C语言 perf_event_open的权限被拒绝，是否有其他方法比使用sudo或改变perf_event_parano

Question

我能找到的关于这个主题的唯一信息是这个链接:perf_event_open总是返回-1，它建议从我所理解的配置CONFIG_HW_PERF_EVENTS，但我仍然得到同样的问题。

我正在实现一个程序，灵感来自perf_event_open的手册页:

static long
perf_event_open(struct perf_event_attr *hw_event, pid_t pid,
int cpu, int group_fd, unsigned long flags)
{
int ret;
ret= syscall(__NR_perf_event_open, hw_event, pid, cpu,
group_fd, flags);
return ret;
}
struct perf_event_attr pe;
int pid = fork();
if (pid > 0 ) {
memset(&pe, 0, sizeof(pe));
pe.type = PERF_TYPE_HARDWARE;
pe.size = sizeof(pe);
pe.config = PERF_COUNT_HW_CPU_CYCLES;
pe.disabled = 0;
pe.exclude_kernel = 0;
pe.exclude_hv = 0;   

fd = perf_event_open(&pe, pid, -1, -1, 0);
if (fd == -1) {
perror(0);
exit(EXIT_FAILURE);
}
}

对于fd，我总是得到一个-1的返回值，而perror表示权限被拒绝。

当然我可以使用sudo来解决这个问题，但是有没有另一种方法来允许执行perf_event_open?

PS:我不想改变perf_event_paranoid文件，它使程序在设置为-1时工作;我想应该是2点。

Answer 1

返回值Linuxperf_event_open()系统调用状态的部分:

...
EACCES Returned when the requested event requires CAP_PERFMON
(since Linux 5.8) or CAP_SYS_ADMIN permissions (or a more
permissive perf_event paranoid setting).  Some common
cases where an unprivileged process may encounter this
error: attaching to a process owned by a different user;
monitoring all processes on a given CPU (i.e., specifying
the pid argument as -1); and not setting exclude_kernel
when the paranoid setting requires it.
...
EPERM  Returned on many (but not all) architectures when an
unsupported exclude_hv, exclude_idle, exclude_user, or
exclude_kernel setting is specified.
It can also happen, as with EACCES, when the requested
event requires CAP_PERFMON (since Linux 5.8) or
CAP_SYS_ADMIN permissions (or a more permissive perf_event
paranoid setting).  This includes setting a breakpoint on
a kernel address, and (since Linux 3.13) setting a kernel
function-trace tracepoint.

从发布的示例代码中，值pe.exclude_kernel = 0;或pe.exclude_hv = 0;可能会导致关于偏执设置的声明的权限问题。