arm64: stacktrace: Better handle corrupted stacks

The arm64 stacktrace code is careful to only dereference frame records
in valid stack ranges, ensuring that a corrupted frame record won

arm64: stacktrace: Better handle corrupted stacks

The arm64 stacktrace code is careful to only dereference frame records
in valid stack ranges, ensuring that a corrupted frame record won't
result in a faulting access.

However, it's still possible for corrupt frame records to result in
infinite loops in the stacktrace code, which is also undesirable.

This patch ensures that we complete a stacktrace in finite time, by
keeping track of which stacks we have already completed unwinding, and
verifying that if the next frame record is on the same stack, it is at a
higher address.

As this has turned out to be particularly subtle, comments are added to
explain the procedure.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Acked-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Tengfei Fan <tengfeif@codeaurora.org>
Signed-off-by: Will Deacon <will@kernel.org>

show more ...

arm64: stacktrace: Factor out backtrace initialisation

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

arm64: stacktrace: Factor out backtrace initialisation

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 <dave.martin@arm.com>
[Mark: drop tsk argument, update more callsites]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

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

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it u

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

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 <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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arm64/stacktrace: Remove the pointless ULONG_MAX marker

Terminating the last trace entry with ULONG_MAX is a completely pointless
exercise and none of the consumers can rely on it becaus

arm64/stacktrace: Remove the pointless ULONG_MAX marker

Terminating the last trace entry with ULONG_MAX is a completely pointless
exercise and none of the consumers can rely on it because it's
inconsistently implemented across architectures. In fact quite some of the
callers remove the entry and adjust stack_trace.nr_entries afterwards.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lkml.kernel.org/r/20190410103644.220247845@linutronix.de

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arm64/stacktrace: Export save_stack_trace_regs()

The ARM64 implements the save_stack_trace_regs function, but it is
unusable for any diagnostic tooling compiled as a kernel module due

arm64/stacktrace: Export save_stack_trace_regs()

The ARM64 implements the save_stack_trace_regs function, but it is
unusable for any diagnostic tooling compiled as a kernel module due
the missing EXPORT_SYMBOL_GPL for the function. Export
save_stack_trace_regs() to align with other architectures such as
s390, openrisc, and powerpc. This is similar to the ARM64 export of
save_stack_trace_tsk() added in git commit e27c7fa015d6.

Signed-off-by: William Cohen <wcohen@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack

The structure of the ret_stack array on the task struct is going to
change, and accessing it directly via the curr_ret_s

arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret_stack

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 <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

show more ...

arm64: function_graph: Remove use of FTRACE_NOTRACE_DEPTH

Functions in the set_graph_notrace no longer subtract FTRACE_NOTRACE_DEPTH
from curr_ret_stack, as that is now implemented via t

arm64: function_graph: Remove use of FTRACE_NOTRACE_DEPTH

Functions in the set_graph_notrace no longer subtract FTRACE_NOTRACE_DEPTH
from curr_ret_stack, as that is now implemented via the trace_recursion
flags. Access to curr_ret_stack no longer needs to worry about checking for
this. curr_ret_stack is still initialized to -1, when there's not a shadow
stack allocated.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

show more ...

arm64: Add stack information to on_accessible_stack

In preparation for enabling the stackleak plugin on arm64,
we need a way to get the bounds of the current stack. Extend
on_accessi

arm64: Add stack information to on_accessible_stack

In preparation for enabling the stackleak plugin on arm64,
we need a way to get the bounds of the current stack. Extend
on_accessible_stack to get this information.

Acked-by: Alexander Popov <alex.popov@linux.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Laura Abbott <labbott@redhat.com>
[will: folded in fix for allmodconfig build breakage w/ sdei]
Signed-off-by: Will Deacon <will.deacon@arm.com>

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Revert "arm64: fix infinite stacktrace"

This reverts commit 7e7df71fd57ff2894d96abb0080922bf39460a79.

When unwinding out of the IRQ stack and onto the interrupted EL1 stack,
we

Revert "arm64: fix infinite stacktrace"

This reverts commit 7e7df71fd57ff2894d96abb0080922bf39460a79.

When unwinding out of the IRQ stack and onto the interrupted EL1 stack,
we cannot rely on the frame pointer being strictly increasing, as this
could terminate the backtrace early depending on how the stacks have
been allocated.

