kopia lustrzana https://github.com/espressif/esp-idf
318 wiersze
8.6 KiB
C
318 wiersze
8.6 KiB
C
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/*
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* SPDX-FileCopyrightText: 2020-2022 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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/**
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* @file DWARF Exception Frames parser header
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*
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* This file describes the frame types for x86, required for
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* parsing `eh_frame` and `eh_frame_hdr`.
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*/
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#define _POSIX_C_SOURCE 200809L
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#define _DEFAULT_SOURCE
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#include <stdio.h>
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#include <signal.h>
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#include <string.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include <assert.h>
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#include <ucontext.h>
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#include "../include/esp_private/eh_frame_parser.h"
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#include "eh_frame_parser_impl.h"
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/**
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* @brief Index of x86 registers in `greg_t` structure.
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*/
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#define REG_EDI 4
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#define REG_ESI 5
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#define REG_EBP 6
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#define REG_ESP 7
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#define REG_EBX 8
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#define REG_EDX 9
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#define REG_ECX 10
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#define REG_EAX 11
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#define REG_EIP 14
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/**
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* @brief Number of functions in the funs structure described below.
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*/
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#define FUNCTIONS_COUNT ((sizeof(funs)/sizeof(*funs)))
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/**
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* @brief Number which will determine the depth of the call stack.
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* Check `main()` for more information.
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*/
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#define NUMBER_TO_TEST (4)
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/**
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* @brief Number of iteration for function `esp_eh_frame_generated_step`.
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*/
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#define NUMBER_OF_ITERATION (2 * NUMBER_TO_TEST + 2 + 1)
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/**
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* @brief Define a simple linked list type and initialize one.
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*/
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struct list_t {
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uint32_t value;
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struct list_t *next;
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};
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static struct list_t head = { 0 };
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/**
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* Few recursive functions to make the the call stack a bit more complex than a
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* single function call would give.
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*/
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bool is_odd(uint32_t n);
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bool is_even(uint32_t n);
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void browse_list(struct list_t* l);
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/**
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* @brief Structure defining a function of our program.
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* This will be used to translate the backtrace.
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*/
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struct functions_info {
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const char* name;
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uintptr_t start;
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uintptr_t end; /* will be filled at runtime */
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};
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/**
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* @brief Structure storing the information about the
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* function that will be part of the backtrace.
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*/
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struct functions_info funs[] = {
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{
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.name = "browse_list",
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.start = (uintptr_t) &browse_list,
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.end = 0
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},
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{
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.name = "is_odd",
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.start = (uintptr_t) &is_odd,
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.end = 0
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},
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{
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.name = "is_even",
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.start = (uintptr_t) &is_even,
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.end = 0
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}
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};
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/**
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* @brief Test whether the address passed as PC is part of the function which
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* name is `function_name`. The global array `funs` is used.
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*
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* @param pc Program counter to test. (address in the program)
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* @param function_name Function name to check the address of.
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*
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* @return true if PC is in the function called `function_name`, false else.
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*/
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bool is_pc_in_function(const uint32_t pc, const char* function_name)
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{
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for (uint32_t i = 0; i < FUNCTIONS_COUNT; i++) {
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const struct functions_info current_fun = funs[i];
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if (strcmp(current_fun.name, function_name) == 0) {
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return current_fun.start <= pc && pc <= current_fun.end;
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}
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}
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/* Function not found. */
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return false;
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}
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/**
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* @brief Number of times `esp_eh_frame_generated_step` is called.
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*/
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static uint32_t iteration = 1;
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/**
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* @brief Override the default function called when a backtrace step is
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* generated.
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*/
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void esp_eh_frame_generated_step(uint32_t pc, uint32_t sp) {
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/* The first PCs in the backtrace are calls to `browse_list()` + 2.
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* This is due to the fact that the list contains all the numbers
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* between NUMBER_TO_TEST to 0 included. Moreover, another call
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* is made when we meet the NULL pointer. */
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if (iteration > 0 && iteration <= (NUMBER_TO_TEST + 2)) {
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assert(is_pc_in_function(pc, "browse_list"));
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} else {
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/**
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* The backtrace should be:
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* - in is_odd when iteration is even.
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* - in is_even when iteration is odd.
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*
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* The backtrace finishes when the iteration reaches the end of
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* browse_list (NUMBER_TO_TEST + 2 iterations), is_even
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* (NUMBER_TO_TEST/2 calls) and is_odd (NUMBER_TO_TEST/2 calls) calls.
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*/
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if (iteration >= NUMBER_OF_ITERATION)
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return;
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else if (iteration % 2 == 0)
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assert(is_pc_in_function(pc, "is_odd"));
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else
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assert(is_pc_in_function(pc, "is_even"));
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}
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/* Number of times this function has been entered. */
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iteration++;
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}
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/**
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* @brief Handler called when SIGSEV signal is sent to the program.
