linux-toradex.git/arch/x86/include/asm/uaccess.h, branch v3.4.78

x86: merge 32/64-bit versions of 'strncpy_from_user()' and speed it up

2012-04-11T16:41:28+00:00

This merges the 32- and 64-bit versions of the x86 strncpy_from_user()
by just rewriting it in C rather than the ancient inline asm versions
that used lodsb/stosb and had been duplicated for (trivial) differences
between the 32-bit and 64-bit versions.

While doing that, it also speeds them up by doing the accesses a word at
a time.  Finally, the new routines also properly handle the case of
hitting the end of the address space, which we have never done correctly
before (fs/namei.c has a hack around it for that reason).

Despite all these improvements, it actually removes more lines than it
adds, due to the de-duplication.  Also, we no longer export (or define)
the legacy __strncpy_from_user() function (that was defined to not do
the user permission checks), since it's not actually used anywhere, and
the user address space checks are built in to the new code.

Other architecture maintainers have been notified that the old hack in
fs/namei.c will be going away in the 3.5 merge window, in case they
copied the x86 approach of being a bit cavalier about the end of the
address space.

Cc: linux-arch@vger.kernel.org
Cc: Ingo Molnar 
Cc: Peter Anvin" 
Signed-off-by: Linus Torvalds

x86-64: Set siginfo and context on vsyscall emulation faults

2011-12-05T11:17:27+00:00

To make this work, we teach the page fault handler how to send
signals on failed uaccess.  This only works for user addresses
(kernel addresses will never hit the page fault handler in the
first place), so we need to generate signals for those
separately.

This gets the tricky case right: if the user buffer spans
multiple pages and only the second page is invalid, we set
cr2 and si_addr correctly.  UML relies on this behavior to
"fault in" pages as needed.

We steal a bit from thread_info.uaccess_err to enable this.
Before this change, uaccess_err was a 32-bit boolean value.

This fixes issues with UML when vsyscall=emulate.

Reported-by: Adrian Bunk 
Signed-off-by: Andy Lutomirski 
Cc: richard -rw- weinberger 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/4c8f91de7ec5cd2ef0f59521a04e1015f11e42b4.1320712291.git.luto@amacapital.net
Signed-off-by: Ingo Molnar

x86, perf: Make copy_from_user_nmi() a library function

2011-07-21T18:41:57+00:00

copy_from_user_nmi() is used in oprofile and perf. Moving it to other
library functions like copy_from_user(). As this is x86 code for 32
and 64 bits, create a new file usercopy.c for unified code.

Signed-off-by: Robert Richter 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20110607172413.GJ20052@erda.amd.com
Signed-off-by: Ingo Molnar

sanitize usage

2011-05-20T19:50:29+00:00

Commit e66eed651fd1 ("list: remove prefetching from regular list
iterators") removed the include of prefetch.h from list.h, which
uncovered several cases that had apparently relied on that rather
obscure header file dependency.

So this fixes things up a bit, using

   grep -L linux/prefetch.h $(git grep -l '[^a-z_]prefetchw*(' -- '*.[ch]')
   grep -L 'prefetchw*(' $(git grep -l 'linux/prefetch.h' -- '*.[ch]')

to guide us in finding files that either need 
inclusion, or have it despite not needing it.

There are more of them around (mostly network drivers), but this gets
many core ones.

Reported-by: Stephen Rothwell 
Signed-off-by: Linus Torvalds

x86, 64-bit: Fix copy_[to/from]_user() checks for the userspace address limit

2011-05-18T10:49:00+00:00

As reported in BZ #30352:

  https://bugzilla.kernel.org/show_bug.cgi?id=30352

there's a kernel bug related to reading the last allowed page on x86_64.

The _copy_to_user() and _copy_from_user() functions use the following
check for address limit:

  if (buf + size >= limit)
	fail();

while it should be more permissive:

  if (buf + size > limit)
	fail();

That's because the size represents the number of bytes being
read/write from/to buf address AND including the buf address.
So the copy function will actually never touch the limit
address even if "buf + size == limit".

Following program fails to use the last page as buffer
due to the wrong limit check:

 #include 
 #include 
 #include 

 #define PAGE_SIZE       (4096)
 #define LAST_PAGE       ((void*)(0x7fffffffe000))

 int main()
 {
        int fds[2], err;
        void * ptr = mmap(LAST_PAGE, PAGE_SIZE, PROT_READ | PROT_WRITE,
                          MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
        assert(ptr == LAST_PAGE);
        err = socketpair(AF_LOCAL, SOCK_STREAM, 0, fds);
        assert(err == 0);
        err = send(fds[0], ptr, PAGE_SIZE, 0);
        perror("send");
        assert(err == PAGE_SIZE);
        err = recv(fds[1], ptr, PAGE_SIZE, MSG_WAITALL);
        perror("recv");
        assert(err == PAGE_SIZE);
        return 0;
 }

The other place checking the addr limit is the access_ok() function,
which is working properly. There's just a misleading comment
for the __range_not_ok() macro - which this patch fixes as well.

