ืืื ืืื ืืงืก-ืืื ืึธืคึผืขืจืืืืื ื ืกืืกืืขืืขื, ืึท ืคึผืจืึธืืจืึทื ืก ืงืึธืืื ืืงืึทืฆืืข ืืื ืื ืึทืจืืืก ืืืขืื ืืื ืื ืึธืคึผืขืจืืืืื ื ืกืืกืืขื ืึทืงืขืจื ืืืจื ืึท ืงืืืื ืืึทื ื ืคืื ืคืึทื ืืงืฉืึทื ื - ืกืืกืืขื ืจืืคื. ืืขื ืืืื ืึทื ืคึฟืึทืจ ืืืืึทืืื ื ืฆืืืขืงื, ืขืก ืงืขื ืืืื ื ืืฆืืง ืฆื ืฉืคึผืืึธื ืืืืฃ ืกืืกืืขื ืงืึทืืืก ืืืึธืก ืืขื ืขื ืขืงืกืึทืงืืืืึทื ืืืจื ืคึผืจืึทืกืขืกืึทื.
ื ื ืืฆื ืืขืืคึผืก ืืืจ ืืึธื ืืืึธืจ ืื "ืึธื ืืืื ืงืขื ืืขืื" ืคืื ืืืืื ืืืืฃ ืืื ืืงืก strace, ืืืึธืก ืืื ืื ืืขืืข ืคืื โโืืขื ืึทืจืืืงื. ืืืืฉืคืืื ืคืื ืื ื ืืฆื ืคืื ืฉืคึผืืึธื ืืืกืจืืื ืืขื ืขื ืืืืืืื ืืืจื ืึท ืงืืจืฅ ืืขืฉืืืืข strace ืืื ืึท ืืึทืฉืจืืึทืืื ื ืคืื ืื ืคึผืืึทื ืคืื ืึทืืึท ืืืืื.
ืฆืืคืจืืื
ืึธืจืืืื ืคืื ืืื ืื
ืื ืืืืคึผื ืฆืืืื ื ืฆืืืืฉื ืืืืื ืืื ืื ืึทืก ืงืขืจื ืืื ืืื ืืงืก ืืื ืกืืกืืขื ืงืึทืืืก. ืกืืกืืขื ืจืืคื, ืกืืกืงืึทืืืก), ืื ืื ืืขืจืึทืงืฉืึทื ืคืื ืืืืื ืืื ืื ืึทืจืืืก ืืืขืื ืึทืงืขืจื ืืืืกืฉืืืกืืขื ืืืจื ืืื.
ืึธืืขืจ ืืื ืืขืจ ืขืจืฉืืขืจ ืขืคื ืืืขื ืืืขืจืกืืข ืคืื โโืืื ืืงืก (, 1975) ืขืก ืืขื ืขื ืืขืืืขื ืงืืื ืืึทืงืืืขื ืืืขืื ืฆื ืฉืคึผืืจ ืื ื ืึทืืืจ ืคืื ืืึทื ืืฆืขืจ ืคึผืจืึทืกืขืกืึทื. ืฆื ืกืึธืืืืข ืืขื ืึทืจืืืกืืขืื, Bell Labs ืืืขื ืืขืจืืืึทื ืืืงื ืฆื ืืขืจ ืืืืึทืืขืจ ืืืขืจืกืืข (, 1979) ืคืืจืืขืืืืื ืึท ื ืืึทืข ืกืืกืืขื ืจืืคื - ptrace.
ptrace ืืื ืืขืืืขืืึธืคึผืขื ืืคึฟืจื ืคึฟืึทืจ ืื ืืขืจืึทืงืืืื ืืืืืืขืจื, ืึธืืขืจ ืืื ืื ืกืืฃ ืคืื ืื 80 ืก (ืืื ืืขืจ ืชืงืืคื ืคืื ืืขืฉืขืคื ) ืืืืฃ ืืขื ืืืืข, ืฉืืึธื ืคืึธืืงืืกื ืืืืืืขืจื - ืกืืกืืขื ืจืืคื ืืจืืืกืขืจื - ืืจืืืก ืืื ืืขืืืืจื ืืืืืืื ืืขื ืืฆื.
ืื ืืขืืืข ืืืขืจืกืืข ืคืื โโืกืืจืึทืกืข ืืื ืืจืืืก ืืืจื Paul Cronenburg ืืืืฃ ืื comp.sources.sun ืืืืืื ื ืจืฉืืื ืืื 1992 ืืื ืึทื ืึธืืืขืจื ืึทืืืื ืฆื ืึท ืคืืจืืืื ื ืืฆื. trace ืคืื ืืื. ืืืืืข ืื ืงืืึธืื ืืื ืืขืจ ืึธืจืืืื ืขื ืืขื ืขื ืืืขื ืคึฟืึทืจ SunOS, ืึธืืขืจ ืืื 1994 strace ืืื ืืขืืืขื ืคึผืึธืจืืื ืฆื ืกืืกืืขื V, ืกืึธืืึทืจืืก ืืื ืื ืื ืงืจืืกืื ืืื ืคืึธืืงืก ืืื ืืงืก.
ืืืึทื ื ืกืืจืึทืกืข ืฉืืืฆื ืืืืื ืืื ืืงืก ืืื ืจืืืืื ืืืืฃ ืื ืืขืืืข ptrace, ืึธืืืืขืจืืจืึธืื ืืื ืคืืืข ืืงืกืืขื ืฉืึทื ื.
ืืึธืืขืจื (ืืื ืืืืขืจ ืึทืงืืืื) ืืึทืื ืืขืจืขืจ strace - . ืืึทื ืง ืฆื ืืื, ืื ื ืืฆื ืงืื ื ืึทืืืึทื ืกืืจืืข ืคึฟืขืึดืงืืืื ืึทืืึท ืืื ืืขืืช ืื ืืืฉืขืงืฉืึทื ืืื ืกืืกืืขื ืงืึทืืืก, ืฉืืืฆื ืคึฟืึทืจ ืึท ืืจืืื ืงืืื ืคืื ืึทืจืงืึทืืขืงืืฉืขืจื ืืื, ืจืืึฟ ืืืคึผืึธืจืืึทื ืืื, . ืึทื ืึทืคืืฉืึทื ืงืืืืื ืคืึธืืขืจื ืึทื ืื ืืจืืจื ืืื ืืขืคืืื ืืืืฃ ืื ืึธืกืืจืืืฉ ืืืืึทื ืคืื ืื ืงืึธื ืกืึธื ืึทื ืกืข ืฆืืืืฉื ืื ืจืืกืืฉืข ืืืึธืจื "ืึธืกืืจืืืฉ" ืืื ืื ืขื ืืืืฉ ืืืึธืจื "ืกืืจืึทืกืข".
