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