11da177e4SLinus Torvalds/* 21da177e4SLinus Torvalds * arch/alpha/lib/ev6-copy_user.S 31da177e4SLinus Torvalds * 41da177e4SLinus Torvalds * 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com> 51da177e4SLinus Torvalds * 61da177e4SLinus Torvalds * Copy to/from user space, handling exceptions as we go.. This 71da177e4SLinus Torvalds * isn't exactly pretty. 81da177e4SLinus Torvalds * 91da177e4SLinus Torvalds * This is essentially the same as "memcpy()", but with a few twists. 101da177e4SLinus Torvalds * Notably, we have to make sure that $0 is always up-to-date and 111da177e4SLinus Torvalds * contains the right "bytes left to copy" value (and that it is updated 121da177e4SLinus Torvalds * only _after_ a successful copy). There is also some rather minor 131da177e4SLinus Torvalds * exception setup stuff.. 141da177e4SLinus Torvalds * 151da177e4SLinus Torvalds * NOTE! This is not directly C-callable, because the calling semantics are 161da177e4SLinus Torvalds * different: 171da177e4SLinus Torvalds * 181da177e4SLinus Torvalds * Inputs: 191da177e4SLinus Torvalds * length in $0 201da177e4SLinus Torvalds * destination address in $6 211da177e4SLinus Torvalds * source address in $7 221da177e4SLinus Torvalds * return address in $28 231da177e4SLinus Torvalds * 241da177e4SLinus Torvalds * Outputs: 251da177e4SLinus Torvalds * bytes left to copy in $0 261da177e4SLinus Torvalds * 271da177e4SLinus Torvalds * Clobbers: 281da177e4SLinus Torvalds * $1,$2,$3,$4,$5,$6,$7 291da177e4SLinus Torvalds * 301da177e4SLinus Torvalds * Much of the information about 21264 scheduling/coding comes from: 311da177e4SLinus Torvalds * Compiler Writer's Guide for the Alpha 21264 321da177e4SLinus Torvalds * abbreviated as 'CWG' in other comments here 331da177e4SLinus Torvalds * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html 341da177e4SLinus Torvalds * Scheduling notation: 351da177e4SLinus Torvalds * E - either cluster 361da177e4SLinus Torvalds * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 371da177e4SLinus Torvalds * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 381da177e4SLinus Torvalds */ 391da177e4SLinus Torvalds 4000fc0e0dSAl Viro#include <asm/export.h> 411da177e4SLinus Torvalds/* Allow an exception for an insn; exit if we get one. */ 421da177e4SLinus Torvalds#define EXI(x,y...) \ 431da177e4SLinus Torvalds 99: x,##y; \ 441da177e4SLinus Torvalds .section __ex_table,"a"; \ 451da177e4SLinus Torvalds .long 99b - .; \ 461da177e4SLinus Torvalds lda $31, $exitin-99b($31); \ 471da177e4SLinus Torvalds .previous 481da177e4SLinus Torvalds 491da177e4SLinus Torvalds#define EXO(x,y...) \ 501da177e4SLinus Torvalds 99: x,##y; \ 511da177e4SLinus Torvalds .section __ex_table,"a"; \ 521da177e4SLinus Torvalds .long 99b - .; \ 531da177e4SLinus Torvalds lda $31, $exitout-99b($31); \ 541da177e4SLinus Torvalds .previous 551da177e4SLinus Torvalds 561da177e4SLinus Torvalds .set noat 571da177e4SLinus Torvalds .align 4 581da177e4SLinus Torvalds .globl __copy_user 591da177e4SLinus Torvalds .ent __copy_user 601da177e4SLinus Torvalds # Pipeline info: Slotting & Comments 611da177e4SLinus Torvalds__copy_user: 621da177e4SLinus Torvalds .prologue 0 631da177e4SLinus Torvalds subq $0, 32, $1 # .. E .. .. : Is this going to be a small copy? 641da177e4SLinus Torvalds beq $0, $zerolength # U .. .. .. : U L U L 651da177e4SLinus Torvalds 661da177e4SLinus Torvalds and $6,7,$3 # .. .. .. E : is leading dest misalignment 671da177e4SLinus Torvalds ble $1, $onebyteloop # .. .. U .. : 1st branch : small amount of data 681da177e4SLinus Torvalds beq $3, $destaligned # .. U .. .. : 2nd (one cycle fetcher stall) 691da177e4SLinus Torvalds subq $3, 8, $3 # E .. .. .. : L U U L : trip counter 701da177e4SLinus Torvalds/* 711da177e4SLinus Torvalds * The fetcher stall also hides the 1 cycle cross-cluster stall for $3 (L --> U) 721da177e4SLinus Torvalds * This loop aligns the destination a byte at a time 731da177e4SLinus Torvalds * We know we have at least one trip through this loop 741da177e4SLinus Torvalds */ 751da177e4SLinus Torvalds$aligndest: 761da177e4SLinus Torvalds EXI( ldbu $1,0($7) ) # .. .. .. L : Keep loads separate from stores 771da177e4SLinus Torvalds addq $6,1,$6 # .. .. E .. : Section 3.8 in the CWG 781da177e4SLinus Torvalds addq $3,1,$3 # .. E .. .. : 791da177e4SLinus Torvalds nop # E .. .. .. : U L U L 801da177e4SLinus Torvalds 811da177e4SLinus Torvalds/* 821da177e4SLinus Torvalds * the -1 is to compensate for the inc($6) done in a previous quadpack 831da177e4SLinus Torvalds * which allows us zero dependencies within either quadpack in the loop 841da177e4SLinus Torvalds */ 851da177e4SLinus Torvalds EXO( stb $1,-1($6) ) # .. .. .. L : 861da177e4SLinus Torvalds addq $7,1,$7 # .. .. E .. : Section 3.8 in the CWG 871da177e4SLinus Torvalds subq $0,1,$0 # .. E .. .. : 881da177e4SLinus Torvalds bne $3, $aligndest # U .. .. .. : U L U L 891da177e4SLinus Torvalds 901da177e4SLinus Torvalds/* 911da177e4SLinus Torvalds * If we fell through into here, we have a minimum of 33 - 7 bytes 921da177e4SLinus Torvalds * If we arrived via branch, we have a minimum of 32 bytes 931da177e4SLinus Torvalds */ 941da177e4SLinus Torvalds$destaligned: 951da177e4SLinus Torvalds and $7,7,$1 # .. .. .. E : Check _current_ source alignment 961da177e4SLinus Torvalds bic $0,7,$4 # .. .. E .. : number bytes as a quadword loop 971da177e4SLinus Torvalds EXI( ldq_u $3,0($7) ) # .. L .. .. : Forward fetch for fallthrough code 981da177e4SLinus Torvalds beq $1,$quadaligned # U .. .. .. : U L U L 991da177e4SLinus Torvalds 1001da177e4SLinus Torvalds/* 1011da177e4SLinus Torvalds * In the worst case, we've just executed an ldq_u here from 0($7) 1021da177e4SLinus Torvalds * and we'll repeat it once if we take the branch 1031da177e4SLinus Torvalds */ 1041da177e4SLinus Torvalds 1051da177e4SLinus Torvalds/* Misaligned quadword loop - not unrolled. Leave it that way. */ 1061da177e4SLinus Torvalds$misquad: 1071da177e4SLinus Torvalds EXI( ldq_u $2,8($7) ) # .. .. .. L : 1081da177e4SLinus Torvalds subq $4,8,$4 # .. .. E .. : 1091da177e4SLinus Torvalds extql $3,$7,$3 # .. U .. .. : 1101da177e4SLinus Torvalds extqh $2,$7,$1 # U .. .. .. : U U L L 1111da177e4SLinus Torvalds 1121da177e4SLinus Torvalds bis $3,$1,$1 # .. .. .. E : 1131da177e4SLinus Torvalds EXO( stq $1,0($6) ) # .. .. L .. : 1141da177e4SLinus Torvalds addq $7,8,$7 # .. E .. .. : 1151da177e4SLinus Torvalds subq $0,8,$0 # E .. .. .. : U L L U 1161da177e4SLinus Torvalds 1171da177e4SLinus Torvalds addq $6,8,$6 # .. .. .. E : 1181da177e4SLinus Torvalds bis $2,$2,$3 # .. .. E .. : 1191da177e4SLinus Torvalds nop # .. E .. .. : 1201da177e4SLinus Torvalds bne $4,$misquad # U .. .. .. : U L U L 1211da177e4SLinus Torvalds 1221da177e4SLinus Torvalds nop # .. .. .. E 1231da177e4SLinus Torvalds nop # .. .. E .. 1241da177e4SLinus Torvalds nop # .. E .. .. 