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+This is a thread-aware gdb stub for the lm32 architecture. It has to be
+linked with the application, which should be debugged. The application has
+to call 'lm32_gdb_stub_install' to setup the stub.
+   The stub remaps _all_ h/w exceptions to an own code (lm32-debug.S), which
+saves all the registers, calls the gdb stub and restores the registers again.
+   The interrupt exceptions gets handled in a special way. Because we remapped
+this exception, we need to do
+ - the same as the original one (in cpu_asm.S),
+ - and, as we might use an ISR for breaking into a running application with
+   gdb, we need to save all registers as well. To be backward compatible
+   the missing callee saved registers gets appended to CPU_Interrupt_frame.
+   There is a mapping in 'gdb_handle_break' for that.
+
+To use this gdb stub, your bsp has to provide the following functions:
+ - void gdb_put_debug_char(char c)
+   Puts the given charater c to the debug console output. The function can
+   block until the character can be written to the output buffer.
+
+ - char gdb_get_debug_char(void)
+   Returns the character in the input buffer of the debug console. If no one
+   is availabe, the function must block.
+
+ - void gdb_console_init()
+   This function can be used to initialize the debug console. Additionally,
+   it should set up the ISR for the debug console to call the function
+   'gdb_handle_break', which is provided by the gdb stub and enable the
+   interrupt for a break symbol on the debug serial port. If no ISR is
+   provided, you won't be able to interrupt a running application.
+
+ - void gdb_ack_irq()
+   If an ISR is used, this function is used to acknowledge the interrupt.
+
+NOTE: the stub don't skip a hardcoded 'break' in the code. So you have to
+   set the PC an instruction further in the debugger (set $pc += 4).
+
+NOTE2: make sure you have the following CFLAGS set:
+     -mbarrel-shift-enabled -mmultiply-enabled -mdivide-enabled 
+     -msign-extend-enabled
+   Without the hardware support, it is done in software. Unfortunately, the
+   stub also uses some shifts and multiplies. If you step through your code,
+   there will be a chance that a breakpoint is set to one of that functions,
+   which then causes an endless loop.
+
+
+EXAMPLES
+
+  char gdb_get_debug_char(void)
+  {
+    /* Wait until there is a byte in RXTX */
+    while (!(uartread(LM32_UART_LSR) & LM32_UART_LSR_DR));
+
+    return (char) uartread(LM32_UART_RBR);
+  }
+
+  void gdb_put_debug_char(char c)
+  {
+    /* Wait until RXTX is empty. */
+    while (!(uartread(LM32_UART_LSR) & LM32_UART_LSR_THRE));
+    uartwrite(LM32_UART_RBR, c);
+  }
+
+  extern void gdb_handle_break(
+    rtems_vector_number vector,
+    CPU_Interrupt_frame *frame
+  );
+  void gdb_console_init()
+  {
+    rtems_isr_entry old;
+
+    /* enable interrupts */
+    uartwrite(LM32_UART_IER, 1);
+
+    rtems_interrupt_catch((rtems_isr_entry) gdb_handle_break, DEBUG_UART_IRQ,
+      &old);
+    lm32_interrupt_unmask(1 << DEBUG_UART_IRQ);
+  }
+
+  void gdb_ack_irq()
+  {
+    lm32_interrupt_ack(1 << DEBUG_UART_IRQ);
+  }
+