This false positive is due to field padding in struct sigqueue. When
this dynamically allocated structure is copied to the stack (in arch-
specific delivery code), kmemcheck sees a read from the padding, which
is, naturally, uninitialized.

Hide the false positive using the __GFP_NOTRACK_FALSE_POSITIVE flag.
Also made the rlimit override code a bit clearer by introducing a new
variable.

Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This false positive is due to the fact that do_mount_root() fakes a
mount option (which is normally read from userspace), and the kernel
unconditionally reads a whole page for the mount option.

Hide the false positive by using the new __getname_gfp() with the
__GFP_NOTRACK_FALSE_POSITIVE flag.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The purpose of this change is to allow __getname() users to pass a
custom GFP mask to kmem_cache_alloc(). This is needed for annotating
a certain kmemcheck false positive.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This gets rid of a heap of false-positive warnings from the tracer
code due to the use of bitfields.

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

2009/2/24 Ingo Molnar <mingo@elte.hu>:
> ok, this is the last warning i have from today's overnight -tip
> testruns - a 32-bit system warning in sock_init_data():
>
> [    2.610389] NET: Registered protocol family 16
> [    2.616138] initcall netlink_proto_init+0x0/0x170 returned 0 after 7812 usecs
> [    2.620010] WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f642c184)
> [    2.624002] 010000000200000000000000604990c000000000000000000000000000000000
> [    2.634076]  i i i i i i u u i i i i i i i i i i i i i i i i i i i i i i i i
> [    2.641038]          ^
> [    2.643376]
> [    2.644004] Pid: 1, comm: swapper Not tainted (2.6.29-rc6-tip-01751-g4d1c22c-dirty #885)
> [    2.648003] EIP: 0060:[<c07141a1>] EFLAGS: 00010282 CPU: 0
> [    2.652008] EIP is at sock_init_data+0xa1/0x190
> [    2.656003] EAX: 0001a800 EBX: f6836c00 ECX: 00463000 EDX: c0e46fe0
> [    2.660003] ESI: f642c180 EDI: c0b83088 EBP: f6863ed8 ESP: c0c412ec
> [    2.664003]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> [    2.668003] CR0: 8005003b CR2: f682c400 CR3: 00b91000 CR4: 000006f0
> [    2.672003] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [    2.676003] DR6: ffff4ff0 DR7: 00000400
> [    2.680002]  [<c07423e5>] __netlink_create+0x35/0xa0
> [    2.684002]  [<c07443cc>] netlink_kernel_create+0x4c/0x140
> [    2.688002]  [<c072755e>] rtnetlink_net_init+0x1e/0x40
> [    2.696002]  [<c071b601>] register_pernet_operations+0x11/0x30
> [    2.700002]  [<c071b72c>] register_pernet_subsys+0x1c/0x30
> [    2.704002]  [<c0bf3c8c>] rtnetlink_init+0x4c/0x100
> [    2.708002]  [<c0bf4669>] netlink_proto_init+0x159/0x170
> [    2.712002]  [<c0101124>] do_one_initcall+0x24/0x150
> [    2.716002]  [<c0bbf3c7>] do_initcalls+0x27/0x40
> [    2.723201]  [<c0bbf3fc>] do_basic_setup+0x1c/0x20
> [    2.728002]  [<c0bbfb8a>] kernel_init+0x5a/0xa0
> [    2.732002]  [<c0103e47>] kernel_thread_helper+0x7/0x10
> [    2.736002]  [<ffffffff>] 0xffffffff

We fix this false positive by annotating the bitfield in struct
sock.
Reported-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This silences a false positive warning with kmemcheck.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The use of bitfields here would lead to false positive warnings with
kmemcheck. Silence them.

(Additionally, one erroneous comment related to the bitfield was also
fixed.)
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

kmemcheck reports a use of uninitialized memory here, but it's not
a real error. The structure in question has just been allocated, and
the whole field is initialized, but it happens in two steps.

We fix the false positive by inserting a kmemcheck annotation.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Add the bitfield API which can be used to annotate bitfields in structs
and get rid of false positive reports.

According to Al Viro, the syntax we were using (putting #ifdef inside
macro arguments) was not valid C. He also suggested using begin/end
markers instead, which is what we do now.

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

We've had some troubles in the past with weird instructions. This
patch adds a self-test framework which can be used to verify that
a certain set of opcodes are decoded correctly. Of course, the
opcodes which are not tested can still give the wrong results.

In short, this is just a safeguard to catch unintentional changes
in the opcode decoder. It does not mean that errors can't still
occur!

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Unify and demacro pte_hidden.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Only _PAGE_HIDDEN when CONFIG_KMEMCHECK is defined, otherwise set it
to 0.  Allows later cleanups.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The Kconfig options of kmemcheck are hidden under arch/x86 which makes porting
to other architectures harder. To fix that, move the Kconfig bits to
lib/Kconfig.kmemcheck and introduce a CONFIG_HAVE_ARCH_KMEMCHECK config option
that architectures can define.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

let it rip!
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>

This adds support for tracking the initializedness of memory that
was allocated with the page allocator. Highmem requests are not
tracked.

Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>

[build fix for !CONFIG_KMEMCHECK]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This is needed for page allocator support to prevent false positives
when accessing pages which are dma-mapped.

