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  1. 13 6月, 2008 1 次提交
    • H
      x86: fix endless page faults in mount_block_root for Linux 2.6 · b29c701d
      由 Henry Nestler 提交于 
      Page faults in kernel address space between PAGE_OFFSET up to
VMALLOC_START should not try to map as vmalloc.

Fix rarely endless page faults inside mount_block_root for root
filesystem at boot time.

All 32bit kernels up to 2.6.25 can fail into this hole.
I can not present this under native linux kernel. I see, that the 64bit
has fixed the problem. I copied the same lines into 32bit part.

Recorded debugs are from coLinux kernel 2.6.22.18 (virtualisation):
http://www.henrynestler.com/colinux/testing/pfn-check-0.7.3/20080410-antinx/bug16-recursive-page-fault-endless.txt
The physicaly memory was trimmed down to 192MB to better catch the bug.
More memory gets the bug more rarely.

Details, how every x86 32bit system can fail:

Start from "mount_block_root",
http://lxr.linux.no/linux/init/do_mounts.c#L297
There the variable "fs_names" got one memory page with 4096 bytes.
Variable "p" walks through the existing file system types. The first
string is no problem.
But, with the second loop in mount_block_root the offset of "p" is not
at beginning of page, the offset is for example +9, if "reiserfs" is the
first in list.
Than calls do_mount_root, and lands in sys_mount.
Remember: Variable "type_page" contains now "fs_type+9" and not contains
a full page.
The sys_mount copies 4096 bytes with function "exact_copy_from_user()":
http://lxr.linux.no/linux/fs/namespace.c#L1540

Mostly exist pages after the buffer "fs_names+4096+9" and the page fault
handler was not called. No problem.

In the case, if the page after "fs_names+4096" is not mapped, the page
fault handler was called from http://lxr.linux.no/linux/fs/namespace.c#L1320

The do_page_fault gots an address 0xc03b4000.
It's kernel address, address >= TASK_SIZE, but not from vmalloc! It's
from "__getname()" alias "kmem_cache_alloc".
The "error_code" is 0. "vmalloc_fault" will be call:
http://lxr.linux.no/linux/arch/i386/mm/fault.c#L332

"vmalloc_fault" tryed to find the physical page for a non existing
virtual memory area. The macro "pte_present" in vmalloc_fault()
got a next page fault for 0xc0000ed0 at:
http://lxr.linux.no/linux/arch/i386/mm/fault.c#L282

No PTE exist for such virtual address. The page fault handler was trying
to sync the physical page for the PTE lockup.

This called vmalloc_fault() again for address 0xc000000, and that also
was not existing. The endless began...

In normal case the cpu would still loop with disabled interrrupts. Under
coLinux this was catched by a stack overflow inside printk debugs.
Signed-off-by: NHenry Nestler <henry.nestler@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      b29c701d
  3. 17 4月, 2008 2 次提交
  5. 28 3月, 2008 1 次提交
    • I
      x86: prefetch fix #2 · 3085354d
      由 Ingo Molnar 提交于 
      Linus noticed a second bug and an uncleanliness:

 - we'd return on any instruction fetch fault

 - we'd use both the value of 16 and the PF_INSTR symbol which are
   the same and make no sense

the cleanup nicely unifies this piece of logic.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3085354d
  7. 27 3月, 2008 1 次提交
  9. 15 2月, 2008 1 次提交
  11. 07 2月, 2008 2 次提交
    • I
      x86: fix deadlock, make pgd_lock irq-safe · 58d5d0d8
      由 Ingo Molnar 提交于 
      lockdep just caught this one:

=================================
[ INFO: inconsistent lock state ]
2.6.24 #38
---------------------------------
inconsistent {in-softirq-W} -> {softirq-on-W} usage.
swapper/1 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (pgd_lock){-+..}, at: [<ffffffff8022a9ea>] mm_init+0x1da/0x250
{in-softirq-W} state was registered at:
  [<ffffffffffffffff>] 0xffffffffffffffff
irq event stamp: 394559
hardirqs last  enabled at (394559): [<ffffffff80267f0a>] get_page_from_freelist+0x30a/0x4c0
hardirqs last disabled at (394558): [<ffffffff80267d25>] get_page_from_freelist+0x125/0x4c0
softirqs last  enabled at (393952): [<ffffffff80232f8e>] __do_softirq+0xce/0xe0
softirqs last disabled at (393945): [<ffffffff8020c57c>] call_softirq+0x1c/0x30

other info that might help us debug this:
no locks held by swapper/1.

stack backtrace:
Pid: 1, comm: swapper Not tainted 2.6.24 #38

Call Trace:
 [<ffffffff8024e1fb>] print_usage_bug+0x18b/0x190
 [<ffffffff8024f55d>] mark_lock+0x53d/0x560
 [<ffffffff8024fffa>] __lock_acquire+0x3ca/0xed0
 [<ffffffff80250ba8>] lock_acquire+0xa8/0xe0
 [<ffffffff8022a9ea>] ? mm_init+0x1da/0x250
 [<ffffffff809bcd10>] _spin_lock+0x30/0x70
 [<ffffffff8022a9ea>] mm_init+0x1da/0x250
 [<ffffffff8022aa99>] mm_alloc+0x39/0x50
 [<ffffffff8028b95a>] bprm_mm_init+0x2a/0x1a0
 [<ffffffff8028d12b>] do_execve+0x7b/0x220
 [<ffffffff80209776>] sys_execve+0x46/0x70
 [<ffffffff8020c214>] kernel_execve+0x64/0xd0
 [<ffffffff8020901e>] ? _stext+0x1e/0x20
 [<ffffffff802090ba>] init_post+0x9a/0xf0
 [<ffffffff809bc5f6>] ? trace_hardirqs_on_thunk+0x35/0x3a
 [<ffffffff8024f75a>] ? trace_hardirqs_on+0xba/0xd0
 [<ffffffff8020c1a8>] ? child_rip+0xa/0x12
 [<ffffffff8020bcbc>] ? restore_args+0x0/0x44
 [<ffffffff8020c19e>] ? child_rip+0x0/0x12

turns out that pgd_lock has been used on 64-bit x86 in an irq-unsafe
way for almost two years, since commit 8c914cb7.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      58d5d0d8
    • T
      x86: make spurious fault handler aware of large mappings · d8b57bb7
      由 Thomas Gleixner 提交于 
      In very rare cases, on certain CPUs, we could end up in the spurious
fault handler and ignore a large pud/pmd mapping. The resulting pte
pointer points into the mapped physical space and dereferencing it
will fault recursively.

Make the code aware of large mappings and do the permission check
on the pmd/pud entry, when a large pud/pmd mapping is detected.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d8b57bb7
  13. 04 2月, 2008 2 次提交
  15. 02 2月, 2008 1 次提交
  17. 30 1月, 2008 29 次提交