From: 'Greg KH'
> Sent: 02 November 2020 13:52
>
> On Mon, Nov 02, 2020 at 09:06:38AM +, David Laight wrote:
> > From: 'Greg KH'
> > > Sent: 23 October 2020 15:47
> > >
> > > On Fri, Oct 23, 2020 at 02:39:24PM +, David Laight wrote:
> > > > From: David Hildenbrand
> > > > > Sent: 23
On Mon, Nov 02, 2020 at 09:06:38AM +, David Laight wrote:
> From: 'Greg KH'
> > Sent: 23 October 2020 15:47
> >
> > On Fri, Oct 23, 2020 at 02:39:24PM +, David Laight wrote:
> > > From: David Hildenbrand
> > > > Sent: 23 October 2020 15:33
> > > ...
> > > > I just checked against upstream
From: 'Greg KH'
> Sent: 23 October 2020 15:47
>
> On Fri, Oct 23, 2020 at 02:39:24PM +, David Laight wrote:
> > From: David Hildenbrand
> > > Sent: 23 October 2020 15:33
> > ...
> > > I just checked against upstream code generated by clang 10 and it
> > > properly discards the upper 32bit via
From: Segher Boessenkool
> Sent: 24 October 2020 18:29
>
> On Fri, Oct 23, 2020 at 09:28:59PM +, David Laight wrote:
> > From: Segher Boessenkool
> > > Sent: 23 October 2020 19:27
> > > On Fri, Oct 23, 2020 at 06:58:57PM +0100, Al Viro wrote:
> > > > On Fri, Oct 23, 2020 at 03:09:30PM +0200,
On Fri, Oct 23, 2020 at 09:28:59PM +, David Laight wrote:
> From: Segher Boessenkool
> > Sent: 23 October 2020 19:27
> > On Fri, Oct 23, 2020 at 06:58:57PM +0100, Al Viro wrote:
> > > On Fri, Oct 23, 2020 at 03:09:30PM +0200, David Hildenbrand wrote:
> > > On arm64 when callee expects a 32bit
From: Segher Boessenkool
> Sent: 23 October 2020 19:27
>
> On Fri, Oct 23, 2020 at 06:58:57PM +0100, Al Viro wrote:
> > On Fri, Oct 23, 2020 at 03:09:30PM +0200, David Hildenbrand wrote:
> >
> > > Now, I am not a compiler expert, but as I already cited, at least on
> > > x86-64 clang expects that
On Fri, Oct 23, 2020 at 06:58:57PM +0100, Al Viro wrote:
> On Fri, Oct 23, 2020 at 03:09:30PM +0200, David Hildenbrand wrote:
>
> > Now, I am not a compiler expert, but as I already cited, at least on
> > x86-64 clang expects that the high bits were cleared by the caller - in
> > contrast to gcc.
On Fri, Oct 23, 2020 at 03:09:30PM +0200, David Hildenbrand wrote:
> Now, I am not a compiler expert, but as I already cited, at least on
> x86-64 clang expects that the high bits were cleared by the caller - in
> contrast to gcc. I suspect it's the same on arm64, but again, I am no
> compiler
On 23.10.20 16:47, 'Greg KH' wrote:
> On Fri, Oct 23, 2020 at 02:39:24PM +, David Laight wrote:
>> From: David Hildenbrand
>>> Sent: 23 October 2020 15:33
>> ...
>>> I just checked against upstream code generated by clang 10 and it
>>> properly discards the upper 32bit via a mov w23 w2.
>>>
On Fri, Oct 23, 2020 at 02:39:24PM +, David Laight wrote:
> From: David Hildenbrand
> > Sent: 23 October 2020 15:33
> ...
> > I just checked against upstream code generated by clang 10 and it
> > properly discards the upper 32bit via a mov w23 w2.
> >
> > So at least clang 10 indeed properly
From: David Hildenbrand
> Sent: 23 October 2020 15:33
...
> I just checked against upstream code generated by clang 10 and it
> properly discards the upper 32bit via a mov w23 w2.
>
> So at least clang 10 indeed properly assumes we could have garbage and
> masks it off.
>
> Maybe the issue is
On 23.10.20 15:09, David Hildenbrand wrote:
> On 23.10.20 14:46, David Laight wrote:
>> From: Greg KH
>>> Sent: 22 October 2020 14:51
>>
>> I've rammed the code into godbolt.
>>
>> https://godbolt.org/z/9v5PPW
>>
>> Definitely a clang bug.
>>
>> Search for [wx]24 in the clang output.