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

As these are allocated using the page allocator, we need to pass
__GFP_NOTRACK before we add page allocator support to kmemcheck.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The xor tests are run on uninitialized data, because it is doesn't
really matter what the underlying data is. Annotate this false-
positive warning.
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

We now have SLAB support for kmemcheck! This means that it doesn't matter
whether one chooses SLAB or SLUB, or indeed whether Linus chooses to chuck
SLAB or SLUB.. ;-)

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Parts of this patch were contributed by Pekka Enberg but merged for
atomicity.

Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>

This patch hooks into the DMA API to prevent the reporting of the
false positives that would otherwise be reported when memory is
accessed that is also used directly by devices.

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

With kmemcheck enabled, the slab allocator needs to do this:

1. Tell kmemcheck to allocate the shadow memory which stores the status of
   each byte in the allocation proper, e.g. whether it is initialized or
   uninitialized.
2. Tell kmemcheck which parts of memory that should be marked uninitialized.
   There are actually a few more states, such as "not yet allocated" and
   "recently freed".

If a slab cache is set up using the SLAB_NOTRACK flag, it will never return
memory that can take page faults because of kmemcheck.

If a slab cache is NOT set up using the SLAB_NOTRACK flag, callers can still
request memory with the __GFP_NOTRACK flag. This does not prevent the page
faults from occuring, however, but marks the object in question as being
initialized so that no warnings will ever be produced for this object.

In addition to (and in contrast to) __GFP_NOTRACK, the
__GFP_NOTRACK_FALSE_POSITIVE flag indicates that the allocation should
not be tracked _because_ it would produce a false positive. Their values
are identical, but need not be so in the future (for example, we could now
enable/disable false positives with a config option).

Parts of this patch were contributed by Pekka Enberg but merged for
atomicity.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The hooks that we modify are:
- Page fault handler (to handle kmemcheck faults)
- Debug exception handler (to hide pages after single-stepping
  the instruction that caused the page fault)

Also redefine memset() to use the optimized version if kmemcheck is
enabled.

(Thanks to Pekka Enberg for minimizing the impact on the page fault
handler.)

As kmemcheck doesn't handle MMX/SSE instructions (yet), we also disable
the optimized xor code, and rely instead on the generic C implementation
in order to avoid false-positive warnings.
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>

[whitespace fixlet]
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>

Lets use kmemcheck_pte_lookup() in kmemcheck_fault() instead of
open-coding it there.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This patch moves the CONFIG_X86_64 ifdef out of kmemcheck_opcode_decode() by
introducing a version of the function that always returns false for
CONFIG_X86_32.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Multiple ifdef'd definitions of the same global variable is ugly and
error-prone. Fix that up.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

The "Bugs, beware!" printout during is cute but confuses users that something
bad happened so change the text to the more boring "Initialized" message.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This patch reorders code in error.c so that we can get rid of the forward
declarations.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

kmemcheck/shadow.c needs to include <linux/module.h> to prevent
the following warnings:

linux-next-20080724/arch/x86/mm/kmemcheck/shadow.c:64: warning : data definition has no type or storage class
linux-next-20080724/arch/x86/mm/kmemcheck/shadow.c:64: warning : type defaults to 'int' in declaration of 'EXPORT_SYMBOL_GPL'
linux-next-20080724/arch/x86/mm/kmemcheck/shadow.c:64: warning : parameter names (without types) in function declaration
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: vegardno@ifi.uio.no
Cc: penberg@cs.helsinki.fi
Cc: akpm <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

General description: kmemcheck is a patch to the linux kernel that
detects use of uninitialized memory. It does this by trapping every
read and write to memory that was allocated dynamically (e.g. using
kmalloc()). If a memory address is read that has not previously been
written to, a message is printed to the kernel log.

Thanks to Andi Kleen for the set_memory_4k() solution.

Andrew Morton suggested documenting the shadow member of struct page.
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

[export kmemcheck_mark_initialized]
[build fix for setup_max_cpus]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegardno@ifi.uio.no>

Thanks to Sitsofe Wheeler, Randy Dunlap, and Jonathan Corbet for providing
input and feedback on this!
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Acked-by: NVegard Nossum <vegardno@ifi.uio.no>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Rationale: kmemcheck needs to be able to schedule a tasklet without
touching any dynamically allocated memory _at_ _all_ (since that would
lead to a recursive page fault). This tasklet is used for writing the
error reports to the kernel log.

The new scheduling function avoids touching any other tasklets by
inserting the new tasklist as the head of the "tasklet_hi" list instead
of on the tail.

Also don't wake up the softirq thread lest the scheduler access some
tracked memory and we go down with a recursive page fault.

In this case, we'd better just wait for the maximum time of 1/HZ for the
message to appear.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Move the SLAB struct kmem_cache definition to <linux/slab_def.h> like
with SLUB so kmemcheck can access ->ctor and ->flags.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

[rebased for mainline inclusion]
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This is needed if the header is to be free-standing.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

This will help kmemcheck (and possibly other debugging tools) since we
can now simply pass regs->bp to the stack tracer instead of specifying
the number of stack frames to skip, which is unreliable if gcc decides
to inline functions, etc.

Note that this makes the API incomplete for other architectures, but I
expect that those can be updated lazily, e.g. when they need it.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>

Fix kernel-doc warnings in recently changed block/ source code.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>