Messages in this thread | | | Date | Mon, 14 Jan 2008 17:32:08 -0800 | From | Jeremy Fitzhardinge <> | Subject | Re: unify pagetable accessors patch causes double fault II |
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Andi Kleen wrote: > On Mon, Jan 14, 2008 at 02:46:00PM -0800, Jeremy Fitzhardinge wrote: > >> Andi Kleen wrote: >> >>>> OK, I see the problem. The problem is that the _PAGE_X defines are >>>> defined with _AC(UL, 1 << _PAGE_BIT_X), which has unsigned long type. >>>> This means that ~_PAGE_X also has unsigned long type, and so when cast >>>> to 64-bit in pte_mkX, it ends up &ing the pte with 0x00000000ffffffxxx, >>>> with predictable results. >>>> >>>> >>> Actually I fixed some of that -- see the pgtable-nx patch on firstfloor -- >>> but >>> it still doesn't work. Or maybe my patch was not complete. >>> >>> >> Yeah, that looks like the right sort of thing, but I wonder if there's >> other places doing an open-coded "pte_val(pte) & ~_PAGE_FOO". My patch >> changes the definition of _PAGE_FOO so it should be OK everywhere. >> > > Yes that's probably better. I just hit it because NX bits went missing. > > >>>> The original code just used signed constants for the _PAGE_X >>>> definitions, which will sign-extend when cast to 64-bit, and so have the >>>> upper bits set when masking. (Well, actually, the old code just >>>> operated on pte_low, so the problem didn't arise; however, pgtable_64.h >>>> also uses integers for its _PAGE_X, which has the same sign-extended >>>> 32->64 casting property). >>>> >>>> I'll put together a fixup patch now. >>>> >>>> >>> I'm leaving now but can test later. >>> >>> >> Can you try this out? It applies after "x86: move all asm/pgtable >> constants into one place". >> > > I just applied over the whole git-x86 patchkit (tip > 2f42671697ea9abc7d10ea7f663d6ef6e8ec6358) + the two build fixes > Unfortunately it didn't work, although the faulting loop is shorter now: >
Just to be clear, these two patches cause this oops to appear? Current x86.git seems to be missing a pile of patches at the moment, so I presume you're using a version which does have my patch set?
> Freeing unused kernel memory: 260k freed > mount[1159]: segfault at b7fcfe98 ip b7ec6b7a sp bfcfcdec error 7 > Eeek! page_mapcount(page) went negative! (-1) > page pfn = bfc33 > page->flags = 80000014 > page->count = 0 > page->mapping = 00000000 > vma->vm_ops = nfs_file_vm_ops+0x0/0x18 > vma->vm_ops->nopage = 0x0 > vma->vm_ops->fault = filemap_fault+0x0/0x34e > vma->vm_file->f_op->mmap = nfs_file_mmap+0x0/0x61 > ------------[ cut here ]------------ > kernel BUG at /home/lsrc/quilt/linux/mm/rmap.c:631! > invalid opcode: 0000 [#1] SMP > Modules linked in: > > Pid: 1159, comm: mount Not tainted (2.6.24-rc7 #55) > EIP: 0060:[<c0152a32>] EFLAGS: 00010282 CPU: 3 > EIP is at page_remove_rmap+0xcc/0xe7 > EAX: 00000037 EBX: c27f8660 ECX: 00000046 EDX: 00000046 > ESI: f7061c60 EDI: f7d87380 EBP: f7060e78 ESP: f7509df8 > DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 > Process mount (pid: 1159, ti=f7508000 task=f7460540 task.ti=f7508000) > Stack: c27f8660 bfc33065 c014d166 00000000 f7061c60 f7509e80 00000000 00000000 > 00000000 00000001 b7fd0000 f7555010 f7d87380 c482e240 00000000 ffffffff > c16e0c0c 00000000 00000000 f7084df8 003d5ee2 b7fd0000 b7fd0000 00000000 > Call Trace: > [<c014d166>] unmap_vmas+0x349/0x5d1 > [<c0150006>] exit_mmap+0x5f/0xcd > [<c011df0a>] mmput+0x25/0x79 > [<c0122636>] do_exit+0x1a9/0x5eb > [<c0122ae3>] sys_exit_group+0x0/0xd > [<c0129dde>] get_signal_to_deliver+0x3e3/0x405 > [<c04334b6>] do_page_fault+0x0/0x69f > [<c0102606>] do_notify_resume+0x7d/0x64e > [<c0120383>] printk+0x14/0x18 > [<c0433874>] do_page_fault+0x3be/0x69f > [<c0433b4c>] do_page_fault+0x696/0x69f > [<c01508c1>] do_munmap+0x181/0x19b > [<c04334b6>] do_page_fault+0x0/0x69f > [<c0102f4e>] work_notifysig+0x13/0x19 > ======================= > Code: 8b 46 44 8b 50 08 b8 d2 95 50 c0 e8 9c ad fe ff 8b 46 4c 85 c0 74 14 8b 40 10 85 c0 74 0d 8b 50 2c b8 f0 95 50 c0 e8 81 ad fe ff <0f> 0b eb fe 8b 53 10 89 d8 5b 5e 83 e2 01 f7 da 83 c2 04 e9 c5 > EIP: [<c0152a32>] page_remove_rmap+0xcc/0xe7 SS:ESP 0068:f7509df8 > ---[ end trace eb3c259ee0695fdd ]--- > Fixing recursive fault but reboot is needed! > eth0: no IPv6 routers present > >
J
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