Re: mis-handling of arm semihosting in libgloss/arm/crt0.S

[Nick Clifton <nickc at redhat dot com>]

Hi Can,

  Sorry for the long delay in replying - I was sidetracked by paying 
customers....

> #define AngelSWI_ARM 			0x123456
> #ifdef __thumb__
> #define AngelSWI 			0xAB
> #else
> #define AngelSWI 			AngelSWI_ARM
> #endif
>
> So, your patch
> +	AngelSWIAsm	AngelSWI
>   	ldr	r0, .LC0	/*  point at values read */
>
> will use 0xAB for all thumb state, which is only correct for thumb2
> and armv6-m here. Considering thumb state on architecture pre armv6,
> as the comment, we are always in ARM mode for startup for these
> architectures, and should use 0x123456 for these archs here.

Good point.  Presumably this version would work:

  #if defined __thumb__ && ! defined __thumb2__
	/* When in thumb mode, but not supporting thumb2 insns, we will
	   always start execution in ARM mode, so use the ARM mode SWI.  */
	AngelSWIAsm	AngelSWI_ARM
  #else
	AngelSWIAsm	AngelSWI
  #endif

> actually found this problem during my work on supporting
> armv7-m/armv6-m in libgloss/arm and have already worked out a patch.
> Hoping I could pass internal review and send it to newlib list ASAP.
> Please help me review it then. :(

Certainly.  If you cc me on the posting I will be sure to review it.

Cheers
  Nick