Hi
I write demo use ptrace/SINGLESTEP to count the number of instructions
executed by the process
The parent process fork+exec a child process, and trace(SINGLESTEP) it,
It works fine under the x86_64 architecture but has an exception under
arm64.
```cpp
//demo.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#ifdef DEBUG
#define dprintf printf
#else
#define dprintf 0 && printf
#endif
int main(int argc, char *argv[])
{
long long counter = 0;
int wait_val;
int pid;
puts("Please wait");
switch (pid = fork()) {
case -1:
perror("fork");
break;
case 0:
ptrace(PTRACE_TRACEME, 0, 0, 0);
execl("/bin/ls", "ls", NULL);
break;
default:
//ptrace(PTRACE_ATTACH, pid, NULL, NULL);
//waitpid(pid, &wait_val, 0);
//while (wait_val == 1407 ) {
while ( 1 )
{
wait(&wait_val);
if(WIFEXITED(&wait_val)) {
break;
}
counter++;
if (ptrace(PTRACE_SINGLESTEP, pid, 0, 0) != 0)
perror("ptrace");
else
dprintf("counter = %lld\n", counter);
}
}
printf("Number of machine instructions : %lld\n", counter);
return 0;
}
```
It run for a long long time and seems never to stop.
./demo /bin/ls
counter = 8033129
counter = 8033130
counter = 8033131
counter = 8033132
counter = 8033133
counter = 8033134
counter = 8033135
counter = 8033136
counter = 8033137
counter = 8033138
counter = 8033139
^C
It return the same results when track other the other C processes
And then I make an assembly demo(just print Hello-World),
It looks just all right
```asm
//hello.s
// as hello.s –o hello.o
// ld hello.o –o hello
.text //code section
.globl _start
_start:
mov x0, 0 // stdout has file descriptor 0
ldr x1, =msg // buffer to write
mov x2, len // size of buffer
mov x8, 64 // sys_write() is at index 64 in kernel functions table
svc #0 // generate kernel call sys_write(stdout, msg, len);
mov x0, 123 // exit code
mov x8, 93 // sys_exit() is at index 93 in kernel functions table
svc #0 // generate kernel call sys_exit(123);
.data //data section
msg:
.ascii "Hello, ARM!\n"
len = . - msg
```
./demo ./hello
./hello : hello
Please wait
Hello, ARM!
Number of machine instructions : 8
I want to know what's going on about it, Is this a bug?
