<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/sh, branch linux-3.4.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>vm: add VM_FAULT_SIGSEGV handling support</title>
<updated>2015-04-14T09:33:57+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2015-01-29T18:51:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=a10ca0dbc2bcf3383fa42dcfeca055f7b5fe1106'/>
<id>a10ca0dbc2bcf3383fa42dcfeca055f7b5fe1106</id>
<content type='text'>
commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream.

The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d4514 ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.

Reported-and-tested-by: Takashi Iwai &lt;tiwai@suse.de&gt;
Tested-by: Jan Engelhardt &lt;jengelh@inai.de&gt;
Acked-by: Heiko Carstens &lt;heiko.carstens@de.ibm.com&gt; # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[bwh: Backported to 3.2:
 - Adjust filenames, context
 - Drop arc, metag, nios2 and lustre changes
 - For sh, patch both 32-bit and 64-bit implementations to use goto bad_area
 - For s390, pass int_code and trans_exc_code as arguments to do_no_context()
   and do_sigsegv()]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
[lizf: Backported to 3.4:
 - adjust context in arch/power/mm/fault.c
 - apply the original change in upstream commit for s390]
Signed-off-by: Zefan Li &lt;lizefan@huawei.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream.

The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d4514 ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.

Reported-and-tested-by: Takashi Iwai &lt;tiwai@suse.de&gt;
Tested-by: Jan Engelhardt &lt;jengelh@inai.de&gt;
Acked-by: Heiko Carstens &lt;heiko.carstens@de.ibm.com&gt; # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
[bwh: Backported to 3.2:
 - Adjust filenames, context
 - Drop arc, metag, nios2 and lustre changes
 - For sh, patch both 32-bit and 64-bit implementations to use goto bad_area
 - For s390, pass int_code and trans_exc_code as arguments to do_no_context()
   and do_sigsegv()]
Signed-off-by: Ben Hutchings &lt;ben@decadent.org.uk&gt;
[lizf: Backported to 3.4:
 - adjust context in arch/power/mm/fault.c
 - apply the original change in upstream commit for s390]
Signed-off-by: Zefan Li &lt;lizefan@huawei.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sh: fix format string bug in stack tracer</title>
<updated>2014-05-06T14:51:45+00:00</updated>
<author>
<name>Matt Fleming</name>
<email>matt.fleming@intel.com</email>
</author>
<published>2014-04-03T21:46:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=5650bff7fdf4f586d05dad9315d4786eba694149'/>
<id>5650bff7fdf4f586d05dad9315d4786eba694149</id>
<content type='text'>
commit a0c32761e73c9999cbf592b702f284221fea8040 upstream.

Kees reported the following error:

   arch/sh/kernel/dumpstack.c: In function 'print_trace_address':
   arch/sh/kernel/dumpstack.c:118:2: error: format not a string literal and no format arguments [-Werror=format-security]

Use the "%s" format so that it's impossible to interpret 'data' as a
format string.

Signed-off-by: Matt Fleming &lt;matt.fleming@intel.com&gt;
Reported-by: Kees Cook &lt;keescook@chromium.org&gt;
Acked-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Paul Mundt &lt;lethal@linux-sh.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit a0c32761e73c9999cbf592b702f284221fea8040 upstream.

Kees reported the following error:

   arch/sh/kernel/dumpstack.c: In function 'print_trace_address':
   arch/sh/kernel/dumpstack.c:118:2: error: format not a string literal and no format arguments [-Werror=format-security]

Use the "%s" format so that it's impossible to interpret 'data' as a
format string.

Signed-off-by: Matt Fleming &lt;matt.fleming@intel.com&gt;
Reported-by: Kees Cook &lt;keescook@chromium.org&gt;
Acked-by: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Paul Mundt &lt;lethal@linux-sh.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sh: always link in helper functions extracted from libgcc</title>
<updated>2014-01-08T17:42:12+00:00</updated>
<author>
<name>Geert Uytterhoeven</name>
<email>geert@linux-m68k.org</email>
</author>
<published>2013-12-19T01:08:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7a12bcd95b59dcf1a715827846baa7c81d1946f9'/>
<id>7a12bcd95b59dcf1a715827846baa7c81d1946f9</id>
<content type='text'>
commit 84ed8a99058e61567f495cc43118344261641c5f upstream.