ืขืก ืืื ืืืื ืืืืืืืง ืึทื ืื ืคืืจืึทืกืข ืกืืกืืขื ืจืืคื ืืื ืืจืืืกืขืจื ืืขื ืขื ืงืืื ืืึธื ืึทืจืืึทื ืืขืจืขืื ื ืืื POSIX, ืืจืึธืฅ ืึท ืืึทื ื ืืขืฉืืืืข ืืื ืืืคึผืืึทืืขื ืืืืฉืึทื ืืื ืืื ืืงืก, ืคืจืขืขืืกื, ืึธืคึผืขื ืืกื ืืื ืืจืืืืฆืืื ืขืื ืืื ืืงืก.
ืกืืจืึทืกืข ืืืื ืืื ืึท ื ืึทืืฉืขื: ืคึผืืืืขื ืืจืึทืกืข
"ืืืจ ืืขื ื ื ืืฉื ืืขืจืืืึทืจื ืฆื ืคึฟืึทืจืฉืืืื ืืขื" (Denis Ritchie, ืืึทืืขืจืงืื ื ืืื ืืืขืจืกืืข 6 ืืื ืืงืก ืืงืืจ ืงืึธื)
ืืื ื ืคืจื ืงืื ืืฉืึทืคื, ืืื ืงืขื ื ืืฉื ืฉืืืื ืฉืืืึทืจืฅ ืืึธืงืกืขืก: ืืื ืืื ื ืืฉื ืฉืคึผืืื ืืื ืืืืืฉ, ืึธืืขืจ ืืขืคืจืืืื ืฆื ืคึฟืึทืจืฉืืืื ืืืืขืจ ืกืืจืืงืืืจ (ืึทืืึทืืฅ ืืขื ืืฆื ืื ืืืึธืจื "ืฆืขืืจืืื," ืึธืืขืจ ืืึธื ื ืื ืืืืืื ืื ืืืื ืืฉืื ืืช). ืืึธืืขืจ ืืึธืก ืืื ืืืึธืก ืื ืื ืคืึธืจืืึทื ืงืืืืืจ ืคืื ืืขืจ ืขืจืฉืืขืจ ืืื ืืงืก ืืื ืื ืืึธืืขืจื ืึธืคึฟื-ืืงืืจ ืืึทืืืขืืื ื ืืื ืึทืืื ื ืึธืขื ื ืฆื ืืืจ.
ืคึฟืึทืจ ืื ืฆืืืขืงื ืคืื ืืขื ืึทืจืืืงื, ืขืก ืืื ืงืจืื ืฆื ืืืกืึทืกืขืืืึทื ืื ืืงืืจ ืงืึธื ืคืื ืกืืจืึทืกืข, ืืืึธืก ืืื ืืขืืืืงืกื ืืืืขืจ ืืขืงืึทืืขืก. ืืืขืจ ืขืก ืืึธื ืืืื ืงืืื ืกืืงืจืืฅ ืคึฟืึทืจ ืืืืขื ืขืจ. ืืขืจืืืขืจ, ืฆื ืืืืึทืื ืืขื ืคึผืจืื ืฆืืคึผ ืคืื ืึธืคึผืขืจืึทืฆืืข ืคืื โโืึทืืึท ืกืืจืึทืกืข ืืืืื, ืืื ืืืขื ืฆืืฉืืขืื ืื ืงืึธื ืคึฟืึทืจ ืึท ืืื ืืึทืืืจืข ืืจืืืกืขืจ - (ืคึผืืจ). ืขืก ืืื ื ืืฉื ืืืืกื ืืื ืฆื ืืึธื ืขืคึผืขืก ืกืคึผืขืฆืืขื, ืึธืืขืจ ืื ืืืืคึผื ืืึทื ืืื ืื ืกืืกืืขื ืงืึทืืืก ืคืื ืื ืคึผืจืึธืืจืึทื - ืขืก ืึทืืืคึผืืฅ:
$ gcc examples/piglet-trace.c -o ptr
$ ptr echo test > /dev/null
BRK(12) -> 94744690540544
ACCESS(21) -> 18446744073709551614
ACCESS(21) -> 18446744073709551614
unknown(257) -> 3
FSTAT(5) -> 0
MMAP(9) -> 140694657216512
CLOSE(3) -> 0
ACCESS(21) -> 18446744073709551614
unknown(257) -> 3
READ(0) -> 832
FSTAT(5) -> 0
MMAP(9) -> 140694657208320
MMAP(9) -> 140694650953728
MPROTECT(10) -> 0
MMAP(9) -> 140694655045632
MMAP(9) -> 140694655070208
CLOSE(3) -> 0
unknown(158) -> 0
MPROTECT(10) -> 0
MPROTECT(10) -> 0
MPROTECT(10) -> 0
MUNMAP(11) -> 0
BRK(12) -> 94744690540544
BRK(12) -> 94744690675712
unknown(257) -> 3
FSTAT(5) -> 0
MMAP(9) -> 140694646390784
CLOSE(3) -> 0
FSTAT(5) -> 0
IOCTL(16) -> 18446744073709551591
WRITE(1) -> 5
CLOSE(3) -> 0
CLOSE(3) -> 0
unknown(231)
Tracee terminatedืคึผืืืืขื ืืจืึทืกืข ืื ืขืจืงืขื ื ืืืขืื ืืื ืืขืจืืขืจ ืคืื ืืื ืืงืก ืกืืกืืขื ืจืืคื (ืืขื. ) ืืื ืึทืจืืขื ืืืืื ืืืืฃ x86-64 ืึทืจืงืึทืืขืงืืฉืขืจ. ืืึธืก ืืื ืืขื ืื ืคึฟืึทืจ ืืืืืื ืืงืจืืื ืฆืืืขืงื.
ืืื ืก ืงืืง ืืื ืื ืึทืจืืขื ืคืื ืืื ืืืขืจ ืงืืึธืื. ืืื ืืขื ืคืึทื ืคืื ืืื ืืงืก, ืืืืึทืืขืจื ืืื ืืจืืืกืขืจื ื ืืฆื, ืืื ืืขืจืืื ื ืืืืื, ืื ืคึผืืจืึทืกืข ืกืืกืืขื ืจืืคื. ืขืก ืึทืจืืขื ืืืจื ืคืึธืจื ืืื ืืขืจ ืขืจืฉืืขืจ ืึทืจืืืืขื ื ืื ืืึทืคึฟืขื ืืืขื ืืืคืืขืจืก, ืคืื ืืืึธืก ืืืจ ื ืึธืจ ืืึทืจืคึฟื PTRACE_TRACEME, PTRACE_SYSCALL ะธ PTRACE_GETREGS.
