第36部分-Linux x86 64位汇编 sysinfo系统调用
第36部分-Linux x86 64位汇编 sysinfo系统调用
Sysinfo可以返回关于系统配置的资源信息。
通过man 查看如下：
NAME
sysinfo - return system information
SYNOPSIS
#include
int sysinfo(struct sysinfo *info);
结构体如下：
struct sysinfo {
long uptime; /* Seconds since boot */
unsigned long loads[3];/* 1, 5, and 15 minute load averages*/
unsigned long totalram; /* Total usable main memory size */
unsigned long freeram; /* Available memory size */
unsigned long sharedram; /* Amount of shared memory */
unsigned long bufferram; /* Memory used by buffers */
unsigned long totalswap; /* Total swap space size */
unsigned long freeswap; /* Swap space still available */
unsigned short procs; /* Number of current processes */
char _f[22]; /* Pads structure to 64 bytes */
};
通过查看文件arch/x86/entry/syscalls/syscall_64.tbl
知道系统调用号是99.
示例
.section .data
result:
uptime:
.int 0,0
load1:
.int 0,0
load5:
.int 0,0
load15:
.int 0,0
totalram:
.int 0,0
freeram:
.int 0,0
sharedram:
.int 0,0
bufferram:
.int 0,0
totalswap:
.int 0,0
freeswap:
.int 0,0
procs:
.byte 0x00, 0x00
.section .text
.globl _start
_start:
nop
movq $result, %rdi
movq $99, %rax
syscall
movq $0, %rbx
movq $60, %rax
syscall
as -g -o sysinfo.o sysinfo.s
ld -o sysinfo sysinfo.o
在执行过程中进行查看如下：
(gdb) x /d &load5
0x6000e1: 23584
(gdb) x /d &load15
0x6000e9: 10656
(gdb) x /d &totalram
0x6000f1: -467349504
(gdb) x /ud &totalram
0x6000f1: -467349504
(gdb) x /u &totalram
0x6000f1: 3827617792
(gdb) x /u &procs
0x600121: 1565
(gdb) x /u &totalswap
0x600111: 999288832
(gdb) x /u &freeswap
0x600119: 999288832
(gdb)