ucontext

[Konstantin Belousov]

On Thu, Oct 24, 2019 at 02:11:33PM +0300, Nick Kostirya via freebsd-arm wrote:
> Hello.
> I want to port MLton to ARM.
> There are file with access to ucontext_t structure.
> 
> 
> static void catcher (__attribute__ ((unused)) int signo,
>                      __attribute__ ((unused)) siginfo_t* info,
>                      void* context) {
>         ucontext_t* ucp = (ucontext_t*)context;
> #if (defined (__x86_64__))
>         GC_handleSigProf ((code_pointer) ucp->uc_mcontext.mc_rip);
> #elif (defined (__i386__))
>         GC_handleSigProf ((code_pointer) ucp->uc_mcontext.mc_eip);
> #else
> #error Profiling handler is missing for this architecture
> #endif
> }
> 
> Please, tell me what should I write for ARM.
> 
> #elif (defined (__arm__))
>         GC_handleSigProf ((code_pointer) ucp->uc_mcontext.mc_vfp_ptr);
> 
> Is it?

I believe you want
	uc_context.__gregs[_REG_PC]
on arm (32bit) and
	uc_context.mc_gpregs.gp_elr
on arm64 for aarch64.

Sometimes the thumb bit (lowest bit in PC) leaks there, then you should
mask it.