From aa0eecb07f27bea25a7cbe4150822be72493e574 Mon Sep 17 00:00:00 2001 From: Carlos O'Donell Date: Thu, 17 Nov 2005 16:32:46 -0500 Subject: [PATCH] [PARISC] Document some register usages in assembly files 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 Signed-off-by: Kyle McMartin --- arch/parisc/kernel/entry.S | 1 + arch/parisc/kernel/syscall.S | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S index c7e66ee5b083..9af4b22a6d77 100644 --- a/arch/parisc/kernel/entry.S +++ b/arch/parisc/kernel/entry.S @@ -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 diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index b29b76b42bb7..d66163492890 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -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! */