Problem while debugging on iMX6 target

Giox79

Good morning,
I'm using the following setup:

QT Creator 4.1.0
gdb 7.9.1
uP iMX6
Qt Version 5.5.1 on target

When I run a simple code example, I get an error in the subroutine:
_dl_debug_initialize

at line:
if (r->r_map == NULL || ldbase != 0)

I don't understand what happens.
The same source code, with a different QT version (QT 4.8) and a different toolchain (for kernel version 3 instead of 4), runs fine.

I understand it is impossible to provide me big hints, but anyone had similar problems?
Here is the output of debugger windows.

 --- token barrier ---
dNOTE: INFERIOR RUN REQUESTED
sRun requested...
dState changed from InferiorStopOk(14) to InferiorRunRequested(10) [master]
sRunning requested...
<2460-exec-continue
>2460^running
dNOTE: INFERIOR RUN OK
sRunning.
dState changed from InferiorRunRequested(10) to InferiorRunOk(11) [master]
>*running,thread-id="all"
dNOTE: INFERIOR STILL RUNNING IN STATE InferiorRunOk.

>~"\nProgram received signal "
>~"SIGSEGV, Segmentation fault.\n"
>~"_dl_debug_initialize (ldbase=4294967292, ns=195720) at dl-debug.c:55\n"
>~"55\t  if (r->r_map == NULL || ldbase != 0)\n"
>*stopped,reason="signal-received",signal-name="SIGSEGV",signal-meaning="Segmentation fault",frame={addr="0x76fdfcbc",func="_dl_debug_initialize",args=[{name="ldbase",value="4294967292"},{name="ns",value="195720"}],file="dl-debug.c",fullname="/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/dl-debug.c",line="55"},thread-id="1",stopped-threads="all",core="0"
dNOTE: INFERIOR SPONTANEOUS STOP
sStopped.
dState changed from InferiorRunOk(11) to InferiorStopOk(14) [master]
dHANDLING SIGNAL SIGSEGV
sStopped: Segmentation fault (Signal SIGSEGV).

<2461-thread-info
>2461^done,threads=[{id="1",target-id="Thread 1171.1171",frame={level="0",addr="0x76fdfcbc",func="_dl_debug_initialize",args=[{name="ldbase",value="4294967292"},{name="ns",value="195720"}],file="dl-debug.c",fullname="/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/dl-debug.c",line="55"},state="stopped",core="0"}],current-thread-id="1"
<2462threadnames 20
<2463python theDumper.fetchStack({"limit":20,"nativemixed":0,"token":2463})

>&"threadnames 20\n"
>~"[]\n"
>2462^done

>&"python theDumper.fetchStack({\"limit\":20,\"nativemixed\":0,\"token\":2463})\n"
>~"frames=[frame={level=\"0\",address=\"0x76fdfcbc\",function=\"_dl_debug_initialize\",file=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/dl-debug.c\",line=\"55\",module=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/lib/.debug/ld-2.22.so\",language=\"c\"},frame={level=\"1\",address=\"0x76fd2118\",function=\"dl_main\",file=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/rtld.c\",line=\"1463\",module=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/lib/.debug/ld-2.22.so\",language=\"c\"},frame={level=\"2\",address=\"0x76fe6c24\",function=\"_dl_sysdep_start\",file=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/dl-sysdep.c\",line=\"249\",module=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/lib/.debug/ld-2.22.so\",language=\"c\"},frame={level=\"3\",address=\"0x76fd3fcc\",function=\"_dl_start_final\",file=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/rtld.c\",line=\"309\",module=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/lib/.debug/ld-2.22.so\",language=\"c\"},frame={level=\"4\",address=\"0x76fd3fcc\",function=\"_dl_start\",file=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/usr/src/debug/glibc/2.22-r0/git/elf/rtld.c\",line=\"415\",module=\"/opt/nobuos-x11/4.1.15-1.2.0/sysroots/cortexa9hf-vfp-neon-nobuos-linux-gnueabi/lib/.debug/ld-2.22.so\",language=\"c\"},frame={level=\"5\",address=\"0x76fcfb10\",function=\"_start\",file=\"\",line=\"0\",module=\"\",language=\"c\"}]\n"
>2463^done
<2464-stack-select-frame 0
<2465python theDumper.fetchVariables({"autoderef":1,"context":"","displaystringlimit":"100","dyntype":1,"expanded":["return","watch","local","inspect"],"fancy":1,"formats":{},"nativemixed":0,"partialvar":"","passexceptions":0,"qobjectnames":0,"resultvarname":"","stringcutoff":"10000","token":2465,"typeformats":{},"watchers":[{"exp":"722d3e725f6d6170","iname":"watch.0"}]})

>2464^done

>&"python theDumper.fetchVariables({\"autoderef\":1,\"context\":\"\",\"displaystringlimit\":\"100\",\"dyntype\":1,\"expanded\":[\"return\",\"watch\",\"local\",\"inspect\"],\"fancy\":1,\"formats\":{},\"nativemixed\":0,\"partialvar\":\"\",\"passexceptions\":0,\"qobjectnames\":0,\"resultvarname\":\"\",\"stringcutoff\":\"10000\",\"token\":2465,\"typeformats\":{},\"watchers\":[{\"exp\":\"722d3e725f6d6170\",\"iname\":\"watch.0\"}]})\n"
>~"data=[{iname=\"local.ldbase\",name=\"ldbase\",numchild=\"0\",type=\"Elf32_Addr\",value=\"4294967292\",},{iname=\"local.ns\",name=\"ns\",numchild=\"0\",type=\"Lmid_t\",value=\"195720\",},{iname=\"local.r\",name=\"r\",numchild=\"0\",type=\"r_debug *\",value=\"0x77e2e8e8\",address=\"0x77e2e8e8\",},{iname=\"watch.0\",wname=\"722d3e725f6d6170\",numchild=\"0\",type=\" \",value=\"<no such value>\",},],typeinfo=[{name=\"73747275637420725f6465627567202a\",size=\"4\"}],partial=\"0\"\n"
>~"\"[{}, [['locals', 377], ['all-local.ldbase', 112], ['all-local.ns', 99], ['all-local.r', 1178], ['watches', 882], ['safePrint', 169]]]\"\n"
>2465^done
 <Rebuild Watchmodel 39 @ 18:51:45.285 [8560ms] >
sFinished retrieving data

Furthermore, another SW built with the toolchain and GDB settings works fine.
Best regards.
Giovanni

jsulm

@Giox79 said in Problem while debugging on iMX6 target:

r

Looks like dereferencing a NULL or dangling pointer. You should check the value of r in that line: is it NULL?
Is _dl_debug_initialize part of that example? If so you can place a

qDebug() << r;

just before the if.

Giox79

Thank you jsulm, it seems tha I'm not able to put a qDebug in this source code line.
I will try in another way.
You are able to use qDebug symbol in this subroutine?
Gio

Giox79

Good morning Mr jsulm,
looking at the debugger page, it seems that the symbol has a valid value, not null.

r Value is 0x77e2e8e8
while
r->r_map value is <no such value>

and

ldbase is
1996288000

It seems the camera is r pointer is no longer valid (because of r->r_map is not valid)
Gio