Re: [PATCH] aarch64: Check for valid inferior thread/regcache before reading pauth registers

[Simon Marchi <simark@simark.ca>]

> ... despite the call to switch_to_no_thread in switch_to_inferior_no_thread from do_target_wait_1
> in the backtrace above, the call to ps_xfer_memory sets inferior_ptid momentarily before reading
> memory:
> 
> 
> static ps_err_e
> ps_xfer_memory (const struct ps_prochandle *ph, psaddr_t addr,
>                 gdb_byte *buf, size_t len, int write)
> {
>   scoped_restore_current_inferior restore_inferior;
>   set_current_inferior (ph->thread->inf);
> 
>   scoped_restore_current_program_space restore_current_progspace;
>   set_current_program_space (ph->thread->inf->pspace);
> 
>   scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
>   inferior_ptid = ph->thread->ptid;
> 
>   CORE_ADDR core_addr = ps_addr_to_core_addr (addr);
> 
>   int ret;
>   if (write)
>     ret = target_write_memory (core_addr, buf, len);
>   else
>     ret = target_read_memory (core_addr, buf, len);
>   return (ret == 0 ? PS_OK : PS_ERR);
> }
> 
> 
> Maybe this shouldn't happen, or maybe it is just an unfortunate state to be in. But this
> prevents the use of target_has_registers to guard against the lack of registers, since,
> although current_thread_ is still nullptr, inferior_ptid is valid and is not null_ptid.
It's needed to set inferior_ptid here because it's how we communicate to
the targets which inferior / thread we want to read or write memory
from.  And we can't set current_thread_ to the the correponding
thread_info *, because it does not exist at this point (we are in the
process of creating it).  And the problem is that
aarch64_remove_non_address_bits assumes there is a current_thread_.  Can
we change aarch64_remove_non_address_bits to get the regcache using the
ptid?

  get_thread_regcache (current_inferior ()->process_target (), inferior_ptid);

Simon