path: root/arch/parisc/kernel/entry.S
diff options
authorJames Bottomley <jejb@parisc-linux.org>2005-10-21 22:53:26 -0400
committerKyle McMartin <kyle@parisc-linux.org>2005-10-21 22:53:26 -0400
commit618febd6784054eea928d712b7e564558a7cefd5 (patch)
tree13a60c377dc5a17f44e9b3b227e5996e0ba7e5a4 /arch/parisc/kernel/entry.S
parentb2450cc1b7ce07d73545ece32db50197d649e230 (diff)
[PARISC] Fix the alloc_slabmgmt panic
Fix the alloc_slabmgmt panic Hopefully this should also fix a lot of other intermittent kernel bugs. The problem has been around since 2.6.9-rc2-pa6 when we allowed floating point registers to be used in kernel code. The essence of the problem is that gcc prefers to use floating point for integer divides and multiples. Further, it can rely on the values in the no clobber fp regs being correct across a function call. Unfortunately, our task switch function only saves the integer no clobber registers, not the fp ones, so if gcc makes a function call to any function in the kernel which could sleep, the values it is relying on in any no clobber floating point register may be lost. In the case of alloc_slabmgmt, the value of the page offset is being stored in %fr12 across a call to kmem_getpages(), which sleeps if no pages are available. Thus, the offset can be trashed and the slab code can end up with a completely bogus address leading to corruption. Kudos to Randolph who came up with the program to trip this problem at will and thus allowed it to be tracked and fixed. Signed-off-by: James Bottomley <jejb@parisc-linux.org> Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
Diffstat (limited to 'arch/parisc/kernel/entry.S')
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 0ca49710d95..166df5bab76 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -863,6 +863,7 @@ __execve:
STREG %r2, -RP_OFFSET(%r30)
+ callee_save_float
load32 _switch_to_ret, %r2
@@ -879,6 +880,7 @@ _switch_to:
mtctl %r0, %cr0 /* Needed for single stepping */
+ callee_rest_float
LDREG -RP_OFFSET(%r30), %r2
bv %r0(%r2)