<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/arch/alpha, branch v4.9.296</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>alpha: Declare virt_to_phys and virt_to_bus parameter as pointer to volatile</title>
<updated>2021-10-06T08:23:40+00:00</updated>
<author>
<name>Guenter Roeck</name>
<email>linux@roeck-us.net</email>
</author>
<published>2021-09-09T05:00:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=41f997233cc8f64dc9519cd6f1f4102c67cfde5d'/>
<id>41f997233cc8f64dc9519cd6f1f4102c67cfde5d</id>
<content type='text'>
[ Upstream commit 35a3f4ef0ab543daa1725b0c963eb8c05e3376f8 ]

Some drivers pass a pointer to volatile data to virt_to_bus() and
virt_to_phys(), and that works fine.  One exception is alpha.  This
results in a number of compile errors such as

  drivers/net/wan/lmc/lmc_main.c: In function 'lmc_softreset':
  drivers/net/wan/lmc/lmc_main.c:1782:50: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

  drivers/atm/ambassador.c: In function 'do_loader_command':
  drivers/atm/ambassador.c:1747:58: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

Declare the parameter of virt_to_phys and virt_to_bus as pointer to
volatile to fix the problem.

Signed-off-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit 35a3f4ef0ab543daa1725b0c963eb8c05e3376f8 ]

Some drivers pass a pointer to volatile data to virt_to_bus() and
virt_to_phys(), and that works fine.  One exception is alpha.  This
results in a number of compile errors such as

  drivers/net/wan/lmc/lmc_main.c: In function 'lmc_softreset':
  drivers/net/wan/lmc/lmc_main.c:1782:50: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

  drivers/atm/ambassador.c: In function 'do_loader_command':
  drivers/atm/ambassador.c:1747:58: error:
	passing argument 1 of 'virt_to_bus' discards 'volatile'
	qualifier from pointer target type

Declare the parameter of virt_to_phys and virt_to_bus as pointer to
volatile to fix the problem.

Signed-off-by: Guenter Roeck &lt;linux@roeck-us.net&gt;
Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: Send stop IPI to send to online CPUs</title>
<updated>2021-08-15T11:01:04+00:00</updated>
<author>
<name>Prarit Bhargava</name>
<email>prarit@redhat.com</email>
</author>
<published>2021-01-05T15:16:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=605ab007767ab46e4dc74a61cf8bb6cf59284116'/>
<id>605ab007767ab46e4dc74a61cf8bb6cf59284116</id>
<content type='text'>
[ Upstream commit caace6ca4e06f09413fb8f8a63319594cfb7d47d ]

This issue was noticed while debugging a shutdown issue where some
secondary CPUs are not being shutdown correctly.  A fix for that [1] requires
that secondary cpus be offlined using the cpu_online_mask so that the
stop operation is a no-op if CPU HOTPLUG is disabled.  I, like the author in
[1] looked at the architectures and found that alpha is one of two
architectures that executes smp_send_stop() on all possible CPUs.

On alpha, smp_send_stop() sends an IPI to all possible CPUs but only needs
to send them to online CPUs.

Send the stop IPI to only the online CPUs.

[1] https://lkml.org/lkml/2020/1/10/250

Signed-off-by: Prarit Bhargava &lt;prarit@redhat.com&gt;
Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit caace6ca4e06f09413fb8f8a63319594cfb7d47d ]

This issue was noticed while debugging a shutdown issue where some
secondary CPUs are not being shutdown correctly.  A fix for that [1] requires
that secondary cpus be offlined using the cpu_online_mask so that the
stop operation is a no-op if CPU HOTPLUG is disabled.  I, like the author in
[1] looked at the architectures and found that alpha is one of two
architectures that executes smp_send_stop() on all possible CPUs.

On alpha, smp_send_stop() sends an IPI to all possible CPUs but only needs
to send them to online CPUs.

Send the stop IPI to only the online CPUs.

[1] https://lkml.org/lkml/2020/1/10/250

Signed-off-by: Prarit Bhargava &lt;prarit@redhat.com&gt;
Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: switch __copy_user() and __do_clean_user() to normal calling conventions</title>
<updated>2021-03-17T15:10:18+00:00</updated>
<author>
<name>Al Viro</name>
<email>viro@zeniv.linux.org.uk</email>
</author>
<published>2016-12-25T01:26:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=4e7957e21602aa284d4c12f1de76359aa758f85e'/>
<id>4e7957e21602aa284d4c12f1de76359aa758f85e</id>
<content type='text'>
commit 8525023121de4848b5f0a7d867ffeadbc477774d upstream.