E.g. landisk_defconfig, which has CONFIG_NTFS_FS=m:

  ERROR: "__ashrdi3" [fs/ntfs/ntfs.ko] undefined!

For "lib-y", if no symbols in a compilation unit are referenced by other
units, the compilation unit will not be included in vmlinux.  This
breaks modules that do reference those symbols.

Use "obj-y" instead to fix this.

http://kisskb.ellerman.id.au/kisskb/buildresult/8838077/

This doesn't fix all cases. There are others, e.g. udivsi3.
This is also not limited to sh, many architectures handle this in the
same way.

A simple solution is to unconditionally include all helper functions.
A more complex solution is to make the choice of "lib-y" or "obj-y" depend
on CONFIG_MODULES:

  obj-$(CONFIG_MODULES) += ...
  lib-y($CONFIG_MODULES) += ...

Signed-off-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Paul Mundt &lt;lethal@linux-sh.org&gt;
Tested-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Reviewed-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 84ed8a99058e61567f495cc43118344261641c5f upstream.

E.g. landisk_defconfig, which has CONFIG_NTFS_FS=m:

  ERROR: "__ashrdi3" [fs/ntfs/ntfs.ko] undefined!

For "lib-y", if no symbols in a compilation unit are referenced by other
units, the compilation unit will not be included in vmlinux.  This
breaks modules that do reference those symbols.

Use "obj-y" instead to fix this.

http://kisskb.ellerman.id.au/kisskb/buildresult/8838077/

This doesn't fix all cases. There are others, e.g. udivsi3.
This is also not limited to sh, many architectures handle this in the
same way.

A simple solution is to unconditionally include all helper functions.
A more complex solution is to make the choice of "lib-y" or "obj-y" depend
on CONFIG_MODULES:

  obj-$(CONFIG_MODULES) += ...
  lib-y($CONFIG_MODULES) += ...

Signed-off-by: Geert Uytterhoeven &lt;geert@linux-m68k.org&gt;
Cc: Paul Mundt &lt;lethal@linux-sh.org&gt;
Tested-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Reviewed-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sh: Fix FDPIC binary loader</title>
<updated>2013-01-21T19:45:14+00:00</updated>
<author>
<name>Thomas Schwinge</name>
<email>thomas@codesourcery.com</email>
</author>
<published>2012-11-16T09:46:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8630dda5a013d1b39280ec9bda2ee9b7e99b68c1'/>
<id>8630dda5a013d1b39280ec9bda2ee9b7e99b68c1</id>
<content type='text'>
commit 4a71997a3279a339e7336ea5d0cd27282e2dea44 upstream.

Ensure that the aux table is properly initialized, even when optional features
are missing.  Without this, the FDPIC loader did not work.  This was meant to
be included in commit d5ab780305bb6d60a7b5a74f18cf84eb6ad153b1.

Signed-off-by: Thomas Schwinge &lt;thomas@codesourcery.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
commit 4a71997a3279a339e7336ea5d0cd27282e2dea44 upstream.

Ensure that the aux table is properly initialized, even when optional features
are missing.  Without this, the FDPIC loader did not work.  This was meant to
be included in commit d5ab780305bb6d60a7b5a74f18cf84eb6ad153b1.

Signed-off-by: Thomas Schwinge &lt;thomas@codesourcery.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sh: Fix up tracepoint build fallout from static key introduction.</title>
<updated>2012-04-27T01:42:38+00:00</updated>
<author>
<name>Nobuhiro Iwamatsu</name>
<email>nobuhiro.iwamatsu.yj@renesas.com</email>
</author>
<published>2012-04-27T01:42:38+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=ec2ccd884ab1e190bc5ddb210c7d5f5ea2ddeba3'/>
<id>ec2ccd884ab1e190bc5ddb210c7d5f5ea2ddeba3</id>
<content type='text'>
With the introduction of static keys, anything using tracepoints blows up
in the following manner:

include/trace/events/oom.h:8:13: error: initializer element is not constant
include/trace/events/oom.h:8:13: error: (near initialization for '__tracepoint_oom_score_adj_update')
include/trace/events/oom.h:8:13: error: initializer element is not constant
include/trace/events/oom.h:8:13: error: (near initialization for '__tracepoint_oom_score_adj_update.key')

This is a result of the STATIC_KEY_INIT_xxx defs wrapping ATOMIC_INIT()
which on sh includes an atomic_t typecast. Given that we don't really
need the typecast for anything anymore, the simplest solution is simply
to kill off the cast.