ืื ืืจืืืกืขืจ ืกืืึทืจืฅ ืืื ืื ืืขืืืืื ืืืขื ืืื ืืงืก ื ืืกื: fork(2) ืืึธื ืืฉืื ืึท ืงืื ื ืคึผืจืึธืฆืขืก, ืืืึธืก ืืื ืงืขืจ ื ืืฆื exec(3) ืืึธื ืืฉืื ืื ืคึผืจืึธืืจืึทื ืืื ืืขืจ ืืขืจื ืขื. ืืขืจ ืืืืื ืกืึทืืึทืืื ืืึธ ืืื ืื ืึทืจืืืกืจืืคื ptrace(PTRACE_TRACEME) ืคืจืืขืจ exec: ืืขืจ ืงืื ื ืคึผืจืึธืฆืขืก ืืงืกืคึผืขืงืฅ ืื ืคืึธืืขืจ ืคึผืจืึธืฆืขืก ืฆื ืืึธื ืืืึธืจ ืขืก:
pid_t child_pid = fork();
switch (child_pid) {
case -1:
err(EXIT_FAILURE, "fork");
case 0:
/* Child here */
/* A traced mode has to be enabled. A parent will have to wait(2) for it
* to happen. */
ptrace(PTRACE_TRACEME, 0, NULL, NULL);
/* Replace itself with a program to be run. */
execvp(argv[1], argv + 1);
err(EXIT_FAILURE, "exec");
}ืืขืจ ืคืึธืืขืจ ืคึผืจืึธืฆืขืก ืืึธื ืืืฆื ืจืืคื wait(2) ืืื ืืขื ืงืื ื ืคึผืจืึธืฆืขืก, ืืึธืก ืืื, ืืึทืื ืืืืขืจ ืึทื ืกืืืืืฉืื ื ืฆื ืฉืคึผืืจ ืืึธืืข ืืื ืคืืจืืขืงืืืขื:
/* Parent */
/* First we wait for the child to set the traced mode (see
* ptrace(PTRACE_TRACEME) above) */
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "traceme -> waitpid");ืืื ืืขื ืคืื ื, ืื ืคึผืจืขืคึผืขืจืืืฉืึทื ื ืืขื ืขื ืืึทื ืฅ ืืื ืืืจ ืงืขื ืขื ืืืื ืืืืึทืืขืจ ืืืืึทื ืฆื ืืจืึทืงืื ื ืกืืกืืขื ืจืืคื ืืื ืึท ืกืึธืฃ ืฉืืืืฃ.
Call ptrace(PTRACE_SYSCALL) ืืขืจืึทื ืืื ืึทื ืกืึทืืกืึทืงืืืึทื ื wait ืืขืจ ืคืึธืืขืจ ืืืขื ืคืึทืจืขื ืืืงื ืึธืืขืจ ืืืืืขืจ ืื ืกืืกืืขื ืจืืคื ืืื ืขืงืกืึทืงืืืืึทื ืึธืืขืจ ืืืืื ื ืึธื ืขืก ืงืึทืืคึผืืืฅ. ืฆืืืืฉื ืฆืืืื ืงืึทืืืก ืืืจ ืงืขื ืขื ืืืจืืคืืจื ืงืืื ืึทืงืฉืึทื ื: ืคืึทืจืืืึทืื ืื ืจืืคื ืืื ืึทื ืึธืืืขืจื ืึทืืืื ืืืื ืขืจ, ืืืืฉื ืื ืึทืจืืืืขื ืื ืึธืืขืจ ืื ืฆืืจืืงืงืืืขื ืืืขืจื.
ืืืจ ื ืึธืจ ืืึทืจืคึฟื ืฆื ืจืืคื ืื ืืึทืคึฟืขื ืฆืืืื ืืึธื ptrace(PTRACE_GETREGS)ืฆื ืืึทืงืืืขื ืื ืจืขืืืกืืจืืจื ืฉืืึทื rax ืืืืืขืจ ืื ืจืืคื (ืกืืกืืขื ืจืืคื ื ืืืขืจ) ืืื ืืืืื ื ืึธื (ืฆืืจืืงืงืืืขื ืืืขืจื).
ืืื ืคืึทืงื, ืื ืฆืืงื:
/* A system call tracing loop, one interation per call. */
for (;;) {
/* A non-portable structure defined for ptrace/GDB/strace usage mostly.
* It allows to conveniently dump and access register state using
* ptrace. */
struct user_regs_struct registers;
/* Enter syscall: continue execution until the next system call
* beginning. Stop right before syscall.
*
* It's possible to change the system call number, system call
* arguments, return value or even avoid executing the system call
* completely. */
if (ptrace(PTRACE_SYSCALL, child_pid, NULL, NULL) == -1)
err(EXIT_FAILURE, "enter_syscall");
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "enter_syscall -> waitpid");
/* According to the x86-64 system call convention on Linux (see man 2
* syscall) the number identifying a syscall should be put into the rax
* general purpose register, with the rest of the arguments residing in
* other general purpose registers (rdi,rsi, rdx, r10, r8, r9). */
if (ptrace(PTRACE_GETREGS, child_pid, NULL, ®isters) == -1)
err(EXIT_FAILURE, "enter_syscall -> getregs");
/* Note how orig_rax is used here. That's because on x86-64 rax is used
* both for executing a syscall, and returning a value from it. To
* differentiate between the cases both rax and orig_rax are updated on
* syscall entry/exit, and only rax is updated on exit. */
print_syscall_enter(registers.orig_rax);
/* Exit syscall: execute of the syscall, and stop on system
* call exit.
*
* More system call tinkering possible: change the return value, record
* time it took to finish the system call, etc. */
if (ptrace(PTRACE_SYSCALL, child_pid, NULL, NULL) == -1)
err(EXIT_FAILURE, "exit_syscall");
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "exit_syscall -> waitpid");
/* Retrieve register state again as we want to inspect system call
* return value. */
if (ptrace(PTRACE_GETREGS, child_pid, NULL, ®isters) == -1) {
/* ESRCH is returned when a child terminates using a syscall and no
* return value is possible, e.g. as a result of exit(2). */
if (errno == ESRCH) {
fprintf(stderr, "nTracee terminatedn");
break;
}
err(EXIT_FAILURE, "exit_syscall -> getregs");
}
/* Done with this system call, let the next iteration handle the next
* one */
print_syscall_exit(registers.rax);
}ืืึธืก ืืื ืืขืจ ืืื ืฆืขืจ ืืจืืืกืขืจ. ืืืฆื ืืืจ ืืืืกื ืืื ืฆื ืึธื ืืืืื ืื ืืืืึทืืขืจ ืคึผืึธืจืืื ื ืืืืฃ ืืื ืืงืก.
ืืึทืกืืงืก: ืคืืืกื ืืืง ืึท ืคึผืจืึธืืจืึทื ืคืืืกื ืืืง ืกืืจืึทืกืข
ืืื ืึท ืขืจืฉืืขืจ ื ืืฆื ืคืึทื strace, ืืึธืืขืจ ืขืก ืืื ืืืขืจื ืฆืืืืจื ืื ืกืืืคึผืืึทืกื ืืืคึฟื - ืืึธื ืืฉืื ื ืึท ืึทืคึผืืึทืงืืืฉืึทื ืคืืืกื ืืืง strace.
