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linux/include/asm-i386
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Zachary Amsden 6e5882cfa2 [PATCH] x86/PAE: Fix pte_clear for the >4GB RAM case 
Proposed fix for ptep_get_and_clear_full PAE bug.  Pte_clear had the same bug,
so use the same fix for both.  Turns out pmd_clear had it as well, but pgds
are not affected.

The problem is rather intricate.  Page table entries in PAE mode are 64-bits
wide, but the only atomic 8-byte write operation available in 32-bit mode is
cmpxchg8b, which is expensive (at least on P4), and thus avoided.  But it can
happen that the processor may prefetch entries into the TLB in the middle of an
operation which clears a page table entry.  So one must always clear the P-bit
in the low word of the page table entry first when clearing it.

Since the sequence *ptep = __pte(0) leaves the order of the write dependent on
the compiler, it must be coded explicitly as a clear of the low word followed
by a clear of the high word.  Further, there must be a write memory barrier
here to enforce proper ordering by the compiler (and, in the future, by the
processor as well).

On > 4GB memory machines, the implementation of pte_clear for PAE was clearly
deficient, as it could leave virtual mappings of physical memory above 4GB
aliased to memory below 4GB in the TLB.  The implementation of
ptep_get_and_clear_full has a similar bug, although not nearly as likely to
occur, since the mappings being cleared are in the process of being destroyed,
and should never be dereferenced again.

But, as luck would have it, it is possible to trigger bugs even without ever
dereferencing these bogus TLB mappings, even if the clear is followed fairly
soon after with a TLB flush or invalidation.  The problem is that memory above
4GB may now be aliased into the first 4GB of memory, and in fact, may hit a
region of memory with non-memory semantics.  These regions include AGP and PCI
space.  As such, these memory regions are not cached by the processor.  This
introduces the bug.

The processor can speculate memory operations, including memory writes, as long
as they are committed with the proper ordering.  Speculating a memory write to
a linear address that has a bogus TLB mapping is possible.  Normally, the
speculation is harmless.  But for cached memory, it does leave the falsely
speculated cacheline unmodified, but in a dirty state.  This cache line will be
eventually written back.  If this cacheline happens to intersect a region of
memory that is not protected by the cache coherency protocol, it can corrupt
data in I/O memory, which is generally a very bad thing to do, and can cause
total system failure or just plain undefined behavior.

