* + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
@ 2010-08-11 23:06 akpm
2010-08-11 23:43 ` Randy Dunlap
0 siblings, 1 reply; 11+ messages in thread
From: akpm @ 2010-08-11 23:06 UTC (permalink / raw)
To: mm-commits; +Cc: akpm, gcosta, hpa, lenb, mingo, tglx, ying.huang
The patch titled
drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
has been added to the -mm tree. Its filename is
drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
From: Andrew Morton <akpm@linux-foundation.org>
Might be an x86 bug? A get_user() on a u64 on i386 expands to
#define __get_user_8(__ret_gu, __val_gu, ptr) \
__get_user_x(X, __ret_gu, __val_gu, ptr)
which emits a call to __get_user_X(), which doesn't exist.
Kludge around it with copy_from_user().
While we're there, teach it how to print size_t's:
drivers/acpi/apei/erst-dbg.c: In function 'erst_dbg_read':
drivers/acpi/apei/erst-dbg.c:106: warning: format '%lx' expects type 'long unsigned int', but argument 3 has type 'ssize_t'
Cc: Glauber Costa <gcosta@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
drivers/acpi/apei/erst-dbg.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff -puN drivers/acpi/apei/erst-dbg.c~drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386 drivers/acpi/apei/erst-dbg.c
--- a/drivers/acpi/apei/erst-dbg.c~drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386
+++ a/drivers/acpi/apei/erst-dbg.c
@@ -57,9 +57,10 @@ static long erst_dbg_ioctl(struct file *
switch (cmd) {
case APEI_ERST_CLEAR_RECORD:
- rc = get_user(record_id, (u64 __user *)arg);
+ rc = copy_from_user(&record_id, (const void __user *)arg,
+ sizeof(record_id));
if (rc)
- return rc;
+ return -EFAULT;
return erst_clear(record_id);
case APEI_ERST_GET_RECORD_COUNT:
rc = erst_get_record_count();
@@ -104,7 +105,7 @@ retry:
goto out;
if (len > ERST_DBG_RECORD_LEN_MAX) {
pr_warning(ERST_DBG_PFX
- "Record (ID: 0x%llx) length is too long: 0x%lx\n",
+ "Record (ID: 0x%llx) length is too long: 0x%zx\n",
id, len);
rc = -EIO;
goto out;
_
Patches currently in -mm which might be from akpm@linux-foundation.org are
origin.patch
acpi-fix-bogus-preemption-logic.patch
writeback-reduce-calls-to-global_page_state-in-balance_dirty_pages.patch
linux-next.patch
linux-next-git-rejects.patch
next-remove-localversion.patch
fs-inodec-work-around-bug.patch
i-need-old-gcc.patch
mm-vmap-area-cache.patch
drivers-acpi-debugfsc-needs-uaccessh.patch
drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch
parport-prevent-arm-boards-frmo-crashing-when-cups-is-loaded-fix.patch
gcc-46-btrfs-clean-up-unused-variables-bugs.patch
hpet-factor-timer-allocate-from-open.patch
leds-route-kbd-leds-through-the-generic-leds-layer.patch
security-add-const-to-security_task_setscheduler.patch
sched-make-sched_param-argument-static-variables-in-some-sched_setscheduler-caller.patch
drivers-scsi-qla4xxx-fix-build.patch
fs-bio-integrityc-return-enomem-on-kmalloc-failure.patch
usb-storage-add-new-no_read_disc_info-quirk-fix.patch
mm.patch
frv-duplicate-output_buffer-of-e03-checkpatch-fixes.patch
sdhci-get-rid-of-card-detect-work-fix.patch
delay-accounting-re-implement-c-for-getdelaysc-to-report-information-on-a-target-command-checkpatch-fixes.patch
pps-add-async-pps-event-handler-fix.patch
memstick-add-driver-for-ricoh-r5c592-card-reader-cleanups.patch
vfs-add-super-operation-writeback_inodes-fix.patch
reiser4-export-remove_from_page_cache-fix.patch
reiser4-export-find_get_pages.patch
reiser4.patch
reiser4-writeback_inodes-implementation-fix.patch
reiser4-fixups.patch
reiser4-broke.patch
journal_add_journal_head-debug.patch
slab-leaks3-default-y.patch
put_bh-debug.patch
getblk-handle-2tb-devices.patch
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-11 23:06 + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree akpm
@ 2010-08-11 23:43 ` Randy Dunlap
2010-08-12 0:33 ` Andrew Morton
0 siblings, 1 reply; 11+ messages in thread
From: Randy Dunlap @ 2010-08-11 23:43 UTC (permalink / raw)
To: linux-kernel; +Cc: akpm, gcosta, hpa, lenb, mingo, tglx, ying.huang
On Wed, 11 Aug 2010 16:06:24 -0700 akpm@linux-foundation.org wrote:
>
> The patch titled
> drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> has been added to the -mm tree. Its filename is
> drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch
>
> Before you just go and hit "reply", please:
> a) Consider who else should be cc'ed
> b) Prefer to cc a suitable mailing list as well
> c) Ideally: find the original patch on the mailing list and do a
> reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
>
> See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> out what to do about this
>
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
>
> ------------------------------------------------------
> Subject: drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> From: Andrew Morton <akpm@linux-foundation.org>
>
> Might be an x86 bug? A get_user() on a u64 on i386 expands to
>
> #define __get_user_8(__ret_gu, __val_gu, ptr) \
> __get_user_x(X, __ret_gu, __val_gu, ptr)
>
> which emits a call to __get_user_X(), which doesn't exist.
>
> Kludge around it with copy_from_user().
>
Reported and fixed yesterday.
>
>
> While we're there, teach it how to print size_t's:
That was also patched, but yours is better.
I missed the cast in Huang's patch.
> drivers/acpi/apei/erst-dbg.c: In function 'erst_dbg_read':
> drivers/acpi/apei/erst-dbg.c:106: warning: format '%lx' expects type 'long unsigned int', but argument 3 has type 'ssize_t'
>
> Cc: Glauber Costa <gcosta@redhat.com>
> Cc: Len Brown <lenb@kernel.org>
> Cc: Huang Ying <ying.huang@intel.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> drivers/acpi/apei/erst-dbg.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff -puN drivers/acpi/apei/erst-dbg.c~drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386 drivers/acpi/apei/erst-dbg.c
> --- a/drivers/acpi/apei/erst-dbg.c~drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386
> +++ a/drivers/acpi/apei/erst-dbg.c
> @@ -57,9 +57,10 @@ static long erst_dbg_ioctl(struct file *
>
> switch (cmd) {
> case APEI_ERST_CLEAR_RECORD:
> - rc = get_user(record_id, (u64 __user *)arg);
> + rc = copy_from_user(&record_id, (const void __user *)arg,
> + sizeof(record_id));
> if (rc)
> - return rc;
> + return -EFAULT;
> return erst_clear(record_id);
> case APEI_ERST_GET_RECORD_COUNT:
> rc = erst_get_record_count();
> @@ -104,7 +105,7 @@ retry:
> goto out;
> if (len > ERST_DBG_RECORD_LEN_MAX) {
> pr_warning(ERST_DBG_PFX
> - "Record (ID: 0x%llx) length is too long: 0x%lx\n",
> + "Record (ID: 0x%llx) length is too long: 0x%zx\n",
> id, len);
> rc = -EIO;
> goto out;
> _
---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-11 23:43 ` Randy Dunlap
@ 2010-08-12 0:33 ` Andrew Morton
2010-08-12 0:42 ` Huang Ying
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: Andrew Morton @ 2010-08-12 0:33 UTC (permalink / raw)
To: Randy Dunlap; +Cc: linux-kernel, gcosta, hpa, lenb, mingo, tglx, ying.huang
On Wed, 11 Aug 2010 16:43:10 -0700 Randy Dunlap <randy.dunlap@oracle.com> wrote:
> On Wed, 11 Aug 2010 16:06:24 -0700 akpm@linux-foundation.org wrote:
>
> >
> > The patch titled
> > drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> > has been added to the -mm tree. Its filename is
> > drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch
> >
> > Before you just go and hit "reply", please:
> > a) Consider who else should be cc'ed
> > b) Prefer to cc a suitable mailing list as well
> > c) Ideally: find the original patch on the mailing list and do a
> > reply-to-all to that, adding suitable additional cc's
> >
> > *** Remember to use Documentation/SubmitChecklist when testing your code ***
> >
> > See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> > out what to do about this
> >
> > The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> >
> > ------------------------------------------------------
> > Subject: drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> > From: Andrew Morton <akpm@linux-foundation.org>
> >
> > Might be an x86 bug? A get_user() on a u64 on i386 expands to
> >
> > #define __get_user_8(__ret_gu, __val_gu, ptr) \
> > __get_user_x(X, __ret_gu, __val_gu, ptr)
> >
> > which emits a call to __get_user_X(), which doesn't exist.
