linux-stable.git/arch/arc/kernel, branch v3.16.67

ARC: U-boot: check arguments paranoidly

2019-05-02T20:41:57+00:00

commit a66f2e57bd566240d8b3884eedf503928fbbe557 upstream.

Handle U-boot arguments paranoidly:
 * don't allow to pass unknown tag.
 * try to use external device tree blob only if corresponding tag
   (TAG_DTB) is set.
 * don't check uboot_tag if kernel build with no ARC_UBOOT_SUPPORT.

NOTE:
If U-boot args are invalid we skip them and try to use embedded device
tree blob. We can't panic on invalid U-boot args as we really pass
invalid args due to bug in U-boot code.
This happens if we don't provide external DTB to U-boot and
don't set 'bootargs' U-boot environment variable (which is default
case at least for HSDK board) In that case we will pass
{r0 = 1 (bootargs in r2); r1 = 0; r2 = 0;} to linux which is invalid.

While I'm at it refactor U-boot arguments handling code.

Tested-by: Corentin LABBE 
Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

arc: Use get_signal() signal_setup_done()

2019-05-02T20:41:41+00:00

commit f6dd2a3f1f8d8df640cfa2d60f85c0b818af1593 upstream.

Use the more generic functions get_signal() signal_setup_done()
for signal delivery.

Signed-off-by: Richard Weinberger 
Acked-by: Vineet Gupta 
[bwh: Backported to 3.16 as dependency of commit 35634ffa1751
 "signal: Always notice exiting tasks"
 - Adjust to apply after "ARC: signal handling robustify"]
Signed-off-by: Ben Hutchings

ARC: show_regs: lockdep: avoid page allocator...

2019-05-02T20:41:24+00:00

commit ab6c03676cb190156603cf4c5ecf97aa406c9c53 upstream.

and use smaller/on-stack buffer instead

The motivation for this change was lockdep splat like below.

| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at ../mm/page_alloc.c:4317
| in_atomic(): 1, irqs_disabled(): 0, pid: 57, name: segv
| no locks held by segv/57.
| Preemption disabled at:
| [<8182f17e>] get_signal+0x4a6/0x7c4
| CPU: 0 PID: 57 Comm: segv Not tainted 4.17.0+ #23
|
| Stack Trace:
|  arc_unwind_core.constprop.1+0xd0/0xf4
|  __might_sleep+0x1f6/0x234
|  __get_free_pages+0x174/0xca0
|  show_regs+0x22/0x330
|  get_signal+0x4ac/0x7c4     # print_fatal_signals() -> preempt_disable()
|  do_signal+0x30/0x224
|  resume_user_mode_begin+0x90/0xd8

So signal handling core calls show_regs() with preemption disabled but
an ensuing GFP_KERNEL page allocator call is flagged by lockdep.

We could have switched to GFP_NOWAIT, but turns out that is not enough
anways and eliding page allocator call leads to less code and
instruction traces to sift thru when debugging pesky crashes.

FWIW, this patch doesn't cure the lockdep splat (which next patch does).

Reviewed-by: William Kucharski 
Signed-off-by: Vineet Gupta 
Signed-off-by: Ben Hutchings

arc: do not export symbols in troubleshoot.c

2019-05-02T20:41:24+00:00

commit be2a7fce397d82b7dc3fdbc61fb0bdab118e65ca upstream.

print_task_path_n_nm() is local to this file, its only user being
show_regs().  Mark the function static and avoid the EXPORT_SYMBOL.

Signed-off-by: Davidlohr Bueso 
Acked-by: Vineet Gupta 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.16 as dependency of commit ab6c03676cb1
 "ARC: show_regs: lockdep: avoid page allocator..."]
Signed-off-by: Ben Hutchings

ARC: clone syscall to setp r25 as thread pointer

2018-12-16T22:09:36+00:00

commit c58a584f05e35d1d4342923cd7aac07d9c3d3d16 upstream.

