linux.git/arch/arm64/kernel/time.c, branch v4.19

arm64: fix unwind_frame() for filtered out fn for function graph tracing

2018-02-23T13:46:38+00:00

do_task_stat() calls get_wchan(), which further does unwind_frame().
unwind_frame() restores frame->pc to original value in case function
graph tracer has modified a return address (LR) in a stack frame to hook
a function return. However, if function graph tracer has hit a filtered
function, then we can't unwind it as ftrace_push_return_trace() has
biased the index(frame->graph) with a 'huge negative'
offset(-FTRACE_NOTRACE_DEPTH).

Moreover, arm64 stack walker defines index(frame->graph) as unsigned
int, which can not compare a -ve number.

Similar problem we can have with calling of walk_stackframe() from
save_stack_trace_tsk() or dump_backtrace().

This patch fixes unwind_frame() to test the index for -ve value and
restore index accordingly before we can restore frame->pc.

Reproducer:

cd /sys/kernel/debug/tracing/
echo schedule > set_graph_notrace
echo 1 > options/display-graph
echo wakeup > current_tracer
ps -ef | grep -i agent

Above commands result in:
Unable to handle kernel paging request at virtual address ffff801bd3d1e000
pgd = ffff8003cbe97c00
[ffff801bd3d1e000] *pgd=0000000000000000, *pud=0000000000000000
Internal error: Oops: 96000006 [#1] SMP
[...]
CPU: 5 PID: 11696 Comm: ps Not tainted 4.11.0+ #33
[...]
task: ffff8003c21ba000 task.stack: ffff8003cc6c0000
PC is at unwind_frame+0x12c/0x180
LR is at get_wchan+0xd4/0x134
pc : [] lr : [] pstate: 60000145
sp : ffff8003cc6c3ab0
x29: ffff8003cc6c3ab0 x28: 0000000000000001
x27: 0000000000000026 x26: 0000000000000026
x25: 00000000000012d8 x24: 0000000000000000
x23: ffff8003c1c04000 x22: ffff000008c83000
x21: ffff8003c1c00000 x20: 000000000000000f
x19: ffff8003c1bc0000 x18: 0000fffffc593690
x17: 0000000000000000 x16: 0000000000000001
x15: 0000b855670e2b60 x14: 0003e97f22cf1d0f
x13: 0000000000000001 x12: 0000000000000000
x11: 00000000e8f4883e x10: 0000000154f47ec8
x9 : 0000000070f367c0 x8 : 0000000000000000
x7 : 00008003f7290000 x6 : 0000000000000018
x5 : 0000000000000000 x4 : ffff8003c1c03cb0
x3 : ffff8003c1c03ca0 x2 : 00000017ffe80000
x1 : ffff8003cc6c3af8 x0 : ffff8003d3e9e000

Process ps (pid: 11696, stack limit = 0xffff8003cc6c0000)
Stack: (0xffff8003cc6c3ab0 to 0xffff8003cc6c4000)
[...]
[] unwind_frame+0x12c/0x180
[] do_task_stat+0x864/0x870
[] proc_tgid_stat+0x3c/0x48
[] proc_single_show+0x5c/0xb8
[] seq_read+0x160/0x414
[] __vfs_read+0x58/0x164
[] vfs_read+0x88/0x144
[] SyS_read+0x60/0xc0
[] __sys_trace_return+0x0/0x4

Fixes: 20380bb390a4 (arm64: ftrace: fix a stack tracer's output under function graph tracer)
Signed-off-by: Pratyush Anand 
Signed-off-by: Jerome Marchand 
[catalin.marinas@arm.com: replace WARN_ON with WARN_ON_ONCE]
Signed-off-by: Catalin Marinas

arm64: unwind: remove sp from struct stackframe

2017-08-09T13:10:29+00:00

The unwind code sets the sp member of struct stackframe to
'frame pointer + 0x10' unconditionally, without regard for whether
doing so produces a legal value. So let's simply remove it now that
we have stopped using it anyway.

Signed-off-by: Ard Biesheuvel 
Signed-off-by: Mark Rutland 
Cc: Catalin Marinas 
Cc: James Morse 
Cc: Will Deacon

clocksource/drivers: Rename clocksource_probe to timer_probe

2017-06-14T09:59:16+00:00

The function name is now renamed to 'timer_probe' for consistency with
the CLOCKSOURCE_OF_DECLARE => TIMER_OF_DECLARE change.

Signed-off-by: Daniel Lezcano 
Acked-by: Viresh Kumar 
Acked-by: Heiko Stuebner 
Reviewed-by: Linus Walleij

arm64: ftrace: fix a stack tracer's output under function graph tracer

2015-12-21T17:26:02+00:00

Function graph tracer modifies a return address (LR) in a stack frame
to hook a function return. This will result in many useless entries
(return_to_handler) showing up in
 a) a stack tracer's output
 b) perf call graph (with perf record -g)
 c) dump_backtrace (at panic et al.)

For example, in case of a),
  $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
  $ echo 1 > /proc/sys/kernel/stack_trace_enabled
  $ cat /sys/kernel/debug/tracing/stack_trace
        Depth    Size   Location    (54 entries)
        -----    ----   --------
  0)     4504      16   gic_raise_softirq+0x28/0x150
  1)     4488      80   smp_cross_call+0x38/0xb8
  2)     4408      48   return_to_handler+0x0/0x40
  3)     4360      32   return_to_handler+0x0/0x40
  ...

