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Diffstat (limited to 'arch/alpha/lib/ev6-copy_user.S')
| -rw-r--r-- | arch/alpha/lib/ev6-copy_user.S | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev6-copy_user.S b/arch/alpha/lib/ev6-copy_user.S new file mode 100644 index 0000000..db42ffe --- /dev/null +++ b/arch/alpha/lib/ev6-copy_user.S @@ -0,0 +1,259 @@ +/* + * arch/alpha/lib/ev6-copy_user.S + * + * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> + * + * Copy to/from user space, handling exceptions as we go.. This + * isn't exactly pretty. + * + * This is essentially the same as "memcpy()", but with a few twists. + * Notably, we have to make sure that $0 is always up-to-date and + * contains the right "bytes left to copy" value (and that it is updated + * only _after_ a successful copy). There is also some rather minor + * exception setup stuff.. + * + * NOTE! This is not directly C-callable, because the calling semantics are + * different: + * + * Inputs: + * length in $0 + * destination address in $6 + * source address in $7 + * return address in $28 + * + * Outputs: + * bytes left to copy in $0 + * + * Clobbers: + * $1,$2,$3,$4,$5,$6,$7 + * + * Much of the information about 21264 scheduling/coding comes from: + * Compiler Writer's Guide for the Alpha 21264 + * abbreviated as 'CWG' in other comments here + * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html + * Scheduling notation: + * E - either cluster + * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 + * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 + */ + +/* Allow an exception for an insn; exit if we get one. */ +#define EXI(x,y...) \ + 99: x,##y; \ + .section __ex_table,"a"; \ + .long 99b - .; \ + lda $31, $exitin-99b($31); \ + .previous + +#define EXO(x,y...) \ + 99: x,##y; \ + .section __ex_table,"a"; \ + .long 99b - .; \ + lda $31, $exitout-99b($31); \ + .previous + + .set noat + .align 4 + .globl __copy_user + .ent __copy_user + # Pipeline info: Slotting & Comments +__copy_user: + .prologue 0 + subq $0, 32, $1 # .. E .. .. : Is this going to be a small copy? + beq $0, $zerolength # U .. .. .. : U L U L + + and $6,7,$3 # .. .. .. E : is leading dest misalignment + ble $1, $onebyteloop # .. .. U .. : 1st branch : small amount of data + beq $3, $destaligned # .. U .. .. : 2nd (one cycle fetcher stall) + subq $3, 8, $3 # E .. .. .. : L U U L : trip counter +/* + * The fetcher stall also hides the 1 cycle cross-cluster stall for $3 (L --> U) + * This loop aligns the destination a byte at a time + * We know we have at least one trip through this loop + */ +$aligndest: + EXI( ldbu $1,0($7) ) # .. .. .. L : Keep loads separate from stores + addq $6,1,$6 # .. .. E .. : Section 3.8 in the CWG + addq $3,1,$3 # .. E .. .. : + nop # E .. .. .. : U L U L + +/* + * the -1 is to compensate for the inc($6) done in a previous quadpack + * which allows us zero dependencies within either quadpack in the loop + */ + EXO( stb $1,-1($6) ) # .. .. .. L : + addq $7,1,$7 # .. .. E .. : Section 3.8 in the CWG + subq $0,1,$0 # .. E .. .. : + bne $3, $aligndest # U .. .. .. : U L U L + +/* + * If we fell through into here, we have a minimum of 33 - 7 bytes + * If we arrived via branch, we have a minimum of 32 bytes + */ +$destaligned: + and $7,7,$1 # .. .. .. E : Check _current_ source alignment + bic $0,7,$4 # .. .. E .. : number bytes as a quadword loop + EXI( ldq_u $3,0($7) ) # .. L .. .. : Forward fetch for fallthrough code + beq $1,$quadaligned # U .. .. .. : U L U L + +/* + * In the worst case, we've just executed an ldq_u here from 0($7) + * and we'll repeat it once if we take the branch + */ + +/* Misaligned quadword loop - not unrolled. Leave it that way. */ +$misquad: + EXI( ldq_u $2,8($7) ) # .. .. .. L : + subq $4,8,$4 # .. .. E .. : + extql $3,$7,$3 # .. U .. .. : + extqh $2,$7,$1 # U .. .. .. : U U L L + + bis $3,$1,$1 # .. .. .. E : + EXO( stq $1,0($6) ) # .. .. L .. : + addq $7,8,$7 # .. E .. .. : + subq $0,8,$0 # E .. .. .. : U L L U + + addq $6,8,$6 # .. .. .. E : + bis $2,$2,$3 # .. .. E .. : + nop # .. E .. .. : + bne $4,$misquad # U .. .. .. : U L U L + + nop # .. .. .. E + nop # .. .. E .. + nop # .. E .. .. + beq $0,$zerolength # U .. .. .. : U L U L + +/* We know we have at least one trip through the byte loop */ + EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad + addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG) + nop # .. E .. .. : + br $31, $dirtyentry # L0 .. .. .. : L U U L +/* Do the trailing byte loop load, then hop into the store part of the loop */ + +/* + * A minimum of (33 - 7) bytes to do a quad at a time. + * Based upon the usage context, it's worth the effort to unroll this loop + * $0 - number of bytes to be moved + * $4 - number of bytes to move as quadwords + * $6 is current destination address + * $7 is current source address + */ +$quadaligned: + subq $4, 32, $2 # .. .. .. E : do not unroll for small stuff + nop # .. .. E .. + nop # .. E .. .. + blt $2, $onequad # U .. .. .. : U L U L + +/* + * There is a significant assumption here that the source and destination + * addresses differ by more than 32 bytes. In this particular case, a + * sparsity of registers further bounds this to be a minimum of 8 bytes. + * But if this isn't met, then the output result will be incorrect. + * Furthermore, due to a lack of available registers, we really can't + * unroll this to be an 8x loop (which would enable us to use the wh64 + * instruction memory hint instruction). + */ +$unroll4: + EXI( ldq $1,0($7) ) # .. .. .. L + EXI( ldq $2,8($7) ) # .. .. L .. + subq $4,32,$4 # .. E .. .. + nop # E .. .. .. : U U L L + + addq $7,16,$7 # .. .. .. E + EXO( stq $1,0($6) ) # .. .. L .. + EXO( stq $2,8($6) ) # .. L .. .. + subq $0,16,$0 # E .. .. .. : U L L U + + addq $6,16,$6 # .. .. .. E + EXI( ldq $1,0($7) ) # .. .. L .. + EXI( ldq $2,8($7) ) # .. L .. .. + subq $4, 32, $3 # E .. .. .. : U U L L : is there enough for another trip? + + EXO( stq $1,0($6) ) # .. .. .. L + EXO( stq $2,8($6) ) # .. .. L .. + subq $0,16,$0 # .. E .. .. + addq $7,16,$7 # E .. .. .. : U L L U + + nop # .. .. .. E + nop # .. .. E .. + addq $6,16,$6 # .. E .. .. + bgt $3,$unroll4 # U .. .. .. : U L U L + + nop + nop + nop + beq $4, $noquads + +$onequad: + EXI( ldq $1,0($7) ) + subq $4,8,$4 + addq $7,8,$7 + nop + + EXO( stq $1,0($6) ) + subq $0,8,$0 + addq $6,8,$6 + bne $4,$onequad + +$noquads: + nop + nop + nop + beq $0,$zerolength + +/* + * For small copies (or the tail of a larger copy), do a very simple byte loop. + * There's no point in doing a lot of complex alignment calculations to try to + * to quadword stuff for a small amount of data. + * $0 - remaining number of bytes left to copy + * $6 - current dest addr + * $7 - current source addr + */ + +$onebyteloop: + EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad + addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG) + nop # .. E .. .. : + nop # E .. .. .. : U L U L + +$dirtyentry: +/* + * the -1 is to compensate for the inc($6) done in a previous quadpack + * which allows us zero dependencies within either quadpack in the loop + */ + EXO ( stb $2,-1($6) ) # .. .. .. L : + addq $7,1,$7 # .. .. E .. : quadpack as the load + subq $0,1,$0 # .. E .. .. : change count _after_ copy + bgt $0,$onebyteloop # U .. .. .. : U L U L + +$zerolength: +$exitout: # Destination for exception recovery(?) + nop # .. .. .. E + nop # .. .. E .. + nop # .. E .. .. + ret $31,($28),1 # L0 .. .. .. : L U L U + +$exitin: + + /* A stupid byte-by-byte zeroing of the rest of the output + buffer. This cures security holes by never leaving + random kernel data around to be copied elsewhere. */ + + nop + nop + nop + mov $0,$1 + +$101: + EXO ( stb $31,0($6) ) # L + subq $1,1,$1 # E + addq $6,1,$6 # E + bgt $1,$101 # U + + nop + nop + nop + ret $31,($28),1 # L0 + + .end __copy_user + |