| //===-- ptrace_example.c --------------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include <asm/ptrace.h> |
| #include <linux/elf.h> |
| #include <stdint.h> |
| #include <stdio.h> |
| #include <sys/prctl.h> |
| #include <sys/ptrace.h> |
| #include <sys/uio.h> |
| #include <sys/wait.h> |
| #include <unistd.h> |
| |
| // The demo program shows how to do basic ptrace operations without lldb |
| // or lldb-server. For the purposes of experimentation or reporting bugs |
| // in kernels. |
| // |
| // It is AArch64 Linux specific, adapt as needed. |
| // |
| // Expected output: |
| // Before breakpoint |
| // After breakpoint |
| |
| void inferior() { |
| if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) { |
| perror("ptrace"); |
| return; |
| } |
| |
| printf("Before breakpoint\n"); |
| |
| // Go into debugger. Instruction replaced with nop later. |
| // We write 2 instuctions because POKETEXT works with |
| // 64 bit values and we don't want to overwrite the |
| // call to printf accidentally. |
| asm volatile("BRK #0 \n nop"); |
| |
| printf("After breakpoint\n"); |
| } |
| |
| void debugger(pid_t child) { |
| int wait_status; |
| // Wait until it hits the breakpoint. |
| wait(&wait_status); |
| |
| while (WIFSTOPPED(wait_status)) { |
| if (WIFEXITED(wait_status)) { |
| printf("inferior exited normally\n"); |
| return; |
| } |
| |
| // Read general purpose registers to find the PC value. |
| struct user_pt_regs regs; |
| struct iovec io; |
| io.iov_base = ®s; |
| io.iov_len = sizeof(regs); |
| if (ptrace(PTRACE_GETREGSET, child, NT_PRSTATUS, &io) < 0) { |
| printf("getregset failed\n"); |
| return; |
| } |
| |
| // Replace brk #0 / nop with nop / nop by writing to memory |
| // at the current PC. |
| uint64_t replace = 0xd503201fd503201f; |
| if (ptrace(PTRACE_POKETEXT, child, regs.pc, replace) < 0) { |
| printf("replacing bkpt failed\n"); |
| return; |
| } |
| |
| // Single step over where the brk was. |
| if (ptrace(PTRACE_SINGLESTEP, child, 0, 0) < 0) { |
| perror("ptrace"); |
| return; |
| } |
| |
| // Wait for single step to be done. |
| wait(&wait_status); |
| |
| // Run to completion. |
| if (ptrace(PTRACE_CONT, child, 0, 0) < 0) { |
| perror("ptrace"); |
| return; |
| } |
| |
| // Wait to see that the inferior exited. |
| wait(&wait_status); |
| } |
| } |
| |
| int main() { |
| pid_t child = fork(); |
| |
| if (child == 0) |
| inferior(); |
| else if (child > 0) |
| debugger(child); |
| else |
| return -1; |
| |
| return 0; |
| } |