> >
> > Kludge around it with copy_from_user().
> >
>
> Reported and fixed yesterday.
Not very well.
+ rc = copy_from_user(&record_id, (void __user *)arg,
+ sizeof(u64));
better to use sizeof(record_id).
Where's Len??
Anyway, this should be fixed in x86 core, I suspect.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 0:33 ` Andrew Morton
@ 2010-08-12 0:42 ` Huang Ying
2010-08-12 1:35 ` H. Peter Anvin
2010-08-12 4:22 ` H. Peter Anvin
2 siblings, 0 replies; 11+ messages in thread
From: Huang Ying @ 2010-08-12 0:42 UTC (permalink / raw)
To: Andrew Morton; +Cc: Randy Dunlap, linux-kernel, gcosta, hpa, lenb, mingo, tglx
On Thu, 2010-08-12 at 08:33 +0800, Andrew Morton wrote:
> On Wed, 11 Aug 2010 16:43:10 -0700 Randy Dunlap <randy.dunlap@oracle.com> wrote:
>
> > On Wed, 11 Aug 2010 16:06:24 -0700 akpm@linux-foundation.org wrote:
> >
> > >
> > > The patch titled
> > > drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> > > has been added to the -mm tree. Its filename is
> > > drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch
> > >
> > > Before you just go and hit "reply", please:
> > > a) Consider who else should be cc'ed
> > > b) Prefer to cc a suitable mailing list as well
> > > c) Ideally: find the original patch on the mailing list and do a
> > > reply-to-all to that, adding suitable additional cc's
> > >
> > > *** Remember to use Documentation/SubmitChecklist when testing your code ***
> > >
> > > See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> > > out what to do about this
> > >
> > > The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> > >
> > > ------------------------------------------------------
> > > Subject: drivers/acpi/apei/erst-dbg.c: get_user(u64) doesn't work on i386
> > > From: Andrew Morton <akpm@linux-foundation.org>
> > >
> > > Might be an x86 bug? A get_user() on a u64 on i386 expands to
> > >
> > > #define __get_user_8(__ret_gu, __val_gu, ptr) \
> > > __get_user_x(X, __ret_gu, __val_gu, ptr)
> > >
> > > which emits a call to __get_user_X(), which doesn't exist.
> > >
> > > Kludge around it with copy_from_user().
> > >
> >
> > Reported and fixed yesterday.
>
> Not very well.
>
> + rc = copy_from_user(&record_id, (void __user *)arg,
> + sizeof(u64));
>
> better to use sizeof(record_id).
Will fix this with a new version. And the ssize printk format string.
> Where's Len??
>
> Anyway, this should be fixed in x86 core, I suspect.
Yes. I think so too.
Best Regards,
Huang Ying
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 0:33 ` Andrew Morton
2010-08-12 0:42 ` Huang Ying
@ 2010-08-12 1:35 ` H. Peter Anvin
2010-08-12 4:22 ` H. Peter Anvin
2 siblings, 0 replies; 11+ messages in thread
From: H. Peter Anvin @ 2010-08-12 1:35 UTC (permalink / raw)
To: Andrew Morton
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx, ying.huang
On 08/11/2010 05:33 PM, Andrew Morton wrote:
>
> Not very well.
>
> + rc = copy_from_user(&record_id, (void __user *)arg,
> + sizeof(u64));
>
> better to use sizeof(record_id).
>
> Where's Len??
>
> Anyway, this should be fixed in x86 core, I suspect.