>> nr_segs
From: Arnd Bergmann
> Sent: 23 October 2020 14:23
>
> On Fri, Oct 23, 2020 at 2:46 PM David Laight wrote:
> >
> > From: Greg KH
> > > Sent: 22 October 2020 14:51
> >
> > I've rammed the code into godbolt.
> >
> > https://godbolt.org/z/9v5PPW
> >
> > Definitely a clang bug.
> >
> > Search for
On 22.10.20 21:24, Al Viro wrote:
> On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote:
>
>> Passing an `unsigned long` as an `unsigned int` does no such
>> narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
>> calls, no masking instructions).
>> So if
On 23.10.20 14:46, David Laight wrote:
> From: Greg KH
>> Sent: 22 October 2020 14:51
>
> I've rammed the code into godbolt.
>
> https://godbolt.org/z/9v5PPW
>
> Definitely a clang bug.
>
> Search for [wx]24 in the clang output.
> nr_segs comes in as w2 and the initial bound checks are done
From: Greg KH
> Sent: 22 October 2020 14:51
I've rammed the code into godbolt.
https://godbolt.org/z/9v5PPW
Definitely a clang bug.
Search for [wx]24 in the clang output.
nr_segs comes in as w2 and the initial bound checks are done on w2.
w24 is loaded from w2 - I don't believe this changes
From: Al Viro
> Sent: 22 October 2020 20:25
>
> On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote:
>
> > Passing an `unsigned long` as an `unsigned int` does no such
> > narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
> > calls, no masking instructions).
> > So
From: Nick Desaulniers
> Sent: 22 October 2020 20:05
>
...
> Passing an `unsigned long` as an `unsigned int` does no such
> narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
> calls, no masking instructions).
Right but is the called function going to use 32bit ops
and/or mask
On Thu, Oct 22, 2020 at 01:59:32PM -0700, Eric Biggers wrote:
> Also note the following program succeeds on Linux 5.9 on x86_64. On kernels
> that have this bug, it should fail. (I couldn't get it to actually fail, so
> it
> must depend on the compiler and/or the kernel config...)
It doesn't.
On Thu, Oct 22, 2020 at 10:00:44AM -0700, Nick Desaulniers wrote:
> On Thu, Oct 22, 2020 at 9:40 AM Matthew Wilcox wrote:
> >
> > On Thu, Oct 22, 2020 at 04:35:17PM +, David Laight wrote:
> > > Wait...
> > > readv(2) defines:
> > > ssize_t readv(int fd, const struct iovec *iov, int
On Thu, Oct 22, 2020 at 12:25 PM Al Viro wrote:
>
> On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote:
>
> > Passing an `unsigned long` as an `unsigned int` does no such
> > narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
> > calls, no masking instructions).
> >
On Thu, Oct 22, 2020 at 09:06:29PM +0100, Al Viro wrote:
> On Thu, Oct 22, 2020 at 08:24:58PM +0100, Al Viro wrote:
>
> > Depending upon the calling conventions, compiler might do truncation in
> > caller or
> > in a callee, but it must be done _somewhere_.
>
> Unless I'm misreading AAPCS64,
>
On Thu, Oct 22, 2020 at 08:24:58PM +0100, Al Viro wrote:
> Depending upon the calling conventions, compiler might do truncation in
> caller or
> in a callee, but it must be done _somewhere_.
Unless I'm misreading AAPCS64,
"Unlike in the 32-bit AAPCS, named integral values must be
On Thu, Oct 22, 2020 at 08:24:58PM +0100, Al Viro wrote:
> On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote:
>
> > Passing an `unsigned long` as an `unsigned int` does no such
> > narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
> > calls, no masking
On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote:
> Passing an `unsigned long` as an `unsigned int` does no such
> narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail
> calls, no masking instructions).
> So if rw_copy_check_uvector() is inlined into import_iovec()
On Thu, Oct 22, 2020 at 11:13 AM Arnd Bergmann wrote:
>
> On Thu, Oct 22, 2020 at 7:54 PM Nick Desaulniers
> wrote:
> > On Thu, Oct 22, 2020 at 9:35 AM David Laight
> > wrote:
> > >
> > > Which makes it a bug in the kernel C syscall wrappers.
> > > They need to explicitly mask the high bits of
On Thu, Oct 22, 2020 at 05:40:40PM +0100, Matthew Wilcox wrote:
> On Thu, Oct 22, 2020 at 04:35:17PM +, David Laight wrote:
> > Wait...