Signed-off-by: Will Deacon <will.deacon@arm.com>

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arm64: fix infinite stacktrace

I've got this infinite stacktrace when debugging another problem:
[ 908.795225] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 908.796176] 1-...

arm64: fix infinite stacktrace

I've got this infinite stacktrace when debugging another problem:
[ 908.795225] INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 908.796176] 1-...!: (1 GPs behind) idle=952/1/4611686018427387904 softirq=1462/1462 fqs=355
[ 908.797692] 2-...!: (1 GPs behind) idle=f42/1/4611686018427387904 softirq=1550/1551 fqs=355
[ 908.799189] (detected by 0, t=2109 jiffies, g=130, c=129, q=235)
[ 908.800284] Task dump for CPU 1:
[ 908.800871] kworker/1:1 R running task 0 32 2 0x00000022
[ 908.802127] Workqueue: writecache-writeabck writecache_writeback [dm_writecache]
[ 908.820285] Call trace:
[ 908.824785] __switch_to+0x68/0x90
[ 908.837661] 0xfffffe00603afd90
[ 908.844119] 0xfffffe00603afd90
[ 908.850091] 0xfffffe00603afd90
[ 908.854285] 0xfffffe00603afd90
[ 908.863538] 0xfffffe00603afd90
[ 908.865523] 0xfffffe00603afd90

The machine just locked up and kept on printing the same line over and
over again. This patch fixes it.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

show more ...

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

do_task_stat() calls get_wchan(), which further does unwind_frame().
unwind_frame() restores frame->pc to origina

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

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 : [<ffff00000808892c>] lr : [<ffff0000080860b8>] 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)
[...]
[<ffff00000808892c>] unwind_frame+0x12c/0x180
[<ffff000008305008>] do_task_stat+0x864/0x870
[<ffff000008305c44>] proc_tgid_stat+0x3c/0x48
[<ffff0000082fde0c>] proc_single_show+0x5c/0xb8
[<ffff0000082b27e0>] seq_read+0x160/0x414
[<ffff000008289e6c>] __vfs_read+0x58/0x164
[<ffff00000828b164>] vfs_read+0x88/0x144
[<ffff00000828c2e8>] SyS_read+0x60/0xc0
[<ffff0000080834a0>] __sys_trace_return+0x0/0x4

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

show more ...

arm64: stacktrace: avoid listing stacktrace functions in stacktrace

The stacktraces always begin as follows:

[<c00117b4>] save_stack_trace_tsk+0x0/0x98
[<c0011870>] save_sta

arm64: stacktrace: avoid listing stacktrace functions in stacktrace

The stacktraces always begin as follows:

[<c00117b4>] save_stack_trace_tsk+0x0/0x98
[<c0011870>] save_stack_trace+0x24/0x28
...

This is because the stack trace code includes the stack frames for
itself. This is incorrect behaviour, and also leads to "skip" doing the
wrong thing (which is the number of stack frames to avoid recording.)

Perversely, it does the right thing when passed a non-current thread.
Fix this by ensuring that we have a known constant number of frames
above the main stack trace function, and always skip these.

This was fixed for arch arm by commit 3683f44c42e9 ("ARM: stacktrace:
avoid listing stacktrace functions in stacktrace")

Link: http://lkml.kernel.org/r/1504078343-28754-1-git-send-email-guptap@codeaurora.org
Signed-off-by: Prakash Gupta <guptap@codeaurora.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

show more ...

arm64: add on_accessible_stack()

Both unwind_frame() and dump_backtrace() try to check whether a stack
address is sane to access, with very similar logic. Both will need
updating in

arm64: add on_accessible_stack()

Both unwind_frame() and dump_backtrace() try to check whether a stack
address is sane to access, with very similar logic. Both will need
updating in order to handle overflow stacks.

Factor out this logic into a helper, so that we can avoid further
duplication when we add overflow stacks.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>

show more ...

arm64: unwind: remove sp from struct stackframe

The unwind code sets the sp member of struct stackframe to
'frame pointer + 0x10' unconditionally, without regard for whether
doing so

arm64: unwind: remove sp from struct stackframe

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 <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

show more ...

arm64: unwind: reference pt_regs via embedded stack frame

As it turns out, the unwind code is slightly broken, and probably has
been for a while. The problem is in the dumping of the exc

arm64: unwind: reference pt_regs via embedded stack frame

As it turns out, the unwind code is slightly broken, and probably has
been for a while. The problem is in the dumping of the exception stack,
which is intended to dump the contents of the pt_regs struct at each
level in the call stack where an exception was taken and routed to a
routine marked as __exception (which means its stack frame is right
below the pt_regs struct on the stack).

'Right below the pt_regs struct' is ill defined, though: the unwind
code assigns 'frame pointer + 0x10' to the .sp member of the stackframe
struct at each level, and dump_backtrace() happily dereferences that as
the pt_regs pointer when encountering an __exception routine. However,
the actual size of the stack frame created by this routine (which could
be one of many __exception routines we have in the kernel) is not known,
and so frame.sp is pretty useless to figure out where struct pt_regs
really is.

