linux-stable.git/arch/arc/kernel/unwind.c, branch linux-4.4.y

ARC: hide unused function unw_hdr_alloc

2019-07-21T07:07:14+00:00

commit fd5de2721ea7d16e2b16c4049ac49f229551b290 upstream.

As kernelci.org reports, this function is not used in
vdk_hs38_defconfig:

arch/arc/kernel/unwind.c:188:14: warning: 'unw_hdr_alloc' defined but not used [-Wunused-function]

Fixes: bc79c9a72165 ("ARC: dw2 unwind: Reinstante unwinding out of modules")
Link: https://kernelci.org/build/id/5d1cae3f59b514300340c132/logs/
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann 
Signed-off-by: Vineet Gupta 
Signed-off-by: Greg Kroah-Hartman

ARC: dw2 unwind: Catch Dwarf SNAFUs early

2015-12-21T08:31:49+00:00

Instead of seeing empty stack traces, let kernel fail early so dwarf
issues can be fixed sooner

Signed-off-by: Vineet Gupta

ARC: dw2 unwind: Don't bail for CIE.version != 1

2015-12-21T08:31:25+00:00

The rudimentary CIE.version == 3 handling is already present in code
(for return address register specification)

Signed-off-by: Vineet Gupta

Revert "ARC: dw2 unwind: Ignore CIE version !=1 gracefully instead of bailing"

2015-12-21T07:59:44+00:00

Blingly ignoring CIE.version != 1 was a bad idea.
It still leaves "desirability" when running perf with callgraphing where libgcc
symbols might show in hotspot.

More importantly, basic CIE.version == 3 support already exists in code:

|
|   retAddrReg = state.version <= 1 ? *ptr++ : get_uleb128(&ptr, end);
|

Next commit with simply add continue-not-bail for CIE.version != 1

This reverts commit 323f41f9e7d0cb5b1d1586aded6682855f1e646d.

ARC: dw2 unwind: Ignore CIE version !=1 gracefully instead of bailing

2015-12-17T05:40:23+00:00

ARC dwarf unwinder only supports CIE version == 1
The boot time dwarf sanitizer (part of binary lookup table constructor)
would simply bail if it saw CIE version == 3, rendering unwinder with a
NULL lookup table.

It seems libgcc linked with kernel does have such entries.

With fallback linear search removed, and a NULL binary lookup table,
unwinder fails to generate any stack trace.

So allow graceful ignoring of unsupported CIE entries.

This problem was initially seen in Alexey's setup (and not mine) as he
was using buildroot built toolchain (libgcc) which doesn't get built with
CFLAGS_FOR_TARGET="-gdwarf-2 which is my default

Fixes STAR 9000985048: "kernel unwinder broken with stock tools"

Fixes: 2e22502c080f ARC: dw2 unwind: Remove falllback linear search thru FDE entries
Reported-by Alexey Brodkin 
Cc: 
Signed-off-by: Vineet Gupta

ARC: dw2 unwind: Reinstante unwinding out of modules

2015-12-17T05:40:23+00:00

The fix which removed linear searching of dwarf (because binary lookup
data always exists) missed out on the fact that modules don't get the
binary lookup tables info. This caused unwinding out of modules to stop
working.

So add binary lookup header setup (equivalent of eh_frame_hdr setup) to
modules as well.

While at it, confine the header setup to within unwinder code,
reducing one API exposed out of unwinder code.

Fixes: 2e22502c080f ARC: dw2 unwind: Remove falllback linear search thru FDE entries
Cc: 
Signed-off-by: Vineet Gupta

ARC: dw2 unwind: Remove falllback linear search thru FDE entries

2015-11-23T16:06:49+00:00

Fixes STAR 9000953410: "perf callgraph profiling causing RCU stalls"

| perf record -g -c 15000 -e cycles /sbin/hackbench
|
| INFO: rcu_preempt self-detected stall on CPU
| 1: (1 GPs behind) idle=609/140000000000002/0 softirq=2914/2915 fqs=603
| Task dump for CPU 1:

in-kernel dwarf unwinder has a fast binary lookup and a fallback linear
search (which iterates thru each of ~11K entries) thus takes 2 orders of
magnitude longer (~3 million cycles vs. 2000). Routines written in hand
assembler lack dwarf info (as we don't support assembler CFI pseudo-ops
yet) fail the unwinder binary lookup, hit linear search, failing
nevertheless in the end.

However the linear search is pointless as binary lookup tables are created
from it in first place. It is impossible to have binary lookup fail while
succeed the linear search. It is pure waste of cycles thus removed by
this patch.

This manifested as RCU stalls / NMI watchdog splat when running
hackbench under perf with callgraph profiling. The triggering condition
was perf counter overflowing in routine lacking dwarf info (like memset)
leading to patheic 3 million cycle unwinder slow path and by the time it
returned new interrupts were already pending (Timer, IPI) and taken
rightaway. The original memset didn't make forward progress, system kept
accruing more interrupts and more unwinder delayes in a vicious feedback
loop, ultimately triggering the NMI diagnostic.

Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta

treewide: Fix typo in printk messages

2015-03-06T22:05:39+00:00

This patch fix spelling typo in printk messages.

Signed-off-by: Masanari Iida 
Acked-by: Randy Dunlap 
Signed-off-by: Jiri Kosina

ARC: warn on improper stack unwind FDE entries

2013-06-27T09:07:59+00:00

Signed-off-by: Vineet Gupta

ARC: DWARF2 .debug_frame based stack unwinder

2013-02-15T17:46:03+00:00

-Originally written by Rajeshwar Ranga
-Derived off of generic unwinder in 2.6.19 and adapted to ARC

Signed-off-by: Vineet Gupta 
Cc: Rajeshwar Ranga