> > readv(2) defines:
> > ssize_t readv(int fd, const struct iovec *iov, int iovcnt);
>
> It doesn't really matter what the manpage says. What does the
On Thu, Oct 22, 2020 at 9:35 AM David Laight wrote:
>
> From: Christoph Hellwig
> > Sent: 22 October 2020 14:24
> >
> > On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> > > My thinking: if the compiler that calls import_iovec() has garbage in
> > > the upper 32 bit
> > >
> > >
On Thu, Oct 22, 2020 at 9:40 AM Matthew Wilcox wrote:
>
> On Thu, Oct 22, 2020 at 04:35:17PM +, David Laight wrote:
> > Wait...
> > readv(2) defines:
> > ssize_t readv(int fd, const struct iovec *iov, int iovcnt);
>
> It doesn't really matter what the manpage says. What does the AOSP
>
From: Matthew Wilcox
> Sent: 22 October 2020 17:41
>
> On Thu, Oct 22, 2020 at 04:35:17PM +, David Laight wrote:
> > Wait...
> > readv(2) defines:
> > ssize_t readv(int fd, const struct iovec *iov, int iovcnt);
>
> It doesn't really matter what the manpage says. What does the AOSP
>
On Thu, Oct 22, 2020 at 04:35:17PM +, David Laight wrote:
> Wait...
> readv(2) defines:
> ssize_t readv(int fd, const struct iovec *iov, int iovcnt);
It doesn't really matter what the manpage says. What does the AOSP
libc header say?
> But the syscall is defined as:
>
>
From: Christoph Hellwig
> Sent: 22 October 2020 14:24
>
> On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> > My thinking: if the compiler that calls import_iovec() has garbage in
> > the upper 32 bit
> >
> > a) gcc will zero it out and not rely on it being zero.
> > b) clang
From: Greg KH
> Sent: 22 October 2020 15:40
>
> On Thu, Oct 22, 2020 at 04:28:20PM +0200, Arnd Bergmann wrote:
...
> > Can you attach the iov_iter.s files from the broken build, plus the
> > one with 'noinline' for comparison? Maybe something can be seen
> > in there.
>
> I don't know how to
On Thu, Oct 22, 2020 at 04:28:20PM +0200, Arnd Bergmann wrote:
> On Thu, Oct 22, 2020 at 3:50 PM Greg KH wrote:
> > On Thu, Oct 22, 2020 at 02:57:59PM +0200, Greg KH wrote:
> > > On Thu, Oct 22, 2020 at 02:42:24PM +0200, David Hildenbrand wrote:
>
> > > > struct iovec *iovec_from_user(const
On Thu, Oct 22, 2020 at 02:57:59PM +0200, Greg KH wrote:
> On Thu, Oct 22, 2020 at 02:42:24PM +0200, David Hildenbrand wrote:
> > On 22.10.20 14:18, Greg KH wrote:
> > > On Thu, Oct 22, 2020 at 12:48:05PM +0200, Greg KH wrote:
> > >> On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand
On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> My thinking: if the compiler that calls import_iovec() has garbage in
> the upper 32 bit
>
> a) gcc will zero it out and not rely on it being zero.
> b) clang will not zero it out, assuming it is zero.
>
> But
>
> a) will zero
On Thu, Oct 22, 2020 at 02:42:24PM +0200, David Hildenbrand wrote:
> On 22.10.20 14:18, Greg KH wrote:
> > On Thu, Oct 22, 2020 at 12:48:05PM +0200, Greg KH wrote:
> >> On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> >>> On 22.10.20 11:32, David Laight wrote:
> From:
On 22.10.20 14:18, Greg KH wrote:
> On Thu, Oct 22, 2020 at 12:48:05PM +0200, Greg KH wrote:
>> On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
>>> On 22.10.20 11:32, David Laight wrote:
From: David Hildenbrand
> Sent: 22 October 2020 10:25
...
> ... especially
On Thu, Oct 22, 2020 at 12:48:05PM +0200, Greg KH wrote:
> On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> > On 22.10.20 11:32, David Laight wrote:
> > > From: David Hildenbrand
> > >> Sent: 22 October 2020 10:25
> > > ...
> > >> ... especially because I recall that clang and
On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote:
> On 22.10.20 11:32, David Laight wrote:
> > From: David Hildenbrand
> >> Sent: 22 October 2020 10:25
> > ...