In case of b),
  $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
  $ perf record -e mem:XXX:x -ag -- sleep 10
  $ perf report
                  ...
                  |          |          |--0.22%-- 0x550f8
                  |          |          |          0x10888
                  |          |          |          el0_svc_naked
                  |          |          |          sys_openat
                  |          |          |          return_to_handler
                  |          |          |          return_to_handler
                  ...

In case of c),
  $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
  $ echo c > /proc/sysrq-trigger
  ...
  Call trace:
  [] sysrq_handle_crash+0x24/0x30
  [] return_to_handler+0x0/0x40
  [] return_to_handler+0x0/0x40
  ...

This patch replaces such entries with real addresses preserved in
current->ret_stack[] at unwind_frame(). This way, we can cover all
the cases.

Reviewed-by: Jungseok Lee 
Signed-off-by: AKASHI Takahiro 
[will: fixed minor context changes conflicting with irq stack bits]
Signed-off-by: Will Deacon

arm64: pass a task parameter to unwind_frame()

2015-12-21T17:26:01+00:00

Function graph tracer modifies a return address (LR) in a stack frame
to hook a function's return. This will result in many useless entries
(return_to_handler) showing up in a call stack list.
We will fix this problem in a later patch ("arm64: ftrace: fix a stack
tracer's output under function graph tracer"). But since real return
addresses are saved in ret_stack[] array in struct task_struct,
unwind functions need to be notified of, in addition to a stack pointer
address, which task is being traced in order to find out real return
addresses.

This patch extends unwind functions' interfaces by adding an extra
argument of a pointer to task_struct.

Signed-off-by: AKASHI Takahiro 
Signed-off-by: Will Deacon

clocksource: cosmetic: Drop OF 'dependency' from symbols

2015-10-01T00:18:39+00:00

Seeing the 'of' characters in a symbol that is being called from
ACPI seems to freak out people. So let's do a bit of pointless
renaming so that these folks do feel at home.

Signed-off-by: Marc Zyngier 
Acked-by: Catalin Marinas 
Reviewed-by: Hanjun Guo 
Acked-by: Thomas Gleixner 
Tested-by: Hanjun Guo 
Signed-off-by: Rafael J. Wysocki

clocksource / arm_arch_timer: Convert to ACPI probing

2015-10-01T00:18:39+00:00

It is now absolutely trivial to convert the arch timer driver to
use ACPI probing, just like its DT counterpart.

Let's enjoy another crapectomy.

Signed-off-by: Marc Zyngier 
Acked-by: Catalin Marinas 
Acked-by: Thomas Gleixner 
Tested-by: Hanjun Guo 
Signed-off-by: Rafael J. Wysocki

arm64: force CONFIG_SMP=y and remove redundant #ifdefs

2015-07-27T10:08:40+00:00

Nobody seems to be producing !SMP systems anymore, so this is just
becoming a source of kernel bugs, particularly if people want to use
coherent DMA with non-shared pages.

This patch forces CONFIG_SMP=y for arm64, removing a modest amount of
code in the process.

Signed-off-by: Will Deacon

clocksource / arch_timer: Parse GTDT to initialize arch timer

2015-03-26T15:13:07+00:00

Using the information presented by GTDT (Generic Timer Description Table)
to initialize the arch timer (not memory-mapped).

CC: Daniel Lezcano 
CC: Thomas Gleixner 
Originally-by: Amit Daniel Kachhap 
Tested-by: Suravee Suthikulpanit 
Tested-by: Yijing Wang 
Tested-by: Mark Langsdorf 
Tested-by: Jon Masters 
Tested-by: Timur Tabi 
Tested-by: Robert Richter 
Acked-by: Robert Richter 
Acked-by: Daniel Lezcano 
Reviewed-by: Grant Likely 
Signed-off-by: Hanjun Guo 
Signed-off-by: Will Deacon

arm64: kernel: initialize broadcast hrtimer based clock event device

2014-05-30T16:48:13+00:00

On platforms implementing CPU power management, the CPUidle subsystem
can allow CPUs to enter idle states where local timers logic is lost on power
down. To keep the software timers functional the kernel relies on an
always-on broadcast timer to be present in the platform to relay the
interrupt signalling the timer expiries.

For platforms implementing CPU core gating that do not implement an always-on
HW timer or implement it in a broken way, this patch adds code to initialize
the kernel hrtimer based clock event device upon boot (which can be chosen as
tick broadcast device by the kernel).
It relies on a dynamically chosen CPU to be always powered-up. This CPU then
relays the timer interrupt to CPUs in deep-idle states through its HW local
timer device.

Having a CPU always-on has implications on power management platform
capabilities and makes CPUidle suboptimal, since at least a CPU is kept
always in a shallow idle state by the kernel to relay timer interrupts,
but at least leaves the kernel with a functional system with some working
power management capabilities.

The hrtimer based clock event device is unconditionally registered, but
has the lowest possible rating such that any broadcast-capable HW clock
event device present will be chosen in preference as the tick broadcast
device.

Reviewed-by: Preeti U Murthy 
Acked-by: Will Deacon 
Acked-by: Mark Rutland 
Signed-off-by: Lorenzo Pieralisi 
Signed-off-by: Will Deacon