Agreed. Looking at it now.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 0:33 ` Andrew Morton
2010-08-12 0:42 ` Huang Ying
2010-08-12 1:35 ` H. Peter Anvin
@ 2010-08-12 4:22 ` H. Peter Anvin
2010-08-12 4:30 ` Andrew Morton
2 siblings, 1 reply; 11+ messages in thread
From: H. Peter Anvin @ 2010-08-12 4:22 UTC (permalink / raw)
To: Andrew Morton
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
[Adding Linux and linux-arch. The context is that get_user/put_user
don't work on 64 bit values on i386.]
On 08/11/2010 05:33 PM, Andrew Morton wrote:
>
> Anyway, this should be fixed in x86 core, I suspect.
After looking at it -- and suffering a bad case of déjà vu -- I'm
reluctant to change it, as get/put_user are specified to work only on
locally atomic data:
* This macro copies a single simple variable from user space to kernel
* space. It supports simple types like char and int, but not larger
* data types like structures or arrays.
Given that u64 is not a simple type on 32 bits, it would appear that the
behavior is intentional.
A user might very well find that supporting u64 and/or structure types
would be beneficial, but it would a) be a semantic change, and b) would
introduce the possibility of a partially completed transfer. That is a
semantic change to the interface. However, it may very well be nicer to
have a generally available get_user()/put_user() for the cases which
would just kick an EFAULT up the stack when they fail anyway.
If there is consensus for making get_user/put_user a general interface,
I'm more than willing to do the x86 changes, but I don't want to do them
a) unilaterally and b) for 2.6.36. This seems like .37 material at this
point.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 4:22 ` H. Peter Anvin
@ 2010-08-12 4:30 ` Andrew Morton
2010-08-12 4:42 ` H. Peter Anvin
2010-08-12 5:06 ` H. Peter Anvin
0 siblings, 2 replies; 11+ messages in thread
From: Andrew Morton @ 2010-08-12 4:30 UTC (permalink / raw)
To: H. Peter Anvin
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
On Wed, 11 Aug 2010 21:22:51 -0700 "H. Peter Anvin" <hpa@zytor.com> wrote:
> [Adding Linux and linux-arch. The context is that get_user/put_user
> don't work on 64 bit values on i386.]
>
> On 08/11/2010 05:33 PM, Andrew Morton wrote:
> >
> > Anyway, this should be fixed in x86 core, I suspect.
>
> After looking at it -- and suffering a bad case of d__j__ vu -- I'm
> reluctant to change it, as get/put_user are specified to work only on
> locally atomic data:
>
> * This macro copies a single simple variable from user space to kernel
> * space. It supports simple types like char and int, but not larger
> * data types like structures or arrays.
>
> Given that u64 is not a simple type on 32 bits, it would appear that the
> behavior is intentional.
>
> A user might very well find that supporting u64 and/or structure types
> would be beneficial, but it would a) be a semantic change, and b) would
> introduce the possibility of a partially completed transfer. That is a
> semantic change to the interface. However, it may very well be nicer to
> have a generally available get_user()/put_user() for the cases which
> would just kick an EFAULT up the stack when they fail anyway.
>
> If there is consensus for making get_user/put_user a general interface,
> I'm more than willing to do the x86 changes, but I don't want to do them
> a) unilaterally and b) for 2.6.36. This seems like .37 material at this
> point.
It occurs so rarely that it's probably not worth bothering about, IMO.
However we should arrange for it to fail at compile time rather than
at link time, please.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 4:30 ` Andrew Morton
@ 2010-08-12 4:42 ` H. Peter Anvin
2010-08-12 5:06 ` H. Peter Anvin
1 sibling, 0 replies; 11+ messages in thread
From: H. Peter Anvin @ 2010-08-12 4:42 UTC (permalink / raw)
To: Andrew Morton
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
On 08/11/2010 09:30 PM, Andrew Morton wrote:
>
> However we should arrange for it to fail at compile time rather than
> at link time, please.
>
That is easy to do, of course.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 4:30 ` Andrew Morton
2010-08-12 4:42 ` H. Peter Anvin
@ 2010-08-12 5:06 ` H. Peter Anvin
2010-08-12 6:03 ` Andrew Morton
1 sibling, 1 reply; 11+ messages in thread
From: H. Peter Anvin @ 2010-08-12 5:06 UTC (permalink / raw)
To: Andrew Morton
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
On 08/11/2010 09:30 PM, Andrew Morton wrote:
>
> It occurs so rarely that it's probably not worth bothering about, IMO.