These bugs are extremely unlikely, but the severity is of such magnitude, and
the fix so simple that I think fixing them immediately is justified.  Also,
they are nearly impossible to debug.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-04-27 12:00:59 -07:00
..
mach-bigsmp [PATCH] x86: convert bigsmp to use flat physical mode 2006-01-06 08:33:37 -08:00
mach-default [PATCH] RTC: Fix up some RTC whitespace and style 2006-03-28 09:16:01 -08:00
mach-es7000 [PATCH] Compilation fix for ES7000 when no ACPI is specified in config (i386) 2006-03-23 07:38:04 -08:00
mach-generic [PATCH] x86: sutomatically enable bigsmp when we have more than 8 CPUs 2005-09-05 00:06:10 -07:00
mach-numaq [PATCH] Do not enforce unique IO_APIC_ID check for xAPIC systems (i386) 2005-06-23 09:45:09 -07:00
mach-summit [PATCH] USB: Always do usb-handoff 2005-10-28 16:47:49 -07:00
mach-visws [PATCH] i386: fix uses of user_mode() vs. user_mode_vm() 2006-03-23 07:38:05 -08:00
mach-voyager [PATCH] i386: fix uses of user_mode() vs. user_mode_vm() 2006-03-23 07:38:05 -08:00
8253pit.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
a.out.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
acpi.h [PATCH] don't call check_acpi_pci() on x86 with ACPI disabled 2006-03-22 07:53:54 -08:00
agp.h [PATCH] i386: inline asm cleanup 2005-09-05 00:06:11 -07:00
alternative.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
apic.h [PATCH] i386: Consolidate modern APIC handling 2006-04-09 11:53:51 -07:00
apicdef.h [PATCH] i386 kdump timer vector lockup fix 2006-03-31 12:18:50 -08:00
arch_hooks.h [PATCH] x86: early printk handling fixes 2006-03-23 07:38:05 -08:00
atomic.h [PATCH] asm-i386/atomic.h: local_irq_save should be used instead of local_irq_disable 2006-04-19 09:13:50 -07:00
auxvec.h [PATCH] auxiliary vector cleanups 2005-09-07 16:57:21 -07:00
bitops.h [PATCH] bitops: i386: use generic bitops 2006-03-26 08:57:12 -08:00
boot.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
bug.h [PATCH] remove all kernel BUGs 2005-05-01 08:59:01 -07:00
bugs.h [PATCH] i386: move SIMD initialization 2006-01-06 08:33:34 -08:00
byteorder.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cache.h [PATCH] Move read_mostly definition to asm/cache.h 2006-03-23 07:38:10 -08:00
cacheflush.h [PATCH] x86/x86_64: mark rodata section read only: x86 parts 2006-01-06 08:33:36 -08:00
checksum.h [NET]: Fix ipl=>ihl typo in ip_fast_csum 2005-08-29 16:02:48 -07:00
cpu.h [PATCH] i386 CPU hotplug 2005-06-25 16:24:29 -07:00
cpufeature.h [PATCH] i386/x86-64: Fix x87 information leak between processes 2006-04-20 07:58:11 -07:00
cputime.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
current.h [PATCH] mark several functions __always_inline 2006-01-14 18:27:15 -08:00
debugreg.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
delay.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
desc.h [PATCH] x86: fix broken SMP boot sequence 2006-02-24 14:31:38 -08:00
div64.h [PATCH] include/asm-i386/: "extern inline" -> "static inline" 2005-09-10 10:06:34 -07:00
dma-mapping.h [PATCH] i386: make pci_map_single/pci_map_sg warn for zero length. 2006-01-11 19:04:56 -08:00
dma.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dmi.h [PATCH] x86_64: Implement early DMI scanning 2006-03-25 09:10:55 -08:00
e820.h [PATCH] x86_64: Introduce e820_all_mapped 2006-04-09 11:53:50 -07:00
edac.h [PATCH] EDAC: core EDAC support code 2006-01-18 19:20:31 -08:00
elf.h [PATCH] fix remaining missing includes 2005-11-07 07:53:41 -08:00
emergency-restart.h [PATCH] i386: Implement machine_emergency_reboot 2005-07-26 14:35:42 -07:00
errno.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
fcntl.h [PATCH] Clean up struct flock64 definitions 2005-09-07 16:57:38 -07:00
fixmap.h [ACPI] delete CONFIG_ACPI_BOOT 2005-08-24 12:08:54 -04:00
floppy.h [PATCH] Remove long dead i386 floppy asm code 2006-03-31 12:18:50 -08:00
futex.h [PATCH] lightweight robust futexes updates 2006-03-27 08:44:49 -08:00
genapic.h [PATCH] Do not enforce unique IO_APIC_ID check for xAPIC systems (i386) 2005-06-23 09:45:09 -07:00
hardirq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
highmem.h [PATCH] kdump: Routines for copying dump pages 2005-06-25 16:24:53 -07:00
hpet.h [PATCH] x86_64: Fix drift with HPET timer enabled 2006-04-09 11:53:53 -07:00
hw_irq.h Revert "i386: move apic init in init_IRQs" 2005-10-31 19:16:17 -08:00
i387.h [PATCH] i386/x86-64: Fix x87 information leak between processes 2006-04-20 07:58:11 -07:00
i8253.h [PATCH] x86: i8253/i8259A lock cleanup 2005-06-30 08:45:10 -07:00
i8259.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ide.h [PATCH] ide: explain the PCI bus test we do in <asm-i386/ide.h> 2005-11-10 00:10:37 +01:00
io_apic.h [ACPI] delete CONFIG_ACPI_BOOT 2005-08-24 12:08:54 -04:00
io.h [PATCH] remove ISA legacy functions: remove the helpers 2006-03-24 07:33:19 -08:00
ioctl.h [PATCH] Generic ioctl.h 2006-01-10 08:01:34 -08:00
ioctls.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ipcbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
irq.h [PATCH] Make vm86 support optional 2006-01-08 20:14:11 -08:00
ist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
kdebug.h [PATCH] Notifier chain update: API changes 2006-03-27 08:44:50 -08:00
kexec.h [PATCH] Kdump: i386 compiler warning fix 2006-01-10 08:01:27 -08:00
kmap_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
kprobes.h [PATCH] x86: kprobes-booster 2006-03-26 08:57:04 -08:00
ldt.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
linkage.h [PATCH] i386: fix prevent_tail_call 2005-05-26 16:16:16 -07:00
local.h [PATCH] make local_t signed 2006-03-31 12:18:55 -08:00
math_emu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mc146818rtc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mca_dma.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mca.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mman.h [PATCH] add asm-generic/mman.h 2006-02-15 15:32:22 -08:00
