471 lines
14 KiB
C
471 lines
14 KiB
C
/*
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* User address space access functions.
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* The non-inlined parts of asm-cris/uaccess.h are here.
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*
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* Copyright (C) 2000, 2003 Axis Communications AB.
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*
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* Written by Hans-Peter Nilsson.
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* Pieces used from memcpy, originally by Kenny Ranerup long time ago.
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*/
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#include <asm/uaccess.h>
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/* Asm:s have been tweaked (within the domain of correctness) to give
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satisfactory results for "gcc version 3.2.1 Axis release R53/1.53-v32".
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Check regularly...
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Note that for CRISv32, the PC saved at a bus-fault is the address
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*at* the faulting instruction, with a special case for instructions
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in delay slots: then it's the address of the branch. Note also that
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in contrast to v10, a postincrement in the instruction is *not*
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performed at a bus-fault; the register is seen having the original
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value in fault handlers. */
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/* Copy to userspace. This is based on the memcpy used for
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kernel-to-kernel copying; see "string.c". */
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unsigned long
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__copy_user (void __user *pdst, const void *psrc, unsigned long pn)
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{
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/* We want the parameters put in special registers.
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Make sure the compiler is able to make something useful of this.
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As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
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FIXME: Comment for old gcc version. Check.
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If gcc was allright, it really would need no temporaries, and no
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stack space to save stuff on. */
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register char *dst __asm__ ("r13") = pdst;
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register const char *src __asm__ ("r11") = psrc;
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register int n __asm__ ("r12") = pn;
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register int retn __asm__ ("r10") = 0;
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/* When src is aligned but not dst, this makes a few extra needless
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cycles. I believe it would take as many to check that the
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re-alignment was unnecessary. */
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if (((unsigned long) dst & 3) != 0
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/* Don't align if we wouldn't copy more than a few bytes; so we
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don't have to check further for overflows. */
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&& n >= 3)
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{
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if ((unsigned long) dst & 1)
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{
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__asm_copy_to_user_1 (dst, src, retn);
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n--;
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}
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if ((unsigned long) dst & 2)
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{
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__asm_copy_to_user_2 (dst, src, retn);
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n -= 2;
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}
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}
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/* Movem is dirt cheap. The overheap is low enough to always use the
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minimum possible block size as the threshold. */
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if (n >= 44)
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{
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/* For large copies we use 'movem'. */
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/* It is not optimal to tell the compiler about clobbering any
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registers; that will move the saving/restoring of those registers
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to the function prologue/epilogue, and make non-movem sizes
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suboptimal. */
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__asm__ volatile ("\
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;; Check that the register asm declaration got right. \n\
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;; The GCC manual explicitly says TRT will happen. \n\
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.ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
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.err \n\
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.endif \n\
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\n\
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;; Save the registers we'll use in the movem process \n\
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;; on the stack. \n\
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subq 11*4,$sp \n\
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movem $r10,[$sp] \n\
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\n\
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;; Now we've got this: \n\
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;; r11 - src \n\
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;; r13 - dst \n\
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;; r12 - n \n\
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\n\
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;; Update n for the first loop \n\
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subq 44,$r12 \n\
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0: \n\
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movem [$r11+],$r10 \n\
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subq 44,$r12 \n\
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1: bge 0b \n\
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movem $r10,[$r13+] \n\
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3: \n\
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addq 44,$r12 ;; compensate for last loop underflowing n \n\
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\n\
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;; Restore registers from stack \n\
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movem [$sp+],$r10 \n\
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2: \n\
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.section .fixup,\"ax\" \n\
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4: \n\
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; When failing on any of the 1..44 bytes in a chunk, we adjust back the \n\
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; source pointer and just drop through to the by-16 and by-4 loops to \n\
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; get the correct number of failing bytes. This necessarily means a \n\
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; few extra exceptions, but invalid user pointers shouldn't happen in \n\
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; time-critical code anyway. \n\
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jump 3b \n\
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subq 44,$r11 \n\
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\n\
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.previous \n\
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.section __ex_table,\"a\" \n\
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.dword 1b,4b \n\
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.previous"
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/* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
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/* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
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}
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while (n >= 16)
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{
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__asm_copy_to_user_16 (dst, src, retn);
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n -= 16;
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}
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/* Having a separate by-four loops cuts down on cache footprint.
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FIXME: Test with and without; increasing switch to be 0..15. */
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while (n >= 4)
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{
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__asm_copy_to_user_4 (dst, src, retn);
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n -= 4;
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}
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switch (n)
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{
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case 0:
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break;
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case 1:
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__asm_copy_to_user_1 (dst, src, retn);
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break;
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case 2:
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__asm_copy_to_user_2 (dst, src, retn);
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break;
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case 3:
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__asm_copy_to_user_3 (dst, src, retn);
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break;
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}
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return retn;
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}
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/* Copy from user to kernel, zeroing the bytes that were inaccessible in
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userland. The return-value is the number of bytes that were
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inaccessible. */
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unsigned long
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__copy_user_zeroing (void __user *pdst, const void *psrc, unsigned long pn)
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{
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/* We want the parameters put in special registers.
