System Call Notes

Invoking System Calls

To invoke a system call:

Set %rax to the system call number (see Full Table below);
Set %rdi, %rsi, %rdx, %r8, %r10, %r9 (in order) according to the glibc prototype given in the manual; then
Perform syscall instruction.

Parameter Orders

The order of the parameter registers is different for system calls!

Parameter	Function Call	System Call
`1`	`%rdi`	`%rdi`
`2`	`%rsi`	`%rsi`
`3`	`%rdx`	`%rdx`
`4`	`%rcx`	`%r8`
`5`	`%r8`	`%r10`
`6`	`%r9`	`%r9`

First Few System Calls

##     RET    sys   %rax                   %rdi               %rsi          %rdx  %r8  %r10  %r9
00  size_t   read  $0x00                 int fd         void * buf  size_t count
01  size_t  write  $0x01                 int fd   const void * buf  size_t count
02  int      open  $0x02  const char * pathname          int flags   mode_t mode
03  int     close  $0x03                 int fd
04  int      stat  $0x04      const char * path  struct stat * buf

Example

    .data
msg:
    .ascii "csx730!\n\0"

    .text
    .globl main
    .type main, @function
main:
    movq $1, %rax               ; // read
    movq $1, %rdi               ; // int fd (stdout)
    movq $msg, %rsi             ; // void * buf (msg)
    movq $8, %rdx               ; // size_t count (8 bytes)
    syscall                     ; // invoke system call
    xorq %rax, %rax             ;

Full Table

The mappings below can be found in <asm/unistd_64.h>. On Nike, you can find <asm/unistd_64.h> in /usr/include/asm/unistd_64.h.

