linux-stable.git/arch/arc/kernel, branch v5.10.78

ARC: Fix CONFIG_STACKDEPOT

2021-09-03T08:09:21+00:00

[ Upstream commit bf79167fd86f3b97390fe2e70231d383526bd9cc ]

Enabling CONFIG_STACKDEPOT results in the following build error.

arc-elf-ld: lib/stackdepot.o: in function `filter_irq_stacks':
stackdepot.c:(.text+0x456): undefined reference to `__irqentry_text_start'
arc-elf-ld: stackdepot.c:(.text+0x456): undefined reference to `__irqentry_text_start'
arc-elf-ld: stackdepot.c:(.text+0x476): undefined reference to `__irqentry_text_end'
arc-elf-ld: stackdepot.c:(.text+0x476): undefined reference to `__irqentry_text_end'
arc-elf-ld: stackdepot.c:(.text+0x484): undefined reference to `__softirqentry_text_start'
arc-elf-ld: stackdepot.c:(.text+0x484): undefined reference to `__softirqentry_text_start'
arc-elf-ld: stackdepot.c:(.text+0x48c): undefined reference to `__softirqentry_text_end'
arc-elf-ld: stackdepot.c:(.text+0x48c): undefined reference to `__softirqentry_text_end'

Other architectures address this problem by adding IRQENTRY_TEXT and
SOFTIRQENTRY_TEXT to the text segment, so do the same here.

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

ARC: fp: set FPU_STATUS.FWE to enable FPU_STATUS update on context switch

2021-08-18T06:59:06+00:00

commit 3a715e80400f452b247caa55344f4f60250ffbcf upstream.

FPU_STATUS register contains FP exception flags bits which are updated
by core as side-effect of FP instructions but can also be manually
wiggled such as by glibc C99 functions fe{raise,clear,test}except() etc.
To effect the update, the programming model requires OR'ing FWE
bit (31). This bit is write-only and RAZ, meaning it is effectively
auto-cleared after write and thus needs to be set everytime: which
is how glibc implements this.

However there's another usecase of FPU_STATUS update, at the time of
Linux task switch when incoming task value needs to be programmed into
the register. This was added as part of f45ba2bd6da0dc ("ARCv2:
fpu: preserve userspace fpu state") which missed OR'ing FWE bit,
meaning the new value is effectively not being written at all.
This patch remedies that.

Interestingly, this snafu was not caught in interm glibc testing as the
race window which relies on a specific exception bit to be set/clear is
really small specially when it nvolves context switch.
Fortunately this was caught by glibc's math/test-fenv-tls test which
repeatedly set/clear exception flags in a big loop, concurrently in main
program and also in a thread.

Fixes: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/54
Fixes: f45ba2bd6da0dc ("ARCv2: fpu: preserve userspace fpu state")
Cc: stable@vger.kernel.org	#5.6+
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

sched/core: Initialize the idle task with preemption disabled

2021-07-14T14:55:50+00:00

[ Upstream commit f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 ]

As pointed out by commit

  de9b8f5dcbd9 ("sched: Fix crash trying to dequeue/enqueue the idle thread")

init_idle() can and will be invoked more than once on the same idle
task. At boot time, it is invoked for the boot CPU thread by
sched_init(). Then smp_init() creates the threads for all the secondary
CPUs and invokes init_idle() on them.

As the hotplug machinery brings the secondaries to life, it will issue
calls to idle_thread_get(), which itself invokes init_idle() yet again.
In this case it's invoked twice more per secondary: at _cpu_up(), and at
bringup_cpu().

Given smp_init() already initializes the idle tasks for all *possible*
CPUs, no further initialization should be required. Now, removing
init_idle() from idle_thread_get() exposes some interesting expectations
with regards to the idle task's preempt_count: the secondary startup always
issues a preempt_disable(), requiring some reset of the preempt count to 0
between hot-unplug and hotplug, which is currently served by
idle_thread_get() -> idle_init().

Given the idle task is supposed to have preemption disabled once and never
see it re-enabled, it seems that what we actually want is to initialize its
preempt_count to PREEMPT_DISABLED and leave it there. Do that, and remove
init_idle() from idle_thread_get().

Secondary startups were patched via coccinelle:

  @begone@
  @@

  -preempt_disable();
  ...
  cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

Signed-off-by: Valentin Schneider 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Link: https://lore.kernel.org/r/20210512094636.2958515-1-valentin.schneider@arm.com
Signed-off-by: Sasha Levin

ARCv2: save ABI registers across signal handling

2021-06-23T12:42:51+00:00

commit 96f1b00138cb8f04c742c82d0a7c460b2202e887 upstream.

ARCv2 has some configuration dependent registers (r30, r58, r59) which
could be targetted by the compiler. To keep the ABI stable, these were
unconditionally part of the glibc ABI
(sysdeps/unix/sysv/linux/arc/sys/ucontext.h:mcontext_t) however we
missed populating them (by saving/restoring them across signal
handling).

This patch fixes the issue by
 - adding arcv2 ABI regs to kernel struct sigcontext
 - populating them during signal handling

Change to struct sigcontext might seem like a glibc ABI change (although
it primarily uses ucontext_t:mcontext_t) but the fact is
 - it has only been extended (existing fields are not touched)
 - the old sigcontext was ABI incomplete to begin with anyways

Fixes: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/53
Cc: 
Tested-by: kernel test robot 
Reported-by: Vladimir Isaev 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARC: entry: fix off-by-one error in syscall number validation

2021-05-19T08:13:10+00:00

commit 3433adc8bd09fc9f29b8baddf33b4ecd1ecd2cdc upstream.

