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https://gitlab.rtems.org/rtems/rtos/rtems.git
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a0957ef636
When memory is accessed by the remote debugging client, the access is sandboxed with setjmp/longjmp and appropriate exception handlers to prevent the attempted access from causing a failure of the debugger or otherwise altering execution. The existing implementation works as expected when the context executing the memory access and the exception context resulting from a failed access do not share a stack. In the case of AArch64, a failed access when the debugger is already in exception context causes a re-entry into exception context where the machine state is pushed onto the same stack that was in use where the exception occurred. When setjmp is called inside a stack frame and the exception occurs outside that stack frame, the stack frame is unwound before the exception occurs and the exception entry overwrites the area previously occupied by the stack frame housing the setjmp and corrupting the link register that is stored there. After restoration of state using longjmp(), this corrupted link register information is loaded from the stack frame and undesired behavior occurs. In the instance of this bug that was encountered, the corrupted link register contained an unaligned pointer which caused an unending cascade of prefetch abort exceptions presenting as a hard hang.
318 lines
10 KiB
C
318 lines
10 KiB
C
/*
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* Copyright (c) 2016-2017 Chris Johns <chrisj@rtems.org>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Debugger for RTEMS.
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*/
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#ifndef _RTEMS_DEBUGGER_TARGET_h
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#define _RTEMS_DEBUGGER_TARGET_h
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#include <setjmp.h>
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#include <rtems/rtems-debugger.h>
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#include "rtems-debugger-threads.h"
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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/*
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* Software breakpoint block size.
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*/
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#define RTEMS_DEBUGGER_TARGET_SWBREAK_NUM 64
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/**
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* Target capabilities mask.
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*/
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#define RTEMS_DEBUGGER_TARGET_CAP_SWBREAK (1 << 0)
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#define RTEMS_DEBUGGER_TARGET_CAP_HWBREAK (1 << 1)
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#define RTEMS_DEBUGGER_TARGET_CAP_HWWATCH (1 << 2)
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/*
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* This target capability indicates that the target implementation uses a pure
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* software break implementation which must not allow breakpoints to be
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* inserted before the actual switch to the thread, be it in interrupt context
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* or otherwise. Such implementations must necessarily implement a thread
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* switch hook and interrupt hooks to handle these situations.
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*/
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#define RTEMS_DEBUGGER_TARGET_CAP_PURE_SWBREAK (1 << 3)
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/**
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* Types of hardware breakpoints.
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*/
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typedef enum rtems_debugger_target_watchpoint
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{
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rtems_debugger_target_hw_read,
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rtems_debugger_target_hw_write,
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rtems_debugger_target_hw_read_write,
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rtems_debugger_target_hw_execute
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} rtems_debugger_target_watchpoint;
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/**
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* Target exception actions.
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*/
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typedef enum rtems_debugger_target_exc_action
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{
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rtems_debugger_target_exc_consumed, /*<< The exception has been consumed. */
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rtems_debugger_target_exc_cascade, /*<< Cascade to a previous handler. */
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rtems_debugger_target_exc_step, /*<< Step an instruction. */
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} rtems_debugger_target_exc_action;
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/**
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* Memory breakpoint. We use thumb mode BKPT which is 2 bytes.
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*/
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#define RTEMS_DEBUGGER_TARGET_SWBREAK_MAX_SIZE (4)
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typedef struct rtems_debugger_target_swbreak {
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void* address;
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uint8_t contents[RTEMS_DEBUGGER_TARGET_SWBREAK_MAX_SIZE];
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} rtems_debugger_target_swbreak;
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/**
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* Target executable memory update handler. If set the handler is
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* called to modify the executable memory. The target's executable
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* memory may not be directly writable. The handler is responsible for
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* making sure the code update is ready to be executed, for example
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* caches are flushed.
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*/
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typedef int (*rtems_debugger_target_code_writer)(void* address,
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const void* data,
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size_t size);
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/**
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* The target data.
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*
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* reg_offset: Table of size_t offset of a register in the register
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* table. The table has one more entry than reg_num where
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* the last entry is the size of the register table.
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*/
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typedef struct rtems_debugger_target {
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int capabilities; /*<< The capabilities to report. */
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size_t reg_num; /*<< The number of registers. */
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const size_t* reg_offset; /*<< The reg offsettable, len = reg_num + 1. */
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const uint8_t* breakpoint; /*<< The breakpoint instruction(s). */
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size_t breakpoint_size; /*<< The breakpoint size. */
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rtems_debugger_block swbreaks; /*<< The software breakpoint block. */
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rtems_debugger_target_code_writer code_writer; /*<< If set use to write to code memory */
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bool memory_access; /*<< Accessing target memory. */
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jmp_buf access_return; /*<< Return from an access fault. */
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uintptr_t step_bp_address; /*<< Stepping break point address */
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rtems_id step_tid; /*<< Stepping task id */
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} rtems_debugger_target;
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/**
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* Create the target.
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*/
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extern int rtems_debugger_target_create(void);
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/**
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* Destroy the target.