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Make sure the compiler is able to make something useful of this.
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As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
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FIXME: Comment for old gcc version. Check.
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If gcc was allright, it really would need no temporaries, and no
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stack space to save stuff on. */
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register char *dst __asm__ ("r13") = pdst;
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register const char *src __asm__ ("r11") = psrc;
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register int n __asm__ ("r12") = pn;
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register int retn __asm__ ("r10") = 0;
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/* The best reason to align src is that we then know that a read-fault
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was for aligned bytes; there's no 1..3 remaining good bytes to
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pickle. */
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if (((unsigned long) src & 3) != 0)
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{
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if (((unsigned long) src & 1) && n != 0)
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{
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__asm_copy_from_user_1 (dst, src, retn);
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n--;
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}
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if (((unsigned long) src & 2) && n >= 2)
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{
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__asm_copy_from_user_2 (dst, src, retn);
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n -= 2;
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}
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/* We only need one check after the unalignment-adjustments, because
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if both adjustments were done, either both or neither reference
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had an exception. */
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if (retn != 0)
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goto copy_exception_bytes;
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}
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/* Movem is dirt cheap. The overheap is low enough to always use the
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minimum possible block size as the threshold. */
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if (n >= 44)
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{
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/* It is not optimal to tell the compiler about clobbering any
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registers; that will move the saving/restoring of those registers
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to the function prologue/epilogue, and make non-movem sizes
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suboptimal. */
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__asm__ volatile ("\
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.ifnc %0%1%2%3,$r13$r11$r12$r10 \n\
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.err \n\
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.endif \n\
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\n\
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;; Save the registers we'll use in the movem process \n\
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;; on the stack. \n\
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subq 11*4,$sp \n\
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movem $r10,[$sp] \n\
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\n\
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;; Now we've got this: \n\
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;; r11 - src \n\
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;; r13 - dst \n\
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;; r12 - n \n\
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\n\
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;; Update n for the first loop \n\
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subq 44,$r12 \n\
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0: \n\
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movem [$r11+],$r10 \n\
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\n\
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subq 44,$r12 \n\
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bge 0b \n\
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movem $r10,[$r13+] \n\
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\n\
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4: \n\
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addq 44,$r12 ;; compensate for last loop underflowing n \n\
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\n\
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;; Restore registers from stack \n\
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movem [$sp+],$r10 \n\
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.section .fixup,\"ax\" \n\
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\n\
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;; Do not jump back into the loop if we fail. For some uses, we get a \n\
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;; page fault somewhere on the line. Without checking for page limits, \n\
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;; we don't know where, but we need to copy accurately and keep an \n\
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;; accurate count; not just clear the whole line. To do that, we fall \n\
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;; down in the code below, proceeding with smaller amounts. It should \n\
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;; be kept in mind that we have to cater to code like what at one time \n\
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;; was in fs/super.c: \n\
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;; i = size - copy_from_user((void *)page, data, size); \n\
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;; which would cause repeated faults while clearing the remainder of \n\
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;; the SIZE bytes at PAGE after the first fault. \n\
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;; A caveat here is that we must not fall through from a failing page \n\
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;; to a valid page. \n\
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\n\
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3: \n\
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jump 4b ;; Fall through, pretending the fault didn't happen. \n\
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nop \n\
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\n\
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.previous \n\
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.section __ex_table,\"a\" \n\
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.dword 0b,3b \n\
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.previous"
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/* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
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/* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
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}
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/* Either we directly start copying here, using dword copying in a loop,
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or we copy as much as possible with 'movem' and then the last block
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(<44 bytes) is copied here. This will work since 'movem' will have
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updated src, dst and n. (Except with failing src.)
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Since we want to keep src accurate, we can't use
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__asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
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retn, but not src (by design; it's value is ignored elsewhere). */
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while (n >= 4)
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{
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__asm_copy_from_user_4 (dst, src, retn);
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n -= 4;
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if (retn)
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goto copy_exception_bytes;
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}
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/* If we get here, there were no memory read faults. */
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switch (n)
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{
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/* These copies are at least "naturally aligned" (so we don't have
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to check each byte), due to the src alignment code before the
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movem loop. The *_3 case *will* get the correct count for retn. */
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case 0:
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/* This case deliberately left in (if you have doubts check the
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generated assembly code). */
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break;
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case 1:
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__asm_copy_from_user_1 (dst, src, retn);
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break;
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case 2:
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__asm_copy_from_user_2 (dst, src, retn);
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break;
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case 3:
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__asm_copy_from_user_3 (dst, src, retn);
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break;
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}
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/* If we get here, retn correctly reflects the number of failing
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bytes. */
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return retn;
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copy_exception_bytes:
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/* We already have "retn" bytes cleared, and need to clear the
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remaining "n" bytes. A non-optimized simple byte-for-byte in-line
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memset is preferred here, since this isn't speed-critical code and
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we'd rather have this a leaf-function than calling memset. */
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{
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char *endp;
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for (endp = dst + n; dst < endp; dst++)
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*dst = 0;
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}
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return retn + n;
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}
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/* Zero userspace. */
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unsigned long
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__do_clear_user (void __user *pto, unsigned long pn)
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{
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/* We want the parameters put in special registers.
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Make sure the compiler is able to make something useful of this.
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As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
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FIXME: Comment for old gcc version. Check.
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If gcc was allright, it really would need no temporaries, and no
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stack space to save stuff on. */
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register char *dst __asm__ ("r13") = pto;
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register int n __asm__ ("r12") = pn;
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register int retn __asm__ ("r10") = 0;
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if (((unsigned long) dst & 3) != 0
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/* Don't align if we wouldn't copy more than a few bytes. */
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&& n >= 3)
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{
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if ((unsigned long) dst & 1)
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{
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__asm_clear_1 (dst, retn);
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n--;
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}
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if ((unsigned long) dst & 2)
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{
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__asm_clear_2 (dst, retn);
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n -= 2;
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}
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}
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/* Decide which copying method to use.
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FIXME: This number is from the "ordinary" kernel memset. */
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if (n >= 48)
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{
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/* For large clears we use 'movem' */
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/* It is not optimal to tell the compiler about clobbering any
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call-saved registers; that will move the saving/restoring of
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those registers to the function prologue/epilogue, and make
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non-movem sizes suboptimal.
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This method is not foolproof; it assumes that the "asm reg"
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declarations at the beginning of the function really are used
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here (beware: they may be moved to temporary registers).
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This way, we do not have to save/move the registers around into
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temporaries; we can safely use them straight away.
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If you want to check that the allocation was right; then
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check the equalities in the first comment. It should say
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something like "r13=r13, r11=r11, r12=r12". */
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__asm__ volatile ("\
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.ifnc %0%1%2,$r13$r12$r10 \n\
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.err \n\
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.endif \n\
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\n\
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;; Save the registers we'll clobber in the movem process \n\
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;; on the stack. Don't mention them to gcc, it will only be \n\
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;; upset. \n\
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subq 11*4,$sp \n\
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movem $r10,[$sp] \n\
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\n\
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clear.d $r0 \n\
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clear.d $r1 \n\
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clear.d $r2 \n\
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clear.d $r3 \n\
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clear.d $r4 \n\
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clear.d $r5 \n\
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clear.d $r6 \n\
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clear.d $r7 \n\
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clear.d $r8 \n\
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clear.d $r9 \n\
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clear.d $r10 \n\
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clear.d $r11 \n\
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\n\
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;; Now we've got this: \n\
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;; r13 - dst \n\
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;; r12 - n \n\
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\n\
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;; Update n for the first loop \n\
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subq 12*4,$r12 \n\
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0: \n\
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subq 12*4,$r12 \n\
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1: \n\
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bge 0b \n\
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movem $r11,[$r13+] \n\
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\n\
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addq 12*4,$r12 ;; compensate for last loop underflowing n \n\
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\n\
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;; Restore registers from stack \n\
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movem [$sp+],$r10 \n\
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2: \n\
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.section .fixup,\"ax\" \n\
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3: \n\
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movem [$sp],$r10 \n\
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addq 12*4,$r10 \n\
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addq 12*4,$r13 \n\
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movem $r10,[$sp] \n\
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jump 0b \n\
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clear.d $r10 \n\
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\n\
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.previous \n\
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.section __ex_table,\"a\" \n\
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.dword 1b,3b \n\
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.previous"
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/* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
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/* Inputs */ : "0" (dst), "1" (n), "2" (retn)
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/* Clobber */ : "r11");
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}
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while (n >= 16)
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{
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__asm_clear_16 (dst, retn);
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n -= 16;
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}
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/* Having a separate by-four loops cuts down on cache footprint.
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FIXME: Test with and without; increasing switch to be 0..15. */
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while (n >= 4)
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{
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__asm_clear_4 (dst, retn);
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n -= 4;
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}
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switch (n)
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{
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case 0:
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break;
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case 1:
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__asm_clear_1 (dst, retn);
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break;
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case 2:
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__asm_clear_2 (dst, retn);
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break;
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case 3:
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__asm_clear_3 (dst, retn);
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break;
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}
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return retn;
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}
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