ืืื ืกืืจ ื ืืฉื ืฆื ืืขืืื ืืื ืื ืกืึธืฃ ืจืฉืืื ืคืื ืงืึทืืืก ืคืื ืึท ืืืคึผืืฉ ืคึผืจืึธืืจืึทื, ืืืจ ืฉืจืืึทืื ืึทืจืื write:
int main(int argc, char *argv[])
{
char str[] = "write me to stdoutn";
/* write(2) is a simple wrapper around a syscall so it should be easy to
* find in the syscall trace. */
if (sizeof(str) != write(STDOUT_FILENO, str, sizeof(str))){
perror("write");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
ืืึธืืืจ ืืืืขื ืืขื ืคึผืจืึธืืจืึทื ืืื ืืึทืื ืืืืขืจ ืึทื ืขืก ืึทืจืืขื:
$ gcc examples/write-simple.c -o write-simple
$ ./write-simple
write me to stdoutืืื ืืขืกืึธืฃ, ืืึธืื ืืื ืื ืืืืคื ืขืก ืืื ืืขืจ ืกืืจืึทืกืข ืงืึธื ืืจืึธื:
$ strace ./write-simple
pexecve("./write", ["./write"], 0x7ffebd6145b0 /* 71 vars */) = 0
brk(NULL) = 0x55ff5489e000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=197410, ...}) = 0
mmap(NULL, 197410, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7a2a633000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "177ELF21133>1260342"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7a2a631000
mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f7a2a04c000
mprotect(0x7f7a2a233000, 2097152, PROT_NONE) = 0
mmap(0x7f7a2a433000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f7a2a433000
mmap(0x7f7a2a439000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f7a2a439000
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7f7a2a6324c0) = 0
mprotect(0x7f7a2a433000, 16384, PROT_READ) = 0
mprotect(0x55ff52b52000, 4096, PROT_READ) = 0
mprotect(0x7f7a2a664000, 4096, PROT_READ) = 0
munmap(0x7f7a2a633000, 197410) = 0
write(1, "write me to stdoutn", 20write me to stdout
) = 20
exit_group(0) = ?ืืืืขืจ "ืืืึธืจืื" ืืื ื ืืฉื ืืืืขืจ ืืืืืื ืืงืจืืื. ืขืก ืืขื ืขื ืฆืืืื ืคึผืจืึธืืืขืืก ืืึธ: ืื ืคึผืจืึธืืจืึทื ืจืขืืืืืึทื ืืื ืืขืืืฉื ืืื ืืขืจ ืจืขืืืืืึทื strace ืืื ืึท ืฉืขืคืข ืคืื โโืกืืกืืขื ืจืืคื ืืืึธืก ืืึธื ื ืื ืืื ืืขืจืขืกืืจื ืืื ืื.
ืืืจ ืงืขื ืขื ืฆืขืืืืื ืื ืคึผืจืึธืืจืึทื ืก ื ืึธืจืืึทื ืจืขืืืืืึทื ืืืึทื ืืื ืกืืจืึทืกืข ืืขืืช ืจืขืืืืืึทื ื ืืฆื ืื -o ืืึทืฉืืืืขื, ืืืึธืก ืจืืืขืจืขืงืฅ ืื ืจืฉืืื ืคืื ืกืืกืืขื ืจืืคื ืฆื ืึทื ืึทืจืืืืขื ื ืืขืงืข.
ืขืก ืืืืืื ืฆื ืืึทื ืืืขื ืืื ืื ืคึผืจืึธืืืขื ืคืื "ืขืงืกืืจืข" ืจืืคื. ืืื ืก ืืืขืจื ืขืืขื ืึทื ืืืจ ืืขื ืขื ืืืืื ืืื ืืขืจืขืกืืจื ืืื ืงืึทืืืก write. ืฉืืืกื -e ืึทืืึทืื ืืืจ ืฆื ืกืคึผืขืฆืืคืืฆืืจื ืืืืกืืจืืงื ืืืจื ืืืึธืก ืกืืกืืขื ืงืึทืืืก ืืืขื ืืืื ืคืืืืขืจื. ืื ืืขืจืกื ืคืึธืืงืก ืฆืืฉืืึทื ื ืึธืคึผืฆืืข ืืื, ืืขืืืืื ืืืขื, trace=*, ืืื ืืืึธืก ืืืจ ืงืขื ืขื ืืึธืื ืืืืื ืื ืงืึทืืืก ืืืึธืก ืืื ืืขืจืขืก ืืื ืื.
ืืืขื ืืขืืืืื ื ืกืืืืึทืืืืื ืืึทืกืื -o ะธ -e ืืืจ ืืืขืื ืืึทืงืืืขื:
$ strace -e trace=write -owrite-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
write(1, "write me to stdoutn", 20
) = 20
+++ exited with 0 +++ืึทืืื, ืืืจ ืืขื, ืขืก ืืื ืคืื ืืจืื ืืขืจ ืฆื ืืืืขื ืขื.
ืืืจ ืงืขื ื ืืืื ืืึทืืืึทืืืงื ืกืืกืืขื ืงืึทืืืก, ืืืฉื ืื ืืืึธืก ืืขื ืขื ืฉืืึทืืืช ืฆื ืืืงืึธืจื ืึทืืึทืงืืืฉืึทื ืืื ืคืจืื:
$ strace -e trace=!brk,mmap,mprotect,munmap -owrite-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
execve("./write-simple", ["./write-simple"], 0x7ffe9972a498 /* 69 vars */) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=124066, ...}) = 0
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "177ELF21133>1260342"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7f00f0be74c0) = 0
write(1, "write me to stdoutn", 20) = 20
exit_group(0) = ?
+++ exited with 0 +++ืืึทืืขืจืงืื ื ืื ืื ืืจืื ืขื ืขืงืกืงืืึทืืืืฉืึทื ืฆืืืื ืืื ืืขืจ ืจืฉืืื ืคืื ืืงืกืงืืืืื ืงืึทืืืก: ืืึธืก ืืื ืคืืจืืื ืื ืืืจื ืื ืืึทืคึฟืขื ืฉืึธื. ืฉืึธื).
ืืื ืืืื ืืืขืจืกืืข ืคืื โโโโglibc, ืึท ืกืืกืืขื ืจืืคื ืืขืจืืึทื ืืืฅ ืืขื ืคึผืจืึธืฆืขืก exit_group, ื ืื ืืขืงืึทืืึธืืขืืืง _exit. ืืึธืก ืืื ืื ืฉืืืขืจืืงืืื ืคืื ืืจืืขืื ืืื ืกืืกืืขื ืงืึทืืืก: ืื ืฆืืืื ื ืืื ืืืึธืก ืื ืคึผืจืึธืืจืึทืืืกื ืึทืจืืขื ืืื ื ืืฉื ืืืืึทื ืฉืืื ืฆื ืกืืกืืขื ืงืึทืืืก. ืืขืจืฆื, ืขืก ืขื ืืขืจืื ืืขื ืงืขืกืืืืขืจ ืืืคึผืขื ืืื ื ืืืืฃ ืื ืืืคึผืืึทืืขื ืืืืฉืึทื ืืื ืคึผืืึทืืคืึธืจืืข.
