linux/arch/alpha/lib/strncpy.S
Ivan Kokshaysky fe4304baf2 alpha: strncpy/strncat fixes
First of all, thanks to Bob Tracy <rct@frus.com> and
Michael Cree <mcree@orcon.net.nz> for testing.
Especially to Bob, as he has done titanic multi-day git-bisect
work that finally helped to reproduce and nail down the bug
(http://bugzilla.kernel.org/show_bug.cgi?id=9457).

[ev6-]stxncpy.S: it's t12, not t2 register that is supposed to contain
the last byte offset upon return. As a result of wrong register use
(which was my fault back in 2003, IIRC), under some circumstances extra
terminating zero bytes were added to destination string. This particularly
led to incorrect DEVPATH strings generated in uevent and therefore to udev
problems.

strncpy.S: unrelated bug I found while testing the above fix - destination
is not properly zero-padded then a byte count exceeds source length.
Actually this is addition to strncpy fix from last year.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Bob Tracy <rct@frus.com>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-12-17 19:28:15 -08:00

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ArmAsm

/*
* arch/alpha/lib/strncpy.S
* Contributed by Richard Henderson (rth@tamu.edu)
*
* Copy no more than COUNT bytes of the null-terminated string from
* SRC to DST. If SRC does not cover all of COUNT, the balance is
* zeroed.
*
* Or, rather, if the kernel cared about that weird ANSI quirk. This
* version has cropped that bit o' nastiness as well as assuming that
* __stxncpy is in range of a branch.
*/
.set noat
.set noreorder
.text
.align 4
.globl strncpy
.ent strncpy
strncpy:
.frame $30, 0, $26
.prologue 0
mov $16, $0 # set return value now
beq $18, $zerolen
unop
bsr $23, __stxncpy # do the work of the copy
unop
bne $18, $multiword # do we have full words left?
subq $24, 1, $3 # nope
subq $27, 1, $4
or $3, $24, $3 # clear the bits between the last
or $4, $27, $4 # written byte and the last byte in COUNT
andnot $3, $4, $4
zap $1, $4, $1
stq_u $1, 0($16)
ret
.align 4
$multiword:
subq $27, 1, $2 # clear the final bits in the prev word
or $2, $27, $2
zapnot $1, $2, $1
subq $18, 1, $18
stq_u $1, 0($16)
addq $16, 8, $16
unop
beq $18, 1f
nop
unop
nop
blbc $18, 0f
stq_u $31, 0($16) # zero one word
subq $18, 1, $18
addq $16, 8, $16
beq $18, 1f
0: stq_u $31, 0($16) # zero two words
subq $18, 2, $18
stq_u $31, 8($16)
addq $16, 16, $16
bne $18, 0b
1: ldq_u $1, 0($16) # clear the leading bits in the final word
subq $24, 1, $2
or $2, $24, $2
zap $1, $2, $1
stq_u $1, 0($16)
$zerolen:
ret
.end strncpy