linux.git/arch/tile/kernel/traps.c, branch v4.16

signal: Don't use structure initializers for struct siginfo

2018-01-23T01:07:08+00:00

The siginfo structure has all manners of holes with the result that a
structure initializer is not guaranteed to initialize all of the bits.
As we have to copy the structure to userspace don't even try to use
a structure initializer.  Instead use clear_siginfo followed by initializing
selected fields.  This gives a guarantee that uninitialized kernel memory
is not copied to userspace.

Signed-off-by: "Eric W. Biederman"

signal: Remove kernel interal si_code magic

2017-07-24T19:30:28+00:00

struct siginfo is a union and the kernel since 2.4 has been hiding a union
tag in the high 16bits of si_code using the values:
__SI_KILL
__SI_TIMER
__SI_POLL
__SI_FAULT
__SI_CHLD
__SI_RT
__SI_MESGQ
__SI_SYS

While this looks plausible on the surface, in practice this situation has
not worked well.

- Injected positive signals are not copied to user space properly
  unless they have these magic high bits set.

- Injected positive signals are not reported properly by signalfd
  unless they have these magic high bits set.

- These kernel internal values leaked to userspace via ptrace_peek_siginfo

- It was possible to inject these kernel internal values and cause the
  the kernel to misbehave.

- Kernel developers got confused and expected these kernel internal values
  in userspace in kernel self tests.

- Kernel developers got confused and set si_code to __SI_FAULT which
  is SI_USER in userspace which causes userspace to think an ordinary user
  sent the signal and that it was not kernel generated.

- The values make it impossible to reorganize the code to transform
  siginfo_copy_to_user into a plain copy_to_user.  As si_code must
  be massaged before being passed to userspace.

So remove these kernel internal si codes and make the kernel code simpler
and more maintainable.

To replace these kernel internal magic si_codes introduce the helper
function siginfo_layout, that takes a signal number and an si_code and
computes which union member of siginfo is being used.  Have
siginfo_layout return an enumeration so that gcc will have enough
information to warn if a switch statement does not handle all of union
members.

A couple of architectures have a messed up ABI that defines signal
specific duplications of SI_USER which causes more special cases in
siginfo_layout than I would like.  The good news is only problem
architectures pay the cost.

Update all of the code that used the previous magic __SI_ values to
use the new SIL_ values and to call siginfo_layout to get those
values.  Escept where not all of the cases are handled remove the
defaults in the switch statements so that if a new case is missed in
the future the lack will show up at compile time.

Modify the code that copies siginfo si_code to userspace to just copy
the value and not cast si_code to a short first.  The high bits are no
longer used to hold a magic union member.

Fixup the siginfo header files to stop including the __SI_ values in
their constants and for the headers that were missing it to properly
update the number of si_codes for each signal type.

The fixes to copy_siginfo_from_user32 implementations has the
interesting property that several of them perviously should never have
worked as the __SI_ values they depended up where kernel internal.
With that dependency gone those implementations should work much
better.

The idea of not passing the __SI_ values out to userspace and then
not reinserting them has been tested with criu and criu worked without
changes.

Ref: 2.4.0-test1
Signed-off-by: "Eric W. Biederman"

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

2017-03-02T07:42:34+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new 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

arch/tile: adopt the new nmi_backtrace framework

2016-10-08T01:46:30+00:00

Previously tile was rolling its own method of capturing backtrace data
in the NMI handlers, but it was relying on running printk() from the NMI
handler, which is not always safe.  So adopt the nmi_backtrace model
(with the new cpumask extension) instead.

So we can call the nmi_backtrace code directly from the nmi handler,
move the nmi_enter()/exit() into the top-level tile NMI handler.

The semantics of the routine change slightly since it is now synchronous
with the remote cores completing the backtraces.  Previously it was
asynchronous, but with protection to avoid starting a new remote
backtrace if the old one was still in progress.