Signed-off-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With the introduction of static keys, anything using tracepoints blows up
in the following manner:

include/trace/events/oom.h:8:13: error: initializer element is not constant
include/trace/events/oom.h:8:13: error: (near initialization for '__tracepoint_oom_score_adj_update')
include/trace/events/oom.h:8:13: error: initializer element is not constant
include/trace/events/oom.h:8:13: error: (near initialization for '__tracepoint_oom_score_adj_update.key')

This is a result of the STATIC_KEY_INIT_xxx defs wrapping ATOMIC_INIT()
which on sh includes an atomic_t typecast. Given that we don't really
need the typecast for anything anymore, the simplest solution is simply
to kill off the cast.

Signed-off-by: Nobuhiro Iwamatsu &lt;nobuhiro.iwamatsu.yj@renesas.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sh: Fix error synchronising kernel page tables</title>
<updated>2012-04-19T06:57:44+00:00</updated>
<author>
<name>Stuart Menefy</name>
<email>stuart.menefy@st.com</email>
</author>
<published>2012-02-14T11:29:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8d9a784d1e2c75e0dcae06f77a02f5e7bb547f3a'/>
<id>8d9a784d1e2c75e0dcae06f77a02f5e7bb547f3a</id>
<content type='text'>
The problem is caused by the interaction of two features in the Linux
memory management code.

A processes address space is described by a struct mm_struct, and
every thread has a pointer to the mm it should run in. The exception
to this are kernel threads, which don't have an mm, and so borrow
the mm from the last thread which ran. The system is bootstrapped
by the initial kernel thread using init's mm (even though init hasn't
been created yet, its mm is the static init_mm).

The other feature is how the kernel handles the page table which
describes the portion of the address space which is only visible when
executing inside the kernel, and which is shared by all threads. On
the SH4 the only portion of the kernel's address space which described
using the page table is called P3, from 0xc0000000 to 0xdfffffff. This
portion of the address space is divided into three:
  - mappings for dma_alloc_coherent()
  - mappings for vmalloc() and ioremap()
  - fixmap mappings, primarily used in copy_user_pages() to create
    kernel mappings of user pages with the correct cache colour.

To optimise the TLB miss handler we don't want to add an additional
condition which checks whether the faulting address is in the user or
the kernel portion of the address space, and so all page tables have a
common portion which describes the kernel part of the address
space. As the SH4 uses a two level page table, only the kernel portion
of first level page table (the pgd entries) is duplicated. These all
point to the same second level entries (the pte's), and so no memory
is wasted.

The reference page table for the kernel is called the swapper_pg_dir,
and when a new page table is created for a new process the kernel
portion of the page table is copied from swapper_pg_dir. This works
fine when changes only occur in the second level of the kernel's page
table, or the first level entries are created before any new user
processes. However if a change occurs to the first level of the page
table, and there are existing processes which don't have this entry in
their page table, this new entry needs to be added. This is done on
demand, when the kernel accesses a P3 address which isn't mapped using
the current page table, the code in vmalloc_fault() copies the entry
from the reference page table (swapper_pg_dir) into the current
processes page table.

The bug which this patch addresses is that the code in vmalloc_fault()
was not copying addresses which fell in the dma_alloc_coherent()
portion of the address space, and it should have been copying any P3
address.

Why we hadn't seen this before, and what made this hard to reproduce,
is that normally the kernel will have called dma_alloc_coherent(), and
accessed the memory mapping created, before any user process
runs. Typically drivers such as USB or SATA will have created and used
mappings of this type during the kernel initialisation, when probing
for the attached devices, before init runs. Ethernet is slightly
different, as it normally only creates and accesses
dma_alloc_coherent() mappings when the network is brought up, but if
kernel level IP configuration is used this will also occur before any
user space process runs. So the first reproduction of this problem
which we saw was occurred when USB and SATA were removed from the
kernel, and then bring up Ethernet from user space using ifconfig.
I'd like to thank Joseph Bormolini who did the hard work reducing the
problem to this simple to reproduce criteria.

