((unsigned long) src & 2) && n >= 2)
{
__asm_copy_from_user_2 (dst, src, retn);
n -= 2;
}
/* We only need one check after the unalignment-adjustments, because
if both adjustments were done, either both or neither reference
had an exception. */
if (retn != 0)
goto copy_exception_bytes;
}
/* Decide which copying method to use. */
if (n >= 44*2) /* Break even between movem and
move16 is at 38.7*2, but modulo 44.
FIXME: We use move4 now. */
{
/* For large copies we use 'movem' */
/* It is not optimal to tell the compiler about clobbering any
registers; that will move the saving/restoring of those registers
to the function prologue/epilogue, and make non-movem sizes
suboptimal.
This method is not foolproof; it assumes that the "asm reg"
declarations at the beginning of the function really are used
here (beware: they may be moved to temporary registers).
This way, we do not have to save/move the registers around into
temporaries; we can safely use them straight away.
If you want to check that the allocation was right; then
check the equalities in the first comment. It should say
"r13=r13, r11=r11, r12=r12" */
__asm__ volatile ("\n\
.ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
.err \n\
.endif \n\
\n\
;; Save the registers we'll use in the movem process \n\
;; on the stack. \n\
subq 11*4,$sp \n\
movem $r10,[$sp] \n\
\n\
;; Now we've got this: \n\
;; r11 - src \n\
;; r13 - dst \n\
;; r12 - n \n\
\n\
;; Update n for the first loop \n\
subq 44,$r12 \n\
0: \n\
movem [$r11+],$r10 \n\
1: \n\
subq 44,$r12 \n\
bge 0b \n\
movem $r10,[$r13+] \n\
\n\
addq 44,$r12 ;; compensate for last loop underflowing n \n\
\n\
;; Restore registers from stack \n\
movem [$sp+],$r10 \n\
4: \n\
.section .fixup,\"ax\" \n\
\n\
;; Do not jump back into the loop if we fail. For some uses, we get a \n\
;; page fault somewhere on the line. Without checking for page limits, \n\
;; we don't know where, but we need to copy accurately and keep an \n\
;; accurate count; not just clear the whole line. To do that, we fall \n\
;; down in the code below, proceeding with smaller amounts. It should \n\
;; be kept in mind that we have to cater to code like what at one time \n\
;; was in fs/super.c: \n\
;; i = size - copy_from_user((void *)page, data, size); \n\
;; which would cause repeated faults while clearing the remainder of \n\
;; the SIZE bytes at PAGE after the first fault. \n\
;; A caveat here is that we must not fall through from a failing page \n\
;; to a valid page. \n\
\n\
3: \n\
movem [$sp+],$r10 \n\
addq 44,$r12 ;; Get back count before faulting point. \n\
subq 44,$r11 ;; Get back pointer to faulting movem-line. \n\
jump 4b ;; Fall through, pretending the fault didn't happen.\n\
\n\
.previous \n\
.section __ex_table,\"a\" \n\
.dword 1b,3b \n\
.previous"
/* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
/* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
}
/* Either we directly start copying here, using dword copying in a loop,
or we copy as much as possible with 'movem' and then the last block
(<44 bytes) is copied here. This will work since 'movem' will have
updated src, dst and n. (Except with failing src.)
Since we want to keep src accurate, we can't use
__asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
retn, but not src (by design; it's value is ignored elsewhere). */
while (n >= 4)
{
__asm_copy_from_user_4 (dst, src, retn);
n -= 4;
if (retn)
goto copy_exception_bytes;
}
/* If we get here, there were no memory read faults. */
switch (n)
{
/* These copies are at least "naturally aligned" (so we don't have
to check each byte), due to the src alignment code before the
movem loop. The *_3 case *will* get the correct count for retn. */
case 0:
/* This case deliberately left in (if you have doubts check the
generated assembly code). */
break;
case 1:
__asm_copy_from_user_1 (dst, src, retn);
break;
case 2:
__asm_copy_from_user_2 (dst, src, retn);
break;
case 3:
__asm_copy_from_user_3 (dst, src, retn);
break;
}
/* If we get here, retn correctly reflects the number of failing
bytes. */
return retn;
copy_exception_bytes:
/* We already have "retn" bytes cleared, and need to clear the
remaining "n" bytes. A non-optimized simple byte-for-byte in-line
memset is preferred here, since this isn't speed-critical code and
we'd rather have this a leaf-function than calling memset. */
{
char *endp;
for (endp = dst + n; dst < endp; dst++)
*dst = 0;
}
return retn + n;
}
EXPORT_SYMBOL(__copy_user_zeroing);
/* Zero userspace. */
unsigned long __do_clear_user(void __user *pto, unsigned long pn)
{
/* We want the parameters put in special registers.
