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Date:   Mon, 20 Jul 2020 11:46:01 +1000 (AEST)
From:   Finn Thain <fthain@telegraphics.com.au>
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
cc:     linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2 13/16] scripts/kallsyms: move ignored symbol types to
 is_ignored_symbol()
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References: <20191123160444.11251-1-yamada.masahiro@socionext.com> <20191123160444.11251-14-yamada.masahiro@socionext.com>
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On Sun, 24 Nov 2019, Masahiro Yamada wrote:

> Collect the ignored patterns to is_ignored_symbol().
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This commit (887df76de67f5) caused a regression in my powerpc builds as it 
causes symbol names to disappear from backtraces:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/smp.c:433 _einittext+0x3f9e5120/0x3feb71b8
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc7-pmac-00055-g887df76de67f5 #18
NIP:  c00aef68 LR: c00af114 CTR: c001272c
REGS: c0705c40 TRAP: 0700   Not tainted  (5.4.0-rc7-pmac-00055-g887df76de67f5)
MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 42000044  XER: 00000000

GPR00: 001f0100 c0705cf8 c06dc300 c070af1c c001258c 00000000 00000000 ef7fb5bc 
GPR08: 08800000 00000100 00000001 00000100 42000044 00000000 c0709040 00000004 
GPR16: 00000001 c06022b4 c058297c 00200002 ffff8cb9 00000000 c06d84a0 c0710000 
GPR24: c0710000 00000000 00000000 c070af1c c070af1c 00000000 c001258c 00000000 
NIP [c00aef68] _einittext+0x3f9e5120/0x3feb71b8
LR [c00af114] _einittext+0x3f9e52cc/0x3feb71b8
Call Trace:
[c0705cf8] [ef006320] 0xef006320 (unreliable)
[c0705d38] [c00af114] _einittext+0x3f9e52cc/0x3feb71b8
[c0705d48] [c00af158] _einittext+0x3f9e5310/0x3feb71b8
[c0705d68] [c0012768] _einittext+0x3f948920/0x3feb71b8
[c0705d78] [c0092c04] _einittext+0x3f9c8dbc/0x3feb71b8
[c0705d88] [c0092d18] _einittext+0x3f9c8ed0/0x3feb71b8
[c0705da8] [c0093a2c] _einittext+0x3f9c9be4/0x3feb71b8
[c0705de8] [c0580224] _einittext+0x3feb63dc/0x3feb71b8
[c0705e48] [c00382ec] _einittext+0x3f96e4a4/0x3feb71b8
[c0705e58] [c000d2a0] _einittext+0x3f943458/0x3feb71b8
[c0705e88] [c001353c] _einittext+0x3f9496f4/0x3feb71b8
--- interrupt: 901 at _einittext+0x3f941058/0x3feb71b8
    LR = _einittext+0x3f941058/0x3feb71b8
[c0705f50] [c06cc214] 0xc06cc214 (unreliable)
[c0705f60] [c057fa20] _einittext+0x3feb5bd8/0x3feb71b8
[c0705f70] [c005de48] _einittext+0x3f994000/0x3feb71b8
[c0705f90] [c005e050] _einittext+0x3f994208/0x3feb71b8
[c0705fa0] [c0004cc8] _einittext+0x3f93ae80/0x3feb71b8
[c0705fb0] [c069a36c] _einittext+0x3ffd0524/0x40000000
[c0705ff0] [00003500] 0x3500
Instruction dump:
7c0803a6 7fa5eb78 7d808120 7ea6ab78 baa10014 38210040 4bfffbb0 7f64db78 
7f85e378 484b31b1 7c601b78 4bfffdf4 <0fe00000> 4bfffd60 9421ffe0 7c0802a6 
---[ end trace a06fef4788747c72 ]---


Prior to that (e.g. 97261e1e2240f), I get backtraces like this:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/smp.c:433 smp_call_function_many+0x318/0x320
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc7-pmac-00054-g97261e1e2240f #20
NIP:  c00aef68 LR: c00af114 CTR: c001272c
REGS: c075dc40 TRAP: 0700   Not tainted  (5.4.0-rc7-pmac-00054-g97261e1e2240f)
MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 42000044  XER: 00000000

GPR00: 001f0100 c075dcf8 c0733300 c0762f1c c001258c 00000000 00000000 ef7fb5bc 
GPR08: 04800000 00000100 00000001 00000100 42000044 00000000 c0761040 00000004 
GPR16: 00000001 c0658e58 c058297c 00200002 ffff8cb9 00000000 c072f4a0 c0760000 
GPR24: c0760000 00000000 00000000 c0762f1c c0762f1c 00000000 c001258c 00000000 
NIP [c00aef68] smp_call_function_many+0x318/0x320
LR [c00af114] smp_call_function+0x34/0x44
Call Trace:
[c075dcf8] [ef006320] 0xef006320 (unreliable)
[c075dd38] [c00af114] smp_call_function+0x34/0x44
[c075dd48] [c00af158] on_each_cpu+0x1c/0x4c
[c075dd68] [c0012768] tau_timeout_smp+0x3c/0x4c
[c075dd78] [c0092c04] call_timer_fn.isra.26+0x20/0x84
[c075dd88] [c0092d18] expire_timers+0xb0/0xc0
[c075dda8] [c0093a2c] run_timer_softirq+0xa4/0x1a4
[c075dde8] [c0580224] __do_softirq+0x11c/0x280
[c075de48] [c00382ec] irq_exit+0xc0/0xd4
[c075de58] [c000d2a0] timer_interrupt+0x154/0x260
[c075de88] [c001353c] ret_from_except+0x0/0x14
--- interrupt: 901 at arch_cpu_idle+0x24/0x78
    LR = arch_cpu_idle+0x24/0x78
[c075df50] [c0723214] 0xc0723214 (unreliable)
[c075df60] [c057fa20] default_idle_call+0x38/0x58
[c075df70] [c005de48] do_idle+0xd4/0x17c
[c075df90] [c005e054] cpu_startup_entry+0x24/0x28
[c075dfa0] [c0004cc8] rest_init+0xa8/0xbc
[c075dfb0] [c06f136c] start_kernel+0x40c/0x420
[c075dff0] [00003500] 0x3500
Instruction dump:
7c0803a6 7fa5eb78 7d808120 7ea6ab78 baa10014 38210040 4bfffbb0 7f64db78 
7f85e378 484b31b1 7c601b78 4bfffdf4 <0fe00000> 4bfffd60 9421ffe0 7c0802a6 
---[ end trace 784c7f15ecd23941 ]---

Has anyone else observed these problems (either the WARNING from 
smp_call_function_many() or the missing symbol names)?

What is the best way to fix this? Should I upgrade binutils?