8294679: RISC-V: Misc crash dump improvements

Reviewed-by: fjiang, shade

Author: RealFYang

src/hotspot/os_cpu/linux_riscv/os_linux_riscv.cpp

@@ -145,6 +145,12 @@ frame os::fetch_frame_from_context(const void* ucVoid) {
   intptr_t* frame_sp = NULL;
   intptr_t* frame_fp = NULL;
   address epc = fetch_frame_from_context(ucVoid, &frame_sp, &frame_fp);
+  if (!is_readable_pointer(epc)) {
+    // Try to recover from calling into bad memory
+    // Assume new frame has not been set up, the same as
+    // compiled frame stack bang
+    return fetch_compiled_frame_from_context(ucVoid);
+  }
   return frame(frame_sp, frame_fp, epc);
 }
 
@@ -357,8 +363,8 @@ void os::print_tos_pc(outputStream *st, const void *context) {
   // Note: it may be unsafe to inspect memory near pc. For example, pc may
   // point to garbage if entry point in an nmethod is corrupted. Leave
   // this at the end, and hope for the best.
-  address pc = os::Posix::ucontext_get_pc(uc);
-  print_instructions(st, pc, UseRVC ? sizeof(char) : 4/*non-compressed native instruction size*/);
+  address pc = os::fetch_frame_from_context(uc).pc();
+  print_instructions(st, pc, UseRVC ? sizeof(char) : (int)NativeInstruction::instruction_size);
   st->cr();
 }