Make sure the compiler is able to make something useful of this.
As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
FIXME: Comment for old gcc version. Check.
If gcc was alright, it really would need no temporaries, and no
stack space to save stuff on. */
register char *dst __asm__ ("r13") = pto;
register int n __asm__ ("r12") = pn;
register int retn __asm__ ("r10") = 0;
if (((unsigned long) dst & 3) != 0
/* Don't align if we wouldn't copy more than a few bytes. */
&& n >= 3)
{
if ((unsigned long) dst & 1)
{
__asm_clear_1 (dst, retn);
n--;
}
if ((unsigned long) dst & 2)
{
__asm_clear_2 (dst, retn);
n -= 2;
}
}
/* Decide which copying method to use.
FIXME: This number is from the "ordinary" kernel memset. */
if (n >= (1*48))
{
/* For large clears we use 'movem' */
/* It is not optimal to tell the compiler about clobbering any
call-saved registers; that will move the saving/restoring of
those registers to the function prologue/epilogue, and make
non-movem sizes suboptimal.
This method is not foolproof; it assumes that the "asm reg"
declarations at the beginning of the function really are used
here (beware: they may be moved to temporary registers).
This way, we do not have to save/move the registers around into
temporaries; we can safely use them straight away.
If you want to check that the allocation was right; then
check the equalities in the first comment. It should say
something like "r13=r13, r11=r11, r12=r12". */
__asm__ volatile ("\n\
.ifnc %0%1%2,$r13$r12$r10 \n\
.err \n\
.endif \n\
\n\
;; Save the registers we'll clobber in the movem process \n\
;; on the stack. Don't mention them to gcc, it will only be \n\
;; upset. \n\
subq 11*4,$sp \n\
movem $r10,[$sp] \n\
\n\
clear.d $r0 \n\
clear.d $r1 \n\
clear.d $r2 \n\
clear.d $r3 \n\
clear.d $r4 \n\
clear.d $r5 \n\
clear.d $r6 \n\
clear.d $r7 \n\
clear.d $r8 \n\
clear.d $r9 \n\
clear.d $r10 \n\
clear.d $r11 \n\
\n\
;; Now we've got this: \n\
;; r13 - dst \n\
;; r12 - n \n\
\n\
;; Update n for the first loop \n\
subq 12*4,$r12 \n\
0: \n\
subq 12*4,$r12 \n\
bge 0b \n\
movem $r11,[$r13+] \n\
1: \n\
addq 12*4,$r12 ;; compensate for last loop underflowing n\n\
\n\
;; Restore registers from stack \n\
movem [$sp+],$r10 \n\
2: \n\
.section .fixup,\"ax\" \n\
3: \n\
move.d [$sp],$r10 \n\
addq 12*4,$r10 \n\
move.d $r10,[$sp] \n\
clear.d $r10 \n\
jump 0b \n\
\n\
4: \n\
movem [$sp+],$r10 \n\
addq 12*4,$r10 \n\
addq 12*4,$r12 \n\
jump 2b \n\
\n\
.previous \n\
.section __ex_table,\"a\" \n\
.dword 0b,3b \n\
.dword 1b,4b \n\
.previous"
/* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
/* Inputs */ : "0" (dst), "1" (n), "2" (retn)
/* Clobber */ : "r11");
}
while (n >= 16)
{
__asm_clear_16 (dst, retn);
n -= 16;
}
/* Having a separate by-four loops cuts down on cache footprint.
FIXME: Test with and without; increasing switch to be 0..15. */
while (n >= 4)
{
__asm_clear_4 (dst, retn);
n -= 4;
}
switch (n)
{
case 0:
break;
case 1:
__asm_clear_1 (dst, retn);
break;
case 2:
__asm_clear_2 (dst, retn);
break;
case 3:
__asm_clear_3 (dst, retn);
break;
}
return retn;
}
EXPORT_SYMBOL(__do_clear_user);
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