Segmentation fault on Raspberry Pi 3 64bit

[matthiakl]

I am not sure whether this is a bug or just a misconfiguration, so any hints are welcome.

I use a custom buildroot system on my Raspberry Pi 3. Recently I switched from 32bit system to 64bit. Everything compiled and runs fine except for mpd. It simply no longer starts and immediately crashes with a segmentation fault.

If I run it with --no-config it prints at least something:

output: No 'audio_output' defined in config file
output: Attempt to detect audio output device
output: Attempting to detect a alsa audio device
ALSA lib conf.c:4553:(snd_config_update_r) Cannot access file /usr/share/alsa/alsa.conf
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM default
alsa_output: Error opening default ALSA device: No such file or directory
Segmentation fault

System Information

Linux version 5.15.76 (aarch64-buildroot-linux-uclibc-gcc.br_real (Buildroot 2022.02.6-dirty) 11.3.0, GNU ld (GNU Binutils) 2.37)

Version

Music Player Daemon 0.23.7 (2022.02.6+)
Copyright 2003-2007 Warren Dukes <[email protected]>
Copyright 2008-2021 Max Kellermann <[email protected]>
This is free software; see the source for copying conditions.  There is NO
warranty; not even MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Database plugins:
 simple proxy

Storage plugins:
 local curl


Decoders plugins:
 [ffmpeg] 16sv 3g2 3gp 4xm 8svx aa3 aac ac3 adx afc aif aifc aiff al alaw amr anim apc ape asf atrac au aud avi avm2 avs bap bfi c93 cak cin cmv cpk daud dct divx dts dv dvd dxa eac3 film flac flc fli fll flx flv g726 gsm gxf iss m1v m2v m2t m2ts m4a m4b m4v mad mj2 mjpeg mjpg mka mkv mlp mm mmf mov mp+ mp1 mp2 mp3 mp4 mpc mpeg mpg mpga mpp mpu mve mvi mxf nc nsv nut nuv oga ogm ogv ogx oma ogg omg opus psp pva qcp qt r3d ra ram rl2 rm rmvb roq rpl rvc shn smk snd sol son spx str swf tak tgi tgq tgv thp ts tsp tta xa xvid uv uv2 vb vid vob voc vp6 vmd wav webm wma wmv wsaud wsvga wv wve rtp://
 [pcm]

Filters:


Tag plugins:


Output plugins:
 null fifo pipe alsa httpd recorder

Encoder plugins:
 null lame wave

Input plugins:
 file io_uring alsa curl ffmpeg

Playlist plugins:
 extm3u m3u pls xspf asx rss cue embcue

Protocols:
 file:// alsa:// ftp:// ftps:// gopher:// http:// https:// rtmp:// rtp:// smb:// srtp://

Other features:
 epoll iconv inotify ipv6 tcp un

Configuration

# Files and directories #######################################################

music_directory		"/media/music"

playlist_directory	"/var/lib/mpd/playlists"

db_file 		"/var/lib/mpd/mpd.db"

#log_file		"disabled"

pid_file		 "/var/run/mpd.pid"

state_file		 "/var/lib/mpd/mpdstate"

sticker_file			"/var/lib/mpd/sticker.sql"

###############################################################################

# General music daemon options ################################################

user				"mpd"

group				"audio"

bind_to_address			"any"

port				"6600"

auto_update	"yes"

###############################################################################

# Permissions #################################################################

password                        "****@read,add,control,admin"

default_permissions             "read,control"

###############################################################################

# Input #######################################################################

input {
        plugin "curl"
#       proxy "proxy.isp.com:8080"
#       proxy_user "user"
#       proxy_password "password"
}

###############################################################################

# Audio Output ################################################################
audio_output {
	type		"alsa"
	name		"ALSA Default"
	mixer_type      "software"	# optional
}

audio_output {
	type		"httpd"
	name		"HTTP Stream"
	encoder		"lame"		# optional, vorbis or lame
	port		"6680"
#	bind_to_address	"0.0.0.0"		# optional, IPv4 or IPv6
	quality		"5.0"			# do not define if bitrate is defined
#	bitrate		"128"			# do not define if quality is defined
	format		"44100:16:1"
	max_clients	"0"			# optional 0=no limit
}

Log

config_file: loading file /etc/mpd.conf
Segmentation fault
Because of the nature of a buildroot system, obtaining a backtrace is no simple task. I will try to get one.

[MaxKellermann]

A crash is always a bug, but note that your MPD version is outdated. And without a backtrace, it's impossible to analyze your crash. See https://mpd.readthedocs.io/en/stable/user.html#mpd-crashes

[matthiakl]

I also tried the latest version with the same result. For the backtrace I have now set up a debug system to catch it:

  Function                            File            Line Address
1 __cxxabiv1::__cxa_throw             eh_throw.cc      81  0x7fa7448b0c 
2 socket_bind_listen                  SocketUtil.cxx   48  0x557ca56c64 
3 ServerSocket::OneServerSocket::Open ServerSocket.cxx 184 0x557ca59fe0 
4 ServerSocket::Open                  ServerSocket.cxx 226 0x557ca59fe0 
5 listen_global_init                  Listen.cxx       154 0x557ca2591c 
6 MainConfigured                      unique_ptr.h     173 0x557ca04ca0 
7 MainOrThrow                         Main.cxx         661 0x557ca05080 
8 mpd_main                            Main.cxx         667 0x557ca05128 
9 main                                Main.cxx         679 0x557ca0514c 

It looks like throwing an exception causes the program to segfault.

[MaxKellermann]

Is this the backtrace of your segfault? If so, then this is a compiler bug and has nothing to do with MPD, but I doubt that. I rather think this isn't the segfault.

[matthiakl]

Yes, it is the correct backtrace. And yes it has nothing to do with MPD, it is a problem with uCLibc. I add a proper answer, but thanks for your effort anyway.

[matthiakl]

In case anyone stumbles upon a similar issue:

It is a bug in uclibc, which does not fully support thread local storage (TLS) on aarch64.
Starting MPD with env LD_BIND_NOW=1 works, but is only a workaround I found.
For now I switched to musl libc and everything runs fine.

• Recent report on the uclibc mailing list: https://www.mail-archive.com/[email protected]/msg01204.html
• Probably the root cause: https://www.mail-archive.com/[email protected]/msg00871.html