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[PARISC] Fix copy_user_page_asm to NOT access past end of page 

2.6.12-rc2-pa3 fix copy_user_page_asm to NOT access past end of page.

My bad. /o\
Lamont confirmed that instructions following a conditional
branch are *alway* executed regardless if the branch is taken or not.
Unless they are nullified (which was missing in this case).

He also noted:
Conditional branches nullify on forward taken branch, and on
non-taken backward branch. Note that .+4 is a backwards branch.

This makes alot more sense than the giberish in the PA20 arch book.

Compiles and boots on both 64-bit (a500) and 32-bit (j6k).

Signed-off-by: Grant Grundler <grundler@parisc-linux.org>

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
This commit is contained in:
Grant Grundler 2005-10-21 22:55:34 -04:00 committed by Kyle McMartin
parent c2709020ad
commit 37318a3cb1
1 changed files with 9 additions and 4 deletions
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13
arch/parisc/kernel/pacache.S
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@ -351,7 +351,11 @@ copy_user_page_asm:
std %r22, 120(%r26)
ldo 128(%r26), %r26
ADDIB> -1, %r1, 1b /* bundle 10 */
/* conditional branches nullify on forward taken branch, and on
* non-taken backward branch. Note that .+4 is a backwards branch.
* The ldd should only get executed if the branch is taken.
*/
ADDIB>,n -1, %r1, 1b /* bundle 10 */
ldd 0(%r25), %r19 /* start next loads */
#else
@ -363,10 +367,10 @@ copy_user_page_asm:
* the full 64 bit register values on interrupt, we can't
* use ldd/std on a 32 bit kernel.
*/
ldw 0(%r25), %r19
ldi 64, %r1 /* PAGE_SIZE/64 == 64 */
1:
ldw 0(%r25), %r19
ldw 4(%r25), %r20
ldw 8(%r25), %r21
ldw 12(%r25), %r22
@ -396,11 +400,12 @@ copy_user_page_asm:
ldw 60(%r25), %r22
stw %r19, 48(%r26)
stw %r20, 52(%r26)
ldo 64(%r25), %r25
stw %r21, 56(%r26)
stw %r22, 60(%r26)
ldo 64(%r26), %r26
ADDIB> -1, %r1, 1b
ldo 64(%r25), %r25
ADDIB>,n -1, %r1, 1b
ldw 0(%r25), %r19
#endif
bv %r0(%r2)
nop