| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * arch/alpha/lib/ev67-strlen_user.S |
| 3 | * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com> |
| 4 | * |
| 5 | * Return the length of the string including the NULL terminator |
| 6 | * (strlen+1) or zero if an error occurred. |
| 7 | * |
| 8 | * In places where it is critical to limit the processing time, |
| 9 | * and the data is not trusted, strnlen_user() should be used. |
| 10 | * It will return a value greater than its second argument if |
| 11 | * that limit would be exceeded. This implementation is allowed |
| 12 | * to access memory beyond the limit, but will not cross a page |
| 13 | * boundary when doing so. |
| 14 | * |
| 15 | * Much of the information about 21264 scheduling/coding comes from: |
| 16 | * Compiler Writer's Guide for the Alpha 21264 |
| 17 | * abbreviated as 'CWG' in other comments here |
| 18 | * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html |
| 19 | * Scheduling notation: |
| 20 | * E - either cluster |
| 21 | * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1 |
| 22 | * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1 |
| 23 | * Try not to change the actual algorithm if possible for consistency. |
| 24 | */ |
| 25 | |
| 26 | #include <asm/regdef.h> |
| 27 | |
| 28 | |
| 29 | /* Allow an exception for an insn; exit if we get one. */ |
| 30 | #define EX(x,y...) \ |
| 31 | 99: x,##y; \ |
| 32 | .section __ex_table,"a"; \ |
| 33 | .long 99b - .; \ |
| 34 | lda v0, $exception-99b(zero); \ |
| 35 | .previous |
| 36 | |
| 37 | |
| 38 | .set noreorder |
| 39 | .set noat |
| 40 | .text |
| 41 | |
| 42 | .globl __strlen_user |
| 43 | .ent __strlen_user |
| 44 | .frame sp, 0, ra |
| 45 | |
| 46 | .align 4 |
| 47 | __strlen_user: |
| 48 | ldah a1, 32767(zero) # do not use plain strlen_user() for strings |
| 49 | # that might be almost 2 GB long; you should |
| 50 | # be using strnlen_user() instead |
| 51 | nop |
| 52 | nop |
| 53 | nop |
| 54 | |
| 55 | .globl __strnlen_user |
| 56 | |
| 57 | .align 4 |
| 58 | __strnlen_user: |
| 59 | .prologue 0 |
| 60 | EX( ldq_u t0, 0(a0) ) # L : load first quadword (a0 may be misaligned) |
| 61 | lda t1, -1(zero) # E : |
| 62 | |
| 63 | insqh t1, a0, t1 # U : |
| 64 | andnot a0, 7, v0 # E : |
| 65 | or t1, t0, t0 # E : |
| 66 | subq a0, 1, a0 # E : get our +1 for the return |
| 67 | |
| 68 | cmpbge zero, t0, t1 # E : t1 <- bitmask: bit i == 1 <==> i-th byte == 0 |
| 69 | subq a1, 7, t2 # E : |
| 70 | subq a0, v0, t0 # E : |
| 71 | bne t1, $found # U : |
| 72 | |
| 73 | addq t2, t0, t2 # E : |
| 74 | addq a1, 1, a1 # E : |
| 75 | nop # E : |
| 76 | nop # E : |
| 77 | |
| 78 | .align 4 |
| 79 | $loop: ble t2, $limit # U : |
| 80 | EX( ldq t0, 8(v0) ) # L : |
| 81 | nop # E : |
| 82 | nop # E : |
| 83 | |
| 84 | cmpbge zero, t0, t1 # E : |
| 85 | subq t2, 8, t2 # E : |
| 86 | addq v0, 8, v0 # E : addr += 8 |
| 87 | beq t1, $loop # U : |
| 88 | |
| 89 | $found: cttz t1, t2 # U0 : |
| 90 | addq v0, t2, v0 # E : |
| 91 | subq v0, a0, v0 # E : |
| 92 | ret # L0 : |
| 93 | |
| 94 | $exception: |
| 95 | nop |
| 96 | nop |
| 97 | nop |
| 98 | ret |
| 99 | |
| 100 | .align 4 # currently redundant |
| 101 | $limit: |
| 102 | nop |
| 103 | nop |
| 104 | subq a1, t2, v0 |
| 105 | ret |
| 106 | |
| 107 | .end __strlen_user |