##	System Call
`0`	`read`
`1`	`write`
`2`	`open`
`3`	`close`
`4`	`stat`
`5`	`fstat`
`6`	`lstat`
`7`	`poll`
`8`	`lseek`
`9`	`mmap`
`10`	`mprotect`
`11`	`munmap`
`12`	`brk`
`13`	`rt_sigaction`
`14`	`rt_sigprocmask`
`15`	`rt_sigreturn`
`16`	`ioctl`
`17`	`pread64`
`18`	`pwrite64`
`19`	`readv`
`20`	`writev`
`21`	`access`
`22`	`pipe`
`23`	`select`
`24`	`sched_yield`
`25`	`mremap`
`26`	`msync`
`27`	`mincore`
`28`	`madvise`
`29`	`shmget`
`30`	`shmat`
`31`	`shmctl`
`32`	`dup`
`33`	`dup2`
`34`	`pause`
`35`	`nanosleep`
`36`	`getitimer`
`37`	`alarm`
`38`	`setitimer`
`39`	`getpid`
`40`	`sendfile`
`41`	`socket`
`42`	`connect`
`43`	`accept`
`44`	`sendto`
`45`	`recvfrom`
`46`	`sendmsg`
`47`	`recvmsg`
`48`	`shutdown`
`49`	`bind`
`50`	`listen`
`51`	`getsockname`
`52`	`getpeername`
`53`	`socketpair`
`54`	`setsockopt`
`55`	`getsockopt`
`56`	`clone`
`57`	`fork`
`58`	`vfork`
`59`	`execve`
`60`	`exit`
`61`	`wait4`
`62`	`kill`
`63`	`uname`
`64`	`semget`
`65`	`semop`
`66`	`semctl`
`67`	`shmdt`
`68`	`msgget`
`69`	`msgsnd`
`70`	`msgrcv`
`71`	`msgctl`
`72`	`fcntl`
`73`	`flock`
`74`	`fsync`
`75`	`fdatasync`
`76`	`truncate`
`77`	`ftruncate`
`78`	`getdents`
`79`	`getcwd`
`80`	`chdir`
`81`	`fchdir`
`82`	`rename`
`83`	`mkdir`
`84`	`rmdir`
`85`	`creat`
`86`	`link`
`87`	`unlink`
`88`	`symlink`
`89`	`readlink`
`90`	`chmod`
`91`	`fchmod`
`92`	`chown`
`93`	`fchown`
`94`	`lchown`
`95`	`umask`
`96`	`gettimeofday`
`97`	`getrlimit`
`98`	`getrusage`
`99`	`sysinfo`
`100`	`times`
`101`	`ptrace`
`102`	`getuid`
`103`	`syslog`
`104`	`getgid`
`105`	`setuid`
`106`	`setgid`
`107`	`geteuid`
`108`	`getegid`
`109`	`setpgid`
`110`	`getppid`
`111`	`getpgrp`
`112`	`setsid`
`113`	`setreuid`
`114`	`setregid`
`115`	`getgroups`
`116`	`setgroups`
`117`	`setresuid`
`118`	`getresuid`
`119`	`setresgid`
`120`	`getresgid`
`121`	`getpgid`
`122`	`setfsuid`
`123`	`setfsgid`
`124`	`getsid`
`125`	`capget`
`126`	`capset`
`127`	`rt_sigpending`
`128`	`rt_sigtimedwait`
`129`	`rt_sigqueueinfo`
`130`	`rt_sigsuspend`
`131`	`sigaltstack`
`132`	`utime`
`133`	`mknod`
`134`	`uselib`
`135`	`personality`
`136`	`ustat`
`137`	`statfs`
`138`	`fstatfs`
`139`	`sysfs`
`140`	`getpriority`
`141`	`setpriority`
`142`	`sched_setparam`
`143`	`sched_getparam`
`144`	`sched_setscheduler`
`145`	`sched_getscheduler`
`146`	`sched_get_priority_max`
`147`	`sched_get_priority_min`
`148`	`sched_rr_get_interval`
`149`	`mlock`
`150`	`munlock`
`151`	`mlockall`
`152`	`munlockall`
`153`	`vhangup`
`154`	`modify_ldt`
`155`	`pivot_root`
`156`	`_sysctl`
`157`	`prctl`
`158`	`arch_prctl`
`159`	`adjtimex`
`160`	`setrlimit`
`161`	`chroot`
`162`	`sync`
`163`	`acct`
`164`	`settimeofday`
`165`	`mount`
`166`	`umount2`
`167`	`swapon`
`168`	`swapoff`
`169`	`reboot`
`170`	`sethostname`
`171`	`setdomainname`
`172`	`iopl`
`173`	`ioperm`
`174`	`create_module`
`175`	`init_module`
`176`	`delete_module`
`177`	`get_kernel_syms`
`178`	`query_module`
`179`	`quotactl`
`180`	`nfsservctl`
`181`	`getpmsg`
`182`	`putpmsg`
`183`	`afs_syscall`
`184`	`tuxcall`
`185`	`security`
`186`	`gettid`
`187`	`readahead`
`188`	`setxattr`
`189`	`lsetxattr`
`190`	`fsetxattr`
`191`	`getxattr`
`192`	`lgetxattr`
`193`	`fgetxattr`
`194`	`listxattr`
`195`	`llistxattr`
`196`	`flistxattr`
`197`	`removexattr`
`198`	`lremovexattr`
`199`	`fremovexattr`
`200`	`tkill`
`201`	`time`
`202`	`futex`
`203`	`sched_setaffinity`
`204`	`sched_getaffinity`
`205`	`set_thread_area`
`206`	`io_setup`
`207`	`io_destroy`
`208`	`io_getevents`
`209`	`io_submit`
`210`	`io_cancel`
`211`	`get_thread_area`
`212`	`lookup_dcookie`
`213`	`epoll_create`
`214`	`epoll_ctl_old`
`215`	`epoll_wait_old`
`216`	`remap_file_pages`
`217`	`getdents64`
`218`	`set_tid_address`
`219`	`restart_syscall`
`220`	`semtimedop`
`221`	`fadvise64`
`222`	`timer_create`
`223`	`timer_settime`
`224`	`timer_gettime`
`225`	`timer_getoverrun`
`226`	`timer_delete`
`227`	`clock_settime`
`228`	`clock_gettime`
`229`	`clock_getres`
`230`	`clock_nanosleep`
`231`	`exit_group`
`232`	`epoll_wait`
`233`	`epoll_ctl`
`234`	`tgkill`
`235`	`utimes`
`236`	`vserver`
`237`	`mbind`
`238`	`set_mempolicy`
`239`	`get_mempolicy`
`240`	`mq_open`
`241`	`mq_unlink`
`242`	`mq_timedsend`
`243`	`mq_timedreceive`
`244`	`mq_notify`
`245`	`mq_getsetattr`
`246`	`kexec_load`
`247`	`waitid`
`248`	`add_key`
`249`	`request_key`
`250`	`keyctl`
`251`	`ioprio_set`
`252`	`ioprio_get`
`253`	`inotify_init`
`254`	`inotify_add_watch`
`255`	`inotify_rm_watch`
`256`	`migrate_pages`
`257`	`openat`
`258`	`mkdirat`
`259`	`mknodat`
`260`	`fchownat`
`261`	`futimesat`
`262`	`newfstatat`
`263`	`unlinkat`
`264`	`renameat`
`265`	`linkat`
`266`	`symlinkat`
`267`	`readlinkat`
`268`	`fchmodat`
`269`	`faccessat`
`270`	`pselect6`
`271`	`ppoll`
`272`	`unshare`
`273`	`set_robust_list`
`274`	`get_robust_list`
`275`	`splice`
`276`	`tee`
`277`	`sync_file_range`
`278`	`vmsplice`
`279`	`move_pages`
`280`	`utimensat`
`281`	`epoll_pwait`
`282`	`signalfd`
`283`	`timerfd_create`
`284`	`eventfd`
`285`	`fallocate`
`286`	`timerfd_settime`
`287`	`timerfd_gettime`
`288`	`accept4`
`289`	`signalfd4`
`290`	`eventfd2`
`291`	`epoll_create1`
`292`	`dup3`
`293`	`pipe2`
`294`	`inotify_init1`
`295`	`preadv`
`296`	`pwritev`
`297`	`rt_tgsigqueueinfo`
`298`	`perf_event_open`
`299`	`recvmmsg`
`300`	`fanotify_init`
`301`	`fanotify_mark`
`302`	`prlimit64`
`303`	`name_to_handle_at`
`304`	`open_by_handle_at`
`305`	`clock_adjtime`
`306`	`syncfs`
`307`	`sendmmsg`
`308`	`setns`
`309`	`get_cpu`
`310`	`process_vm_readv`
`311`	`process_vm_writev`