ืืึทืกืืงืก: ืคืึทืจืืื ืื ืืขื ืคึผืจืึธืฆืขืก ืืืืฃ ืื ืคืืืขื
ืืืืืขืก, ืื ืคึผืืจืึทืกืข ืกืืกืืขื ืจืืคื ืืืืฃ ืืืึธืก ืขืก ืืื ืืขืืืขื ืืขืืืื strace, ืงืขื ื ืึธืจ ืืืื ืืขืืืืื ื ืืืขื ืคืืืกื ืืืง ืื ืคึผืจืึธืืจืึทื ืืื ืึท ืกืคึผืขืฆืืขื ืืึธืืข. ืื ืืึทืืจืขื ืขืฆืื ื ืงืขื ืืึธืื ืืขืืืืื ืืืืึทื ืืื ืื ืืขื ืคืื ืืืขืจืกืืข 6 ืืื ืืงืก. ื ืึธืืืึทืืืึทืก, ืืึธืก ืืื ื ืื ืืขืจ ืืขื ืื: ืืื ืืืจ ืืึทืจืคึฟื ืฆื ืคืึธืจืฉื ืื ืคืจืืืืขืืขื ืคืื ืึท ืืจืืขืื ืคึผืจืึธืืจืึทื. ื ืืืคึผืืฉ ืืืึทืฉืคึผืื ืืื ืึท ืคึผืจืึธืฆืขืก ืืคืืขืฉืืขืื ืืืืฃ ืึท ืฉืขืคึผื ืึธืืขืจ ืกืืืคึผืื ื. ืืขืจืืืขืจ ืืึธืืขืจื strace ืงืขื ืขื ืคืึทืจืืื ืื ืคึผืจืึทืกืขืกืึทื ืืืืฃ ืื ืคืืืขื.
ืคืจืืืื ื ืืืึทืฉืคึผืื :
int main(int argc, char *argv[])
{
(void) argc; (void) argv;
char str[] = "write men";
write(STDOUT_FILENO, str, sizeof(str));
/* Sleep indefinitely or until a signal arrives */
pause();
write(STDOUT_FILENO, str, sizeof(str));
return EXIT_SUCCESS;
}ืืึธืืืจ ืืืืขื ืืขื ืคึผืจืึธืืจืึทื ืืื ืืึทืื ืืืืขืจ ืึทื ืขืก ืืื ืคืึทืจืคืจืืืจื:
$ gcc examples/write-sleep.c -o write-sleep
$ ./write-sleep
./write-sleep
write me
^C
$ืืืฆื ืืึธืื ืืื ืื ืคึผืจืืืืจื ืฆื ืคืึทืจืืื ืื ืขืก:
$ ./write-sleep &
[1] 15329
write me
$ strace -p 15329
strace: Process 15329 attached
pause(
^Cstrace: Process 15329 detached
<detached ...>ืคึผืจืึธืืจืึทื ืืคืืขืฉืืขืื ืืืจื ืจืืคื pause. ืืืืืจ ืืขื ืืื ืื ืจืขืืืืจื ืืืืฃ ืื ืกืืื ืืื:
$ strace -o write-sleep.log -p 15329 &
strace: Process 15329 attached
$
$ kill -CONT 15329
$ cat write-sleep.log
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
pause(
$
$ kill -TERM 15329
$ cat write-sleep.log
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
+++ killed by SIGTERM +++ืืืจ ืืึธื ืืฉื ืื ืคืึทืจืคืจืืืจื ืคึผืจืึธืืจืึทื ืืื ืืื ืืืื ืืขืฉืจืืื ืขืก ื ืืฆื strace. ืฆืืืื ืืื ืื ืืขืืืืจื ืงืืึธืจ: ืื ืคึผืืืืข ืกืืกืืขื ืจืืคื ืืื ืึธืจื ืกืืื ืึทืื ืึธื ืืึทื ืืืขืจืก ืืื, ืืขืจ ืื ืืขืจืขืกืืื ืืื, ืกืืจืึทืกืข ืืึธื ืืืึธืจืก ื ืื ืืืืื ืกืืกืืขื ืจืืคื, ืึธืืขืจ ืืืื ืื ืงืึทืืื ื ืกืืื ืึทืื.
ืืืึทืฉืคึผืื: ืืจืึทืงืื ื ืงืื ื ืคึผืจืึทืกืขืกืึทื
ืืจืืขืื ืืื ืคึผืจืึทืกืขืกืึทื ืืืจื ืึท ืจืืคื fork - ืื ืืงืขืจ ืคืื ืึทืืข ืืื ืืงืก. ืืึธืืืจ ืืขื ืืื ืกืืจืึทืกืข ืึทืจืืขื ืืื ืึท ืคึผืจืึธืฆืขืก ืืืื ื ืืฆื ืื ืืืืฉืคึผืื ืคืื ืึท ืคึผืฉืื "ืืจืืืื ื" :
int main(int argc, char *argv[])
{
pid_t parent_pid = getpid();
pid_t child_pid = fork();
if (child_pid == 0) {
/* A child is born! */
child_pid = getpid();
/* In the end of the day printf is just a call to write(2). */
printf("child (self=%d)n", child_pid);
exit(EXIT_SUCCESS);
}
printf("parent (self=%d, child=%d)n", parent_pid, child_pid);
wait(NULL);
exit(EXIT_SUCCESS);
}ืืึธ ืืขืจ ืึธืจืืืื ืขื ืคึผืจืึธืฆืขืก ืงืจืืืืฅ ืึท ืงืื ื ืคึผืจืึธืฆืขืก, ืืืืืข ืฉืจืืืื ืฆื ื ืึธืจืืึทื ืจืขืืืืืึทื:
$ gcc examples/fork-write.c -o fork-write
$ ./fork-write
parent (self=11274, child=11275)
child (self=11275)ืืืจื ืคืขืืืงืืึทื, ืืืจ ืืืขืื ืืืืื ืืขื ืกืืกืืขื ืจืืคื ืคืื ืื ืคืึธืืขืจ ืคึผืจืึธืฆืขืก:
$ strace -e trace=write -ofork-write.log ./fork-write
child (self=22049)
parent (self=22048, child=22049)
$ cat fork-write.log
write(1, "parent (self=22048, child=22049)"..., 33) = 33
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22049, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
+++ exited with 0 +++ืื ืคืึธื ืืขืืคึผืก ืืืจ ืฉืคึผืืจ ืื ืืื ืฆืข ืคึผืจืึธืฆืขืก ืืืื -f, ืืืึธืก strace ืืึธื ืืืึธืจืก ืกืืกืืขื ืจืืคื ืืื ืงืื ื ืคึผืจืึทืกืขืกืึทื. ืืขื ืืืกืืฃ ืฆื ืืขืืขืจ ืฉืืจื ืคืื ืคึผืจืึธืืืงืฆืืข pid ืคึผืจืึธืฆืขืก ืืืึธืก ืืืื ืึท ืกืืกืืขื ืจืขืืืืืึทื:
$ strace -f -e trace=write -ofork-write.log ./fork-write
parent (self=22710, child=22711)
child (self=22711)
$ cat fork-write.log
22710 write(1, "parent (self=22710, child=22711)"..., 33) = 33
22711 write(1, "child (self=22711)n", 19) = 19
22711 +++ exited with 0 +++
22710 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22711, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
22710 +++ exited with 0 +++ืืื ืืขื ืงืึธื ืืขืงืกื, ืคืืืืขืจืื ื ืืืจื ืืจืืคึผืข ืคืื โโืกืืกืืขื ืงืึทืืืก ืงืขื ืขื ืืืื ื ืืฆืืง:
$ strace -f -e trace=%process -ofork-write.log ./fork-write
parent (self=23610, child=23611)
child (self=23611)
$ cat fork-write.log
23610 execve("./fork-write", ["./fork-write"], 0x7fff696ff720 /* 63 vars */) = 0
23610 arch_prctl(ARCH_SET_FS, 0x7f3d03ba44c0) = 0
23610 clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f3d03ba4790) = 23611
23610 wait4(-1, <unfinished ...>
23611 exit_group(0) = ?
