Hi Waldemar,
On 05/04/16 20:49, Waldemar Brodkorb wrote:
Hi uClinux/elf2flt devs,
How can I debug an issue with the following error while
executing:
~ # ./hello
BINFMT_FLAT: reloc outside program 0xb5890000 (0 - 0x125a4/0x8b0c),
killing hello!
SEGV
The target is an ARM Cortex-M4 device. The error is only happening
when libpthread from uClibc-ng is used in the binary. Non-threading
applications are working fine. (Linuxthreads.old used)
The problem was reported by Thomas Petazzoni from Buildroot project.
On the build system I used this example code:
http://timmurphy.org/2010/05/04/pthreads-in-c-a-minimal-working-example/
$ /usr/bin/arm-openadk-uclinux-uclibceabi-gcc -o hello hello.c -lpthread
$ /usr/bin/arm-openadk-uclinux-uclibceabi-flthdr -k hello
$ /usr/bin/arm-openadk-uclinux-uclibceabi-flthdr -p hello
hello
Magic: bFLT
Rev: 4
Build Date: Tue Apr 5 12:28:25 2016
Entry: 0x45
Data Start: 0x8b4c
Data End: 0xe384
BSS End: 0x125e0
Stack Size: 0x1000
Reloc Start: 0xe384
Reloc Count: 0x197
Flags: 0x11 ( Load-to-Ram Kernel-Traced-Load )
On the target system:
~ # ./hello
BINFMT_FLAT: Loading file: ./hello
Mapping is 70020000, Entry point is 45, data_start is 8b4c
Load ./hello: TEXT=70020040-70028b4c DATA=70028b50-7002e388
BSS=7002e388-700325e4
BINFMT_FLAT: reloc outside program 0xb5890000 (0 - 0x125a4/0x8b0c),
killing hello!
SEGV
You can find readelf, objdump -x, objdump -D and the source of
hello.c here:
http://debug.openadk.org/arm-pthreads/
If you compile supplying "-v" in the elf2flt flags then it
will produce a verbose output that contains all the relocation
information. That will be helpful here. (Post it here too if
you want).
Stracing the process does not work:
~ # ./strace ./hello
BINFMT_FLAT: Loading file: ./hello
./strace: Can't attach to 45: No such process
~ # Mapping is 70560000, Entry point is 45, data_start is 8b4c
Load ./hello: TEXT=70560040-70568b4c DATA=70568b50-7056e388
BSS=7056e388-705725e4
BINFMT_FLAT: reloc outside program 0xb5890000 (0 - 0x125a4/0x8b0c),
killing hello!
strace won't help you here. The program isn't running yet, the
relocation failure is at exec time.
gdbserver (gdb 7.11) does not compile for me as it uses fork():
build-gnulib-gdbserver/import/libgnu.a
build-libiberty-gdbserver/libiberty.a -lthread_db
linux-low.o: In function `linux_create_inferior':
linux-low.c:(.text+0x25d2): undefined reference to `fork'
linux-ptrace.o: In function `linux_child_function':
linux-ptrace.c:(.text+0x24): undefined reference to `fork'
linux-ptrace.o: In function `linux_check_ptrace_features':
linux-ptrace.c:(.text+0x10a): undefined reference to `fork'
thread-db.o: In function `thread_db_init':
thread-db.c:(.text+0x520): undefined reference to `td_thr_tlsbase'
collect2: error: ld returned 1 exit status
That won't help you here either (at least for this specific
problem). It is the exec step this program that is failing.
I searched the internet and found that it might be stack size
related. But even compiling example code and C library with
-Wl,-elf2flt=-s16384 didn't help.
Ok, that is always a good thing to try first.
Any help is appreciated,
The verbose elf2flt output may give some clues. You may need to
instrument the kernel's fs/binfmt_flat.c code to match up reloc
numbers though if nothing is obviously wrong in the verbose
reloc information.
Regards
Greg
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