linux.git/arch/arm64/kernel/time.c, branch v6.0

arm64: Make profile_pc() use arch_stack_walk()

2021-12-10T14:06:04+00:00

To enable RELIABLE_STACKTRACE and LIVEPATCH on arm64, we need to
substantially rework arm64's unwinding code. As part of this, we want to
minimize the set of unwind interfaces we expose, and avoid open-coding
of unwind logic outside of stacktrace.c.

Currently profile_pc() walks the stack of an interrupted context by
calling start_backtrace() with the context's PC and FP, and iterating
unwind steps using walk_stackframe(). This is functionally equivalent to
calling arch_stack_walk() with the interrupted context's pt_regs, which
will start with the PC and FP from the regs.

Make profile_pc() use arch_stack_walk(). This simplifies profile_pc(),
and in future will alow us to make walk_stackframe() private to
stacktrace.c.

At the same time, we remove the early return for when regs->pc is not in
lock functions, as this will be handled by the first call to the
profile_pc_cb() callback.

There should be no functional change as a result of this patch.

Signed-off-by: Madhavan T. Venkataraman 
Reviewed-by: Mark Rutland 
[Mark: remove early return, elaborate commit message, fix includes]
Signed-off-by: Mark Rutland 
Reviewed-by: Mark Brown 
Link: https://lore.kernel.org/r/20211129142849.3056714-8-mark.rutland@arm.com
Signed-off-by: Catalin Marinas

arm64: time: Replace by

2020-02-12T17:26:38+00:00

The arm64 time code is not a clock provider, and just needs to call
of_clk_init().

Hence it can include  instead of .

Reviewed-by: Stephen Boyd 
Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Will Deacon

arm64: Retrieve stolen time as paravirtualized guest

2019-10-21T18:20:31+00:00

Enable paravirtualization features when running under a hypervisor
supporting the PV_TIME_ST hypercall.

For each (v)CPU, we ask the hypervisor for the location of a shared
page which the hypervisor will use to report stolen time to us. We set
pv_time_ops to the stolen time function which simply reads the stolen
value from the shared page for a VCPU. We guarantee single-copy
atomicity using READ_ONCE which means we can also read the stolen
time for another VCPU than the currently running one while it is
potentially being updated by the hypervisor.

Signed-off-by: Steven Price 
Signed-off-by: Marc Zyngier

arm64: stacktrace: Factor out backtrace initialisation

2019-07-22T10:44:08+00:00

Some common code is required by each stacktrace user to initialise
struct stackframe before the first call to unwind_frame().

In preparation for adding to the common code, this patch factors it
out into a separate function start_backtrace(), and modifies the
stacktrace callers appropriately.

No functional change.

Signed-off-by: Dave Martin 
[Mark: drop tsk argument, update more callsites]
Signed-off-by: Mark Rutland 
Reviewed-by: James Morse 
Acked-by: Catalin Marinas 
Signed-off-by: Will Deacon

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 234

2019-06-19T15:09:07+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation this program is
  distributed in the hope that it will be useful but without any
  warranty without even the implied warranty of merchantability or
  fitness for a particular purpose see the gnu general public license
  for more details you should have received a copy of the gnu general
  public license along with this program if not see http www gnu org
  licenses

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 503 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Alexios Zavras 
Reviewed-by: Allison Randal 
Reviewed-by: Enrico Weigelt 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de
Signed-off-by: Greg Kroah-Hartman

arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack

2018-12-22T13:21:02+00:00

The structure of the ret_stack array on the task struct is going to
change, and accessing it directly via the curr_ret_stack index will no
longer give the ret_stack entry that holds the return address. To access
that, architectures must now use ftrace_graph_get_ret_stack() to get the
associated ret_stack that matches the saved return address.

Cc: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon 
Cc: Mark Rutland 
Cc: Catalin Marinas 
Signed-off-by: Steven Rostedt (VMware)

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