Question ARM sim target and Cortex M

[Luis Machado]

Hi Fredrik,

On 10/24/20 6:02 AM, Fredrik Hederstierna via Gdb wrote:
> Hi,
> 
> I have a question about using ARM target simulator and bare metal Cortex M elf.
> 
> I tried to start my arm-none-eabi with my program:
> 
> $ arm-none-eabi-gdb myprog.elf
> ...
> (gdb) target sim
> Connected to the simulator.
> (gdb) load
> Loading section .text, size 0x549f0 lma 0x2800
> Loading section .data, size 0x934 lma 0x571f0
> Loading section .ARM.exidx, size 0x8 lma 0x57b24
> Start address 0x28ff
> Transfer rate: 2791776 bits in <1 sec.
> (gdb) run
> Starting program: /home/fredrik/build/myprog.elf
> Unknown machine type '22'; please update sim_create_inferior.
> [Inferior 1 (process 42000) exited normally]
> (gdb)
> 
> Looking in <sim/arm/wrapper.c> I see missing handling alot of newer targets > arm_5?
> Looking in <bfd/bfd-in2.h>:
> 
> bfd/bfd-in2.h:#define bfd_mach_arm_5TEJ      14
> bfd/bfd-in2.h:#define bfd_mach_arm_6         15
> bfd/bfd-in2.h:#define bfd_mach_arm_6KZ       16
> bfd/bfd-in2.h:#define bfd_mach_arm_6T2       17
> bfd/bfd-in2.h:#define bfd_mach_arm_6K        18
> bfd/bfd-in2.h:#define bfd_mach_arm_7         19
> bfd/bfd-in2.h:#define bfd_mach_arm_6M        20
> bfd/bfd-in2.h:#define bfd_mach_arm_6SM       21
> bfd/bfd-in2.h:#define bfd_mach_arm_7EM       22
> bfd/bfd-in2.h:#define bfd_mach_arm_8         23
> bfd/bfd-in2.h:#define bfd_mach_arm_8R        24
> bfd/bfd-in2.h:#define bfd_mach_arm_8M_BASE   25
> bfd/bfd-in2.h:#define bfd_mach_arm_8M_MAIN   26
> bfd/bfd-in2.h:#define bfd_mach_arm_8_1M_MAIN 27
> 
> My target is Cortex-M4 so its ID '22' meaning <bfd_mach_arm_7EM>,
> cannot I run Cortex-M4 in target simulator, or what do I do wrong here?
> Are there more targets that could be added in eg <sim/arm/wrapper.c>, or am I looking in the wrong place?
> 
> Thanks! BR Fredrik
> 

Overall, the ARM/AArch64 sim targets should not be considered up-to-date 
nor complete. In fact, I think they are fairly outdated and shouldn't be 
considered for any serious simulator-based work/testing. Only casual 
trivial testing.

I'd recommend QEMU instead, which is much better supported in terms of 
features.

Of course, folks are welcome to update the sim targets.