(2014/08/15 0:33), Arnaldo Carvalho de Melo wrote: > Hi Masami, > > I was trying to figure out why sys_perf_event_open was returning > EACCES when trying to record, as a non priviledged user, a 'ping' > process started by this user, while it has no problem doing the same > thing if the monitored process is 'sleep' (reusing of ptrace perms seems > to be what is causing this, but I digress), when I stumbled in something > annoying: > > [root@ssdandy ~]# perf probe -v -L icmp_rcv > Looking at the vmlinux_path (6 entries long) > Using /lib/modules/3.16.0+/build/vmlinux for symbols > Failed to open debuginfo file. > Error: Failed to show lines. (-2) > [root@ssdandy ~]# > > Huh? Why? So I went to look to see why it was "failing to open debuginfo > file": > > [root@ssdandy ~]# ls -la /lib/modules/3.16.0+/build/vmlinux > -rwxrwxr-x. 3 acme acme 22505817 Aug 13 11:54 > /lib/modules/3.16.0+/build/vmlinux > [root@ssdandy ~]# ls -la /lib/modules/3.16.0+/build > lrwxrwxrwx. 1 root root 29 Aug 13 12:10 /lib/modules/3.16.0+/build -> > /home/acme/git/build/v3.16.0+ > > The file is there, but... I forgot I had disabled CONFIG_DEBUG_INFO on > this machine: > > [root@ssdandy ~]# ls -la /lib/modules/3.16.0+/build/.config > -rw-rw-r--. 1 acme acme 136217 Aug 13 11:40 > /lib/modules/3.16.0+/build/.config > [root@ssdandy ~]# grep CONFIG_DEBUG_INFO > /lib/modules/3.16.0+/build/.config > # CONFIG_DEBUG_INFO is not set > [root@ssdandy ~]# > > So, only the CFI ELF section was there, not the other with the -g stuff: > > [root@ssdandy ~]# readelf -SW /lib/modules/3.16.0+/build/vmlinux | grep > \.debug_ > [29] .debug_frame PROGBITS 0000000000000000 1266030 0021d0 00 0 0 8 > [root@ssdandy ~]# > > So, I suggest that we improve that error message to be more clear: > > [root@ssdandy ~]# perf probe -L icmp_rcv > Failed to open debuginfo file. > Error: The /lib/modules/3.16.0+/build/vmlinux file has no > debugging information, rebuild with CONFIG_DEBUG_INFO=y > > [root@ssdandy ~]# > > Since it knows it is a kernel image file, and that the config option to > enable it is CONFIG_DEBUG_INFO.
OK, it seems better for me too. It will be a bit different message, but I'm sure to mention that config option for users. Thank you! -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