They used to need odd calling conventions due to old exception handling
mechanism, the last remnants of which had disappeared back in 2002.

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&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 8525023121de4848b5f0a7d867ffeadbc477774d upstream.

They used to need odd calling conventions due to old exception handling
mechanism, the last remnants of which had disappeared back in 2002.

Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: Package string routines together</title>
<updated>2021-03-17T15:10:18+00:00</updated>
<author>
<name>Richard Henderson</name>
<email>rth@twiddle.net</email>
</author>
<published>2017-06-23T21:20:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=8d8f9b3df7d32e2eb358bb34c42ca603c20b705e'/>
<id>8d8f9b3df7d32e2eb358bb34c42ca603c20b705e</id>
<content type='text'>
commit 4758ce82e66711b1a4557577e30a5f9b88d4a4b5 upstream.

There are direct branches between {str*cpy,str*cat} and stx*cpy.
Ensure the branches are within range by merging these objects.

Signed-off-by: Richard Henderson &lt;rth@twiddle.net&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&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 4758ce82e66711b1a4557577e30a5f9b88d4a4b5 upstream.

There are direct branches between {str*cpy,str*cat} and stx*cpy.
Ensure the branches are within range by merging these objects.

Signed-off-by: Richard Henderson &lt;rth@twiddle.net&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: make short build log available for division routines</title>
<updated>2021-03-17T15:10:18+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2016-09-11T07:42:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=d7a8d0240331e3efd3022f4e49f7fdbff6b6be75'/>
<id>d7a8d0240331e3efd3022f4e49f7fdbff6b6be75</id>
<content type='text'>
commit 3eec0291830e4c28d09f73bab247f3b59172022b upstream.

This enables the Kbuild standard log style as follows:

  AS      arch/alpha/lib/__divlu.o
  AS      arch/alpha/lib/__divqu.o
  AS      arch/alpha/lib/__remlu.o
  AS      arch/alpha/lib/__remqu.o

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&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 3eec0291830e4c28d09f73bab247f3b59172022b upstream.

This enables the Kbuild standard log style as follows:

  AS      arch/alpha/lib/__divlu.o
  AS      arch/alpha/lib/__divqu.o
  AS      arch/alpha/lib/__remlu.o
  AS      arch/alpha/lib/__remqu.o

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: merge build rules of division routines</title>
<updated>2021-03-17T15:10:18+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2016-09-11T07:42:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=83306862879f01d6365e6a5361156a354b0c91f8'/>
<id>83306862879f01d6365e6a5361156a354b0c91f8</id>
<content type='text'>
commit e19a4e3f1bffe45b8e2ea67fcfb0c9c88278c4cc upstream.

These four objects are generated by the same build rule, with
different compile options.  The build rules can be merged.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&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 e19a4e3f1bffe45b8e2ea67fcfb0c9c88278c4cc upstream.

These four objects are generated by the same build rule, with
different compile options.  The build rules can be merged.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: add $(src)/ rather than $(obj)/ to make source file path</title>
<updated>2021-03-17T15:10:18+00:00</updated>
<author>
<name>Masahiro Yamada</name>
<email>yamada.masahiro@socionext.com</email>
</author>
<published>2016-09-11T07:42:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=721e7cd6c56abe7d5696695e38ec4a77c631c3bd'/>
<id>721e7cd6c56abe7d5696695e38ec4a77c631c3bd</id>
<content type='text'>
commit 5ed78e5523fd9ba77b8444d380d54da1f88c53fc upstream.

$(ev6-y)divide.S is a source file, not a build-time generated file.
So, it should be prefixed with $(src)/ rather than $(obj)/.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&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 5ed78e5523fd9ba77b8444d380d54da1f88c53fc upstream.

$(ev6-y)divide.S is a source file, not a build-time generated file.
So, it should be prefixed with $(src)/ rather than $(obj)/.