The last page of the user-space address range is a guard page and
Brian Gerst observed that the guard page itself due to an erratum on K8 cpus
(#121 Sequential Execution Across Non-Canonical Boundary Causes Processor
Hang).

However, the test code is using the last valid page before the guard page.
The bug is that the last byte before the guard page can't be read
because of the off-by-one error. The guard page is left in place.

This bug would normally not show up because the last page is
part of the process stack and never accessed via syscalls.

Signed-off-by: Jiri Olsa 
Acked-by: Brian Gerst 
Acked-by: Linus Torvalds 
Cc: 
Link: http://lkml.kernel.org/r/1305210630-7136-1-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar

x86, 64-bit: Move K8 B step iret fixup to fault entry asm

2009-10-12T16:29:46+00:00

Move the handling of truncated %rip from an iret fault to the fault
entry path.

This allows x86-64 to use the standard search_extable() function.

Signed-off-by: Brian Gerst 
Cc: Linus Torvalds 
Cc: Jan Beulich 
LKML-Reference: <1255357103-5418-1-git-send-email-brgerst@gmail.com>
Signed-off-by: Ingo Molnar

x86: Fix movq immediate operand constraints in uaccess.h

2009-07-21T06:27:39+00:00

The movq instruction, generated by __put_user_asm() when used for
64-bit data, takes a sign-extended immediate ("e") not a zero-extended
immediate ("Z").

Signed-off-by: H. Peter Anvin 
Cc: Uros Bizjak 
Cc: stable@kernel.org

x86, 64-bit: Clean up user address masking

2009-06-20T22:40:00+00:00

The discussion about using "access_ok()" in get_user_pages_fast() (see
commit 7f8189068726492950bf1a2dcfd9b51314560abf: "x86: don't use
'access_ok()' as a range check in get_user_pages_fast()" for details and
end result), made us notice that x86-64 was really being very sloppy
about virtual address checking.

So be way more careful and straightforward about masking x86-64 virtual
addresses:

 - All the VIRTUAL_MASK* variants now cover half of the address
   space, it's not like we can use the full mask on a signed
   integer, and the larger mask just invites mistakes when
   applying it to either half of the 48-bit address space.

 - /proc/kcore's kc_offset_to_vaddr() becomes a lot more
   obvious when it transforms a file offset into a
   (kernel-half) virtual address.

 - Unify/simplify the 32-bit and 64-bit USER_DS definition to
   be based on TASK_SIZE_MAX.

This cleanup and more careful/obvious user virtual address checking also
uncovered a buglet in the x86-64 implementation of strnlen_user(): it
would do an "access_ok()" check on the whole potential area, even if the
string itself was much shorter, and thus return an error even for valid
strings. Our sloppy checking had hidden this.

So this fixes 'strnlen_user()' to do this properly, the same way we
already handled user strings in 'strncpy_from_user()'.  Namely by just
checking the first byte, and then relying on fault handling for the
rest.  That always works, since we impose a guard page that cannot be
mapped at the end of the user space address space (and even if we
didn't, we'd have the address space hole).

Acked-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andrew Morton 
Cc: Nick Piggin 
Cc: Hugh Dickins 
Cc: H. Peter Anvin 
Cc: Thomas Gleixner 
Cc: Alan Cox 
Signed-off-by: Linus Torvalds

perf_counter, x86: Improve interactions with fast-gup

2009-06-19T14:55:16+00:00

Improve a few details in perfcounter call-chain recording that
makes use of fast-GUP:

- Use ACCESS_ONCE() to observe the pte value. ptes are fundamentally
  racy and can be changed on another CPU, so we have to be careful
  about how we access them. The PAE branch is already careful with
  read-barriers - but the non-PAE and 64-bit side needs an
  ACCESS_ONCE() to make sure the pte value is observed only once.

- make the checks a bit stricter so that we can feed it any kind of
  cra^H^H^H user-space input ;-)

Acked-by: Peter Zijlstra 
Signed-off-by: Ingo Molnar

x86: uaccess: use errret as error value in __put_user_size()

2009-02-05T01:28:21+00:00

Impact: cleanup

In __put_user_size() macro errret is used for error value.
But if size is 8, errret isn't passed to__put_user_asm_u64().
This behavior is inconsistent.

Signed-off-by: Hiroshi Shimamoto 
Signed-off-by: H. Peter Anvin