<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/x86, branch v3.7</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2012-12-01T21:08:36+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-12-01T21:08:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=b3c3a9cf2a28ee4a8d0b62e2e58c61e9ca9bb47b'/>
<id>b3c3a9cf2a28ee4a8d0b62e2e58c61e9ca9bb47b</id>
<content type='text'>
Pull RCU fix from Ingo Molnar:
 "Fix leaking RCU extended quiescent state, which might trigger warnings
  and mess up the extended quiescent state tracking logic into thinking
  that we are in "RCU user mode" while we aren't."

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Fix unrecovered RCU user mode in syscall_trace_leave()
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull RCU fix from Ingo Molnar:
 "Fix leaking RCU extended quiescent state, which might trigger warnings
  and mess up the extended quiescent state tracking logic into thinking
  that we are in "RCU user mode" while we aren't."

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Fix unrecovered RCU user mode in syscall_trace_leave()
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2012-12-01T21:07:48+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-12-01T21:07:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=455e987c0c2eb2c9045dc854559474cf41509965'/>
<id>455e987c0c2eb2c9045dc854559474cf41509965</id>
<content type='text'>
Pull perf fixes from Ingo Molnar:
 "This is mostly about unbreaking architectures that took the UAPI
  changes in the v3.7 cycle, plus misc fixes."

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix building perf kvm on non x86 arches
  perf kvm: Rename perf_kvm to perf_kvm_stat
  perf: Make perf build for x86 with UAPI disintegration applied
  perf powerpc: Use uapi/unistd.h to fix build error
  tools: Pass the target in descend
  tools: Honour the O= flag when tool build called from a higher Makefile
  tools: Define a Makefile function to do subdir processing
  x86: Export asm/{svm.h,vmx.h,perf_regs.h}
  perf tools: Fix strbuf_addf() when the buffer needs to grow
  perf header: Fix numa topology printing
  perf, powerpc: Fix hw breakpoints returning -ENOSPC
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull perf fixes from Ingo Molnar:
 "This is mostly about unbreaking architectures that took the UAPI
  changes in the v3.7 cycle, plus misc fixes."

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf kvm: Fix building perf kvm on non x86 arches
  perf kvm: Rename perf_kvm to perf_kvm_stat
  perf: Make perf build for x86 with UAPI disintegration applied
  perf powerpc: Use uapi/unistd.h to fix build error
  tools: Pass the target in descend
  tools: Honour the O= flag when tool build called from a higher Makefile
  tools: Define a Makefile function to do subdir processing
  x86: Export asm/{svm.h,vmx.h,perf_regs.h}
  perf tools: Fix strbuf_addf() when the buffer needs to grow
  perf header: Fix numa topology printing
  perf, powerpc: Fix hw breakpoints returning -ENOSPC
</pre>
</div>
</content>
</entry>
<entry>
<title>x86, fpu: Avoid FPU lazy restore after suspend</title>
<updated>2012-11-30T21:48:05+00:00</updated>
<author>
<name>Vincent Palatin</name>
<email>vpalatin@chromium.org</email>
</author>
<published>2012-11-30T20:15:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=644c154186386bb1fa6446bc5e037b9ed098db46'/>
<id>644c154186386bb1fa6446bc5e037b9ed098db46</id>
<content type='text'>
When a cpu enters S3 state, the FPU state is lost.
After resuming for S3, if we try to lazy restore the FPU for a process running
on the same CPU, this will result in a corrupted FPU context.

Ensure that "fpu_owner_task" is properly invalided when (re-)initializing a CPU,
so nobody will try to lazy restore a state which doesn't exist in the hardware.

Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off,
by doing thousands of suspend/resume cycles with 4 processes doing FPU
operations running. Without the patch, a process is killed after a
few hundreds cycles by a SIGFPE.