Signed-off-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Cc: Guenter Roeck &lt;linux@roeck-us.net&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: fix annotation of io{read,write}{16,32}be()</title>
<updated>2020-08-26T08:29:05+00:00</updated>
<author>
<name>Luc Van Oostenryck</name>
<email>luc.vanoostenryck@gmail.com</email>
</author>
<published>2020-08-12T01:33:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=cc0c6b17f948bd40862ea8db34e0e46741d995fb'/>
<id>cc0c6b17f948bd40862ea8db34e0e46741d995fb</id>
<content type='text'>
[ Upstream commit bd72866b8da499e60633ff28f8a4f6e09ca78efe ]

These accessors must be used to read/write a big-endian bus.  The value
returned or written is native-endian.

However, these accessors are defined using be{16,32}_to_cpu() or
cpu_to_be{16,32}() to make the endian conversion but these expect a
__be{16,32} when none is present.  Keeping them would need a force cast
that would solve nothing at all.

So, do the conversion using swab{16,32}, like done in asm-generic for
similar situations.

Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Signed-off-by: Luc Van Oostenryck &lt;luc.vanoostenryck@gmail.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Cc: Matt Turner &lt;mattst88@gmail.com&gt;
Cc: Stephen Boyd &lt;sboyd@kernel.org&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Link: http://lkml.kernel.org/r/20200622114232.80039-1-luc.vanoostenryck@gmail.com
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
[ Upstream commit bd72866b8da499e60633ff28f8a4f6e09ca78efe ]

These accessors must be used to read/write a big-endian bus.  The value
returned or written is native-endian.

However, these accessors are defined using be{16,32}_to_cpu() or
cpu_to_be{16,32}() to make the endian conversion but these expect a
__be{16,32} when none is present.  Keeping them would need a force cast
that would solve nothing at all.

So, do the conversion using swab{16,32}, like done in asm-generic for
similar situations.

Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Signed-off-by: Luc Van Oostenryck &lt;luc.vanoostenryck@gmail.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Cc: Matt Turner &lt;mattst88@gmail.com&gt;
Cc: Stephen Boyd &lt;sboyd@kernel.org&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Link: http://lkml.kernel.org/r/20200622114232.80039-1-luc.vanoostenryck@gmail.com
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Sasha Levin &lt;sashal@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: Fix Eiger NR_IRQS to 128</title>
<updated>2019-02-20T09:18:32+00:00</updated>
<author>
<name>Meelis Roos</name>
<email>mroos@linux.ee</email>
</author>
<published>2018-10-12T09:27:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=597613d1bcb287251e729103d595c15c45d6d35c'/>
<id>597613d1bcb287251e729103d595c15c45d6d35c</id>
<content type='text'>
commit bfc913682464f45bc4d6044084e370f9048de9d5 upstream.

Eiger machine vector definition has nr_irqs 128, and working 2.6.26
boot shows SCSI getting IRQ-s 64 and 65. Current kernel boot fails
because Symbios SCSI fails to request IRQ-s and does not find the disks.
It has been broken at least since 3.18 - the earliest I could test with
my gcc-5.

The headers have moved around and possibly another order of defines has
worked in the past - but since 128 seems to be correct and used, fix
arch/alpha/include/asm/irq.h to have NR_IRQS=128 for Eiger.

This fixes 4.19-rc7 boot on my Force Flexor A264 (Eiger subarch).

Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Meelis Roos &lt;mroos@linux.ee&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&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 bfc913682464f45bc4d6044084e370f9048de9d5 upstream.

Eiger machine vector definition has nr_irqs 128, and working 2.6.26
boot shows SCSI getting IRQ-s 64 and 65. Current kernel boot fails
because Symbios SCSI fails to request IRQ-s and does not find the disks.
It has been broken at least since 3.18 - the earliest I could test with
my gcc-5.

The headers have moved around and possibly another order of defines has
worked in the past - but since 128 seems to be correct and used, fix
arch/alpha/include/asm/irq.h to have NR_IRQS=128 for Eiger.

This fixes 4.19-rc7 boot on my Force Flexor A264 (Eiger subarch).

Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Meelis Roos &lt;mroos@linux.ee&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>alpha: fix page fault handling for r16-r18 targets</title>
<updated>2019-02-20T09:18:32+00:00</updated>
<author>
<name>Sergei Trofimovich</name>
<email>slyfox@gentoo.org</email>
</author>
<published>2018-12-31T11:53:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7ef531f45fdb53ea34beb3800182cabc1e28dce2'/>
<id>7ef531f45fdb53ea34beb3800182cabc1e28dce2</id>
<content type='text'>
commit 491af60ffb848b59e82f7c9145833222e0bf27a5 upstream.

Fix page fault handling code to fixup r16-r18 registers.
Before the patch code had off-by-two registers bug.
This bug caused overwriting of ps,pc,gp registers instead
of fixing intended r16,r17,r18 (see `struct pt_regs`).

More details:

Initially Dmitry noticed a kernel bug as a failure
on strace test suite. Test passes unmapped userspace
pointer to io_submit:

```c
    #include &lt;err.h&gt;
    #include &lt;unistd.h&gt;
    #include &lt;sys/mman.h&gt;
    #include &lt;asm/unistd.h&gt;
    int main(void)
    {
        unsigned long ctx = 0;
        if (syscall(__NR_io_setup, 1, &amp;ctx))
            err(1, "io_setup");
        const size_t page_size = sysconf(_SC_PAGESIZE);
        const size_t size = page_size * 2;
        void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        if (MAP_FAILED == ptr)
            err(1, "mmap(%zu)", size);
        if (munmap(ptr, size))
            err(1, "munmap");
        syscall(__NR_io_submit, ctx, 1, ptr + page_size);
        syscall(__NR_io_destroy, ctx);
        return 0;
    }
```

Running this test causes kernel to crash when handling page fault:

```
    Unable to handle kernel paging request at virtual address ffffffffffff9468
    CPU 3
    aio(26027): Oops 0
    pc = [&lt;fffffc00004eddf8&gt;]  ra = [&lt;fffffc00004edd5c&gt;]  ps = 0000    Not tainted
    pc is at sys_io_submit+0x108/0x200
    ra is at sys_io_submit+0x6c/0x200
    v0 = fffffc00c58e6300  t0 = fffffffffffffff2  t1 = 000002000025e000
    t2 = fffffc01f159fef8  t3 = fffffc0001009640  t4 = fffffc0000e0f6e0
    t5 = 0000020001002e9e  t6 = 4c41564e49452031  t7 = fffffc01f159c000
    s0 = 0000000000000002  s1 = 000002000025e000  s2 = 0000000000000000
    s3 = 0000000000000000  s4 = 0000000000000000  s5 = fffffffffffffff2
    s6 = fffffc00c58e6300
    a0 = fffffc00c58e6300  a1 = 0000000000000000  a2 = 000002000025e000
    a3 = 00000200001ac260  a4 = 00000200001ac1e8  a5 = 0000000000000001
    t8 = 0000000000000008  t9 = 000000011f8bce30  t10= 00000200001ac440
    t11= 0000000000000000  pv = fffffc00006fd320  at = 0000000000000000
    gp = 0000000000000000  sp = 00000000265fd174
    Disabling lock debugging due to kernel taint
    Trace:
    [&lt;fffffc0000311404&gt;] entSys+0xa4/0xc0
```

Here `gp` has invalid value. `gp is s overwritten by a fixup for the
following page fault handler in `io_submit` syscall handler:

```
    __se_sys_io_submit
    ...
        ldq     a1,0(t1)
        bne     t0,4280 &lt;__se_sys_io_submit+0x180&gt;
```

After a page fault `t0` should contain -EFALUT and `a1` is 0.
Instead `gp` was overwritten in place of `a1`.

This happens due to a off-by-two bug in `dpf_reg()` for `r16-r18`
(aka `a0-a2`).

I think the bug went unnoticed for a long time as `gp` is one
of scratch registers. Any kernel function call would re-calculate `gp`.

Dmitry tracked down the bug origin back to 2.1.32 kernel version
where trap_a{0,1,2} fields were inserted into struct pt_regs.
And even before that `dpf_reg()` contained off-by-one error.

Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reported-and-reviewed-by: "Dmitry V. Levin" &lt;ldv@altlinux.org&gt;
Cc: stable@vger.kernel.org # v2.1.32+
Bug: https://bugs.gentoo.org/672040
Signed-off-by: Sergei Trofimovich &lt;slyfox@gentoo.org&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&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 491af60ffb848b59e82f7c9145833222e0bf27a5 upstream.

