Re: [PATCH] gdb: add support for handling core dumps on arm-none-eabi

Fredrik Hederstierna via Gdb-patches
2020-10-26T15:49:28Z

> From: Luis Machado <luis.machado@linaro.org>
> Sent: Monday, October 26, 2020 12:24 PM
>
>>> Luis and Alan (both GDB ARM maintainers) also expressed the desire to
>>> have the format documented.  Alan suggested a section in the GDB manual,
>>> in the ARM-specific section.  I think it is a good idea.  This is
>>> important, so we have something to point to when people ask "what format
>>> should I generate so GDB can read it".
>>
>> Yes, it was suggested by someone to adding an arm-none section in "G.5.3 ARM Features".
>> How to proceed on this? I guess the current design is same as *ix minus all specific *ix parts that could be stripped out from documentation.
>
> I recall also suggesting discussing the core file format out in the open
> through the gdb@sourcware.org mailing list (here
> https://urldefense.com/v3/__https://sourceware.org/pipermail/gdb-patches/2020-October/172721.html__;!!BFCLnRDDbM3FOmw!sNi8byoH5SSID20XZ9bMNX2DOjXF4ZJcrHvYbpgAnuXp0WCSVEiMdf2v2kNX1j4uVrbATpFt$ ).
> That would make it easier to others interested in this to contribute and
> provide their thoughts.
>
> It makes it a bit harder to design things based on patches directly.

Yes, agree, re-engineering is not preferred design,
and the Linux format is far more complex that what a none-corefile would need probably.
I tried to strip out everything but 'memory' and 'registers',
so the none corefile should be a regular valid ELF file, with memory and registers only I guess.

I tried to find a good specification/documentation source for corefiles, but it is not very clear where to look...
Found this as a starting point
https://stackoverflow.com/questions/5986366/elf-core-file-format

This is the current format when trying from ARM simulator:

fredrik@legion ~/src/armv4t_coretest$ readelf -aA test.core
ELF Header:
Magic: 7f 45 4c 46 01 01 01 61 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: ARM
ABI Version: 0
Type: CORE (Core file)
Machine: ARM
Version: 0x1
Entry point address: 0x0
Start of program headers: 52 (bytes into file)
Start of section headers: 8084 (bytes into file)
Flags: 0x0
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 5
Size of section headers: 40 (bytes)
Number of section headers: 7
Section header string table index: 6

Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] note0 NOTE 00000000 001e44 000138 00 A 0 0 1
[ 2] load PROGBITS 00010000 0000d4 000100 00 AX 0 0 1
[ 3] load PROGBITS 00080000 0001d4 000000 00 WA 0 0 1
[ 4] load PROGBITS 00080000 0001d4 000400 00 WA 0 0 1
[ 5] load PROGBITS 000fe790 0005d4 001870 00 WA 0 0 1
[ 6] .shstrtab STRTAB 00000000 001f7c 000016 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
y (purecode), p (processor specific)

There are no section groups in this file.

Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
NOTE 0x001e44 0x00000000 0x00000000 0x00138 0x00000 R 0x1
LOAD 0x0000d4 0x00010000 0x00000000 0x00100 0x00100 R E 0x1
LOAD 0x0001d4 0x00080000 0x00000000 0x00000 0x00000 RW 0x1
LOAD 0x0001d4 0x00080000 0x00000000 0x00400 0x00400 RW 0x1
LOAD 0x0005d4 0x000fe790 0x00000000 0x01870 0x01870 RW 0x1

Section to Segment mapping:
Segment Sections...
00
01 load
02 load
03 load load
04 load

There is no dynamic section in this file.
There are no relocations in this file.
There are no unwind sections in this file.
No version information found in this file.

Displaying notes found at file offset 0x00001e44 with length 0x00000138:
Owner Data size Description
CORE 0x0000007c NT_PRPSINFO (prpsinfo structure)
CORE 0x00000094 NT_PRSTATUS (prstatus structure)

/Fredrik