Cc: Duncan Laurie &lt;dlaurie@chromium.org&gt;
Cc: Olof Johansson &lt;olofj@chromium.org&gt;
Cc: &lt;stable@kernel.org&gt; v3.4+ # for 3.4 need to replace this_cpu_write by percpu_write
Signed-off-by: Vincent Palatin &lt;vpalatin@chromium.org&gt;
Link: http://lkml.kernel.org/r/1354306532-1014-1-git-send-email-vpalatin@chromium.org
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When a cpu enters S3 state, the FPU state is lost.
After resuming for S3, if we try to lazy restore the FPU for a process running
on the same CPU, this will result in a corrupted FPU context.

Ensure that "fpu_owner_task" is properly invalided when (re-)initializing a CPU,
so nobody will try to lazy restore a state which doesn't exist in the hardware.

Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off,
by doing thousands of suspend/resume cycles with 4 processes doing FPU
operations running. Without the patch, a process is killed after a
few hundreds cycles by a SIGFPE.

Cc: Duncan Laurie &lt;dlaurie@chromium.org&gt;
Cc: Olof Johansson &lt;olofj@chromium.org&gt;
Cc: &lt;stable@kernel.org&gt; v3.4+ # for 3.4 need to replace this_cpu_write by percpu_write
Signed-off-by: Vincent Palatin &lt;vpalatin@chromium.org&gt;
Link: http://lkml.kernel.org/r/1354306532-1014-1-git-send-email-vpalatin@chromium.org
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86-32: Unbreak booting on some 486 clones</title>
<updated>2012-11-27T17:26:33+00:00</updated>
<author>
<name>H. Peter Anvin</name>
<email>hpa@linux.intel.com</email>
</author>
<published>2012-11-27T16:54:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=6662c34fa9c60a48aaa5879cb229cd9a84de9c22'/>
<id>6662c34fa9c60a48aaa5879cb229cd9a84de9c22</id>
<content type='text'>
There appear to have been some 486 clones, including the "enhanced"
version of Am486, which have CPUID but not CR4.  These 486 clones had
only the FPU flag, if any, unlike the Intel 486s with CPUID, which
also had VME and therefore needed CR4.

Therefore, look at the basic CPUID flags and require at least one bit
other than bit 0 before we modify CR4.

Thanks to Christian Ludloff of sandpile.org for confirming this as a
problem.

Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
There appear to have been some 486 clones, including the "enhanced"
version of Am486, which have CPUID but not CR4.  These 486 clones had
only the FPU flag, if any, unlike the Intel 486s with CPUID, which
also had VME and therefore needed CR4.

Therefore, look at the basic CPUID flags and require at least one bit
other than bit 0 before we modify CR4.

Thanks to Christian Ludloff of sandpile.org for confirming this as a
problem.

Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86, kvm: Remove incorrect redundant assembly constraint</title>
<updated>2012-11-26T23:52:48+00:00</updated>
<author>
<name>H. Peter Anvin</name>
<email>hpa@linux.intel.com</email>
</author>
<published>2012-11-21T22:41:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=cb7cb2864e758a1b040040bc55e404c677c911cb'/>
<id>cb7cb2864e758a1b040040bc55e404c677c911cb</id>
<content type='text'>
In __emulate_1op_rax_rdx, we use "+a" and "+d" which are input/output
constraints, and *then* use "a" and "d" as input constraints.  This is
incorrect, but happens to work on some versions of gcc.

However, it breaks gcc with -O0 and icc, and may break on future
versions of gcc.

Reported-and-tested-by: Melanie Blower &lt;melanie.blower@intel.com&gt;
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Link: http://lkml.kernel.org/r/B3584E72CFEBED439A3ECA9BCE67A4EF1B17AF90@FMSMSX107.amr.corp.intel.com
Reviewed-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Acked-by: Marcelo Tosatti &lt;mtosatti@redhat.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In __emulate_1op_rax_rdx, we use "+a" and "+d" which are input/output
constraints, and *then* use "a" and "d" as input constraints.  This is
incorrect, but happens to work on some versions of gcc.

However, it breaks gcc with -O0 and icc, and may break on future
versions of gcc.

