get_size.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright 2014 Sony Mobile Communications Inc.
  4 *
  5 * Selftest for runtime system size
  6 *
  7 * Prints the amount of RAM that the currently running system is using.
  8 *
  9 * This program tries to be as small as possible itself, to
 10 * avoid perturbing the system memory utilization with its
 11 * own execution.  It also attempts to have as few dependencies
 12 * on kernel features as possible.
 13 *
 14 * It should be statically linked, with startup libs avoided.  It uses
 15 * no library calls except the syscall() function for the following 3
 16 * syscalls:
 17 *   sysinfo(), write(), and _exit()
 18 *
 19 * For output, it avoids printf (which in some C libraries
 20 * has large external dependencies) by  implementing it's own
 21 * number output and print routines, and using __builtin_strlen()
 22 *
 23 * The test may crash if any of the above syscalls fails because in some
 24 * libc implementations (e.g. the GNU C Library) errno is saved in
 25 * thread-local storage, which does not get initialized due to avoiding
 26 * startup libs.
 27 */
 28
 29#include <sys/sysinfo.h>
 30#include <unistd.h>
 31#include <sys/syscall.h>
 32
 33#define STDOUT_FILENO 1
 34
 35static int print(const char *s)
 36{
 37	size_t len = 0;
 38
 39	while (s[len] != '\0')
 40		len++;
 41
 42	return syscall(SYS_write, STDOUT_FILENO, s, len);
 43}
 44
 45static inline char *num_to_str(unsigned long num, char *buf, int len)
 46{
 47	unsigned int digit;
 48
 49	/* put digits in buffer from back to front */
 50	buf += len - 1;
 51	*buf = 0;
 52	do {
 53		digit = num % 10;
 54		*(--buf) = digit + '0';
 55		num /= 10;
 56	} while (num > 0);
 57
 58	return buf;
 59}
 60
 61static int print_num(unsigned long num)
 62{
 63	char num_buf[30];
 64
 65	return print(num_to_str(num, num_buf, sizeof(num_buf)));
 66}
 67
 68static int print_k_value(const char *s, unsigned long num, unsigned long units)
 69{
 70	unsigned long long temp;
 71	int ccode;
 72
 73	print(s);
 74
 75	temp = num;
 76	temp = (temp * units)/1024;
 77	num = temp;
 78	ccode = print_num(num);
 79	print("\n");
 80	return ccode;
 81}
 82
 83/* this program has no main(), as startup libraries are not used */
 84void _start(void)
 85{
 86	int ccode;
 87	struct sysinfo info;
 88	unsigned long used;
 89	static const char *test_name = " get runtime memory use\n";
 90
 91	print("TAP version 13\n");
 92	print("# Testing system size.\n");
 93
 94	ccode = syscall(SYS_sysinfo, &info);
 95	if (ccode < 0) {
 96		print("not ok 1");
 97		print(test_name);
 98		print(" ---\n reason: \"could not get sysinfo\"\n ...\n");
 99		syscall(SYS_exit, ccode);
100	}
101	print("ok 1");
102	print(test_name);
103
104	/* ignore cache complexities for now */
105	used = info.totalram - info.freeram - info.bufferram;
106	print("# System runtime memory report (units in Kilobytes):\n");
107	print(" ---\n");
108	print_k_value(" Total:  ", info.totalram, info.mem_unit);
109	print_k_value(" Free:   ", info.freeram, info.mem_unit);
110	print_k_value(" Buffer: ", info.bufferram, info.mem_unit);
111	print_k_value(" In use: ", used, info.mem_unit);
112	print(" ...\n");
113	print("1..1\n");
114
115	syscall(SYS_exit, 0);
116}