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/*
* arch/alpha/lib/strlen_user.S
*
* Return the length of the string including the NUL 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.
*/
#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 3
__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
.globl __strnlen_user
.align 3
__strnlen_user:
.prologue 0
EX( ldq_u t0, 0(a0) ) # load first quadword (a0 may be misaligned)
lda t1, -1(zero)
insqh t1, a0, t1
andnot a0, 7, v0
or t1, t0, t0
subq a0, 1, a0 # get our +1 for the return
cmpbge zero, t0, t1 # t1 <- bitmask: bit i == 1 <==> i-th byte == 0
subq a1, 7, t2
subq a0, v0, t0
bne t1, $found
addq t2, t0, t2
addq a1, 1, a1
.align 3
$loop: ble t2, $limit
EX( ldq t0, 8(v0) )
subq t2, 8, t2
addq v0, 8, v0 # addr += 8
cmpbge zero, t0, t1
beq t1, $loop
$found: negq t1, t2 # clear all but least set bit
and t1, t2, t1
and t1, 0xf0, t2 # binary search for that set bit
and t1, 0xcc, t3
and t1, 0xaa, t4
cmovne t2, 4, t2
cmovne t3, 2, t3
cmovne t4, 1, t4
addq t2, t3, t2
addq v0, t4, v0
addq v0, t2, v0
nop # dual issue next two on ev4 and ev5
subq v0, a0, v0
$exception:
ret
.align 3 # currently redundant
$limit:
subq a1, t2, v0
ret
.end __strlen_user
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