ARM interworking with different linker sections

[Eric de Jong]

Hello Nick,

I use gcc 3.2.1, binutils 2.13.1  and newlib 1.10.0. They are compiled on cygwin
1.3.19-1 with --target=arm-unknown-elf.

Attached you will find interwork.zip. After a make, I did an
"arm-unknown-elf-objdump -d a.out > a.s"
If you look in the file 'a.s' at line 182 you will see:

1c6: f831f000  bl 22c <LedLoop_rom_thumb+0x88>

The last address in 'a.s' is 0x20a, 0x22c does not exist.

Please note the following about the attached project:
- for simplicity, no startup files are included
- the makefile is configured to compile thumbfunc.c with -mthumb
and -mthumb-interwork flag,
  all other files compile with -mthumb-interwork flag
- in thumbfunc.h, you will find for LedLoop_rom_thumb and SetLeds: __attribute__
((section(".virtrom")))
- the linker file link_rom.cmd will put section .virtrom behind all other
sections (but still in ram, before rom section at 0x1000000)


----- Original Message -----
From: "Nick Clifton"
Subject: Re: ARM interworking with different linker sections


Hi Eric,

> Function main (arm function) calls LedLoop_rom_thumb (thumb function) which
> calls SetLeds (arm function)
> Calling LedLoop_rom_thumb works well, the interworking stub
> LedLoop_rom_thumb_from_arm is called at 0xee4 which calls LedLoop_rom_thumb at
> 0x1315 (0x1314 with thumb mode bit). However the call to SetLeds is translated
> in a call to 0x2128. At this location there is no code or data present.
> arm-objdump -S a.out reveils that the stub SetLeds_from_thumb is located at
> 0xedc.
>
> When I move LedLoop_rom to segment .text all works well.
> When I move LedLoop_rom and SetLeds to segment .text all works well too.
>
> Who can help?

Please can you supply som emore details of the problem:

  * What version of the compiler, assembler and linker are you using ?

  * Do you have a *small* reproducible test case that demonstrates the
    problem ?

Cheers
        Nick

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