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Diffstat (limited to 'arch/alpha/lib/ev67-strlen_user.S')
| -rw-r--r-- | arch/alpha/lib/ev67-strlen_user.S | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev67-strlen_user.S b/arch/alpha/lib/ev67-strlen_user.S new file mode 100644 index 00000000..57e0d77b --- /dev/null +++ b/arch/alpha/lib/ev67-strlen_user.S @@ -0,0 +1,107 @@ +/* + * arch/alpha/lib/ev67-strlen_user.S + * 21264 version contributed by Rick Gorton <rick.gorton@api-networks.com> + * + * Return the length of the string including the NULL terminator + * (strlen+1) or zero if an error occurred. + * + * In places where it is critical to limit the processing time, + * and the data is not trusted, strnlen_user() should be used. + * It will return a value greater than its second argument if + * that limit would be exceeded. This implementation is allowed + * to access memory beyond the limit, but will not cross a page + * boundary when doing so. + * + * 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 + * Try not to change the actual algorithm if possible for consistency. + */ + +#include <asm/regdef.h> + + +/* Allow an exception for an insn; exit if we get one. */ +#define EX(x,y...) \ + 99: x,##y; \ + .section __ex_table,"a"; \ + .long 99b - .; \ + lda v0, $exception-99b(zero); \ + .previous + + + .set noreorder + .set noat + .text + + .globl __strlen_user + .ent __strlen_user + .frame sp, 0, ra + + .align 4 +__strlen_user: + ldah a1, 32767(zero) # do not use plain strlen_user() for strings + # that might be almost 2 GB long; you should + # be using strnlen_user() instead + nop + nop + nop + + .globl __strnlen_user + + .align 4 +__strnlen_user: + .prologue 0 + EX( ldq_u t0, 0(a0) ) # L : load first quadword (a0 may be misaligned) + lda t1, -1(zero) # E : + + insqh t1, a0, t1 # U : + andnot a0, 7, v0 # E : + or t1, t0, t0 # E : + subq a0, 1, a0 # E : get our +1 for the return + + cmpbge zero, t0, t1 # E : t1 <- bitmask: bit i == 1 <==> i-th byte == 0 + subq a1, 7, t2 # E : + subq a0, v0, t0 # E : + bne t1, $found # U : + + addq t2, t0, t2 # E : + addq a1, 1, a1 # E : + nop # E : + nop # E : + + .align 4 +$loop: ble t2, $limit # U : + EX( ldq t0, 8(v0) ) # L : + nop # E : + nop # E : + + cmpbge zero, t0, t1 # E : + subq t2, 8, t2 # E : + addq v0, 8, v0 # E : addr += 8 + beq t1, $loop # U : + +$found: cttz t1, t2 # U0 : + addq v0, t2, v0 # E : + subq v0, a0, v0 # E : + ret # L0 : + +$exception: + nop + nop + nop + ret + + .align 4 # currently redundant +$limit: + nop + nop + subq a1, t2, v0 + ret + + .end __strlen_user |