1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
259 lines
7.3 KiB
ArmAsm
259 lines
7.3 KiB
ArmAsm
/*
|
|
* arch/alpha/lib/ev6-copy_user.S
|
|
*
|
|
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
|
|
*
|
|
* Copy to/from user space, handling exceptions as we go.. This
|
|
* isn't exactly pretty.
|
|
*
|
|
* This is essentially the same as "memcpy()", but with a few twists.
|
|
* Notably, we have to make sure that $0 is always up-to-date and
|
|
* contains the right "bytes left to copy" value (and that it is updated
|
|
* only _after_ a successful copy). There is also some rather minor
|
|
* exception setup stuff..
|
|
*
|
|
* NOTE! This is not directly C-callable, because the calling semantics are
|
|
* different:
|
|
*
|
|
* Inputs:
|
|
* length in $0
|
|
* destination address in $6
|
|
* source address in $7
|
|
* return address in $28
|
|
*
|
|
* Outputs:
|
|
* bytes left to copy in $0
|
|
*
|
|
* Clobbers:
|
|
* $1,$2,$3,$4,$5,$6,$7
|
|
*
|
|
* 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
|
|
*/
|
|
|
|
/* Allow an exception for an insn; exit if we get one. */
|
|
#define EXI(x,y...) \
|
|
99: x,##y; \
|
|
.section __ex_table,"a"; \
|
|
.long 99b - .; \
|
|
lda $31, $exitin-99b($31); \
|
|
.previous
|
|
|
|
#define EXO(x,y...) \
|
|
99: x,##y; \
|
|
.section __ex_table,"a"; \
|
|
.long 99b - .; \
|
|
lda $31, $exitout-99b($31); \
|
|
.previous
|
|
|
|
.set noat
|
|
.align 4
|
|
.globl __copy_user
|
|
.ent __copy_user
|
|
# Pipeline info: Slotting & Comments
|
|
__copy_user:
|
|
.prologue 0
|
|
subq $0, 32, $1 # .. E .. .. : Is this going to be a small copy?
|
|
beq $0, $zerolength # U .. .. .. : U L U L
|
|
|
|
and $6,7,$3 # .. .. .. E : is leading dest misalignment
|
|
ble $1, $onebyteloop # .. .. U .. : 1st branch : small amount of data
|
|
beq $3, $destaligned # .. U .. .. : 2nd (one cycle fetcher stall)
|
|
subq $3, 8, $3 # E .. .. .. : L U U L : trip counter
|
|
/*
|
|
* The fetcher stall also hides the 1 cycle cross-cluster stall for $3 (L --> U)
|
|
* This loop aligns the destination a byte at a time
|
|
* We know we have at least one trip through this loop
|
|
*/
|
|
$aligndest:
|
|
EXI( ldbu $1,0($7) ) # .. .. .. L : Keep loads separate from stores
|
|
addq $6,1,$6 # .. .. E .. : Section 3.8 in the CWG
|
|
addq $3,1,$3 # .. E .. .. :
|
|
nop # E .. .. .. : U L U L
|
|
|
|
/*
|
|
* the -1 is to compensate for the inc($6) done in a previous quadpack
|
|
* which allows us zero dependencies within either quadpack in the loop
|
|
*/
|
|
EXO( stb $1,-1($6) ) # .. .. .. L :
|
|
addq $7,1,$7 # .. .. E .. : Section 3.8 in the CWG
|
|
subq $0,1,$0 # .. E .. .. :
|
|
bne $3, $aligndest # U .. .. .. : U L U L
|
|
|
|
/*
|
|
* If we fell through into here, we have a minimum of 33 - 7 bytes
|
|
* If we arrived via branch, we have a minimum of 32 bytes
|
|
*/
|
|
$destaligned:
|
|
and $7,7,$1 # .. .. .. E : Check _current_ source alignment
|
|
bic $0,7,$4 # .. .. E .. : number bytes as a quadword loop
|
|
EXI( ldq_u $3,0($7) ) # .. L .. .. : Forward fetch for fallthrough code
|
|
beq $1,$quadaligned # U .. .. .. : U L U L
|
|
|
|
/*
|
|
* In the worst case, we've just executed an ldq_u here from 0($7)
|
|
* and we'll repeat it once if we take the branch
|
|
*/
|
|
|
|
/* Misaligned quadword loop - not unrolled. Leave it that way. */
|
|
$misquad:
|
|
EXI( ldq_u $2,8($7) ) # .. .. .. L :
|
|
subq $4,8,$4 # .. .. E .. :
|
|
extql $3,$7,$3 # .. U .. .. :
|
|
extqh $2,$7,$1 # U .. .. .. : U U L L
|
|
|
|
bis $3,$1,$1 # .. .. .. E :
|
|
EXO( stq $1,0($6) ) # .. .. L .. :
|
|
addq $7,8,$7 # .. E .. .. :
|
|
subq $0,8,$0 # E .. .. .. : U L L U
|
|
|
|
addq $6,8,$6 # .. .. .. E :
|
|
bis $2,$2,$3 # .. .. E .. :
|
|
nop # .. E .. .. :
|
|
bne $4,$misquad # U .. .. .. : U L U L
|
|
|
|
nop # .. .. .. E
|
|
nop # .. .. E ..
|
|
nop # .. E .. ..
