sysinfo.c

linux下获取一些环境信息的代码

// Copyright (C) 1992-1998 by Michael K. Johnson, [e-mail]
// Copyright 1998-2003 Albert Cahalan
//
// This file is placed under the conditions of the GNU Library
// General Public License, version 2, or any later version.
// See file COPYING for information on distribution conditions.
//
// File for parsing top-level /proc entities. */
//
// June 2003, Fabian Frederick, disk and slab info

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <locale.h>

#include <unistd.h>
#include <fcntl.h>
#include "version.h"
#include "sysinfo.h" /* include self to verify prototypes */

#ifndef HZ
#include <netinet/in.h>  /* htons */
#endif

long smp_num_cpus;     /* number of CPUs */

#define BAD_OPEN_MESSAGE					\
"Error: /proc must be mounted\n"				\
"  To mount /proc at boot you need an /etc/fstab line like:\n"	\
"      /proc   /proc   proc    defaults\n"			\
"  In the meantime, run \"mount /proc /proc -t proc\"\n"

#define STAT_FILE    "/proc/stat"
static int stat_fd = -1;
#define UPTIME_FILE  "/proc/uptime"
static int uptime_fd = -1;
#define LOADAVG_FILE "/proc/loadavg"
static int loadavg_fd = -1;
#define MEMINFO_FILE "/proc/meminfo"
static int meminfo_fd = -1;
#define VMINFO_FILE "/proc/vmstat"
static int vminfo_fd = -1;

static char buf[1024];

/* This macro opens filename only if necessary and seeks to 0 so
 * that successive calls to the functions are more efficient.
 * It also reads the current contents of the file into the global buf.
 */
#define FILE_TO_BUF(filename, fd) do{				\
    static int local_n;						\
    if (fd == -1 && (fd = open(filename, O_RDONLY)) == -1) {	\
	fputs(BAD_OPEN_MESSAGE, stderr);			\
	fflush(NULL);						\
	_exit(102);						\
    }								\
    lseek(fd, 0L, SEEK_SET);					\
    if ((local_n = read(fd, buf, sizeof buf - 1)) < 0) {	\
	perror(filename);					\
	fflush(NULL);						\
	_exit(103);						\
    }								\
    buf[local_n] = '\0';					\
}while(0)

/* evals 'x' twice */
#define SET_IF_DESIRED(x,y) do{  if(x) *(x) = (y); }while(0)


/***********************************************************************/
int uptime(double *restrict uptime_secs, double *restrict idle_secs) {
    double up=0, idle=0;
    char *restrict savelocale;

    FILE_TO_BUF(UPTIME_FILE,uptime_fd);
    savelocale = setlocale(LC_NUMERIC, NULL);
    setlocale(LC_NUMERIC,"C");
    if (sscanf(buf, "%lf %lf", &up, &idle) < 2) {
        setlocale(LC_NUMERIC,savelocale);
        fputs("bad data in " UPTIME_FILE "\n", stderr);
	    return 0;
    }
    setlocale(LC_NUMERIC,savelocale);
    SET_IF_DESIRED(uptime_secs, up);
    SET_IF_DESIRED(idle_secs, idle);
    return up;	/* assume never be zero seconds in practice */
}

/***********************************************************************
 * Some values in /proc are expressed in units of 1/HZ seconds, where HZ
 * is the kernel clock tick rate. One of these units is called a jiffy.
 * The HZ value used in the kernel may vary according to hacker desire.
 * According to Linus Torvalds, this is not true. He considers the values
 * in /proc as being in architecture-dependant units that have no relation
 * to the kernel clock tick rate. Examination of the kernel source code
 * reveals that opinion as wishful thinking.
 *
 * In any case, we need the HZ constant as used in /proc. (the real HZ value
 * may differ, but we don't care) There are several ways we could get HZ:
 *
 * 1. Include the kernel header file. If it changes, recompile this library.
 * 2. Use the sysconf() function. When HZ changes, recompile the C library!
 * 3. Ask the kernel. This is obviously correct...
 *
 * Linus Torvalds won't let us ask the kernel, because he thinks we should
 * not know the HZ value. Oh well, we don't have to listen to him.
 * Someone smuggled out the HZ value. :-)
 *
 * This code should work fine, even if Linus fixes the kernel to match his
 * stated behavior. The code only fails in case of a partial conversion.
 *
 * Recent update: on some architectures, the 2.4 kernel provides an
 * ELF note to indicate HZ. This may be for ARM or user-mode Linux
 * support. This ought to be investigated. Note that sysconf() is still
 * unreliable, because it doesn't return an error code when it is
 * used with a kernel that doesn't support the ELF note. On some other
 * architectures there may be a system call or sysctl() that will work.
 */