>
I think the real question is if we want people to convert:
if (copy_from_user(foo, bar, sizeof *foo))
return -EFAULT;
... into ...
if (get_user(*foo, bar))
return -EFAULT;
... or ...
rv = get_user(*foo, bar);
if (rv)
return rv;
... where *foo is a structure type. It does have the advantage that a
single API does everything, simple or not, but has the disadvantage that
the partial-access semantics are now less explicit.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 5:06 ` H. Peter Anvin
@ 2010-08-12 6:03 ` Andrew Morton
2010-08-12 6:10 ` H. Peter Anvin
0 siblings, 1 reply; 11+ messages in thread
From: Andrew Morton @ 2010-08-12 6:03 UTC (permalink / raw)
To: H. Peter Anvin
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
On Wed, 11 Aug 2010 22:06:08 -0700 "H. Peter Anvin" <hpa@zytor.com> wrote:
> On 08/11/2010 09:30 PM, Andrew Morton wrote:
> >
> > It occurs so rarely that it's probably not worth bothering about, IMO.
> >
>
> I think the real question is if we want people to convert:
>
> if (copy_from_user(foo, bar, sizeof *foo))
> return -EFAULT;
>
> ... into ...
>
> if (get_user(*foo, bar))
> return -EFAULT;
>
> ... or ...
>
> rv = get_user(*foo, bar);
> if (rv)
> return rv;
>
> ... where *foo is a structure type. It does have the advantage that a
> single API does everything, simple or not, but has the disadvantage that
> the partial-access semantics are now less explicit.
>
Well, anyone who does get_user() on a struct while expecting it to be
atomic gets to own both pieces. I think the problem here is
specifically u64/s64. These work on 64-bit but don't work on 32-bit.
Is the atomicity really a problem? If userspace updates the 64-bit
number while the kernel is copying it, the kernel gets a garbage
number. But so what? Userspace can feed the kernel garbage numbers in
lots of ways, and the kernel must be able to cope with it
appropriately.
<I suspect you can do get_user() on a 4-byte or 8-byte struct right now
and it'll work>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree
2010-08-12 6:03 ` Andrew Morton
@ 2010-08-12 6:10 ` H. Peter Anvin
0 siblings, 0 replies; 11+ messages in thread
From: H. Peter Anvin @ 2010-08-12 6:10 UTC (permalink / raw)
To: Andrew Morton
Cc: Randy Dunlap, linux-kernel, gcosta, lenb, mingo, tglx,
ying.huang, Linux Arch Mailing List, Linus Torvalds
[-- Attachment #1: Type: text/plain, Size: 268 bytes --]
On 08/11/2010 11:03 PM, Andrew Morton wrote:
> <I suspect you can do get_user() on a 4-byte or 8-byte struct right now
> and it'll work>
Not so:
/home/hpa/kernel/linux-2.6-tip.urgent/arch/x86/lib/testuser.c:12: error:
conversion to non-scalar type requested
-hpa
[-- Attachment #2: testuser.c --]
[-- Type: text/x-csrc, Size: 194 bytes --]
#include <linux/types.h>
#include <linux/uaccess.h>
struct foo {
u16 a, b;
};
int bluttan(struct foo *foo)
{
struct foo bar;
if (get_user(bar, foo))
return -1;
return bar.a + bar.b;
}
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2010-08-12 6:11 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-08-11 23:06 + drivers-acpi-apei-erst-dbgc-get_useru64-doesnt-work-on-i386.patch added to -mm tree akpm
2010-08-11 23:43 ` Randy Dunlap
2010-08-12 0:33 ` Andrew Morton
2010-08-12 0:42 ` Huang Ying
2010-08-12 1:35 ` H. Peter Anvin
2010-08-12 4:22 ` H. Peter Anvin
2010-08-12 4:30 ` Andrew Morton
2010-08-12 4:42 ` H. Peter Anvin
2010-08-12 5:06 ` H. Peter Anvin
2010-08-12 6:03 ` Andrew Morton
2010-08-12 6:10 ` H. Peter Anvin
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.