23611 +++ exited with 0 +++
23610 <... wait4 resumed> NULL, 0, NULL) = 23611
23610 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=23611, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
23610 exit_group(0) = ?
23610 +++ exited with 0 +++ืืืจื ืืขื ืืืขื, ืืืึธืก ืกืืกืืขื ืจืืคื ืืื ืืขื ืืฆื ืฆื ืฉืึทืคึฟื ืึท ื ืืึทืข ืคึผืจืึธืฆืขืก?
ืืืึทืฉืคึผืื: ืืขืงืข ืคึผืึทืืก ืึทื ืฉืืึธื ืคืื ืืึทื ืืึทืื
ืืืืกื ืคืื ืืขืงืข ืืืกืงืจืืคึผืืึธืจืก ืืื ืืืืขืจ ื ืืฆืืง, ืึธืืขืจ ืื ื ืขืืขื ืคืื ืื ืกืคึผืขืฆืืคืืฉ ืืขืงืขืก ืืืึธืก ืึท ืคึผืจืึธืืจืึทื ืึทืงืกืขืก ืงืขื ืขื ืืืื ืืืื ื ืืฆืืง.
ืื ืืืืึทืืขืจ ืฉืจืืืื ืื ืฉืืจื ืฆื ืึท ืฆืืึทืืืืืึทืืืง ืืขืงืข:
void do_write(int out_fd)
{
char str[] = "write me to a filen";
if (sizeof(str) != write(out_fd, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
char tmp_filename_template[] = "/tmp/output_fileXXXXXX";
int out_fd = mkstemp(tmp_filename_template);
if (out_fd == -1) {
perror("mkstemp");
exit(EXIT_FAILURE);
}
do_write(out_fd);
return EXIT_SUCCESS;
}ืืขืฉืึทืก ืึท ื ืึธืจืืึทื ืจืืคื strace ืืืขื ืืืืึทืื ืื ืืืขืจื ืคืื ืื ืืืกืงืจืืคึผืืึธืจ ื ืืืขืจ ืืืจืืืขืืื ืืขื ืฆื ืื ืกืืกืืขื ืจืืคื:
$ strace -e trace=write -o write-tmp-file.log ./write-tmp-file
$ cat write-tmp-file.log
write(3, "write me to a filen", 20) = 20
+++ exited with 0 +++ืืื ืึท ืคืึธื -y ืื ื ืืฆื ืืืืืื ืื ืืจื ืฆื ืืขืจ ืืขืงืข ืืืึธืก ืื ืืืกืงืจืืคึผืืึธืจ ืงืึธืจืึทืกืคึผืึทื ืื:
$ strace -y -e trace=write -o write-tmp-file.log ./write-tmp-file
$ cat write-tmp-file.log
write(3</tmp/output_fileCf5MyW>, "write me to a filen", 20) = 20
+++ exited with 0 +++ืืืึทืฉืคึผืื: ืืขืงืข ืึทืงืกืขืก ืืจืึทืงืื ื
ืื ืื ืืขืจ ื ืืฆืืง ืฉืืจืื: ืืืืึทืื ืืืืื ืกืืกืืขื ืงืึทืืืก ืคึฟืึทืจืืื ืื ืืื ืึท ืกืคึผืขืฆืืคืืฉ ืืขืงืข. ืืืืึทืืขืจ ืึทืคึผืคึผืขื ืื ืึท ืฉืืจื ืฆื ืึท ืึทืจืืืืจืึทืจืืฉ ืืขืงืข ืืืจืืืขืืื ืืขื ืืื ืึทื ืึทืจืืืืขื ื:
void do_write(int out_fd)
{
char str[] = "write me to a filen";
if (sizeof(str) != write(out_fd, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
/*
* Path will be provided by the first program argument.
* */
const char *path = argv[1];
/*
* Open an existing file for writing in append mode.