In your case the situation is slightly different, and turns out to
depends on the exact kernel configuration (which we had) and your
ramdisk contents (which we didn't - hence the need for some assumptions).

In this case the problem is a side effect of kernel level module
loading. Kernel subsystems sometimes trigger the load of kernel
modules directly, for example the crypto subsystem tries to load the
cryptomgr and MTD tries to load modules for Flash partitioning if
these are not built into the kernel. This is done by the kernel
creating a user process which runs insmod to try and load the
appropriate module.

In order for this to cause problems the system must be running with a
initrd or initramfs, which contains an insmod executable - if the
kernel can't find an insmod to run, no user process is created, and
the problem doesn't occur.  If an insmod is found, a process is
created to run it, which will inherit the kernel portion of the
swapper_pg_dir first level page table. It doesn't matter whether the
inmod is successful or not, but when the the kernel scheduler context
switches back to the kernel initialisation thread, the insmod's mm is
'borrowed' by the kernel thread, as it doesn't have an address space
of its own. (Reference counting is used to ensure this mm is not
destroyed, even though the user process which caused its creation may no
longer exist.) If this address space doesn't have a first level page
table entry for the consistent mappings, and a driver tries to access
such a mapping, we are in the same situation as described above,
except this time in a kernel thread rather than a user thread
executing inside the kernel.

See bugzilla: 15425, 15836, 15862, 16106, 16793

Signed-off-by: Stuart Menefy &lt;stuart.menefy@st.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The problem is caused by the interaction of two features in the Linux
memory management code.

A processes address space is described by a struct mm_struct, and
every thread has a pointer to the mm it should run in. The exception
to this are kernel threads, which don't have an mm, and so borrow
the mm from the last thread which ran. The system is bootstrapped
by the initial kernel thread using init's mm (even though init hasn't
been created yet, its mm is the static init_mm).

The other feature is how the kernel handles the page table which
describes the portion of the address space which is only visible when
executing inside the kernel, and which is shared by all threads. On
the SH4 the only portion of the kernel's address space which described
using the page table is called P3, from 0xc0000000 to 0xdfffffff. This
portion of the address space is divided into three:
  - mappings for dma_alloc_coherent()
  - mappings for vmalloc() and ioremap()
  - fixmap mappings, primarily used in copy_user_pages() to create
    kernel mappings of user pages with the correct cache colour.

To optimise the TLB miss handler we don't want to add an additional
condition which checks whether the faulting address is in the user or
the kernel portion of the address space, and so all page tables have a
common portion which describes the kernel part of the address
space. As the SH4 uses a two level page table, only the kernel portion
of first level page table (the pgd entries) is duplicated. These all
point to the same second level entries (the pte's), and so no memory
is wasted.

The reference page table for the kernel is called the swapper_pg_dir,
and when a new page table is created for a new process the kernel
portion of the page table is copied from swapper_pg_dir. This works
fine when changes only occur in the second level of the kernel's page
table, or the first level entries are created before any new user
processes. However if a change occurs to the first level of the page
table, and there are existing processes which don't have this entry in
their page table, this new entry needs to be added. This is done on
demand, when the kernel accesses a P3 address which isn't mapped using
the current page table, the code in vmalloc_fault() copies the entry
from the reference page table (swapper_pg_dir) into the current
processes page table.

The bug which this patch addresses is that the code in vmalloc_fault()
was not copying addresses which fell in the dma_alloc_coherent()
portion of the address space, and it should have been copying any P3
address.

Why we hadn't seen this before, and what made this hard to reproduce,
is that normally the kernel will have called dma_alloc_coherent(), and
accessed the memory mapping created, before any user process
runs. Typically drivers such as USB or SATA will have created and used
mappings of this type during the kernel initialisation, when probing
for the attached devices, before init runs. Ethernet is slightly
different, as it normally only creates and accesses
dma_alloc_coherent() mappings when the network is brought up, but if
kernel level IP configuration is used this will also occur before any
user space process runs. So the first reproduction of this problem
which we saw was occurred when USB and SATA were removed from the
kernel, and then bring up Ethernet from user space using ifconfig.
I'd like to thank Joseph Bormolini who did the hard work reducing the
problem to this simple to reproduce criteria.