1251da177e4SLinus Torvalds beq $0,$zerolength # U .. .. .. : U L U L 1261da177e4SLinus Torvalds 1271da177e4SLinus Torvalds/* We know we have at least one trip through the byte loop */ 1281da177e4SLinus Torvalds EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad 1291da177e4SLinus Torvalds addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG) 1301da177e4SLinus Torvalds nop # .. E .. .. : 1311da177e4SLinus Torvalds br $31, $dirtyentry # L0 .. .. .. : L U U L 1321da177e4SLinus Torvalds/* Do the trailing byte loop load, then hop into the store part of the loop */ 1331da177e4SLinus Torvalds 1341da177e4SLinus Torvalds/* 1351da177e4SLinus Torvalds * A minimum of (33 - 7) bytes to do a quad at a time. 1361da177e4SLinus Torvalds * Based upon the usage context, it's worth the effort to unroll this loop 1371da177e4SLinus Torvalds * $0 - number of bytes to be moved 1381da177e4SLinus Torvalds * $4 - number of bytes to move as quadwords 1391da177e4SLinus Torvalds * $6 is current destination address 1401da177e4SLinus Torvalds * $7 is current source address 1411da177e4SLinus Torvalds */ 1421da177e4SLinus Torvalds$quadaligned: 1431da177e4SLinus Torvalds subq $4, 32, $2 # .. .. .. E : do not unroll for small stuff 1441da177e4SLinus Torvalds nop # .. .. E .. 1451da177e4SLinus Torvalds nop # .. E .. .. 1461da177e4SLinus Torvalds blt $2, $onequad # U .. .. .. : U L U L 1471da177e4SLinus Torvalds 1481da177e4SLinus Torvalds/* 1491da177e4SLinus Torvalds * There is a significant assumption here that the source and destination 1501da177e4SLinus Torvalds * addresses differ by more than 32 bytes. In this particular case, a 1511da177e4SLinus Torvalds * sparsity of registers further bounds this to be a minimum of 8 bytes. 1521da177e4SLinus Torvalds * But if this isn't met, then the output result will be incorrect. 1531da177e4SLinus Torvalds * Furthermore, due to a lack of available registers, we really can't 1541da177e4SLinus Torvalds * unroll this to be an 8x loop (which would enable us to use the wh64 1551da177e4SLinus Torvalds * instruction memory hint instruction). 1561da177e4SLinus Torvalds */ 1571da177e4SLinus Torvalds$unroll4: 1581da177e4SLinus Torvalds EXI( ldq $1,0($7) ) # .. .. .. L 1591da177e4SLinus Torvalds EXI( ldq $2,8($7) ) # .. .. L .. 1601da177e4SLinus Torvalds subq $4,32,$4 # .. E .. .. 1611da177e4SLinus Torvalds nop # E .. .. .. : U U L L 1621da177e4SLinus Torvalds 1631da177e4SLinus Torvalds addq $7,16,$7 # .. .. .. E 1641da177e4SLinus Torvalds EXO( stq $1,0($6) ) # .. .. L .. 1651da177e4SLinus Torvalds EXO( stq $2,8($6) ) # .. L .. .. 1661da177e4SLinus Torvalds subq $0,16,$0 # E .. .. .. : U L L U 1671da177e4SLinus Torvalds 1681da177e4SLinus Torvalds addq $6,16,$6 # .. .. .. E 1691da177e4SLinus Torvalds EXI( ldq $1,0($7) ) # .. .. L .. 1701da177e4SLinus Torvalds EXI( ldq $2,8($7) ) # .. L .. .. 1711da177e4SLinus Torvalds subq $4, 32, $3 # E .. .. .. : U U L L : is there enough for another trip? 1721da177e4SLinus Torvalds 1731da177e4SLinus Torvalds EXO( stq $1,0($6) ) # .. .. .. L 1741da177e4SLinus Torvalds EXO( stq $2,8($6) ) # .. .. L .. 1751da177e4SLinus Torvalds subq $0,16,$0 # .. E .. .. 1761da177e4SLinus Torvalds addq $7,16,$7 # E .. .. .. : U L L U 1771da177e4SLinus Torvalds 1781da177e4SLinus Torvalds nop # .. .. .. E 1791da177e4SLinus Torvalds nop # .. .. E .. 1801da177e4SLinus Torvalds addq $6,16,$6 # .. E .. .. 