// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2014 Sony Mobile Communications Inc.
 *
 * Selftest for runtime system size
 *
 * Prints the amount of RAM that the currently running system is using.
 *
 * This program tries to be as small as possible itself, to
 * avoid perturbing the system memory utilization with its
 * own execution.  It also attempts to have as few dependencies
 * on kernel features as possible.
 *
 * It should be statically linked, with startup libs avoided.  It uses
 * no library calls except the syscall() function for the following 3
 * syscalls:
 *   sysinfo(), write(), and _exit()
 *
 * For output, it avoids printf (which in some C libraries
 * has large external dependencies) by  implementing it's own
 * number output and print routines, and using __builtin_strlen()
 *
 * The test may crash if any of the above syscalls fails because in some
 * libc implementations (e.g. the GNU C Library) errno is saved in
 * thread-local storage, which does not get initialized due to avoiding
 * startup libs.
 */

#include <sys/sysinfo.h>
#include <unistd.h>
#include <sys/syscall.h>

#define STDOUT_FILENO 1

static int print(const char *s)
{
        size_t len = 0;

        while (s[len] != '\0')
                len++;

        return syscall(SYS_write, STDOUT_FILENO, s, len);
}

static inline char *num_to_str(unsigned long num, char *buf, int len)
{
        unsigned int digit;

        /* put digits in buffer from back to front */
        buf += len - 1;
        *buf = 0;
        do {
                digit = num % 10;
                *(--buf) = digit + '0';
                num /= 10;
        } while (num > 0);

        return buf;
}

static int print_num(unsigned long num)
{
        char num_buf[30];

        return print(num_to_str(num, num_buf, sizeof(num_buf)));
}

static int print_k_value(const char *s, unsigned long num, unsigned long units)
{
        unsigned long long temp;
        int ccode;

        print(s);

        temp = num;
        temp = (temp * units)/1024;
        num = temp;
        ccode = print_num(num);
        print("\n");
        return ccode;
}

/* this program has no main(), as startup libraries are not used */
void _start(void)
{
        int ccode;
        struct sysinfo info;
        unsigned long used;
        static const char *test_name = " get runtime memory use\n";

        print("TAP version 13\n");
        print("# Testing system size.\n");

        ccode = syscall(SYS_sysinfo, &info);
        if (ccode < 0) {
                print("not ok 1");
                print(test_name);
                print(" ---\n reason: \"could not get sysinfo\"\n ...\n");
                syscall(SYS_exit, ccode);
        }
        print("ok 1");
        print(test_name);

        /* ignore cache complexities for now */
        used = info.totalram - info.freeram - info.bufferram;
        print("# System runtime memory report (units in Kilobytes):\n");
        print(" ---\n");
        print_k_value(" Total:  ", info.totalram, info.mem_unit);
        print_k_value(" Free:   ", info.freeram, info.mem_unit);
        print_k_value(" Buffer: ", info.bufferram, info.mem_unit);
        print_k_value(" In use: ", used, info.mem_unit);
        print(" ...\n");
        print("1..1\n");

        syscall(SYS_exit, 0);
}