So it seems the only way to ensure that we can find our struct pt_regs
when walking the stack frames is to put it at a known fixed offset of
the stack frame pointer that is passed to such __exception routines.
The simplest way to do that is to put it inside pt_regs itself, which is
the main change implemented by this patch. As a bonus, doing this allows
us to get rid of a fair amount of cruft related to walking from one stack
to the other, which is especially nice since we intend to introduce yet
another stack for overflow handling once we add support for vmapped
stacks. It also fixes an inconsistency where we only add a stack frame
pointing to ELR_EL1 if we are executing from the IRQ stack but not when
we are executing from the task stack.

To consistly identify exceptions regs even in the presence of exceptions
taken from entry code, we must check whether the next frame was created
by entry text, rather than whether the current frame was crated by
exception text.

To avoid backtracing using PCs that fall in the idmap, or are controlled
by userspace, we must explcitly zero the FP and LR in startup paths, and
must ensure that the frame embedded in pt_regs is zeroed upon entry from
EL0. To avoid these NULL entries showin in the backtrace, unwind_frame()
is updated to avoid them.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
[Mark: compare current frame against .entry.text, avoid bogus PCs]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

show more ...

arm64: unwind: disregard frame.sp when validating frame pointer

Currently, when unwinding the call stack, we validate the frame pointer
of each frame against frame.sp, whose value is not

arm64: unwind: disregard frame.sp when validating frame pointer

Currently, when unwinding the call stack, we validate the frame pointer
of each frame against frame.sp, whose value is not clearly defined, and
which makes it more difficult to link stack frames together across
different stacks. It is far better to simply check whether the frame
pointer itself points into a valid stack.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

show more ...

arm64: unwind: avoid percpu indirection for irq stack

Our IRQ_STACK_PTR() and on_irq_stack() helpers both take a cpu argument,
used to generate a percpu address. In all cases, they are p

arm64: unwind: avoid percpu indirection for irq stack

Our IRQ_STACK_PTR() and on_irq_stack() helpers both take a cpu argument,
used to generate a percpu address. In all cases, they are passed
{raw_,}smp_processor_id(), so this parameter is redundant.

Since {raw_,}smp_processor_id() use a percpu variable internally, this
approach means we generate a percpu offset to find the current cpu, then
use this to index an array of percpu offsets, which we then use to find
the current CPU's IRQ stack pointer. Thus, most of the work is
redundant.

Instead, we can consistently use raw_cpu_ptr() to generate the CPU's
irq_stack pointer by simply adding the percpu offset to the irq_stack
address, which is simpler in both respects.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>

show more ...

arm64: Export save_stack_trace_tsk()

The kernel watchdog is a great debugging tool for finding tasks that
consume a disproportionate amount of CPU time in contiguous chunks. One
can

arm64: Export save_stack_trace_tsk()

The kernel watchdog is a great debugging tool for finding tasks that
consume a disproportionate amount of CPU time in contiguous chunks. One
can imagine building a similar watchdog for arbitrary driver threads
using save_stack_trace_tsk() and print_stack_trace(). However, this is
not viable for dynamically loaded driver modules on ARM platforms
because save_stack_trace_tsk() is not exported for those architectures.
Export save_stack_trace_tsk() for the ARM64 architecture to align with
x86 and support various debugging use cases such as arbitrary driver
thread watchdog timers.

Signed-off-by: Dustin Brown <dustinb@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

show more ...

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>

We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will ha

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>

We are going to split <linux/sched/task_stack.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/task_stack.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

show more ...

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be p

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/debug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

show more ...

arm64: prep stack walkers for THREAD_INFO_IN_TASK

When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed
before a task is destroyed. To account for this, the stacks are

arm64: prep stack walkers for THREAD_INFO_IN_TASK

When CONFIG_THREAD_INFO_IN_TASK is selected, task stacks may be freed
before a task is destroyed. To account for this, the stacks are
refcounted, and when manipulating the stack of another task, it is
necessary to get/put the stack to ensure it isn't freed and/or re-used
while we do so.

This patch reworks the arm64 stack walking code to account for this.
When CONFIG_THREAD_INFO_IN_TASK is not selected these perform no
refcounting, and this should only be a structural change that does not
affect behaviour.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

show more ...

arm64: unexport walk_stackframe

The walk_stackframe functions is architecture-specific, with a varying
prototype, and common code should not use it directly. None of its
current user

arm64: unexport walk_stackframe

The walk_stackframe functions is architecture-specific, with a varying
prototype, and common code should not use it directly. None of its
current users can be built as modules. With THREAD_INFO_IN_TASK, users
will also need to hold a stack reference before calling it.

