proc-self-syscall failed on arm32

am57xx-evm:/home/linaro# cat proc-self-syscall.c
/*
 * Copyright © 2018 Alexey Dobriyan <[email protected]>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

static inline ssize_t sys_read(int fd, void *buf, size_t len)
{
        return syscall(SYS_read, fd, buf, len);
}

int main(void)
{
        char buf1[64];
        char buf2[64];
        int fd;
        int ret;
        ssize_t rv;

        fd = open("/proc/self/syscall", O_RDONLY);
        if (fd == -1) {
                if (errno == ENOENT)
                        return 2;
                return 1;
        }

        /* Do direct system call as libc can wrap anything. */
        snprintf(buf1, sizeof(buf1), "%ld 0x%lx 0x%lx 0x%lx",
                 (long)SYS_read, (long)fd, (long)buf2, (long)sizeof(buf2));

        memset(buf2, 0, sizeof(buf2));
        rv = sys_read(fd, buf2, sizeof(buf2));
        printf("sys_read rv = %d \n", rv);
        if (rv < 0) {
                printf(" %d  < 0 \n", rv);
                return 1;
        }
        if (rv < strlen(buf1)) {
                printf("strlen = %d \n", strlen(buf1));
                return 1;
        }
        ret = strncmp(buf1, buf2, strlen(buf1));
        printf("ret = %d \n", ret);
        if (ret != 0) {
                printf("buf1 = %s \n", buf1);
                printf("buf2 = %s \n", buf2);
                printf("strlen(buf1) = %d \n", strlen(buf1));
                return 1;
        }
        printf("clean exit\n");
        return 0;
}
am57xx-evm:/home/linaro#
am57xx-evm:/home/linaro# gcc  proc-self-syscall.c -o proc-self-syscall
am57xx-evm:/home/linaro# ./proc-self-syscall
sys_read rv = 64
ret = 3
buf1 = 3 0x3 0xbe947bcc 0x40
buf2 = 0 0x3 0xbe947bcc 0x40 0xbe947bcc 0x40 0xbe947bcc 0xbe947b90 0xb63 0x3 0xbe947bcc 0x40
strlen(buf1) = 21
am57xx-evm:/home/linaro# echo $?
1
am57xx-evm:/home/linaro#