> >> ... especially because I recall that clang and gcc behave slightly
> >> differently:
> >>
> >>
On 22.10.20 11:32, David Laight wrote:
> From: David Hildenbrand
>> Sent: 22 October 2020 10:25
> ...
>> ... especially because I recall that clang and gcc behave slightly
>> differently:
>>
>> https://github.com/hjl-tools/x86-psABI/issues/2
>>
>> "Function args are different: narrow types are
From: David Hildenbrand
> Sent: 22 October 2020 10:25
...
> ... especially because I recall that clang and gcc behave slightly
> differently:
>
> https://github.com/hjl-tools/x86-psABI/issues/2
>
> "Function args are different: narrow types are sign or zero extended to
> 32 bits, depending on
From: David Hildenbrand
> Sent: 22 October 2020 10:19
>
> On 22.10.20 11:01, Greg KH wrote:
> > On Thu, Oct 22, 2020 at 10:48:59AM +0200, David Hildenbrand wrote:
> >> On 22.10.20 10:40, David Laight wrote:
> >>> From: David Hildenbrand
> Sent: 22 October 2020 09:35
>
> On 22.10.20
On 22.10.20 11:19, David Hildenbrand wrote:
> On 22.10.20 11:01, Greg KH wrote:
>> On Thu, Oct 22, 2020 at 10:48:59AM +0200, David Hildenbrand wrote:
>>> On 22.10.20 10:40, David Laight wrote:
From: David Hildenbrand
> Sent: 22 October 2020 09:35
>
> On 22.10.20 10:26, Greg KH
On 22.10.20 11:01, Greg KH wrote:
> On Thu, Oct 22, 2020 at 10:48:59AM +0200, David Hildenbrand wrote:
>> On 22.10.20 10:40, David Laight wrote:
>>> From: David Hildenbrand
Sent: 22 October 2020 09:35
On 22.10.20 10:26, Greg KH wrote:
> On Thu, Oct 22, 2020 at 12:39:14AM +0100,
From: Greg KH
> Sent: 22 October 2020 10:02
...
> I'm running some more tests, trying to narrow things down as just adding
> a "noinline" to the function that got moved here doesn't work on Linus's
> tree at the moment because the function was split into multiple
> functions.
I was going to look
From: David Hildenbrand
> Sent: 22 October 2020 09:49
...
> >>> But, this looks now to be a compiler bug. I'm using the latest version
> >>> of clang and if I put "noinline" at the front of the function,
> >>> everything works.
> >>
> >> Well, the compiler can do more invasive optimizations when
On Thu, Oct 22, 2020 at 10:48:59AM +0200, David Hildenbrand wrote:
> On 22.10.20 10:40, David Laight wrote:
> > From: David Hildenbrand
> >> Sent: 22 October 2020 09:35
> >>
> >> On 22.10.20 10:26, Greg KH wrote:
> >>> On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote:
> On Wed, Oct 21,
On 22.10.20 10:40, David Laight wrote:
> From: David Hildenbrand
>> Sent: 22 October 2020 09:35
>>
>> On 22.10.20 10:26, Greg KH wrote:
>>> On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote:
On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote:
> On Fri, Sep 25, 2020 at
From: David Hildenbrand
> Sent: 22 October 2020 09:35
>
> On 22.10.20 10:26, Greg KH wrote:
> > On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote:
> >> On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote:
> >>> On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
>
On 22.10.20 10:26, Greg KH wrote:
> On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote:
>> On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote:
>>> On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
From: David Laight
This lets the compiler inline it into
On Thu, Oct 22, 2020 at 12:39:14AM +0100, Al Viro wrote:
> On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote:
> > On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
> > > From: David Laight
> > >
> > > This lets the compiler inline it into import_iovec() generating
> > >
On Wed, Oct 21, 2020 at 06:13:01PM +0200, Greg KH wrote:
> On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
> > From: David Laight
> >
> > This lets the compiler inline it into import_iovec() generating
> > much better code.
> >
> > Signed-off-by: David Laight
> >
From: Greg KH
> Sent: 21 October 2020 17:13
>
> On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
> > From: David Laight
> >
> > This lets the compiler inline it into import_iovec() generating
> > much better code.
> >
> > Signed-off-by: David Laight
> > Signed-off-by:
On Fri, Sep 25, 2020 at 06:51:39AM +0200, Christoph Hellwig wrote:
> From: David Laight
>
> This lets the compiler inline it into import_iovec() generating
> much better code.
>
> Signed-off-by: David Laight
> Signed-off-by: Christoph Hellwig
> ---
> fs/read_write.c | 179
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