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*/
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extern int rtems_debugger_target_destroy(void);
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/**
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* Configure the target. This is architecture specific.
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*/
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extern int rtems_debugger_target_configure(rtems_debugger_target* target);
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/**
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* Enable the target.
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*/
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extern int rtems_debugger_target_enable(void);
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/**
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* Disable the target.
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*/
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extern int rtems_debugger_target_disable(void);
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/**
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* Return the capabilities mask for the target.
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*/
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extern uint32_t rtems_debugger_target_capabilities(void);
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/**
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* Return the number of regisers.
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*/
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extern size_t rtems_debugger_target_reg_num(void);
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/**
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* Return the offset of a register in the register table.
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*/
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extern size_t rtems_debugger_target_reg_size(size_t reg);
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/**
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* Return the offset of a register in the register table.
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*/
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extern size_t rtems_debugger_target_reg_offset(size_t reg);
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/**
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* Return the size of register table.
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*/
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extern size_t rtems_debugger_target_reg_table_size(void);
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/**
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* Read the regosters.
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*/
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extern int rtems_debugger_target_read_regs(rtems_debugger_thread* thread);
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/**
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* Write the regosters.
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*/
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extern int rtems_debugger_target_write_regs(rtems_debugger_thread* thread);
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/**
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* Return the thread's program counter (PC).
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*/
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extern uintptr_t rtems_debugger_target_reg_pc(rtems_debugger_thread* thread);
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/**
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* Return the frame's program counter (PC).
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*/
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extern uintptr_t rtems_debugger_target_frame_pc(CPU_Exception_frame* frame);
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/**
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* Return the thread's stack pointer (SP).
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*/
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extern uintptr_t rtems_debugger_target_reg_sp(rtems_debugger_thread* thread);
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/**
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* Return the thread's TCB stack pointer (SP).
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*/
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extern uintptr_t rtems_debugger_target_tcb_sp(rtems_debugger_thread* thread);
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/**
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* The thread is stepping. Setup the thread to step an instruction.
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*/
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extern int rtems_debugger_target_thread_stepping(rtems_debugger_thread* thread);
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/**
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* Return the signal for the exception.
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*/
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extern int rtems_debugger_target_exception_to_signal(CPU_Exception_frame* frame);
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/**
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* Print the target exception registers.
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*/
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extern void rtems_debugger_target_exception_print(CPU_Exception_frame* frame);
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/**
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* Software breakpoints. These are also referred to as memory breakpoints.
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*/
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extern int rtems_debugger_target_swbreak_control(bool insert,
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uintptr_t addr,
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DB_UINT kind);
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/**
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* Insert software breakpoints into the memory.
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*/
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extern int rtems_debugger_target_swbreak_insert(void);
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/**
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* Remove software breakpoints from the memory.
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*/
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extern int rtems_debugger_target_swbreak_remove(void);
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/**
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* Determine whether a software breakpoint is configured for the given address.
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*/
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extern bool rtems_debugger_target_swbreak_is_configured( uintptr_t addr );
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/**
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* Insert hardware breakpoints into the hardware.
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*/
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extern int rtems_debugger_target_hwbreak_insert(void);
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/**
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* Remove hardware breakpoints from the hardware.
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*/
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extern int rtems_debugger_target_hwbreak_remove(void);
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/**
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* Hardware breakpoints.
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*/
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extern int rtems_debugger_target_hwbreak_control(rtems_debugger_target_watchpoint type,
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bool insert,
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uintptr_t addr,
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DB_UINT kind);
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/**
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* Target exception processor.
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*/
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extern rtems_debugger_target_exc_action
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rtems_debugger_target_exception(CPU_Exception_frame* frame);
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/**
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* See if the thread is an exception thread.
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*/
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extern void rtems_debugger_target_exception_thread(rtems_debugger_thread* thread);
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/**
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* If the thread is an exception thread, resume it.
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*/
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extern void rtems_debugger_target_exception_thread_resume(rtems_debugger_thread* thread);
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/**
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* Target instruction cache sync. This depends on the target but it normally
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* means a data cache flush and an instruction cache invalidate.
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*/
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extern int rtems_debugger_target_cache_sync(rtems_debugger_target_swbreak* swbreak);
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/**
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* Start a target memory access. If 0 is return the access can proceed and if
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* -1 is return the access has failed.
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*
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* The call to setjmp() must not reside inside a stack frame relative to the
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* expected location of the possible failure. If the debugger is already
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* executing in exception context and setjmp is called with its own stack frame,
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* that stack frame will be released before the failure. The failure causes an
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* exception which will continue using the same stack and is highly likely to
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* overwrite stack information which is critical for the debugger to continue
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* execution.
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*/
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#define rtems_debugger_target_start_memory_access() \
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({ \
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rtems_debugger->target->memory_access = true, \
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setjmp(rtems_debugger->target->access_return); \
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})
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/**
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* End a target memory access.
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*/
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extern void rtems_debugger_target_end_memory_access(void);
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/**
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* Is this a target memory access?
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*/
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extern bool rtems_debugger_target_is_memory_access(void);
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif
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