Per ARC TLS ABI, r25 is designated TP (thread pointer register).
However so far kernel didn't do any special treatment, like setting up
usermode r25, even for CLONE_SETTLS. We instead relied on libc runtime
to do this, in say clone libc wrapper [1]. This was deliberate to keep
kernel ABI agnostic (userspace could potentially change TP, specially
for different ARC ISA say ARCompact vs. ARCv2 with different spare
registers etc)

However userspace setting up r25, after clone syscall opens a race, if
child is not scheduled and gets a signal instead. It starts off in
userspace not in clone but in a signal handler and anything TP sepcific
there such as pthread_self() fails which showed up with uClibc
testsuite nptl/tst-kill6 [2]

Fix this by having kernel populate r25 to TP value. So this locks in
ABI, but it was not going to change anyways, and fwiw is same for both
ARCompact (arc700 core) and ARCvs (HS3x cores)

[1] https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/libc/sysdeps/linux/arc/clone.S
[2] https://github.com/wbx-github/uclibc-ng-test/blob/master/test/nptl/tst-kill6.c

Fixes: ARC STAR 9001378481
Reported-by: Nikita Sobolev 
Signed-off-by: Vineet Gupta 
Signed-off-by: Ben Hutchings

ARC: Re-enable MMU upon Machine Check exception

2017-11-26T13:50:29+00:00

commit 1ee55a8f7f6b7ca4c0c59e0b4b4e3584a085c2d3 upstream.

I recently came upon a scenario where I would get a double fault
machine check exception tiriggered by a kernel module.
However the ensuing crash stacktrace (ksym lookup) was not working
correctly.

Turns out that machine check auto-disables MMU while modules are allocated
in kernel vaddr spapce.

This patch re-enables the MMU before start printing the stacktrace
making stacktracing of modules work upon a fatal exception.

Signed-off-by: Jose Abreu 
Reviewed-by: Alexey Brodkin 
Signed-off-by: Vineet Gupta 
[vgupta: moved code into low level handler to avoid in 2 places]
Signed-off-by: Ben Hutchings

ARC: [arcompact] brown paper bag bug in unaligned access delay slot fixup

2017-03-16T02:27:10+00:00

commit a524c218bc94c705886a0e0fedeee45d1931da32 upstream.

Reported-by: Jo-Philipp Wich 
Fixes: 9aed02feae57bf7 ("ARC: [arcompact] handle unaligned access delay slot")
Cc: linux-kernel@vger.kernel.org
Cc: linux-snps-arc@lists.infradead.org
Signed-off-by: Vineet Gupta 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

ARC: [arcompact] handle unaligned access delay slot corner case

2017-03-16T02:27:07+00:00

commit 9aed02feae57bf7a40cb04ea0e3017cb7a998db4 upstream.

After emulating an unaligned access in delay slot of a branch, we
pretend as the delay slot never happened - so return back to actual
branch target (or next PC if branch was not taken).

Curently we did this by handling STATUS32.DE, we also need to clear the
BTA.T bit, which is disregarded when returning from original misaligned
exception, but could cause weirdness if it took the interrupt return
path (in case interrupt was acive too)

One ARC700 customer ran into this when enabling unaligned access fixup
for kernel mode accesses as well

Signed-off-by: Vineet Gupta 
Signed-off-by: Ben Hutchings

arc: don't leak bits of kernel stack into coredump

2017-02-23T03:54:00+00:00

commit 7798bf2140ebcc36eafec6a4194fffd8d585d471 upstream.

On faulting sigreturn we do get SIGSEGV, all right, but anything
we'd put into pt_regs could end up in the coredump.  And since
__copy_from_user() never zeroed on arc, we'd better bugger off
on its failure without copying random uninitialized bits of
kernel stack into pt_regs...

Signed-off-by: Al Viro 
[bwh: Backported to 3.16:
 - Adjust context
 - Don't change the single return statement]
Signed-off-by: Ben Hutchings

arc: unwind: warn only once if DW2_UNWIND is disabled

2016-08-22T21:38:22+00:00

commit 9bd54517ee86cb164c734f72ea95aeba4804f10b upstream.

If CONFIG_ARC_DW2_UNWIND is disabled every time arc_unwind_core()
gets called following message gets printed in debug console:
----------------->8---------------
CONFIG_ARC_DW2_UNWIND needs to be enabled
----------------->8---------------

That message makes sense if user indeed wants to see a backtrace or
get nice function call-graphs in perf but what if user disabled
unwinder for the purpose? Why pollute his debug console?

So instead we'll warn user about possibly missing feature once and
let him decide if that was what he or she really wanted.

Signed-off-by: Alexey Brodkin 
Signed-off-by: Vineet Gupta 
Signed-off-by: Ben Hutchings