Reported-and-tested-by: Melanie Blower &lt;melanie.blower@intel.com&gt;
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Link: http://lkml.kernel.org/r/B3584E72CFEBED439A3ECA9BCE67A4EF1B17AF90@FMSMSX107.amr.corp.intel.com
Reviewed-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
Acked-by: Marcelo Tosatti &lt;mtosatti@redhat.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2012-11-24T06:03:14+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-11-24T06:03:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=2654ad44b5f7a5f1b12d722a37d9b9df69d57899'/>
<id>2654ad44b5f7a5f1b12d722a37d9b9df69d57899</id>
<content type='text'>
Pull x86 arch fixes from Peter Anvin:
 "Here is a collection of fixes for 3.7-rc7.  This is a superset of
  tglx' earlier pull request."

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86-64: Fix ordering of CFI directives and recent ASM_CLAC additions
  x86, microcode, AMD: Add support for family 16h processors
  x86-32: Export kernel_stack_pointer() for modules
  x86-32: Fix invalid stack address while in softirq
  x86, efi: Fix processor-specific memcpy() build error
  x86: remove dummy long from EFI stub
  x86, mm: Correct vmflag test for checking VM_HUGETLB
  x86, amd: Disable way access filter on Piledriver CPUs
  x86/mce: Do not change worker's running cpu in cmci_rediscover().
  x86/ce4100: Fix PCI configuration register access for devices without interrupts
  x86/ce4100: Fix reboot by forcing the reboot method to be KBD
  x86/ce4100: Fix pm_poweroff
  MAINTAINERS: Update email address for Robert Richter
  x86, microcode_amd: Change email addresses, MAINTAINERS entry
  MAINTAINERS: Change Boris' email address
  EDAC: Change Boris' email address
  x86, AMD: Change Boris' email address
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull x86 arch fixes from Peter Anvin:
 "Here is a collection of fixes for 3.7-rc7.  This is a superset of
  tglx' earlier pull request."

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86-64: Fix ordering of CFI directives and recent ASM_CLAC additions
  x86, microcode, AMD: Add support for family 16h processors
  x86-32: Export kernel_stack_pointer() for modules
  x86-32: Fix invalid stack address while in softirq
  x86, efi: Fix processor-specific memcpy() build error
  x86: remove dummy long from EFI stub
  x86, mm: Correct vmflag test for checking VM_HUGETLB
  x86, amd: Disable way access filter on Piledriver CPUs
  x86/mce: Do not change worker's running cpu in cmci_rediscover().
  x86/ce4100: Fix PCI configuration register access for devices without interrupts
  x86/ce4100: Fix reboot by forcing the reboot method to be KBD
  x86/ce4100: Fix pm_poweroff
  MAINTAINERS: Update email address for Robert Richter
  x86, microcode_amd: Change email addresses, MAINTAINERS entry
  MAINTAINERS: Change Boris' email address
  EDAC: Change Boris' email address
  x86, AMD: Change Boris' email address
</pre>
</div>
</content>
</entry>
<entry>
<title>x86-64: Fix ordering of CFI directives and recent ASM_CLAC additions</title>
<updated>2012-11-21T06:23:57+00:00</updated>
<author>
<name>Jan Beulich</name>
<email>JBeulich@suse.com</email>
</author>
<published>2012-11-02T11:18:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=ee4eb87be2c3f69c2c4d9f1c1d98e363a7ad18ab'/>
<id>ee4eb87be2c3f69c2c4d9f1c1d98e363a7ad18ab</id>
<content type='text'>
While these got added in the right place everywhere else, entry_64.S
is the odd one where they ended up before the initial CFI directive(s).
In order to cover the full code ranges, the CFI directive must be
first, though.

Signed-off-by: Jan Beulich &lt;jbeulich@suse.com&gt;
Link: http://lkml.kernel.org/r/5093BA1F02000078000A600E@nat28.tlf.novell.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
While these got added in the right place everywhere else, entry_64.S
is the odd one where they ended up before the initial CFI directive(s).
In order to cover the full code ranges, the CFI directive must be
first, though.