Fix page fault handling code to fixup r16-r18 registers.
Before the patch code had off-by-two registers bug.
This bug caused overwriting of ps,pc,gp registers instead
of fixing intended r16,r17,r18 (see `struct pt_regs`).

More details:

Initially Dmitry noticed a kernel bug as a failure
on strace test suite. Test passes unmapped userspace
pointer to io_submit:

```c
    #include &lt;err.h&gt;
    #include &lt;unistd.h&gt;
    #include &lt;sys/mman.h&gt;
    #include &lt;asm/unistd.h&gt;
    int main(void)
    {
        unsigned long ctx = 0;
        if (syscall(__NR_io_setup, 1, &amp;ctx))
            err(1, "io_setup");
        const size_t page_size = sysconf(_SC_PAGESIZE);
        const size_t size = page_size * 2;
        void *ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        if (MAP_FAILED == ptr)
            err(1, "mmap(%zu)", size);
        if (munmap(ptr, size))
            err(1, "munmap");
        syscall(__NR_io_submit, ctx, 1, ptr + page_size);
        syscall(__NR_io_destroy, ctx);
        return 0;
    }
```

Running this test causes kernel to crash when handling page fault:

```
    Unable to handle kernel paging request at virtual address ffffffffffff9468
    CPU 3
    aio(26027): Oops 0
    pc = [&lt;fffffc00004eddf8&gt;]  ra = [&lt;fffffc00004edd5c&gt;]  ps = 0000    Not tainted
    pc is at sys_io_submit+0x108/0x200
    ra is at sys_io_submit+0x6c/0x200
    v0 = fffffc00c58e6300  t0 = fffffffffffffff2  t1 = 000002000025e000
    t2 = fffffc01f159fef8  t3 = fffffc0001009640  t4 = fffffc0000e0f6e0
    t5 = 0000020001002e9e  t6 = 4c41564e49452031  t7 = fffffc01f159c000
    s0 = 0000000000000002  s1 = 000002000025e000  s2 = 0000000000000000
    s3 = 0000000000000000  s4 = 0000000000000000  s5 = fffffffffffffff2
    s6 = fffffc00c58e6300
    a0 = fffffc00c58e6300  a1 = 0000000000000000  a2 = 000002000025e000
    a3 = 00000200001ac260  a4 = 00000200001ac1e8  a5 = 0000000000000001
    t8 = 0000000000000008  t9 = 000000011f8bce30  t10= 00000200001ac440
    t11= 0000000000000000  pv = fffffc00006fd320  at = 0000000000000000
    gp = 0000000000000000  sp = 00000000265fd174
    Disabling lock debugging due to kernel taint
    Trace:
    [&lt;fffffc0000311404&gt;] entSys+0xa4/0xc0
```

Here `gp` has invalid value. `gp is s overwritten by a fixup for the
following page fault handler in `io_submit` syscall handler:

```
    __se_sys_io_submit
    ...
        ldq     a1,0(t1)
        bne     t0,4280 &lt;__se_sys_io_submit+0x180&gt;
```

After a page fault `t0` should contain -EFALUT and `a1` is 0.
Instead `gp` was overwritten in place of `a1`.

This happens due to a off-by-two bug in `dpf_reg()` for `r16-r18`
(aka `a0-a2`).

I think the bug went unnoticed for a long time as `gp` is one
of scratch registers. Any kernel function call would re-calculate `gp`.

Dmitry tracked down the bug origin back to 2.1.32 kernel version
where trap_a{0,1,2} fields were inserted into struct pt_regs.
And even before that `dpf_reg()` contained off-by-one error.

Cc: Richard Henderson &lt;rth@twiddle.net&gt;
Cc: Ivan Kokshaysky &lt;ink@jurassic.park.msu.ru&gt;
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reported-and-reviewed-by: "Dmitry V. Levin" &lt;ldv@altlinux.org&gt;
Cc: stable@vger.kernel.org # v2.1.32+
Bug: https://bugs.gentoo.org/672040
Signed-off-by: Sergei Trofimovich &lt;slyfox@gentoo.org&gt;
Signed-off-by: Matt Turner &lt;mattst88@gmail.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</pre>
</div>
</content>
</entry>
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