unsigned long long Hertz;

static void old_Hertz_hack(void){
  unsigned long long user_j, nice_j, sys_j, other_j;  /* jiffies (clock ticks) */
  double up_1, up_2, seconds;
  unsigned long long jiffies;
  unsigned h;
  char *restrict savelocale;

  savelocale = setlocale(LC_NUMERIC, NULL);
  setlocale(LC_NUMERIC, "C");
  do{
    FILE_TO_BUF(UPTIME_FILE,uptime_fd);  sscanf(buf, "%lf", &up_1);
    /* uptime(&up_1, NULL); */
    FILE_TO_BUF(STAT_FILE,stat_fd);
    sscanf(buf, "cpu %Lu %Lu %Lu %Lu", &user_j, &nice_j, &sys_j, &other_j);
    FILE_TO_BUF(UPTIME_FILE,uptime_fd);  sscanf(buf, "%lf", &up_2);
    /* uptime(&up_2, NULL); */
  } while((long long)( (up_2-up_1)*1000.0/up_1 )); /* want under 0.1% error */
  setlocale(LC_NUMERIC, savelocale);
  jiffies = user_j + nice_j + sys_j + other_j;
  seconds = (up_1 + up_2) / 2;
  h = (unsigned)( (double)jiffies/seconds/smp_num_cpus );
  /* actual values used by 2.4 kernels: 32 64 100 128 1000 1024 1200 */
  switch(h){
  case    9 ...   11 :  Hertz =   10; break; /* S/390 (sometimes) */
  case   18 ...   22 :  Hertz =   20; break; /* user-mode Linux */
  case   30 ...   34 :  Hertz =   32; break; /* ia64 emulator */
  case   48 ...   52 :  Hertz =   50; break;
  case   58 ...   61 :  Hertz =   60; break;
  case   62 ...   65 :  Hertz =   64; break; /* StrongARM /Shark */
  case   95 ...  105 :  Hertz =  100; break; /* normal Linux */
  case  124 ...  132 :  Hertz =  128; break; /* MIPS, ARM */
  case  195 ...  204 :  Hertz =  200; break; /* normal << 1 */
  case  253 ...  260 :  Hertz =  256; break;
  case  393 ...  408 :  Hertz =  400; break; /* normal << 2 */
  case  790 ...  808 :  Hertz =  800; break; /* normal << 3 */
  case  990 ... 1010 :  Hertz = 1000; break; /* ARM */
  case 1015 ... 1035 :  Hertz = 1024; break; /* Alpha, ia64 */
  case 1180 ... 1220 :  Hertz = 1200; break; /* Alpha */
  default:
#ifdef HZ
    Hertz = (unsigned long long)HZ;    /* <asm/param.h> */
#else
    /* If 32-bit or big-endian (not Alpha or ia64), assume HZ is 100. */
    Hertz = (sizeof(long)==sizeof(int) || htons(999)==999) ? 100UL : 1024UL;
#endif
    fprintf(stderr, "Unknown HZ value! (%d) Assume %Ld.\n", h, Hertz);
  }
}

// same as:   euid != uid || egid != gid
#ifndef AT_SECURE
#define AT_SECURE      23     // secure mode boolean (true if setuid, etc.)
#endif

#ifndef AT_CLKTCK
#define AT_CLKTCK       17    // frequency of times()
#endif

#define NOTE_NOT_FOUND 42

//extern char** environ;

/* for ELF executables, notes are pushed before environment and args */
static unsigned long find_elf_note(unsigned long findme){
  unsigned long *ep = (unsigned long *)environ;
  while(*ep++);
  while(*ep){
    if(ep[0]==findme) return ep[1];
    ep+=2;
  }
  return NOTE_NOT_FOUND;
}

int have_privs;

static int check_for_privs(void){
  unsigned long rc = find_elf_note(AT_SECURE);
  if(rc==NOTE_NOT_FOUND){
    // not valid to run this code after UID or GID change!
    // (if needed, may use AT_UID and friends instead)
    rc = geteuid() != getuid() || getegid() != getgid();
  }
  return !!rc;
}

static void init_libproc(void) __attribute__((constructor));
static void init_libproc(void){
  have_privs = check_for_privs();
  // ought to count CPUs in /proc/stat instead of relying
  // on glibc, which foolishly tries to parse /proc/cpuinfo
  //
  // SourceForge has an old Alpha running Linux 2.2.20 that
  // appears to have a non-SMP kernel on a 2-way SMP box.
  // _SC_NPROCESSORS_CONF returns 2, resulting in HZ=512
  // _SC_NPROCESSORS_ONLN returns 1, which should work OK
  smp_num_cpus = sysconf(_SC_NPROCESSORS_ONLN);
  if(smp_num_cpus<1) smp_num_cpus=1; /* SPARC glibc is buggy */

  if(linux_version_code > LINUX_VERSION(2, 4, 0)){ 
    Hertz = find_elf_note(AT_CLKTCK);
    if(Hertz!=NOTE_NOT_FOUND) return;
    fputs("2.4+ kernel w/o ELF notes? -- report this\n", stderr);
  }
  old_Hertz_hack();
}

#if 0
/***********************************************************************
 * The /proc filesystem calculates idle=jiffies-(user+nice+sys) and we
 * recover jiffies by adding up the 4 or 5 numbers we are given. SMP kernels
 * (as of pre-2.4 era) can report idle time going backwards, perhaps due
 * to non-atomic reads and updates. There is no locking for these values.
 */
#ifndef NAN
#define NAN (-0.0)
#endif
#define JT unsigned long long
void eight_cpu_numbers(double *restrict uret, double *restrict nret, double *restrict sret, double *restrict iret, double *restrict wret, double *restrict xret, double *restrict yret, double *restrict zret){
    double tmp_u, tmp_n, tmp_s, tmp_i, tmp_w, tmp_x, tmp_y, tmp_z;
    double scale;  /* scale values to % */
    static JT old_u, old_n, old_s, old_i, old_w, old_x, old_y, old_z;
    JT new_u, new_n, new_s, new_i, new_w, new_x, new_y, new_z;
    JT ticks_past; /* avoid div-by-0 by not calling too often :-( */

    tmp_w = 0.0;
    new_w = 0;
    tmp_x = 0.0;
    new_x = 0;
    tmp_y = 0.0;
    new_y = 0;
    tmp_z = 0.0;
    new_z = 0;
 
    FILE_TO_BUF(STAT_FILE,stat_fd);
    sscanf(buf, "cpu %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu", &new_u, &new_n, &new_s, &new_i, &new_w, &new_x, &new_y, &new_z);
    ticks_past = (new_u+new_n+new_s+new_i+new_w+new_x+new_y+new_z)-(old_u+old_n+old_s+old_i+old_w+old_x+old_y+old_z);
    if(ticks_past){
      scale = 100.0 / (double)ticks_past;
      tmp_u = ( (double)new_u - (double)old_u ) * scale;
      tmp_n = ( (double)new_n - (double)old_n ) * scale;
      tmp_s = ( (double)new_s - (double)old_s ) * scale;
      tmp_i = ( (double)new_i - (double)old_i ) * scale;
      tmp_w = ( (double)new_w - (double)old_w ) * scale;
      tmp_x = ( (double)new_x - (double)old_x ) * scale;
      tmp_y = ( (double)new_y - (double)old_y ) * scale;
      tmp_z = ( (double)new_z - (double)old_z ) * scale;
    }else{
      tmp_u = NAN;
      tmp_n = NAN;
      tmp_s = NAN;
      tmp_i = NAN;
      tmp_w = NAN;
      tmp_x = NAN;
      tmp_y = NAN;
      tmp_z = NAN;
    }
    SET_IF_DESIRED(uret, tmp_u);
    SET_IF_DESIRED(nret, tmp_n);
    SET_IF_DESIRED(sret, tmp_s);
    SET_IF_DESIRED(iret, tmp_i);
    SET_IF_DESIRED(wret, tmp_w);
    SET_IF_DESIRED(xret, tmp_x);
    SET_IF_DESIRED(yret, tmp_y);
    SET_IF_DESIRED(zret, tmp_z);
    old_u=new_u;
    old_n=new_n;
    old_s=new_s;
    old_i=new_i;
    old_w=new_w;
    old_x=new_x;
    old_y=new_y;
    old_z=new_z;
}
#undef JT
#endif