Signed-off-by: Jan Beulich &lt;jbeulich@suse.com&gt;
Link: http://lkml.kernel.org/r/5093BA1F02000078000A600E@nat28.tlf.novell.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86, microcode, AMD: Add support for family 16h processors</title>
<updated>2012-11-21T06:23:28+00:00</updated>
<author>
<name>Boris Ostrovsky</name>
<email>boris.ostrovsky@amd.com</email>
</author>
<published>2012-11-15T18:41:50+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=36c46ca4f322a7bf89aad5462a3a1f61713edce7'/>
<id>36c46ca4f322a7bf89aad5462a3a1f61713edce7</id>
<content type='text'>
Add valid patch size for family 16h processors.

[ hpa: promoting to urgent/stable since it is hw enabling and trivial ]

Signed-off-by: Boris Ostrovsky &lt;boris.ostrovsky@amd.com&gt;
Acked-by: Andreas Herrmann &lt;herrmann.der.user@googlemail.com&gt;
Link: http://lkml.kernel.org/r/1353004910-2204-1-git-send-email-boris.ostrovsky@amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add valid patch size for family 16h processors.

[ hpa: promoting to urgent/stable since it is hw enabling and trivial ]

Signed-off-by: Boris Ostrovsky &lt;boris.ostrovsky@amd.com&gt;
Acked-by: Andreas Herrmann &lt;herrmann.der.user@googlemail.com&gt;
Link: http://lkml.kernel.org/r/1353004910-2204-1-git-send-email-boris.ostrovsky@amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86-32: Export kernel_stack_pointer() for modules</title>
<updated>2012-11-21T06:23:23+00:00</updated>
<author>
<name>H. Peter Anvin</name>
<email>hpa@linux.intel.com</email>
</author>
<published>2012-11-21T06:21:02+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=cb57a2b4cff7edf2a4e32c0163200e9434807e0a'/>
<id>cb57a2b4cff7edf2a4e32c0163200e9434807e0a</id>
<content type='text'>
Modules, in particular oprofile (and possibly other similar tools)
need kernel_stack_pointer(), so export it using EXPORT_SYMBOL_GPL().

Cc: Yang Wei &lt;wei.yang@windriver.com&gt;
Cc: Robert Richter &lt;robert.richter@amd.com&gt;
Cc: Jun Zhang &lt;jun.zhang@intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/20120912135059.GZ8285@erda.amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Modules, in particular oprofile (and possibly other similar tools)
need kernel_stack_pointer(), so export it using EXPORT_SYMBOL_GPL().

Cc: Yang Wei &lt;wei.yang@windriver.com&gt;
Cc: Robert Richter &lt;robert.richter@amd.com&gt;
Cc: Jun Zhang &lt;jun.zhang@intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Link: http://lkml.kernel.org/r/20120912135059.GZ8285@erda.amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>x86-32: Fix invalid stack address while in softirq</title>
<updated>2012-11-21T06:23:20+00:00</updated>
<author>
<name>Robert Richter</name>
<email>robert.richter@amd.com</email>
</author>
<published>2012-09-03T18:54:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=1022623842cb72ee4d0dbf02f6937f38c92c3f41'/>
<id>1022623842cb72ee4d0dbf02f6937f38c92c3f41</id>
<content type='text'>
In 32 bit the stack address provided by kernel_stack_pointer() may
point to an invalid range causing NULL pointer access or page faults
while in NMI (see trace below). This happens if called in softirq
context and if the stack is empty. The address at &amp;regs-&gt;sp is then
out of range.

Fixing this by checking if regs and &amp;regs-&gt;sp are in the same stack
context. Otherwise return the previous stack pointer stored in struct
thread_info. If that address is invalid too, return address of regs.