In your case the situation is slightly different, and turns out to
depends on the exact kernel configuration (which we had) and your
ramdisk contents (which we didn't - hence the need for some assumptions).

In this case the problem is a side effect of kernel level module
loading. Kernel subsystems sometimes trigger the load of kernel
modules directly, for example the crypto subsystem tries to load the
cryptomgr and MTD tries to load modules for Flash partitioning if
these are not built into the kernel. This is done by the kernel
creating a user process which runs insmod to try and load the
appropriate module.

In order for this to cause problems the system must be running with a
initrd or initramfs, which contains an insmod executable - if the
kernel can't find an insmod to run, no user process is created, and
the problem doesn't occur.  If an insmod is found, a process is
created to run it, which will inherit the kernel portion of the
swapper_pg_dir first level page table. It doesn't matter whether the
inmod is successful or not, but when the the kernel scheduler context
switches back to the kernel initialisation thread, the insmod's mm is
'borrowed' by the kernel thread, as it doesn't have an address space
of its own. (Reference counting is used to ensure this mm is not
destroyed, even though the user process which caused its creation may no
longer exist.) If this address space doesn't have a first level page
table entry for the consistent mappings, and a driver tries to access
such a mapping, we are in the same situation as described above,
except this time in a kernel thread rather than a user thread
executing inside the kernel.

See bugzilla: 15425, 15836, 15862, 16106, 16793

Signed-off-by: Stuart Menefy &lt;stuart.menefy@st.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'sh-for-linus' of git://github.com/pmundt/linux-sh</title>
<updated>2012-04-07T16:52:46+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-04-07T16:52:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=664481ed45cdbda2ab853ddd3c2690b69aca9103'/>
<id>664481ed45cdbda2ab853ddd3c2690b69aca9103</id>
<content type='text'>
Pull SuperH fixes from Paul Mundt.

* tag 'sh-for-linus' of git://github.com/pmundt/linux-sh:
  sh: fix clock-sh7757 for the latest sh_mobile_sdhi driver
  serial: sh-sci: use serial_port_in/out vs sci_in/out.
  sh: vsyscall: Fix up .eh_frame generation.
  sh: dma: Fix up device attribute mismatch from sysdev fallout.
  sh: dwarf unwinder depends on SHcompact.
  sh: fix up fallout from system.h disintegration.
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull SuperH fixes from Paul Mundt.

* tag 'sh-for-linus' of git://github.com/pmundt/linux-sh:
  sh: fix clock-sh7757 for the latest sh_mobile_sdhi driver
  serial: sh-sci: use serial_port_in/out vs sci_in/out.
  sh: vsyscall: Fix up .eh_frame generation.
  sh: dma: Fix up device attribute mismatch from sysdev fallout.
  sh: dwarf unwinder depends on SHcompact.
  sh: fix up fallout from system.h disintegration.
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-linus' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping</title>
<updated>2012-04-05T00:13:43+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-04-05T00:13:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=58bca4a8fa90fcf9069379653b396b2cec642f7f'/>
<id>58bca4a8fa90fcf9069379653b396b2cec642f7f</id>
<content type='text'>
Pull DMA mapping branch from Marek Szyprowski:
 "Short summary for the whole series:

  A few limitations have been identified in the current dma-mapping
  design and its implementations for various architectures.  There exist
  more than one function for allocating and freeing the buffers:
  currently these 3 are used dma_{alloc, free}_coherent,
  dma_{alloc,free}_writecombine, dma_{alloc,free}_noncoherent.