We have NR_syscall syscalls from [0 .. NR_syscall-1].
However the check for invalid syscall number is "> NR_syscall" as
opposed to >=. This off-by-one error erronesously allows "NR_syscall"
to be treated as valid syscall causeing out-of-bounds access into
syscall-call table ensuing a crash (holes within syscall table have a
invalid-entry handler but this is beyond the array implementing the
table).

This problem showed up on v5.6 kernel when testing glibc 2.33 (v5.10
kernel capable, includng faccessat2 syscall 439). The v5.6 kernel has
NR_syscalls=439 (0 to 438). Due to the bug, 439 passed by glibc was
not handled as -ENOSYS but processed leading to a crash.

Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/48
Reported-by: Shahab Vahedi 
Cc: 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

arc: kernel: Return -EFAULT if copy_to_user() fails

2021-04-21T11:00:51+00:00

[ Upstream commit 46e152186cd89d940b26726fff11eb3f4935b45a ]

The copy_to_user() function returns the number of bytes remaining to be
copied, but we want to return -EFAULT if the copy doesn't complete.

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

ARC: stack unwinding: reorganize how initial register state setup

2020-11-18T04:12:01+00:00

This is a non-functional change, if anything a better fall-back
handling.

Signed-off-by: Vineet Gupta

ARC: stack unwinding: don't assume non-current task is sleeping

2020-11-18T04:12:01+00:00

To start stack unwinding (SP, PC and BLINK) are needed. When the
explicit execution context (pt_regs etc) is not available, unwinder
assumes the task is sleeping (in __switch_to()) and fetches SP and BLINK
from kernel mode stack.

But this assumption is not true, specially in a SMP system, when top
runs on 1 core, there may be active running processes on all cores.

So when unwinding non courrent tasks, ensure they are NOT running.

And while at it, handle the self unwinding case explicitly.

This came out of investigation of a customer reported hang with
rcutorture+top

Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/31
Signed-off-by: Vineet Gupta

ARC: [plat-hsdk] Remap CCMs super early in asm boot trampoline

2020-11-02T19:45:09+00:00

ARC HSDK platform stopped booting on released v5.10-rc1, getting stuck
in startup of non master SMP cores.

This was bisected to upstream commit 7fef431be9c9ac25
"(mm/page_alloc: place pages to tail in __free_pages_core())"
That commit itself is harmless, it just exposed a subtle assumption in
our platform code (hence CC'ing linux-mm just as FYI in case some other
arches / platforms trip on it).

The upstream commit is semantically disruptive as it reverses the order
of page allocations (actually it can be good test for hardware
verification to exercise different memory patterns altogether).
For ARC HSDK platform that meant a remapped memory region (pertaining to
unused Closely Coupled Memory) started getting used early for dynamice
allocations, while not effectively remapped on all the cores, triggering
memory error exception on those cores.

The fix is to move the CCM remapping from early platform code to to early core
boot code. And while it is undesirable to riddle common boot code with
platform quirks, there is no other way to do this since the faltering code
involves setting up stack itself so even function calls are not allowed at
that point.

If anyone is interested, all the gory details can be found at Link below.

Link: https://github.com/foss-for-synopsys-dwc-arc-processors/linux/issues/32
Cc: David Hildenbrand 
Cc: linux-mm@kvack.org
Signed-off-by: Vineet Gupta

ARC: stack unwinding: avoid indefinite looping

2020-11-02T19:45:08+00:00

Currently stack unwinder is a while(1) loop which relies on the dwarf
unwinder to signal termination, which in turn relies on dwarf info to do
so. This in theory could cause an infinite loop if the dwarf info was
somehow messed up or the register contents were etc.

This fix thus detects the excessive looping and breaks the loop.

| Mem: 26184K used, 1009136K free, 0K shrd, 0K buff, 14416K cached
| CPU:  0.0% usr 72.8% sys  0.0% nic 27.1% idle  0.0% io  0.0% irq  0.0% sirq
| Load average: 4.33 2.60 1.11 2/74 139
|   PID  PPID USER     STAT   VSZ %VSZ CPU %CPU COMMAND
|   133     2 root     SWN      0  0.0   3 22.9 [rcu_torture_rea]
|   132     2 root     SWN      0  0.0   0 22.0 [rcu_torture_rea]
|   131     2 root     SWN      0  0.0   3 21.5 [rcu_torture_rea]
|   126     2 root     RW       0  0.0   2  5.4 [rcu_torture_wri]
|   129     2 root     SWN      0  0.0   0  0.2 [rcu_torture_fak]
|   137     2 root     SW       0  0.0   0  0.2 [rcu_torture_cbf]
|   127     2 root     SWN      0  0.0   0  0.1 [rcu_torture_fak]
|   138   115 root     R     1464  0.1   2  0.1 top
|   130     2 root     SWN      0  0.0   0  0.1 [rcu_torture_fak]
|   128     2 root     SWN      0  0.0   0  0.1 [rcu_torture_fak]
|   115     1 root     S     1472  0.1   1  0.0 -/bin/sh
|   104     1 root     S     1464  0.1   0  0.0 inetd
|     1     0 root     S     1456  0.1   2  0.0 init
|    78     1 root     S     1456  0.1   0  0.0 syslogd -O /var/log/messages
|   134     2 root     SW       0  0.0   2  0.0 [rcu_torture_sta]
|    10     2 root     IW       0  0.0   1  0.0 [rcu_preempt]
|    88     2 root     IW       0  0.0   1  0.0 [kworker/1:1-eve]
|    66     2 root     IW       0  0.0   2  0.0 [kworker/2:2-eve]
|    39     2 root     IW       0  0.0   2  0.0 [kworker/2:1-eve]
| unwinder looping too long, aborting !

Cc: 
Signed-off-by: Vineet Gupta