There's no reason for it to be exported, and it's very easy to misuse,
so unexport it for now.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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arm64: factor out current_stack_pointer

We define current_stack_pointer in <asm/thread_info.h>, though other
files and header relying upon it do not have this necessary include, and

arm64: factor out current_stack_pointer

We define current_stack_pointer in <asm/thread_info.h>, though other
files and header relying upon it do not have this necessary include, and
are thus fragile to changes in the header soup.

Subsequent patches will affect the header soup such that directly
including <asm/thread_info.h> may result in a circular header include in
some of these cases, so we can't simply include <asm/thread_info.h>.

Instead, factor current_thread_info into its own header, and have all
existing users include this explicitly.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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arm64: fix dump_backtrace/unwind_frame with NULL tsk

In some places, dump_backtrace() is called with a NULL tsk parameter,
e.g. in bug_handler() in arch/arm64, or indirectly via show_sta

arm64: fix dump_backtrace/unwind_frame with NULL tsk

In some places, dump_backtrace() is called with a NULL tsk parameter,
e.g. in bug_handler() in arch/arm64, or indirectly via show_stack() in
core code. The expectation is that this is treated as if current were
passed instead of NULL. Similar is true of unwind_frame().

Commit a80a0eb70c358f8c ("arm64: make irq_stack_ptr more robust") didn't
take this into account. In dump_backtrace() it compares tsk against
current *before* we check if tsk is NULL, and in unwind_frame() we never
set tsk if it is NULL.

Due to this, we won't initialise irq_stack_ptr in either function. In
dump_backtrace() this results in calling dump_mem() for memory
immediately above the IRQ stack range, rather than for the relevant
range on the task stack. In unwind_frame we'll reject unwinding frames
on the IRQ stack.

In either case this results in incomplete or misleading backtrace
information, but is not otherwise problematic. The initial percpu areas
(including the IRQ stacks) are allocated in the linear map, and dump_mem
uses __get_user(), so we shouldn't access anything with side-effects,
and will handle holes safely.

This patch fixes the issue by having both functions handle the NULL tsk
case before doing anything else with tsk.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Fixes: a80a0eb70c358f8c ("arm64: make irq_stack_ptr more robust")
Acked-by: James Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

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arm64: ftrace: add save_stack_trace_regs()

Currently, enabling stacktrace of a kprobe events generates warning:

echo stacktrace > /sys/kernel/debug/tracing/trace_options
ech

arm64: ftrace: add save_stack_trace_regs()

Currently, enabling stacktrace of a kprobe events generates warning:

echo stacktrace > /sys/kernel/debug/tracing/trace_options
echo "p xhci_irq" > /sys/kernel/debug/tracing/kprobe_events
echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable

save_stack_trace_regs() not implemented yet.
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at ../kernel/stacktrace.c:74 save_stack_trace_regs+0x3c/0x48
Modules linked in:

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc4-dirty #5128
Hardware name: ARM Juno development board (r1) (DT)
task: ffff800975dd1900 task.stack: ffff800975ddc000
PC is at save_stack_trace_regs+0x3c/0x48
LR is at save_stack_trace_regs+0x3c/0x48
pc : [<ffff000008126c64>] lr : [<ffff000008126c64>] pstate: 600003c5
sp : ffff80097ef52c00

Call trace:
save_stack_trace_regs+0x3c/0x48
__ftrace_trace_stack+0x168/0x208
trace_buffer_unlock_commit_regs+0x5c/0x7c
kprobe_trace_func+0x308/0x3d8
kprobe_dispatcher+0x58/0x60
kprobe_breakpoint_handler+0xbc/0x18c
brk_handler+0x50/0x90
do_debug_exception+0x50/0xbc

This patch implements save_stack_trace_regs(), so that stacktrace of a
kprobe events can be obtained.

After this patch, there is no warning and we can see the stacktrace for
kprobe events in trace buffer.

more /sys/kernel/debug/tracing/trace
<idle>-0 [004] d.h. 1356.000496: p_xhci_irq_0:(xhci_irq+0x0/0x9ac)
<idle>-0 [004] d.h. 1356.000497: <stack trace>
=> xhci_irq
=> __handle_irq_event_percpu
=> handle_irq_event_percpu
=> handle_irq_event
=> handle_fasteoi_irq
=> generic_handle_irq
=> __handle_domain_irq
=> gic_handle_irq
=> el1_irq
=> arch_cpu_idle
=> default_idle_call
=> cpu_startup_entry
=> secondary_start_kernel
=>

Tested-by: David A. Long <dave.long@linaro.org>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

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