  For most of the systems these calls are almost equivalent and can be
  interchanged.  For others, especially the truly non-coherent ones
  (like ARM), the difference can be easily noticed in overall driver
  performance.  Sadly not all architectures provide implementations for
  all of them, so the drivers might need to be adapted and cannot be
  easily shared between different architectures.  The provided patches
  unify all these functions and hide the differences under the already
  existing dma attributes concept.  The thread with more references is
  available here:

    http://www.spinics.net/lists/linux-sh/msg09777.html

  These patches are also a prerequisite for unifying DMA-mapping
  implementation on ARM architecture with the common one provided by
  dma_map_ops structure and extending it with IOMMU support.  More
  information is available in the following thread:

    http://thread.gmane.org/gmane.linux.kernel.cross-arch/12819

  More works on dma-mapping framework are planned, especially in the
  area of buffer sharing and managing the shared mappings (together with
  the recently introduced dma_buf interface: commit d15bd7ee445d
  "dma-buf: Introduce dma buffer sharing mechanism").

  The patches in the current set introduce a new alloc/free methods
  (with support for memory attributes) in dma_map_ops structure, which
  will later replace dma_alloc_coherent and dma_alloc_writecombine
  functions."

People finally started piping up with support for merging this, so I'm
merging it as the last of the pending stuff from the merge window.
Looks like pohmelfs is going to wait for 3.5 and more external support
for merging.

* 'for-linus' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping:
  common: DMA-mapping: add NON-CONSISTENT attribute
  common: DMA-mapping: add WRITE_COMBINE attribute
  common: dma-mapping: introduce mmap method
  common: dma-mapping: remove old alloc_coherent and free_coherent methods
  Hexagon: adapt for dma_map_ops changes
  Unicore32: adapt for dma_map_ops changes
  Microblaze: adapt for dma_map_ops changes
  SH: adapt for dma_map_ops changes
  Alpha: adapt for dma_map_ops changes
  SPARC: adapt for dma_map_ops changes
  PowerPC: adapt for dma_map_ops changes
  MIPS: adapt for dma_map_ops changes
  X86 &amp; IA64: adapt for dma_map_ops changes
  common: dma-mapping: introduce generic alloc() and free() methods
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull DMA mapping branch from Marek Szyprowski:
 "Short summary for the whole series:

  A few limitations have been identified in the current dma-mapping
  design and its implementations for various architectures.  There exist
  more than one function for allocating and freeing the buffers:
  currently these 3 are used dma_{alloc, free}_coherent,
  dma_{alloc,free}_writecombine, dma_{alloc,free}_noncoherent.

  For most of the systems these calls are almost equivalent and can be
  interchanged.  For others, especially the truly non-coherent ones
  (like ARM), the difference can be easily noticed in overall driver
  performance.  Sadly not all architectures provide implementations for
  all of them, so the drivers might need to be adapted and cannot be
  easily shared between different architectures.  The provided patches
  unify all these functions and hide the differences under the already
  existing dma attributes concept.  The thread with more references is
  available here:

    http://www.spinics.net/lists/linux-sh/msg09777.html

  These patches are also a prerequisite for unifying DMA-mapping
  implementation on ARM architecture with the common one provided by
  dma_map_ops structure and extending it with IOMMU support.  More
  information is available in the following thread:

    http://thread.gmane.org/gmane.linux.kernel.cross-arch/12819

  More works on dma-mapping framework are planned, especially in the
  area of buffer sharing and managing the shared mappings (together with
  the recently introduced dma_buf interface: commit d15bd7ee445d
  "dma-buf: Introduce dma buffer sharing mechanism").

  The patches in the current set introduce a new alloc/free methods
  (with support for memory attributes) in dma_map_ops structure, which
  will later replace dma_alloc_coherent and dma_alloc_writecombine
  functions."

People finally started piping up with support for merging this, so I'm
merging it as the last of the pending stuff from the merge window.
Looks like pohmelfs is going to wait for 3.5 and more external support
for merging.

