When I read arm-tdep.c:copy_ldr_str_ldrb_strb, I feel pretty hard to
understand two lines of code,

      dsc->modinsn[0] = 0xe58ff014;  /* str pc, [pc, #20].  */
      dsc->modinsn[1] = 0xe59f4010;  /* ldr r4, [pc, #16].  */

Shall program get SIGSEGV when executing `str pc, [pc, #20]' during
displaced stepping?  A simple test case confirmed my guess, which is
included in arm-disp-step.S in this patch.

If it is a bug here, this patch is to address it.  These two lines of
code is to compute the offset of `str pc'.  In this patch, we can do
this in a different way,

	str pc, [sp, #-4]
	ldr r4, [sp, #-4]

OK for mainline and 7.2 branch?

-- 
Yao (齐尧)