Anhad Singh
2c307616d8
Even though it might seem like it, it is not necessary that write(2) is the only system call performed. It could be that the libc has to allocate memory (via MMAP) or makes use of a futex. To produce consistant results, only log on SYS_write and when the syscall number has been patched. Signed-off-by: Anhad Singh <andypython@protonmail.com>
86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
#include <signal.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <sys/ptrace.h>
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#include <sys/user.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "test_helpers.h"
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#ifdef __linux__
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#define SYS_write 1
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#endif
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#ifdef __redox__
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#define SYS_write 0x21000004
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#endif
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int main() {
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int pid = fork();
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ERROR_IF(fork, pid, == -1);
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if (pid == 0) {
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// Test behavior on Redox when TRACEME hasn't been activated
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// before waitpid is invoked!
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sleep(1);
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int result = ptrace(PTRACE_TRACEME, 0, NULL, NULL);
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ERROR_IF(ptrace, result, == -1);
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UNEXP_IF(ptrace, result, != 0);
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// Alert parent: I'm ready
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result = raise(SIGSTOP);
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ERROR_IF(raise, result, == -1);
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UNEXP_IF(raise, result, != 0);
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puts("This is printed to STDOUT.");
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puts("Or, at least, that's what I thought.");
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puts("But all write(...) syscalls are actually redirected to STDERR by the tracer.");
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puts("Big surprise, right!");
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} else {
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// Wait for child process to be ready
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int result = waitpid(pid, NULL, 0);
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ERROR_IF(waitpid, result, == -1);
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int status;
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while (true) {
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// puts("----- Pre-syscall -----");
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result = ptrace(PTRACE_SYSCALL, pid, NULL, NULL);
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ERROR_IF(ptrace, result, == -1);
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UNEXP_IF(ptrace, result, != 0);
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// puts("Wait...");
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result = waitpid(pid, &status, 0);
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ERROR_IF(waitpid, result, == -1);
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if (WIFEXITED(status))
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break;
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struct user_regs_struct regs;
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// puts("Get regs");
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result = ptrace(PTRACE_GETREGS, pid, NULL, ®s);
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ERROR_IF(ptrace, result, == -1);
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if (regs.orig_rax == SYS_write || regs.orig_rax == SYS_write) {
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regs.rdi = 2;
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puts("Set regs");
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result = ptrace(PTRACE_SETREGS, pid, NULL, ®s);
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ERROR_IF(ptrace, result, == -1);
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}
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// puts("Post-syscall");
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result = ptrace(PTRACE_SYSCALL, pid, NULL, NULL);
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ERROR_IF(ptrace, result, == -1);
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UNEXP_IF(ptrace, result, != 0);
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// puts("Wait...");
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result = waitpid(pid, &status, 0);
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ERROR_IF(waitpid, result, == -1);
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if (WIFEXITED(status))
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break;
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}
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printf("Child exited with status %d\n", WEXITSTATUS(status));
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}
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}
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