 BUG: unable to handle kernel NULL pointer dereference at 0000000a
 IP: [&lt;c1004237&gt;] print_context_stack+0x6e/0x8d
 *pde = 00000000
 Oops: 0000 [#1] SMP
 Modules linked in:
 Pid: 4434, comm: perl Not tainted 3.6.0-rc3-oprofile-i386-standard-g4411a05 #4 Hewlett-Packard HP xw9400 Workstation/0A1Ch
 EIP: 0060:[&lt;c1004237&gt;] EFLAGS: 00010093 CPU: 0
 EIP is at print_context_stack+0x6e/0x8d
 EAX: ffffe000 EBX: 0000000a ECX: f4435f94 EDX: 0000000a
 ESI: f4435f94 EDI: f4435f94 EBP: f5409ec0 ESP: f5409ea0
  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
 CR0: 8005003b CR2: 0000000a CR3: 34ac9000 CR4: 000007d0
 DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
 DR6: ffff0ff0 DR7: 00000400
 Process perl (pid: 4434, ti=f5408000 task=f5637850 task.ti=f4434000)
 Stack:
  000003e8 ffffe000 00001ffc f4e39b00 00000000 0000000a f4435f94 c155198c
  f5409ef0 c1003723 c155198c f5409f04 00000000 f5409edc 00000000 00000000
  f5409ee8 f4435f94 f5409fc4 00000001 f5409f1c c12dce1c 00000000 c155198c
 Call Trace:
  [&lt;c1003723&gt;] dump_trace+0x7b/0xa1
  [&lt;c12dce1c&gt;] x86_backtrace+0x40/0x88
  [&lt;c12db712&gt;] ? oprofile_add_sample+0x56/0x84
  [&lt;c12db731&gt;] oprofile_add_sample+0x75/0x84
  [&lt;c12ddb5b&gt;] op_amd_check_ctrs+0x46/0x260
  [&lt;c12dd40d&gt;] profile_exceptions_notify+0x23/0x4c
  [&lt;c1395034&gt;] nmi_handle+0x31/0x4a
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c13950ed&gt;] do_nmi+0xa0/0x2ff
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c13949e5&gt;] nmi_stack_correct+0x28/0x2d
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c1003603&gt;] ? do_softirq+0x4b/0x7f
  &lt;IRQ&gt;
  [&lt;c102a06f&gt;] irq_exit+0x35/0x5b
  [&lt;c1018f56&gt;] smp_apic_timer_interrupt+0x6c/0x7a
  [&lt;c1394746&gt;] apic_timer_interrupt+0x2a/0x30
 Code: 89 fe eb 08 31 c9 8b 45 0c ff 55 ec 83 c3 04 83 7d 10 00 74 0c 3b 5d 10 73 26 3b 5d e4 73 0c eb 1f 3b 5d f0 76 1a 3b 5d e8 73 15 &lt;8b&gt; 13 89 d0 89 55 e0 e8 ad 42 03 00 85 c0 8b 55 e0 75 a6 eb cc
 EIP: [&lt;c1004237&gt;] print_context_stack+0x6e/0x8d SS:ESP 0068:f5409ea0
 CR2: 000000000000000a
 ---[ end trace 62afee3481b00012 ]---
 Kernel panic - not syncing: Fatal exception in interrupt

V2:
* add comments to kernel_stack_pointer()
* always return a valid stack address by falling back to the address
  of regs

Reported-by: Yang Wei &lt;wei.yang@windriver.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Robert Richter &lt;robert.richter@amd.com&gt;
Link: http://lkml.kernel.org/r/20120912135059.GZ8285@erda.amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Cc: Jun Zhang &lt;jun.zhang@intel.com&gt;
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In 32 bit the stack address provided by kernel_stack_pointer() may
point to an invalid range causing NULL pointer access or page faults
while in NMI (see trace below). This happens if called in softirq
context and if the stack is empty. The address at &amp;regs-&gt;sp is then
out of range.

Fixing this by checking if regs and &amp;regs-&gt;sp are in the same stack
context. Otherwise return the previous stack pointer stored in struct
thread_info. If that address is invalid too, return address of regs.