* 'for-linus' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping:
  common: DMA-mapping: add NON-CONSISTENT attribute
  common: DMA-mapping: add WRITE_COMBINE attribute
  common: dma-mapping: introduce mmap method
  common: dma-mapping: remove old alloc_coherent and free_coherent methods
  Hexagon: adapt for dma_map_ops changes
  Unicore32: adapt for dma_map_ops changes
  Microblaze: adapt for dma_map_ops changes
  SH: adapt for dma_map_ops changes
  Alpha: adapt for dma_map_ops changes
  SPARC: adapt for dma_map_ops changes
  PowerPC: adapt for dma_map_ops changes
  MIPS: adapt for dma_map_ops changes
  X86 &amp; IA64: adapt for dma_map_ops changes
  common: dma-mapping: introduce generic alloc() and free() methods
</pre>
</div>
</content>
</entry>
<entry>
<title>sh: fix clock-sh7757 for the latest sh_mobile_sdhi driver</title>
<updated>2012-04-04T15:06:35+00:00</updated>
<author>
<name>Shimoda, Yoshihiro</name>
<email>yoshihiro.shimoda.uh@renesas.com</email>
</author>
<published>2012-04-04T02:56:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=a052d2c31b7b87e9b4bdee634af666b5e830e56f'/>
<id>a052d2c31b7b87e9b4bdee634af666b5e830e56f</id>
<content type='text'>
The commit 996bc8aebd2cd5b6d4c5d85085f171fa2447f364 (mmc: sh_mobile_sdhi:
do not manage PM clocks manually) modified the sh_mobile_sdhi driver to
remove the clk_enable/clk_disable. So, we need to change
the "CLKDEV_CON_ID" to "CLKDEV_DEV_ID".

If we don't change this, we will see the following error from the driver:
    sh_mobile_sdhi sh_mobile_sdhi.0: timeout waiting for hardware interrupt (CMD52)

Signed-off-by: Yoshihiro Shimoda &lt;yoshihiro.shimoda.uh@renesas.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The commit 996bc8aebd2cd5b6d4c5d85085f171fa2447f364 (mmc: sh_mobile_sdhi:
do not manage PM clocks manually) modified the sh_mobile_sdhi driver to
remove the clk_enable/clk_disable. So, we need to change
the "CLKDEV_CON_ID" to "CLKDEV_DEV_ID".

If we don't change this, we will see the following error from the driver:
    sh_mobile_sdhi sh_mobile_sdhi.0: timeout waiting for hardware interrupt (CMD52)

Signed-off-by: Yoshihiro Shimoda &lt;yoshihiro.shimoda.uh@renesas.com&gt;
Signed-off-by: Paul Mundt &lt;lethal@linux-sh.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild</title>
<updated>2012-03-31T01:15:43+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2012-03-31T01:15:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=923f79743c76583ed4684e2c80c8da51a7268af3'/>
<id>923f79743c76583ed4684e2c80c8da51a7268af3</id>
<content type='text'>
Pull kbuild changes from Michal Marek:
 - Unification of cmd_uimage among archs that use it
 - make headers_check tries harder before reporting a missing
   &lt;linux/types.h&gt; include
 - kbuild portability fix for shells that do not support echo -e
 - make clean descends into samples/
 - setlocalversion grep fix
 - modpost typo fix
 - dtc warnings fix

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  setlocalversion: Use "grep -q" instead of piping output to "read dummy"
  modpost: fix ALL_INIT_DATA_SECTIONS
  Kbuild: centralize MKIMAGE and cmd_uimage definitions
  headers_check: recursively search for linux/types.h inclusion
  scripts/Kbuild.include: Fix portability problem of "echo -e"
  scripts: dtc: fix compile warnings
  kbuild: clean up samples directory
  kbuild: disable -Wmissing-field-initializers for W=1
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull kbuild changes from Michal Marek:
 - Unification of cmd_uimage among archs that use it
 - make headers_check tries harder before reporting a missing
   &lt;linux/types.h&gt; include
 - kbuild portability fix for shells that do not support echo -e
 - make clean descends into samples/
 - setlocalversion grep fix
 - modpost typo fix
 - dtc warnings fix

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  setlocalversion: Use "grep -q" instead of piping output to "read dummy"
  modpost: fix ALL_INIT_DATA_SECTIONS
  Kbuild: centralize MKIMAGE and cmd_uimage definitions
  headers_check: recursively search for linux/types.h inclusion
  scripts/Kbuild.include: Fix portability problem of "echo -e"
  scripts: dtc: fix compile warnings
  kbuild: clean up samples directory
  kbuild: disable -Wmissing-field-initializers for W=1
</pre>
</div>
</content>
</entry>
</feed>