* */
int out_fd = open(path, O_APPEND | O_WRONLY);
if (out_fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
do_write(out_fd);
return EXIT_SUCCESS;
}
ืืืจื ืคืขืืืงืืึทื strace ืืืกืคึผืืืื ืึท ืคึผืืึทืฅ ืคืื ืืื ืืืืืง ืืื ืคึฟืึธืจืืึทืฆืืข. ืคืึธื -P ืืื ืึทื ืึทืจืืืืขื ื ื ืกืืจืึทืกืข ืฆื ืืจืืงื ืืืืื ืจืืคื ืฆื ืื ืกืคึผืขืกืึทืคืืื ืืขืงืข:
$ strace -y -P/tmp/test_file.log -o write-file.log ./write-file /tmp/test_file.log
$ cat write-file.log
openat(AT_FDCWD, "/tmp/test_file.log", O_WRONLY|O_APPEND) = 3</tmp/test_file.log>
write(3</tmp/test_file.log>, "write me to a filen", 20) = 20
+++ exited with 0 +++ืืืึทืฉืคึผืื: Multithreaded ืืืืื
ื ืืฆื strace ืงืขื ืขื ืืืื ืืขืืคื ืืืขื ืืจืืขืื ืืื ืืึทืืื-ืืจืขืืื . ืื ืคืืืืขื ืืข ืคึผืจืึธืืจืึทื ืฉืจืืืื ืฆื ื ืึธืจืืึทื ืจืขืืืืืึทื ืคืื ืฆืืืื ืกืืจืืื:
void *thread(void *arg)
{
(void) arg;
printf("Secondary thread: workingn");
sleep(1);
printf("Secondary thread: donen");
return NULL;
}
int main(int argc, char *argv[])
{
printf("Initial thread: launching a threadn");
pthread_t thr;
if (0 != pthread_create(&thr, NULL, thread, NULL)) {
fprintf(stderr, "Initial thread: failed to create a thread");
exit(EXIT_FAILURE);
}
printf("Initial thread: joining a threadn");
if (0 != pthread_join(thr, NULL)) {
fprintf(stderr, "Initial thread: failed to join a thread");
exit(EXIT_FAILURE);
};
printf("Initial thread: done");
exit(EXIT_SUCCESS);
}ืืขืืืืื ืืืขื, ืขืก ืืืื ืืืื ืงืึทืืคึผืืืื ืืื ืึท ืกืคึผืขืฆืืขื ืืจืืก ืฆื ืื ืืื ืงืขืจ - ืื -pthread ืคืึธื:
$ gcc examples/thread-write.c -pthread -o thread-write
$ ./thread-write
/thread-write
Initial thread: launching a thread
Initial thread: joining a thread
Secondary thread: working
Secondary thread: done
Initial thread: done
$Flag -f, ืืื ืืื ืื ืคืึทื ืคืื ืจืขืืืืขืจ ืคึผืจืึทืกืขืกืึทื, ืืืขื ืืืืื ืื ืคึผืื ืคืื ืืขื ืคึผืจืึธืฆืขืก ืฆื ืื ืึธื ืืืื ืคืื ืืขืืขืจ ืฉืืจื.
ืืขืืืืื ืืืขื, ืืืจ ืืขื ืขื ื ืืฉื ืืขืจืขืื ืืืขืื ืึท ืคืึธืืขื ืืืขื ืืืคืืขืจ ืืื ืืขื ืืื ืขื ืคืื ืื ืืืคึผืืึทืืขื ืืืืฉืึทื ืคืื ืื POSIX ืคึฟืขืืขื ื ืึธืจืืึทื, ืึธืืขืจ ืืืขืื ืื ื ืืืขืจ ืืขื ืืฆื ืืืจื ืื ืึทืจืืขื ืกืงืขืืืฉืืืขืจ ืืื ืืื ืืงืก. ืคึฟืื ืื ืืขืฆืืข ืคืื ื ืคืื ืืืื ืื ื, ืขืก ืืขื ืขื ืงืืื ืคึผืจืึทืกืขืกืึทื ืึธืืขืจ ืคึฟืขืืขื - ืขืก ืืขื ืขื ืืึทืกืงืก ืืืึธืก ืืึทืจืคึฟื ืฆื ืืืื ืคืื ืื ืืขืจืืขืืืืื ืฆืืืืฉื ืื ืื ืืืฆื ืงืึธืจืขืก ืคืื ืื ืืึทืฉืื.
ืืืขื ืืจืืขืื ืืื ืงืืืคื ืคึฟืขืืขื, ืกืืกืืขื ืจืืคื ืืืขืจื ืฆื ืคืืืข:
$ strace -f -othread-write.log ./thread-write
$ wc -l thread-write.log
60 thread-write.logืขืก ืืืื ืืื ืขื ืฆื ืืึทืืจืขื ืขืฆื ืืื ืืืืื ืฆื ืคึผืจืึธืฆืขืก ืคืึทืจืืืึทืืืื ื ืืื ืกืืกืืขื ืจืืคื write:
$ strace -f -e trace="%process,write" -othread-write.log ./thread-write
$ cat thread-write.log
18211 execve("./thread-write", ["./thread-write"], 0x7ffc6b8d58f0 /* 64 vars */) = 0
18211 arch_prctl(ARCH_SET_FS, 0x7f38ea3b7740) = 0
18211 write(1, "Initial thread: launching a thre"..., 35) = 35
18211 clone(child_stack=0x7f38e9ba2fb0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f38e9ba39d0, tls=0x7f38e9ba3700, child_tidptr=0x7f38e9ba39d0) = 18212
18211 write(1, "Initial thread: joining a thread"..., 33) = 33
18212 write(1, "Secondary thread: workingn", 26) = 26
18212 write(1, "Secondary thread: donen", 23) = 23
18212 exit(0) = ?
18212 +++ exited with 0 +++
18211 write(1, "Initial thread: done", 20) = 20
18211 exit_group(0) = ?
18211 +++ exited with 0 +++ืืื, ืฉืืืืช. ืืืึธืก ืกืืกืืขื ืจืืคื ืืื ืืขื ืืฆื ืฆื ืฉืึทืคึฟื ืึท ื ืืึท ืคืึธืืขื? ืืื ืืื ืื ืจืืคื ืคึฟืึทืจ ืคึฟืขืืขื ืึทื ืืขืจืฉ ืคืื ืื ืจืืคื ืคึฟืึทืจ ืคึผืจืึทืกืขืกืึทื?
