linux.git/arch/xtensa/kernel/syscall.c, branch v4.19

mm: add ksys_fadvise64_64() helper; remove in-kernel call to sys_fadvise64_64()

2018-04-02T18:16:10+00:00

Using the ksys_fadvise64_64() helper allows us to avoid the in-kernel
calls to the sys_fadvise64_64() syscall. The ksys_ prefix denotes that
this function is meant as a drop-in replacement for the syscall. In
particular, it uses the same calling convention as ksys_fadvise64_64().

Some compat stubs called sys_fadvise64(), which then just passed through
the arguments to sys_fadvise64_64(). Get rid of this indirection, and call
ksys_fadvise64_64() directly.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Andrew Morton 
Cc: linux-mm@kvack.org
Signed-off-by: Dominik Brodowski

mm: larger stack guard gap, between vmas

2017-06-19T13:50:20+00:00

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov 
Original-patch-by: Michal Hocko 
Signed-off-by: Hugh Dickins 
Acked-by: Michal Hocko 
Tested-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds

sched/headers: Prepare for new header dependencies before moving more code to

2017-03-02T07:42:30+00:00

We are going to split more MM APIs out of , which
will have to be picked up from a couple of .c files.

The APIs that we are going to move are:

  arch_pick_mmap_layout()
  arch_get_unmapped_area()
  arch_get_unmapped_area_topdown()
  mm_update_next_owner()

Include the header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

Replace with globally

2016-12-24T19:46:01+00:00

This was entirely automated, using the script by Al:

  PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*'
  sed -i -e "s!$PATT!#include !" \
        $(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)

to do the replacement at the end of the merge window.

Requested-by: Al Viro 
Signed-off-by: Linus Torvalds

xtensa: nommu: don't provide arch_get_unmapped_area

2014-10-21T09:28:48+00:00

Nommu unconditionally provides arch_get_unmapped_area that always
returns -ENOMEM.

Signed-off-by: Max Filippov

xtensa: avoid mmap cache aliasing

2013-02-24T03:12:53+00:00

Provide arch_get_unmapped_area function aligning shared memory mapping
addresses to the biggest of the page size or the cache way size. That
guarantees that corresponding virtual addresses of shared mappings are
cached by the same cache sets.

Signed-off-by: Max Filippov 
Signed-off-by: Chris Zankel

xtensa: clean up files to make them code-style compliant

2012-12-19T05:10:25+00:00

Remove heading and trailing spaces, trim trailing lines, and wrap lines
that are longer than 80 characters.

Signed-off-by: Chris Zankel

xtensa: allow multi-inclusion for uapi/unistd.h

2012-10-25T21:53:36+00:00

Xtensa implements a method that allows to generate a arbitrary output
for each system call by defining the __SYSCALL(number, function, num_args).
This usually requires to include uapi/unistd.h twice. Instead of removing
the guard agains multiple inclusion entirely, allow to include unistd.h again
only if __SYSCALL is defined. Note that __SYSCALL gets always undefined at
the end of the file.

Signed-off-by: Chris Zankel

UAPI: (Scripted) Disintegrate arch/xtensa/include/asm

2012-10-16T04:48:53+00:00

UAPI: (Scripted) Disintegrate arch/xtensa/include/asm

Signed-off-by: David Howells 
Acked-by: Arnd Bergmann 
Acked-by: Thomas Gleixner 
Acked-by: Michael Kerrisk 
Acked-by: Paul E. McKenney 
Acked-by: Dave Jones 
Signed-off-by: Max Filippov 
Signed-off-by: Chris Zankel

ipc: add COMPAT_SHMLBA support

2012-07-31T00:25:20+00:00

If the SHMLBA definition for a native task differs from the definition for
a compat task, the do_shmat() function would need to handle both.

This patch introduces COMPAT_SHMLBA, which is used by the compat shmat
syscall when calling the ipc code and allows architectures such as AArch64
(where the native SHMLBA is 64k but the compat (AArch32) definition is
16k) to provide the correct semantics for compat IPC system calls.

Cc: David S. Miller 
Cc: Chris Zankel 
Cc: Arnd Bergmann 
Acked-by: Catalin Marinas 
Signed-off-by: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds