info.c

包括初始化、进程管理、进程通信、内存管理、设备管理、中断、文件系统、系统调用等精选源码分析。

/*
 * linux/kernel/info.c
 *
 * Copyright (C) 1992 Darren Senn
 */

/* This implements the sysinfo() system call */

#include <linux/mm.h>
#include <linux/unistd.h>
#include <linux/swap.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>

asmlinkage long sys_sysinfo(struct sysinfo *info)
{
	struct sysinfo val;

	memset((char *)&val, 0, sizeof(struct sysinfo));

	cli();
	val.uptime = jiffies / HZ;

	val.loads[0] = avenrun[0] << (SI_LOAD_SHIFT - FSHIFT);
	val.loads[1] = avenrun[1] << (SI_LOAD_SHIFT - FSHIFT);
	val.loads[2] = avenrun[2] << (SI_LOAD_SHIFT - FSHIFT);

	val.procs = nr_threads-1;
	sti();

	si_meminfo(&val);
	si_swapinfo(&val);

	{
		/* If the sum of all the available memory (i.e. ram + swap +
		 * highmem) is less then can be stored in a 32 bit unsigned long
		 * then we can be binary compatible with 2.2.x kernels.  If not,
		 * well, who cares since in that case 2.2.x was broken anyways...
		 *
		 *  -Erik Andersen <[e-mail]> */

		unsigned long mem_total = val.totalram + val.totalswap;
		if ( !(mem_total < val.totalram || mem_total < val.totalswap)) {
			unsigned long mem_total2 = mem_total + val.totalhigh; 
			if (!(mem_total2 < mem_total || mem_total2 < val.totalhigh))
			{
				/* If mem_total did not overflow.  Divide all memory values by
				 * mem_unit and set mem_unit=1.  This leaves things compatible with
				 * 2.2.x, and also retains compatibility with earlier 2.4.x
				 * kernels...  */

				int bitcount = 0;
				while (val.mem_unit > 1) 
				{
					bitcount++;
					val.mem_unit >>= 1;
				}
				val.totalram <<= bitcount;
				val.freeram <<= bitcount;
				val.sharedram <<= bitcount;
				val.bufferram <<= bitcount;
				val.totalswap <<= bitcount;
				val.freeswap <<= bitcount;
				val.totalhigh <<= bitcount;
				val.freehigh <<= bitcount;
			}
		}
	}

	if (copy_to_user(info, &val, sizeof(struct sysinfo)))
		return -EFAULT;
	return 0;
}