ืืขื ืงืืึทืก: ืคึผืจืึธืฆืขืก ืึธื ืืืืื ืืื ืืขืจ ืฆืืื ืคืื ืึท ืกืืกืืขื ืจืืคื
ืืืื ืขืจ ืคืื ืื ืืขืฆืื ืก ืืจืืืก strace ืงืืืคึผืึทืืืืึทืืื - ืืืืึทืื ืืืง ืื ืึธื ืืืืื ืคืื ืคืื ืงืฆืืข ืจืืคื ืืื ืืขืจ ืฆืืื ืคืื ืื ืกืืกืืขื ืจืืคื. ืคึผืฉืื :
void do_write(void)
{
char str[] = "write me to stdoutn";
if (sizeof(str) != write(STDOUT_FILENO, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
do_write();
return EXIT_SUCCESS;
}ืืขืืืืื ืืืขื, ืื ืคึผืจืึธืืจืึทื ืจืขืืืืืึทื ืืืขืจื ืืืืขืจ ืืืึทืืืืึทื ืึทืก, ืืื, ืืื ืืขืจืฆื ืฆื ืื ืคืึธื -k (ืจืืคื ืกืืึทืง ืึทืจืืืกืืืืึทืื), ืขืก ืืืื ืืื ืขื ืฆื ืคืืืืขืจ ืกืืกืืขื ืจืืคื ืืืจื ื ืึธืืขื:
$ gcc examples/write-simple.c -o write-simple
$ strace -k -e trace=write -o write-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
write(1, "write me to stdoutn", 20) = 20
> /lib/x86_64-linux-gnu/libc-2.27.so(__write+0x14) [0x110154]
> /home/vkazanov/projects-my/strace-post/write-simple(do_write+0x50) [0x78a]
> /home/vkazanov/projects-my/strace-post/write-simple(main+0x14) [0x7d1]
> /lib/x86_64-linux-gnu/libc-2.27.so(__libc_start_main+0xe7) [0x21b97]
> /home/vkazanov/projects-my/strace-post/write-simple(_start+0x2a) [0x65a]
+++ exited with 0 +++ืืขื ืงืืึทืก: ืืขืืช ืื ืืืฉืขืงืฉืึทื
ืืื ื ืึธื ืึท ื ืืึทืข ืืื ืืืืขืจ ื ืืฆืืง ืฉืืจืื: ืืขืืช ืื ืืืฉืขืงืฉืึทื. ืืึธ , ืฉืจืืืื ืฆืืืื ืฉืืจืืช ืฆื ืื ืจืขืืืืืึทื ืืืึทื:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
void do_write(const char *str, ssize_t len)
{
if (len != write(STDOUT_FILENO, str, (size_t)len)){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
(void) argc; (void) argv;
char str1[] = "write me 1n";
do_write(str1, sizeof(str1));
char str2[] = "write me 2n";
do_write(str2, sizeof(str2));
return EXIT_SUCCESS;
}ืืื ืก ืฉืคึผืืจ ืืืืืข ืฉืจืืึทืื ืจืืคื:
$ gcc examples/write-twice.c -o write-twice
$ ./write-twice
write me 1
write me 2
$ strace -e trace=write -owrite-twice.log ./write-twice
write me 1
write me 2
$ cat write-twice.log
write(1, "write me 1n", 12) = 12
write(1, "write me 2n", 12) = 12
+++ exited with 0 +++ืืืฆื ืืืจ ื ืืฆื ืืขื ืืืืกืืจืืง injectืฆื ืึทืจืืึทื ืืืืื ืึท ืืขืืช EBADF ืืื ืึทืืข ืฉืจืืึทืื ืงืึทืืืก:
$ strace -e trace=write -e inject=write:error=EBADF -owrite-twice.log ./write-twice
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = -1 EBADF (Bad file descriptor) (INJECTED)
+++ exited with 1 +++ืขืก ืืื ืืฉืืงืึทืืืข ืืืึธืก ืขืจืจืึธืจืก ืืขื ืขื ืืืืืขืงืขืจื ืึทืืข ืืฉืึทืืึทื ืืืฉืื write, ืึทืจืืึทื ืืขืจืขืื ื ืื ืจืืคื ืคืึทืจืืึธืจืื ืืื ืืขืจ ืคึผืขืจืึธืจ. ืขืก ื ืึธืจ ืืืื ืืื ืขื ืฆื ืฆืืจืืงืงืืืขื ืึท ืืขืืช ืคึฟืึทืจ ืืขืจ ืขืจืฉืืขืจ ืคืื ืื ืงืึทืืืก:
$ strace -e trace=write -e inject=write:error=EBADF:when=1 -owrite-twice.log ./write-twice
write: Bad file descriptor
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = 27
+++ exited with 1 +++ืืืขืจ ืื ืฆืืืืืืข:
$ strace -e trace=write -e inject=write:error=EBADF:when=2 -owrite-twice.log ./write-twice
write me 1
write: Bad file descriptor
$ cat write-twice.log
write(1, "write me 1n", 12) = 12
write(1, "write me 2n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = 27
+++ exited with 1 +++ืขืก ืืื ื ืื ื ืืืืืง ืฆื ืกืคึผืขืฆืืคืืฆืืจื ืืขื ืืืคึผ ืคืื ืืขืืช:
$ strace -e trace=write -e fault=write:when=1 -owrite-twice.log ./write-twice
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 ENOSYS (Function not implemented) (INJECTED)
write(3, "write: Function not implementedn", 32) = 32
+++ exited with 1 +++ืืื ืงืึธืืืื ืึทืฆืืข ืืื ืื ืืขืจืข ืคืืึทืืก, ืืืจ ืงืขื ืขื "ืืจืขืื" ืึทืงืกืขืก ืฆื ืึท ืกืคึผืขืฆืืคืืฉ ืืขืงืข. ืืืึทืฉืคึผืื:
$ strace -y -P/tmp/test_file.log -e inject=file:error=ENOENT -o write-file.log ./write-file /tmp/test_file.log
open: No such file or directory
$ cat write-file.log
openat(AT_FDCWD, "/tmp/test_file.log", O_WRONLY|O_APPEND) = -1 ENOENT (No such file or directory) (INJECTED)
+++ exited with 1 +++ืึทืืืฅ ืืขืืช ืื ืืืฉืขืงืฉืึทื, ืืึทืงืขื ืขื ืืืืืื ืืืขื ืืืจ ืจืืคื ืึธืืขืจ ืืึทืงืืืขื ืกืืื ืึทืื.
ืึทืคืืขืจืืืึธืจื
ื ืืฆื strace - ืึท ืคึผืฉืื ืืื ืคืึทืจืืึธืืืขื ืืขืฆืืึทื. ืึธืืขืจ ืืื ืึทืืืฉืึทื ืฆื ืกืืกืืขื ืจืืคื, ืื ืืขืจืข ืึทืกืคึผืขืงืฅ ืคืื ืื ืึธืคึผืขืจืึทืฆืืข ืคืื โโืืืืื ืืื ืื ืึธืคึผืขืจืืืืื ื ืกืืกืืขื ืงืขื ืขื ืืืื ืืืืึทืื. ืคึฟืึทืจ ืืืึทืฉืคึผืื, ืขืก ืงืขื ืขื ืฉืคึผืืจ ืงืึทืืืก ืฆื ืืื ืึทืืืงืึทืืื ืืื ืืงื ืืืืืจืขืจืื. , ืืื ืงืขื ืขื ืงืืงื ืืื ืื ืึธืคึผืขืจืึทืฆืืข ืคืื โโืื ืึธืคึผืขืจืืืืื ื ืกืืกืืขื ะธ , ืืื ืึทืืึทืื ืืืจ ืฆื ืืืคึผืื ืคืึธืจืฉื ืคึผืจืึธืืจืึทื ืคืึธืจืฉืืขืืื ื . ืืื, ืขืก ืืื strace - ืืขืจ ืขืจืฉืืขืจ ืฉืืจื ืคืื ืคืึทืจืืืืืืงืื ื ืืื ืคืึทื ืคืื ืคึผืจืึธืืืขืืก ืืื ืืืื ืืืืื ืืื ืื ืืขืจืข ืืขื ืืฉื ืก ืืืืื, ืืื ืืื ื ืืฆื ืขืก ืืืึท ืืื ืืกืืขืจ ืึท ืคึผืึธืจ ืคืื ืืื ืึท ืืืึธื.
ืืื ืงืืจืฅ, ืืืื ืืืจ ืืืืข ืืื ืืงืก, ืืืืขื ืขื man 1 strace ืืื ืคืืื ืคืจืื ืฆื ืงืืง ืืื ืืืื ืืืืื!
ืืงืืจ: www.habr.com