1811da177e4SLinus Torvalds bgt $3,$unroll4 # U .. .. .. : U L U L 1821da177e4SLinus Torvalds 1831da177e4SLinus Torvalds nop 1841da177e4SLinus Torvalds nop 1851da177e4SLinus Torvalds nop 1861da177e4SLinus Torvalds beq $4, $noquads 1871da177e4SLinus Torvalds 1881da177e4SLinus Torvalds$onequad: 1891da177e4SLinus Torvalds EXI( ldq $1,0($7) ) 1901da177e4SLinus Torvalds subq $4,8,$4 1911da177e4SLinus Torvalds addq $7,8,$7 1921da177e4SLinus Torvalds nop 1931da177e4SLinus Torvalds 1941da177e4SLinus Torvalds EXO( stq $1,0($6) ) 1951da177e4SLinus Torvalds subq $0,8,$0 1961da177e4SLinus Torvalds addq $6,8,$6 1971da177e4SLinus Torvalds bne $4,$onequad 1981da177e4SLinus Torvalds 1991da177e4SLinus Torvalds$noquads: 2001da177e4SLinus Torvalds nop 2011da177e4SLinus Torvalds nop 2021da177e4SLinus Torvalds nop 2031da177e4SLinus Torvalds beq $0,$zerolength 2041da177e4SLinus Torvalds 2051da177e4SLinus Torvalds/* 2061da177e4SLinus Torvalds * For small copies (or the tail of a larger copy), do a very simple byte loop. 2071da177e4SLinus Torvalds * There's no point in doing a lot of complex alignment calculations to try to 2081da177e4SLinus Torvalds * to quadword stuff for a small amount of data. 2091da177e4SLinus Torvalds * $0 - remaining number of bytes left to copy 2101da177e4SLinus Torvalds * $6 - current dest addr 2111da177e4SLinus Torvalds * $7 - current source addr 2121da177e4SLinus Torvalds */ 2131da177e4SLinus Torvalds 2141da177e4SLinus Torvalds$onebyteloop: 2151da177e4SLinus Torvalds EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad 2161da177e4SLinus Torvalds addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG) 2171da177e4SLinus Torvalds nop # .. E .. .. : 2181da177e4SLinus Torvalds nop # E .. .. .. : U L U L 2191da177e4SLinus Torvalds 2201da177e4SLinus Torvalds$dirtyentry: 2211da177e4SLinus Torvalds/* 2221da177e4SLinus Torvalds * the -1 is to compensate for the inc($6) done in a previous quadpack 2231da177e4SLinus Torvalds * which allows us zero dependencies within either quadpack in the loop 2241da177e4SLinus Torvalds */ 2251da177e4SLinus Torvalds EXO ( stb $2,-1($6) ) # .. .. .. L : 2261da177e4SLinus Torvalds addq $7,1,$7 # .. .. E .. : quadpack as the load 2271da177e4SLinus Torvalds subq $0,1,$0 # .. E .. .. : change count _after_ copy 2281da177e4SLinus Torvalds bgt $0,$onebyteloop # U .. .. .. : U L U L 2291da177e4SLinus Torvalds 2301da177e4SLinus Torvalds$zerolength: 2311da177e4SLinus Torvalds$exitout: # Destination for exception recovery(?) 2321da177e4SLinus Torvalds nop # .. .. .. E 2331da177e4SLinus Torvalds nop # .. .. E .. 2341da177e4SLinus Torvalds nop # .. E .. .. 2351da177e4SLinus Torvalds ret $31,($28),1 # L0 .. .. .. : L U L U 2361da177e4SLinus Torvalds 2371da177e4SLinus Torvalds$exitin: 2381da177e4SLinus Torvalds 2391da177e4SLinus Torvalds /* A stupid byte-by-byte zeroing of the rest of the output 2401da177e4SLinus Torvalds buffer. This cures security holes by never leaving 2411da177e4SLinus Torvalds random kernel data around to be copied elsewhere. */ 2421da177e4SLinus Torvalds 2431da177e4SLinus Torvalds nop 2441da177e4SLinus Torvalds nop 2451da177e4SLinus Torvalds nop 2461da177e4SLinus Torvalds mov $0,$1 2471da177e4SLinus Torvalds 2481da177e4SLinus Torvalds$101: 2491da177e4SLinus Torvalds EXO ( stb $31,0($6) ) # L 2501da177e4SLinus Torvalds subq $1,1,$1 # E 2511da177e4SLinus Torvalds addq $6,1,$6 # E 2521da177e4SLinus Torvalds bgt $1,$101 # U 2531da177e4SLinus Torvalds 2541da177e4SLinus Torvalds nop 2551da177e4SLinus Torvalds nop 2561da177e4SLinus Torvalds nop 2571da177e4SLinus Torvalds ret $31,($28),1 # L0 2581da177e4SLinus Torvalds 2591da177e4SLinus Torvalds .end __copy_user 26000fc0e0dSAl Viro EXPORT_SYMBOL(__copy_user) 261