 BUG: unable to handle kernel NULL pointer dereference at 0000000a
 IP: [&lt;c1004237&gt;] print_context_stack+0x6e/0x8d
 *pde = 00000000
 Oops: 0000 [#1] SMP
 Modules linked in:
 Pid: 4434, comm: perl Not tainted 3.6.0-rc3-oprofile-i386-standard-g4411a05 #4 Hewlett-Packard HP xw9400 Workstation/0A1Ch
 EIP: 0060:[&lt;c1004237&gt;] EFLAGS: 00010093 CPU: 0
 EIP is at print_context_stack+0x6e/0x8d
 EAX: ffffe000 EBX: 0000000a ECX: f4435f94 EDX: 0000000a
 ESI: f4435f94 EDI: f4435f94 EBP: f5409ec0 ESP: f5409ea0
  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
 CR0: 8005003b CR2: 0000000a CR3: 34ac9000 CR4: 000007d0
 DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
 DR6: ffff0ff0 DR7: 00000400
 Process perl (pid: 4434, ti=f5408000 task=f5637850 task.ti=f4434000)
 Stack:
  000003e8 ffffe000 00001ffc f4e39b00 00000000 0000000a f4435f94 c155198c
  f5409ef0 c1003723 c155198c f5409f04 00000000 f5409edc 00000000 00000000
  f5409ee8 f4435f94 f5409fc4 00000001 f5409f1c c12dce1c 00000000 c155198c
 Call Trace:
  [&lt;c1003723&gt;] dump_trace+0x7b/0xa1
  [&lt;c12dce1c&gt;] x86_backtrace+0x40/0x88
  [&lt;c12db712&gt;] ? oprofile_add_sample+0x56/0x84
  [&lt;c12db731&gt;] oprofile_add_sample+0x75/0x84
  [&lt;c12ddb5b&gt;] op_amd_check_ctrs+0x46/0x260
  [&lt;c12dd40d&gt;] profile_exceptions_notify+0x23/0x4c
  [&lt;c1395034&gt;] nmi_handle+0x31/0x4a
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c13950ed&gt;] do_nmi+0xa0/0x2ff
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c13949e5&gt;] nmi_stack_correct+0x28/0x2d
  [&lt;c1029dc5&gt;] ? ftrace_define_fields_irq_handler_entry+0x45/0x45
  [&lt;c1003603&gt;] ? do_softirq+0x4b/0x7f
  &lt;IRQ&gt;
  [&lt;c102a06f&gt;] irq_exit+0x35/0x5b
  [&lt;c1018f56&gt;] smp_apic_timer_interrupt+0x6c/0x7a
  [&lt;c1394746&gt;] apic_timer_interrupt+0x2a/0x30
 Code: 89 fe eb 08 31 c9 8b 45 0c ff 55 ec 83 c3 04 83 7d 10 00 74 0c 3b 5d 10 73 26 3b 5d e4 73 0c eb 1f 3b 5d f0 76 1a 3b 5d e8 73 15 &lt;8b&gt; 13 89 d0 89 55 e0 e8 ad 42 03 00 85 c0 8b 55 e0 75 a6 eb cc
 EIP: [&lt;c1004237&gt;] print_context_stack+0x6e/0x8d SS:ESP 0068:f5409ea0
 CR2: 000000000000000a
 ---[ end trace 62afee3481b00012 ]---
 Kernel panic - not syncing: Fatal exception in interrupt

V2:
* add comments to kernel_stack_pointer()
* always return a valid stack address by falling back to the address
  of regs

Reported-by: Yang Wei &lt;wei.yang@windriver.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Robert Richter &lt;robert.richter@amd.com&gt;
Link: http://lkml.kernel.org/r/20120912135059.GZ8285@erda.amd.com
Signed-off-by: H. Peter Anvin &lt;hpa@linux.intel.com&gt;
Cc: Jun Zhang &lt;jun.zhang@intel.com&gt;
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