// SPDX-License-Identifier: GPL-2.0
/*
 * Capability utilities
 */

#include "cap.h"
#include "debug.h"
#include <errno.h>
#include <string.h>
#include <sys/syscall.h>
#include <unistd.h>

#define MAX_LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_3

bool perf_cap__capable(int cap, bool *used_root)
{
        struct __user_cap_header_struct header = {
                .version = _LINUX_CAPABILITY_VERSION_3,
                .pid = 0,
        };
        struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S] = {};
        __u32 cap_val;

        *used_root = false;
        while (syscall(SYS_capget, &header, &data[0]) == -1) {
                /* Retry, first attempt has set the header.version correctly. */
                if (errno == EINVAL && header.version != _LINUX_CAPABILITY_VERSION_3 &&
                    header.version == _LINUX_CAPABILITY_VERSION_1)
                        continue;

                pr_debug2("capget syscall failed (%m) fall back on root check\n");
                *used_root = true;
                return geteuid() == 0;
        }

        /* Extract the relevant capability bit. */
        if (cap >= 32) {
                if (header.version == _LINUX_CAPABILITY_VERSION_3) {
                        cap_val = data[1].effective;
                } else {
                        /* Capability beyond 32 is requested but only 32 are supported. */
                        return false;
                }
        } else {
                cap_val = data[0].effective;
        }
        return (cap_val & (1 << (cap & 0x1f))) != 0;
}