mmu_context.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmx.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmzone.h [PATCH] unify pfn_to_page: i386 pfn_to_page 2006-03-27 08:44:44 -08:00
module.h [PATCH] Base support for AMD Geode GX/LX processors 2006-01-06 08:33:38 -08:00
mpspec_def.h [PATCH] mpspec: remove unneeded packed attribute 2006-01-06 08:33:39 -08:00
mpspec.h [PATCH] mptspec: remove duplicate #include 2006-04-11 06:18:34 -07:00
msgbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
msi.h [PATCH] PCI: Change MSI to use physical delivery mode always 2005-11-10 16:09:18 -08:00
msr.h [PATCH] x86: more asm cleanups 2005-09-05 00:06:12 -07:00
mtrr.h [PATCH] Fix the imlicit declaration of mtrr_centaur_report_mcr in arch/i386/kernel/cpu/centaur.c 2006-03-23 07:38:06 -08:00
mutex.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
namei.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
nmi.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
node.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
numa.h [PATCH] x86-64: Use ACPI PXM to parse PCI<->node assignments 2005-09-12 10:49:57 -07:00
numaq.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
page.h [PATCH] unify pfn_to_page: i386 pfn_to_page 2006-03-27 08:44:44 -08:00
param.h [PATCH] Avoid namespace pollution in <asm/param.h> 2006-01-02 08:38:38 -08:00
parport.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pci-direct.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pci.h Revert PCIBIOS_MIN_IO changes for 2.6.13 2005-08-14 18:21:30 -07:00
percpu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgalloc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-2level-defs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-2level.h [PATCH] x86/PAE: Fix pte_clear for the >4GB RAM case 2006-04-27 12:00:59 -07:00
pgtable-3level-defs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgtable-3level.h [PATCH] x86/PAE: Fix pte_clear for the >4GB RAM case 2006-04-27 12:00:59 -07:00
pgtable.h [PATCH] x86/PAE: Fix pte_clear for the >4GB RAM case 2006-04-27 12:00:59 -07:00
poll.h [PATCH] POLLRDHUP/EPOLLRDHUP handling for half-closed devices notifications 2006-03-25 08:22:56 -08:00
posix_types.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
processor.h [PATCH] arch/i386/kernel/microcode.c: remove the obsolete microcode_ioctl 2006-03-28 09:16:06 -08:00
ptrace.h [PATCH] PTRACE_SYSEMU is only for i386 and clashes with other ptrace codes of other archs 2006-01-08 20:14:04 -08:00
resource.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rtc.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rwlock.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
rwsem.h [PATCH] add sem_is_read/write_locked() 2005-10-29 21:40:35 -07:00
scatterlist.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
seccomp.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sections.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
segment.h [PATCH] x86: Pnp segments in segment h 2006-01-06 08:33:34 -08:00
semaphore.h [PATCH] x86: SMP alternatives 2006-03-23 07:38:04 -08:00
sembuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
serial.h [PATCH] Serial: Split 8250 port table (part 2) 2005-06-29 18:45:19 +01:00
setup.h [PATCH] unify PFN_* macros 2006-03-27 08:44:48 -08:00
shmbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmparam.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sigcontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
siginfo.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
signal.h [PATCH] Handle TIF_RESTORE_SIGMASK for i386 2006-01-18 19:20:29 -08:00
smp.h [PATCH] PCI: Change MSI to use physical delivery mode always 2005-11-10 16:09:18 -08:00
socket.h [NET]: Introduce SO_{SND,RCV}BUFFORCE socket options 2005-08-29 15:31:35 -07:00
sockios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sparsemem.h [PATCH] sparsemem memory model for i386 2005-06-23 09:45:05 -07:00
spinlock_types.h [PATCH] spinlock consolidation 2005-09-10 10:06:21 -07:00
spinlock.h [PATCH] i386 spinlocks: disable interrupts only if we enabled them 2006-03-23 07:38:06 -08:00
srat.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
stat.h [PATCH] 2TB files: st_blocks is invalid when calling stat64 2006-03-26 08:57:00 -08:00
statfs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
string.h [PATCH] mark several functions __always_inline 2006-01-14 18:27:15 -08:00
suspend.h [PATCH] i386: Use loaddebug macro consistently 2005-04-16 15:24:46 -07:00
system.h [PATCH] kill include/linux/platform.h, default_idle() cleanup 2006-03-24 07:33:21 -08:00
termbits.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
termios.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
thread_info.h [PATCH] i386: fix singlestepping though a syscall 2006-02-17 08:55:21 -08:00
timer.h [PATCH] add suspend/resume for timer 2005-09-05 00:06:18 -07:00
timex.h [PATCH] x86: cpu_khz type fix 2005-06-23 09:45:11 -07:00
tlb.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
tlbflush.h [PATCH] seccomp: tsc disable 2005-06-27 15:11:44 -07:00
topology.h [PATCH] sched: new sched domain for representing multi-core 2006-03-27 08:44:43 -08:00
types.h [PATCH] 2TB files: add blkcnt_t 2006-03-26 08:57:00 -08:00
uaccess.h [PATCH] i386: Add a temporary to make put_user more type safe 2006-03-23 07:38:04 -08:00
ucontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unaligned.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unistd.h [PATCH] Add support for the sys_vmsplice syscall 2006-04-26 10:59:21 +02:00
user.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vga.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vic.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
vm86.h [PATCH] Make vm86 support optional 2006-01-08 20:14:11 -08:00
voyager.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
xor.h [PATCH] i386: inline asm cleanup 2005-09-05 00:06:11 -07:00