[llvm-dev] Debug symbols are missing in elf

[Nagaraju Mekala via llvm-dev]

On Saturday, April 18, 2020, David Blaikie <dblaikie at gmail.com> wrote:

>
>
> On Sat, Apr 18, 2020 at 3:02 AM Nagaraju Mekala via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hello All,
>>
>> I was trying to add Microblaze  target to LLVM backend. I was able to
>> generate object file with relocations. and debug symbols.
>>
>> When I try to link this object file with microblaze GCC linker I am
>> getting below errors and debug symbols are missing in it.
>>
>> mb-objdump: DWARF error: found dwarf version '15877', this reader only
>> handles version 2, 3, 4 and 5 information
>> mb--objdump: DWARF error: found dwarf version '3328', this reader only
>> handles version 2, 3, 4 and 5 information
>> mb--objdump: DWARF error: found dwarf version '1280', this reader only
>> handles version 2, 3, 4 and 5 information
>>
>> Any idea when does the above errors will come?
>> The llvm generated object file has debug symbols,
>
>
> When you say "has debug symbols" what do you mean? What tools have you
> used to observe these symbols/information?
>

I have observed the debug sections with mb-objdump with -xSD flag
(binutils based objdump which we use it with mb-gcc compiler). Even with
readelf I was able to get the dwarf sections.
Attached is the dwarf dump generated with readelf --debug-dump helloworld.o
command..

where as elf doesn't have.
>>
>
> I take it you mean the linked executable? (the "ELF" file format is used
> for both the object files and the linked executable)
>
>
>
 Sorry for the confusion. You are correct, I meant the linked executable.

I tried modifying MCTarget layer a lot but not able to find the root-cause.
>> Any clue is much appreciated.
>>
>> ex:
>> hello.c
>> int main()
>> {
>>     printf("Hello World\n\r");
>>     printf("Successfully ran Hello World application");
>>     return 0;
>> }
>>
>> hello.o objdump:
>> int main()
>> {
>>    0:   10a00000        addk    r5, r0, r0
>>    4:   f8a1002c        swi     r5, r1, 44
>>
>>     printf("Hello World\n\r");
>>    8:   b0000000        imm     0
>>                         8: R_MICROBLAZE_64      .rodata.str1.1
>>    c:   a0c00000        ori     r6, r0, 0
>>   10:   f8a10028        swi     r5, r1, 40
>>   14:   b0000000        imm     0
>>                         14: R_MICROBLAZE_64_PCREL       printf
>>   18:   b9f40000        brlid   r15, 0
>>   1c:   10a60000        addk    r5, r6, r0
>>     printf("Successfully ran Hello World application");
>>   20:   b0000000        imm     0
>>                         20: R_MICROBLAZE_64     .rodata.str1.1+0xe
>>   24:   a0a00000        ori     r5, r0, 0
>>   28:   b0000000        imm     0
>>                         28: R_MICROBLAZE_64_PCREL       printf
>>   2c:   b9f40000        brlid   r15, 0
>>   30:   f8610024        swi     r3, r1, 36
>>     return 0;
>>   34:   e8a10028        lwi     r5, r1, 40
>>   38:   f8610020        swi     r3, r1, 32
>>   3c:   10650000        addk    r3, r5, r0
>>   40:   b60f0008        rtsd    r15, 8
>>   44:   80000000        or      r0, r0, r0
>>   ....
>>   ...
>>
>> hello.elf objdump
>> 8000021c <main>:
>> 8000021c:       10a00000        addk    r5, r0, r0
>> 80000220:       f8a1002c        swi     r5, r1, 44
>> 80000224:       b0008000        imm     -32768
>> 80000228:       a0c0f418        ori     r6, r0, -3048
>> 8000022c:       f8a10028        swi     r5, r1, 40
>> 80000230:       b9f400ec        brlid   r15, 236
>> 80000234:       10a60000        addk    r5, r6, r0
>> 80000238:       b0008000        imm     -32768
>> 8000023c:       a0a0f426        ori     r5, r0, -3034
>> 80000240:       b9f400dc        brlid   r15, 220
>> 80000244:       f8610024        swi     r3, r1, 36
>> 80000248:       e8a10028        lwi     r5, r1, 40
>> 8000024c:       f8610020        swi     r3, r1, 32
>> 80000250:       10650000        addk    r3, r5, r0
>> 80000254:       b60f0008        rtsd    r15, 8
>> 80000258:       80000000        or      r0, r0, r0
>>
>> Thanks in Advance,
>> Nagaraju
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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