|
|
beq $0,$zerolength # U .. .. .. : U L U L
|
|
|
|
/* We know we have at least one trip through the byte loop */
|
|
EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad
|
|
addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG)
|
|
nop # .. E .. .. :
|
|
br $31, $dirtyentry # L0 .. .. .. : L U U L
|
|
/* Do the trailing byte loop load, then hop into the store part of the loop */
|
|
|
|
/*
|
|
* A minimum of (33 - 7) bytes to do a quad at a time.
|
|
* Based upon the usage context, it's worth the effort to unroll this loop
|
|
* $0 - number of bytes to be moved
|
|
* $4 - number of bytes to move as quadwords
|
|
* $6 is current destination address
|
|
* $7 is current source address
|
|
*/
|
|
$quadaligned:
|
|
subq $4, 32, $2 # .. .. .. E : do not unroll for small stuff
|
|
nop # .. .. E ..
|
|
nop # .. E .. ..
|
|
blt $2, $onequad # U .. .. .. : U L U L
|
|
|
|
/*
|
|
* There is a significant assumption here that the source and destination
|
|
* addresses differ by more than 32 bytes. In this particular case, a
|
|
* sparsity of registers further bounds this to be a minimum of 8 bytes.
|
|
* But if this isn't met, then the output result will be incorrect.
|
|
* Furthermore, due to a lack of available registers, we really can't
|
|
* unroll this to be an 8x loop (which would enable us to use the wh64
|
|
* instruction memory hint instruction).
|
|
*/
|
|
$unroll4:
|
|
EXI( ldq $1,0($7) ) # .. .. .. L
|
|
EXI( ldq $2,8($7) ) # .. .. L ..
|
|
subq $4,32,$4 # .. E .. ..
|
|
nop # E .. .. .. : U U L L
|
|
|
|
addq $7,16,$7 # .. .. .. E
|
|
EXO( stq $1,0($6) ) # .. .. L ..
|
|
EXO( stq $2,8($6) ) # .. L .. ..
|
|
subq $0,16,$0 # E .. .. .. : U L L U
|
|
|
|
addq $6,16,$6 # .. .. .. E
|
|
EXI( ldq $1,0($7) ) # .. .. L ..
|
|
EXI( ldq $2,8($7) ) # .. L .. ..
|
|
subq $4, 32, $3 # E .. .. .. : U U L L : is there enough for another trip?
|
|
|
|
EXO( stq $1,0($6) ) # .. .. .. L
|
|
EXO( stq $2,8($6) ) # .. .. L ..
|
|
subq $0,16,$0 # .. E .. ..
|
|
addq $7,16,$7 # E .. .. .. : U L L U
|
|
|
|
nop # .. .. .. E
|
|
nop # .. .. E ..
|
|
addq $6,16,$6 # .. E .. ..
|
|
bgt $3,$unroll4 # U .. .. .. : U L U L
|
|
|
|
nop
|
|
nop
|
|
nop
|
|
beq $4, $noquads
|
|
|
|
$onequad:
|
|
EXI( ldq $1,0($7) )
|
|
subq $4,8,$4
|
|
addq $7,8,$7
|
|
nop
|
|
|
|
EXO( stq $1,0($6) )
|
|
subq $0,8,$0
|
|
addq $6,8,$6
|
|
bne $4,$onequad
|
|
|
|
$noquads:
|
|
nop
|
|
nop
|
|
nop
|
|
beq $0,$zerolength
|
|
|
|
/*
|
|
* For small copies (or the tail of a larger copy), do a very simple byte loop.
|
|
* There's no point in doing a lot of complex alignment calculations to try to
|
|
* to quadword stuff for a small amount of data.
|
|
* $0 - remaining number of bytes left to copy
|
|
* $6 - current dest addr
|
|
* $7 - current source addr
|
|
*/
|
|
|
|
$onebyteloop:
|
|
EXI ( ldbu $2,0($7) ) # .. .. .. L : No loads in the same quad
|
|
addq $6,1,$6 # .. .. E .. : as the store (Section 3.8 in CWG)
|
|
nop # .. E .. .. :
|
|
nop # E .. .. .. : U L U L
|
|
|
|
$dirtyentry:
|
|
/*
|
|
* the -1 is to compensate for the inc($6) done in a previous quadpack
|
|
* which allows us zero dependencies within either quadpack in the loop
|
|
*/
|
|
EXO ( stb $2,-1($6) ) # .. .. .. L :
|
|
addq $7,1,$7 # .. .. E .. : quadpack as the load
|
|
subq $0,1,$0 # .. E .. .. : change count _after_ copy
|
|
bgt $0,$onebyteloop # U .. .. .. : U L U L
|
|
|
|
$zerolength:
|
|
$exitout: # Destination for exception recovery(?)
|
|
nop # .. .. .. E
|
|
nop # .. .. E ..
|
|
nop # .. E .. ..
|
|
ret $31,($28),1 # L0 .. .. .. : L U L U
|
|
|
|
$exitin:
|
|
|
|
/* A stupid byte-by-byte zeroing of the rest of the output
|
|
buffer. This cures security holes by never leaving
|
|
random kernel data around to be copied elsewhere. */
|
|
|
|
nop
|
|
nop
|
|
nop
|
|
mov $0,$1
|
|
|
|
$101:
|
|
EXO ( stb $31,0($6) ) # L
|
|
subq $1,1,$1 # E
|
|
addq $6,1,$6 # E
|
|
bgt $1,$101 # U
|
|
|
|
nop
|
|
nop
|
|
nop
|
|
ret $31,($28),1 # L0
|
|
|
|
.end __copy_user
|
|
|