As tglx points out, there are no in-tree module users of
save_stack_trace_tsk_reliable() and its x86 counterpart is not
exported, so remove the powerpc symbol export.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
[text copied from commit 9bbd4c56b0
("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 powerpc 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.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Move try_get_task_stack() below tsk == NULL check in show_stack()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
To match its x86 counterpart, save_stack_trace_tsk_reliable() should
return -EINVAL in cases that it is currently returning 1. No caller is
currently differentiating non-zero error codes, but let's keep the
arch-specific implementations consistent.
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Mostly cosmetic changes:
- Group common stack pointer code at the top
- Simplify the first frame logic
- Code stackframe iteration into for...loop construct
- Check for trace->nr_entries overflow before adding any into the array
Suggested-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
The bottom-most stack frame (the first to be unwound) may be largely
uninitialized, for the "Power Architecture 64-Bit ELF V2 ABI" only
requires its backchain pointer to be set.
The reliable stack tracer should be careful when verifying this frame:
skip checks on STACK_FRAME_LR_SAVE and STACK_FRAME_MARKER offsets that
may contain uninitialized residual data.
Fixes: df78d3f614 ("powerpc/livepatch: Implement reliable stack tracing for the consistency model")
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
I broke the build when CONFIG_NMI_IPI=n with my recent commit to add
arch_trigger_cpumask_backtrace(), eg:
stacktrace.c:(.text+0x1b0): undefined reference to `.smp_send_safe_nmi_ipi'
We should rework the CONFIG symbols here in future to avoid these
double barrelled ifdefs but for now they fix the build.
Fixes: 5cc05910f2 ("powerpc/64s: Wire up arch_trigger_cpumask_backtrace()")
Reported-by: Christophe LEROY <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This now has new code in it written by Nick and I, and switch to a
SPDX tag.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
This allows eg. the RCU stall detector, or the soft/hardlockup
detectors to trigger a backtrace on all CPUs.
We implement this by sending a "safe" NMI, which will actually only
send an IPI. Unfortunately the generic code prints "NMI", so that's a
little confusing but we can probably live with it.
If one of the CPUs doesn't respond to the IPI, we then print some info
from it's paca and do a backtrace based on its saved_r1.
Example output:
INFO: rcu_sched detected stalls on CPUs/tasks:
2-...0: (0 ticks this GP) idle=1be/1/4611686018427387904 softirq=1055/1055 fqs=25735
(detected by 4, t=58847 jiffies, g=58, c=57, q=1258)
Sending NMI from CPU 4 to CPUs 2:
CPU 2 didn't respond to backtrace IPI, inspecting paca.
irq_soft_mask: 0x01 in_mce: 0 in_nmi: 0 current: 3623 (bash)
Back trace of paca->saved_r1 (0xc0000000e1c83ba0) (possibly stale):
Call Trace:
[c0000000e1c83ba0] [0000000000000014] 0x14 (unreliable)
[c0000000e1c83bc0] [c000000000765798] lkdtm_do_action+0x48/0x80
[c0000000e1c83bf0] [c000000000765a40] direct_entry+0x110/0x1b0
[c0000000e1c83c90] [c00000000058e650] full_proxy_write+0x90/0xe0
[c0000000e1c83ce0] [c0000000003aae3c] __vfs_write+0x6c/0x1f0
[c0000000e1c83d80] [c0000000003ab214] vfs_write+0xd4/0x240
[c0000000e1c83dd0] [c0000000003ab5cc] ksys_write+0x6c/0x110
[c0000000e1c83e30] [c00000000000b860] system_call+0x58/0x6c
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
The "Power Architecture 64-Bit ELF V2 ABI" says in section 2.3.2.3:
[...] There are several rules that must be adhered to in order to ensure
reliable and consistent call chain backtracing:
* Before a function calls any other function, it shall establish its
own stack frame, whose size shall be a multiple of 16 bytes.
– In instances where a function’s prologue creates a stack frame, the
back-chain word of the stack frame shall be updated atomically with
the value of the stack pointer (r1) when a back chain is implemented.
(This must be supported as default by all ELF V2 ABI-compliant
environments.)
[...]
– The function shall save the link register that contains its return
address in the LR save doubleword of its caller’s stack frame before
calling another function.
To me this sounds like the equivalent of HAVE_RELIABLE_STACKTRACE.
This patch may be unneccessarily limited to ppc64le, but OTOH the only
user of this flag so far is livepatching, which is only implemented on
PPCs with 64-LE, a.k.a. ELF ABI v2.
Feel free to add other ppc variants, but so far only ppc64le got tested.
