Re: gdb built with musl libc segfault


Lluis Campos
 

Hi again,

On 04.04.2019 12:58, Lluis Campos wrote:

On 03.04.2019 18:59, Khem Raj wrote:
On Tue, Apr 2, 2019 at 4:51 AM Lluis Campos <lluis.campos@northern.tech> wrote:
Hi all,

This is my very first question in the Yocto mailing list. Very exited!
Please let me know if I should use other list for this.


I am building an image using musl libc instead of gnu libc. I am not
using yocto-tiny distro, instead I achieve this by setting on my local.conf:

TCLIBC = "musl"


My app (mender) got a segfault just starting. See output from strace:

root@raspberrypi3:~# strace mender
execve("/usr/bin/mender", ["mender"], 0x7ee65e10 /* 13 vars */) = 0
set_tls(0x76f1bffc)                     = 0
set_tid_address(0x76f1bfa0)             = 3020
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x530bc8} ---
+++ killed by SIGSEGV +++
Segmentation fault


To be able to debug the process, I added gdb to my image adding to my
local.conf:

CORE_IMAGE_EXTRA_INSTALL += "packagegroup-core-buildessential
packagegroup-core-tools-debug"


Then, ironically, gdb itself also segfaults:

root@raspberrypi3:~# strace gdb 2>&1 | tail
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
getdents64(3, /* 6 entries */, 2048)    = 144
getdents64(3, /* 0 entries */, 2048)    = 0
close(3)                                = 0
ioctl(0, TIOCGWINSZ, {ws_row=25, ws_col=74, ws_xpixel=0, ws_ypixel=0}) = 0
getcwd("/home/root", 4096)              = 11
access("/usr/local/bin/gdb", X_OK)      = -1 ENOENT (No such file or
directory)
access("/usr/bin/gdb", X_OK)            = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=0x7e35aff0} ---
+++ killed by SIGSEGV +++


So, what is going on here? My guess is that some recipes are being
wrongly linked with gnu libc instead of musl, and then cannot run in my
device.

Any ideas on how to debug the issue?
We have switched to using PIE by default in last few releases, can you
try master but comment out
require conf/distro/include/security_flags.inc
in your distro conf file.
Hi Khem,

Thanks for your help.

Commenting out this line seems to work!

FYI,

Enabling back the require of security_flags.in, and instead applying no security flags only to my recipe is enough.

I have added to my conf/local.conf:

SECURITY_CFLAGS_pn-mender = "${SECURITY_NOPIE_CFLAGS}"
SECURITY_LDFLAGS_pn-mender = ""

So I will continue this way until I find the root cause on my CGO code.

Thanks again for your help.




I will try to figure out exactly which exact option is causing the issue.



Thanks!


Lluís Campos
mender.io
Northen Tech

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