Link: http://lkml.kernel.org/r/1472487169-14923-4-git-send-email-cmetcalf@mellanox.com
Signed-off-by: Chris Metcalf 
Cc: Daniel Thompson  [arm]
Cc: Petr Mladek 
Cc: Aaron Tomlin 
Cc: Peter Zijlstra (Intel) 
Cc: "Rafael J. Wysocki" 
Cc: Russell King 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

arch/tile: move user_exit() to early kernel entry sequence

2016-01-18T19:49:30+00:00

This ensures that we always notify context tracking that we
have exited from user space no matter how we enter the kernel.
It is similar to how arm64 handles context tracking, for example.

This allows the removal of all the exception_enter() calls that
were added in commit 49e4e15619cd ("tile: support CONTEXT_TRACKING and
thus NOHZ_FULL").

Signed-off-by: Chris Metcalf

tile: improve stack backtrace

2015-05-11T15:22:40+00:00

This commit fixes a number of issues with the tile backtrace code.

- Don't try to identify userspace shared object or executable paths
  if we are doing a backtrace from an interrupt; it's not legal,
  and also unlikely to be interesting.  Likewise, don't try to do
  it for other address spaces, since d_path() assumes it is being
  called in "current" context.

- Move "in_backtrace" from thread_struct to thread_info.
  This way we can access it even if our stack thread_info has been
  clobbered, which makes backtracing more robust.

- Avoid using "current" directly when testing for is_sigreturn().
  Since "current" may be corrupt, we're better off using kbt->task
  explicitly to look up the vdso_base for the current task.
  Conveniently, this simplifies the internal APIs (we only need
  one is_sigreturn() function now).

- Avoid bogus "Odd fault" warning when pc/sp/ex1 are all zero,
  as is true for kernel threads above the last frame.

- Hook into Tejun Heo's dump_stack() framework in lib/dump_stack.c.

- Write last entry in save_stack_trace() as ULONG_MAX, not zero,
  since ftrace (at least) relies on finding that marker.

- Implement save_stack_trace_regs() and save_strack_trace_user(),
  and set CONFIG_USER_STACKTRACE_SUPPORT.

Signed-off-by: Chris Metcalf

tile: support delivering NMIs for multicore backtrace

2015-05-11T15:22:31+00:00

A new hypervisor service was added some time ago (MDE 4.2.1 or
later, or MDE 4.3 or later) that allows cores to request NMIs
to be delivered to other cores.  Use this facility to deliver
a request that causes a backtrace to be generated on each core,
and hook it into the magic SysRq functionality.

Signed-off-by: Chris Metcalf

tile: support CONTEXT_TRACKING and thus NOHZ_FULL

2015-04-17T18:01:10+00:00

Add the TIF_NOHZ flag appropriately.

Add call to user_exit() on entry to do_work_pending() and on entry
to syscalls via do_syscall_trace_enter(), and also the top of
do_syscall_trace_exit() just because it's done in x86.

Add call to user_enter() at the bottom of do_work_pending() once we
have no more work to do before returning to userspace.

Wrap all the trap code in exception_enter() / exception_exit().

Signed-off-by: Chris Metcalf 
Acked-by: Frederic Weisbecker

tile: Use the more common pr_warn instead of pr_warning

2014-11-11T20:51:42+00:00

And other message logging neatening.

Other miscellanea:

o coalesce formats
o realign arguments
o standardize a couple of macros
o use __func__ instead of embedding the function name

Signed-off-by: Joe Perches 
Signed-off-by: Chris Metcalf

tile: use ARRAY_SIZE

2014-10-02T14:19:32+00:00

ARRAY_SIZE is more concise to use when the size of an array is divided
by the size of its type or the size of its first element.

The semantic patch that makes this change is as follows:

// 
@i@
@@

@@
type T;
T[] E;
@@

- (sizeof(E)/sizeof(T))
+ ARRAY_SIZE(E)
// 

Signed-off-by: Himangi Saraogi 
Acked-by: Julia Lawall 
Signed-off-by: Chris Metcalf