This change also implements save_stack_trace_tsk_reliable() for ppc64le
that checks for the above conditions, where possible.
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Nicolai Stange <nstange@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
For the current task, the kernel stack would only tell the last time the
process was rescheduled, if ever. Use the current stack pointer for the
current task.
Otherwise, every once in a while, the stacktrace printed when reading
/proc/self/stack would look like the process is running in userspace,
while it's not, which some may consider as a bug.
This is also consistent with some other architectures, like x86 and arm,
at least.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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>
It has come to my attention that kprobe event stack tracing does not
work on powerpc. You can see with the following:
# cd /sys/kernel/debug/tracing
# echo stacktrace > trace_options
# echo 'p kfree' > kprobe_events
# echo 1 > events/kprobes/enable
Will print the following warning:
save_stack_trace_regs() not implemented yet.
Although save_stack_trace() (which normal event stack traces use) is
implemented, save_stack_trace_regs() which kprobe events use is not.
This is a cheap attempt to implement that function.
Note, This may have issues if a task tries to get a stack trace from
another task with its regs, because it just passes in "current" to
save_context_stack(). But this does solve the issue with stack tracing
kprobe events.
Reported-by: Chunyu Hu <chuhu@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Michael points out that __get_SP() is a pretty horrible
function name. Let's give it a better name.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Li Zhong points out an issue with our current __get_SP()
implementation. If ftrace function tracing is enabled (ie -pg
profiling using _mcount) we spill a stack frame on 64bit all the
time.
If a function calls __get_SP() and later calls a function that is
tail call optimised, we will pop the stack frame and the value
returned by __get_SP() is no longer valid. An example from Li can
be found in save_stack_trace -> save_context_stack:
c0000000000432c0 <.save_stack_trace>:
c0000000000432c0: mflr r0
c0000000000432c4: std r0,16(r1)
c0000000000432c8: stdu r1,-128(r1) <-- stack frame for _mcount
c0000000000432cc: std r3,112(r1)
c0000000000432d0: bl <._mcount>
c0000000000432d4: nop
c0000000000432d8: mr r4,r1 <-- __get_SP()
c0000000000432dc: ld r5,632(r13)
c0000000000432e0: ld r3,112(r1)
c0000000000432e4: li r6,1
c0000000000432e8: addi r1,r1,128 <-- pop stack frame
c0000000000432ec: ld r0,16(r1)
c0000000000432f0: mtlr r0
c0000000000432f4: b <.save_context_stack> <-- tail call optimized
save_context_stack ends up with a stack pointer below the current
one, and it is likely to be scribbled over.
Fix this by making __get_SP() a function which returns the
callers stack frame. Also replace inline assembly which grabs
the stack pointer in save_stack_trace and show_stack with
__get_SP().
This also fixes an issue with perf_arch_fetch_caller_regs().
It currently unwinds the stack once, which will skip a
valid stack frame on a leaf function. With the __get_SP() fixes
in this patch, we never need to unwind the stack frame to get
to the first interesting frame.
We have to export __get_SP() because perf_arch_fetch_caller_regs()
(which is used in modules) calls it from a header file.
Reported-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
All these files were including module.h just for the basic
EXPORT_SYMBOL infrastructure. We can shift them off to the
export.h header which is a way smaller footprint and thus
realize some compile time gains.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Removed duplicated include file <linux/module.h> in
arch/powerpc/kernel/stacktrace.c.
Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
We need to pass the kernel stack pointer instead of the user space
stack pointer in save_stack_trace_tsk().
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Implement save_stack_trace_tsk on powerpc, so that we can run with
latencytop.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Today's linux-next build (powerpc allmodconfig) failed like this:
ERROR: ".save_stack_trace" [tests/backtracetest.ko] undefined!
But save_stack_trace is exported in arch/powerpc/kernel/stacktrace.c
I couldn't figure it out until I noticed these earlier warnings:
arch/powerpc/kernel/stacktrace.c:47: warning: data definition has no type or storage class
arch/powerpc/kernel/stacktrace.c:47: warning: type defaults to 'int' in declaration of 'EXPORT_SYMBOL_GPL'
arch/powerpc/kernel/stacktrace.c:47: warning: parameter names (without types) in function declaration
I applied the patch below.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: <linuxppc-dev@ozlabs.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Andrew Morton reported this against linux-next:
ERROR: ".save_stack_trace" [tests/backtracetest.ko] undefined!
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove the inclusion of asm-offsets.h from stacktrace.c. It isn't
supposed to be included in C code and it causes problems with multiple
definitions of things.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This adds stacktrace support for powerpc, which will be needed for
lockdep.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