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*
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* @param signal Signal received byt the program. Shall be SIGSEGV.
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* @param info Structure containing info about the error itself. Ignored.
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* @param ucontext Context of the program when the error occurred. This
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* is used to retrieve the CPU registers value.
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*/
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void signal_handler(int signal, siginfo_t *info, void *ucontext) {
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/* Setup the execution frame as expected by the eh_frame_parser.
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* Indeed, the registers index defined in ucontext.h are NOT the same
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* the registers index DWARF is expecting. */
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ucontext_t* context = (ucontext_t*) ucontext;
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greg_t *gregset = context->uc_mcontext.gregs;
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x86ExcFrame frame = {
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.eax = gregset[REG_EAX],
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.ecx = gregset[REG_ECX],
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.edx = gregset[REG_EDX],
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.ebx = gregset[REG_EBX],
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.esp = gregset[REG_ESP],
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.ebp = gregset[REG_EBP],
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.esi = gregset[REG_ESI],
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.edi = gregset[REG_EDI],
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.eip = gregset[REG_EIP]
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};
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/* The following function will use panic_print_str and panic_print_hex
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* function to output the data.
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* Instead of replacing stdout file descriptor with a pipe, we can simply
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* replace these functions to store the data instead of printing them.
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*/
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esp_eh_frame_print_backtrace(&frame);
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/* No assert has been triggered, the backtrace succeeded if the number of
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* iterations of function `esp_eh_frame_generated_step` is correct. */
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if (iteration == NUMBER_OF_ITERATION) {
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printf("\e[32m\e[1mAll tests passed \e[0m\r\n");
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} else {
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printf("\e[31m\e[1mWrong length of backtrace (%d iteration, expected %d) \e[0m\r\n",
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iteration, NUMBER_OF_ITERATION);
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exit(1);
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}
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/* Everything went fine, exit normally. */
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exit(0);
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}
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/**
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* @brief Browse the list passed as an argument.
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* The following function will trigger a SIGSEV signal on purpose, in order to
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* generate the backtrace.
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*
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* @param l List to browse.
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*/
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void browse_list(struct list_t* l) {
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browse_list(l->next);
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}
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/**
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* @brief Add a number to the global list `head`.
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*
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* @param n Number to add in the list.
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*/
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void add_number_to_list(uint32_t n) {
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struct list_t* l = malloc(sizeof(struct list_t));
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l->value = n;
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l->next = head.next;
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head.next = l;
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}
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/**
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* @brief Test if the number passed is even.
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* This function will fail, on purpose.
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*
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* @param n Number to test.
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*
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* @return true if even, false else.
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*/
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bool is_even(uint32_t n) {
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add_number_to_list(n);
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if (n == 0) {
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browse_list(head.next);
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return true;
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}
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return is_odd(n - 1);
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}
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/**
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* @brief Test if the number passed is odd.
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* This function will fail, on purpose.
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*
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* @param n Number to test.
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*
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* @return true if odd, false else.
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*/
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bool is_odd(uint32_t n) {
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add_number_to_list(n);
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if (n == 0) {
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browse_list(head.next);
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return false;
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}
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return is_even(n - 1);
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}
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/**
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* @brief Initiliaze the global `funs` array.
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*/
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static inline void initialize_functions_info(void)
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{
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for (uint32_t i = 0; i < FUNCTIONS_COUNT; i++) {
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/* Each of the functions defined in this structure finishes
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* with the following instructions:
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* leave (0xc9)
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* ret (0xc3)
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* Thus, we will look for these instructions. */
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uint8_t* instructions = (uint8_t*) funs[i].start;
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while (instructions[0] != 0xc9 || instructions[1] != 0xc3)
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instructions++;
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instructions += 1;
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funs[i].end = (uintptr_t) instructions;
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}
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}
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/**
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* Call the previous functions to create a complex call stack and fail.
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*/
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int main (int argc, char** argv)
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{
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/* Initialize the structure holding information about the signal to override. */
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struct sigaction sig = {
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.sa_mask = 0,
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.sa_flags = SA_SIGINFO,
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.sa_restorer = NULL,
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.sa_sigaction = signal_handler
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};
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/* Look for the functions end functions. */
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initialize_functions_info();
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/* Override default SIGSEV signal callback. */
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int res = sigaction(SIGSEGV, &sig, NULL);
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if (res) {
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perror("Could not override SIGSEV signal");
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return 1;
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}
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/* Trigger the segmentation fault with a complex backtrace. */
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is_even(NUMBER_TO_TEST);
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return 0;
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}
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