linux-stable.git/arch/arc/kernel, branch v4.19.78

ARC: show_regs: lockdep: re-enable preemption

2019-09-16T06:22:02+00:00

[ Upstream commit f731a8e89f8c78985707c626680f3e24c7a60772 ]

signal handling core calls show_regs() with preemption disabled which
on ARC takes mmap_sem for mm/vma access, causing lockdep splat.

| [ARCLinux]# ./segv-null-ptr
| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at kernel/fork.c:1011
| in_atomic(): 1, irqs_disabled(): 0, pid: 70, name: segv-null-ptr
| no locks held by segv-null-ptr/70.
| CPU: 0 PID: 70 Comm: segv-null-ptr Not tainted 4.18.0+ #69
|
| Stack Trace:
|  arc_unwind_core+0xcc/0x100
|  ___might_sleep+0x17a/0x190
|  mmput+0x16/0xb8
|  show_regs+0x52/0x310
|  get_signal+0x5ee/0x610
|  do_signal+0x2c/0x218
|  resume_user_mode_begin+0x90/0xd8

Workaround by re-enabling preemption temporarily.

Note that the preemption disabling in core code around show_regs()
was introduced by commit 3a9f84d354ce ("signals, debug: fix BUG: using
smp_processor_id() in preemptible code in print_fatal_signal()")

to silence a differnt lockdep seen on x86 bakc in 2009.

Cc: 
Signed-off-by: Vineet Gupta 
Signed-off-by: Sasha Levin

ARC: enable uboot support unconditionally

2019-08-06T17:06:57+00:00

commit 493a2f812446e92bcb1e69a77381b4d39808d730 upstream.

After reworking U-boot args handling code and adding paranoid
arguments check we can eliminate CONFIG_ARC_UBOOT_SUPPORT and
enable uboot support unconditionally.

For JTAG case we can assume that core registers will come up
reset value of 0 or in worst case we rely on user passing
'-on=clear_regs' to Metaware debugger.

Cc: stable@vger.kernel.org
Tested-by: Corentin LABBE 
Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARC: hide unused function unw_hdr_alloc

2019-07-21T07:03:14+00:00

commit fd5de2721ea7d16e2b16c4049ac49f229551b290 upstream.

As kernelci.org reports, this function is not used in
vdk_hs38_defconfig:

arch/arc/kernel/unwind.c:188:14: warning: 'unw_hdr_alloc' defined but not used [-Wunused-function]

Fixes: bc79c9a72165 ("ARC: dw2 unwind: Reinstante unwinding out of modules")
Link: https://kernelci.org/build/id/5d1cae3f59b514300340c132/logs/
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARC: u-boot args: check that magic number is correct

2019-04-20T07:15:54+00:00

[ Upstream commit edb64bca50cd736c6894cc6081d5263c007ce005 ]

In case of devboards we really often disable bootloader and load
Linux image in memory via JTAG. Even if kernel tries to verify
uboot_tag and uboot_arg there is sill a chance that we treat some
garbage in registers as valid u-boot arguments in JTAG case.
E.g. it is enough to have '1' in r0 to treat any value in r2 as
a boot command line.

So check that magic number passed from u-boot is correct and drop
u-boot arguments otherwise. That helps to reduce the possibility
of using garbage as u-boot arguments in JTAG case.

We can safely check U-boot magic value (0x0) in linux passed via
r1 register as U-boot pass it from the beginning. So there is no
backward-compatibility issues.

Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta 
Signed-off-by: Sasha Levin

ARCv2: don't assume core 0x54 has dual issue

2019-03-23T19:09:51+00:00

[ Upstream commit 7b2e932f633bcb7b190fc7031ce6dac75f8c3472 ]

The first release of core4 (0x54) was dual issue only (HS4x).
Newer releases allow hardware to be configured as single issue (HS3x)
or dual issue.

Prevent accessing a HS4x only aux register in HS3x, which otherwise
leads to illegal instruction exceptions

Signed-off-by: Vineet Gupta 
Signed-off-by: Sasha Levin

ARCv2: support manual regfile save on interrupts

2019-03-23T19:09:51+00:00

[ Upstream commit e494239a007e601448110ac304fe055951f9de3b ]

There's a hardware bug which affects the HSDK platform, triggered by
micro-ops for auto-saving regfile on taken interrupt. The workaround is
to inhibit autosave.

Signed-off-by: Vineet Gupta 
Signed-off-by: Sasha Levin

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

2019-03-05T16:58:48+00:00

[ Upstream commit ab6c03676cb190156603cf4c5ecf97aa406c9c53 ]

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: Sasha Levin

ARC: U-boot: check arguments paranoidly

2019-02-27T09:09:00+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.

Cc: stable@vger.kernel.org
Tested-by: Corentin LABBE 
Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARCv2: Enable unaligned access in early ASM code

2019-02-27T09:09:00+00:00

commit 252f6e8eae909bc075a1b1e3b9efb095ae4c0b56 upstream.

It is currently done in arc_init_IRQ() which might be too late
considering gcc 7.3.1 onwards (GNU 2018.03) generates unaligned
memory accesses by default

Cc: stable@vger.kernel.org #4.4+
Signed-off-by: Eugeniy Paltsev 
Signed-off-by: Vineet Gupta 
[vgupta: rewrote changelog]
Signed-off-by: Greg Kroah-Hartman

ARC: clone syscall to setp r25 as thread pointer

2018-10-05T21:33:29+00:00

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
Cc: stable@vger.kernel.org
Reported-by: Nikita Sobolev 
Signed-off-by: Vineet Gupta