Hello!
This fix breaks x64_64:
commit f33ea7f404e592e4563b12101b7a4d17da6558d7
tree 1d587ad8a06cb6d2e3a187f0312c8a524ffefe53
parent 5cb4cc0d8211c490537c8568001958fc76741312
author Nick Piggin <[email protected]> Wed, 03 Aug 2005 20:24:01
+1000
committer Linus Torvalds <[email protected]> Wed, 03 Aug 2005
09:12:05 -0700
* include/linux/mm.h, mm/memory.c:
[PATCH] fix get_user_pages bug
...
The system doesn't boot. Most processes are killed by VM.
The patch does more than it claims. It actually redefines VM_FAULT_OOM
and VM_FAULT_SIGBUS. Unfortunately, a quick look at
arch/x86_64/mm/fault.c shows that the return value of handle_mm_fault()
is compared with numerical constants. This patch helps partly:
--- arch/x86_64/mm/fault.c
+++ arch/x86_64/mm/fault.c
@@ -439,15 +439,15 @@ good_area:
* the fault.
*/
switch (handle_mm_fault(mm, vma, address, write)) {
- case 1:
+ case VM_FAULT_MINOR:
tsk->min_flt++;
break;
- case 2:
+ case VM_FAULT_MAJOR:
tsk->maj_flt++;
break;
- case 0:
+ case VM_FAULT_SIGBUS:
goto do_sigbus;
- default:
+ case VM_FAULT_OOM:
goto out_of_memory;
}
Now the system boot goes a little further and then the kernel reports a
BUG in mm/memory.c:985. Apparently __handle_mm_fault() returns
something unexpected. My guess is that some x86_64 specific functions
return -1 and 0 when they mean VM_FAULT_SIGBUS and VM_FAULT_OOM.
Returning -1 would trigger BUG(), returning 0 would be treated as
VM_FAULT_OOM rather than VM_FAULT_SIGBUS.
I'm not sure I'll be able to fix it quickly, but I hope the gurus will
beat me at that. In the meantime, please don't make any releases unless
the "commit f33ea7f404e592e4563b12101b7a4d17da6558d7" is reverted.
--
Regards,
Pavel Roskin
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