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[PARISC] Document some register usages in assembly files

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Document clobbers and args in entry.S and syscall.S.

entry.S: Add comment to indicate that cr27 may recycle and EDEADLOCK
detection is not 100% correct. Since this is only enabled when using
ENABLE_LWS_DEBUG, the user is warned by the comment.

Signed-off-by: Carlos O'Donell <carlos@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
This commit is contained in:
Carlos O'Donell 2005-11-17 16:32:46 -05:00 committed by Kyle McMartin
parent 75be99a8c5
commit aa0eecb07f
2 changed files with 3 additions and 1 deletions
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1
arch/parisc/kernel/entry.S
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@ -1846,6 +1846,7 @@ sys_clone_wrapper:
ldo -16(%r30),%r29 /* Reference param save area */
#endif
/* WARNING - Clobbers r19 and r21, userspace must save these! */
STREG %r2,PT_GR19(%r1) /* save for child */
STREG %r30,PT_GR21(%r1)
BL sys_clone,%r2

3
arch/parisc/kernel/syscall.S
View file

@ -164,7 +164,7 @@ linux_gateway_entry:
#endif
STREG %r2, TASK_PT_GR30(%r1) /* ... and save it */
STREG %r20, TASK_PT_GR20(%r1)
STREG %r20, TASK_PT_GR20(%r1) /* Syscall number */
STREG %r21, TASK_PT_GR21(%r1)
STREG %r22, TASK_PT_GR22(%r1)
STREG %r23, TASK_PT_GR23(%r1) /* 4th argument */
@ -527,6 +527,7 @@ lws_compare_and_swap:
We *must* giveup this call and fail.
*/
ldw 4(%sr2,%r20), %r28 /* Load thread register */
/* WARNING: If cr27 cycles to the same value we have problems */
mfctl %cr27, %r21 /* Get current thread register */
cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */
b lws_exit /* Return error! */