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x86_64 Linux Syscalls
In this chapter we will be looking at the x86_64 Linux syscalls, which are the
core interface between user-space applications and the kernel. They allow
applications to request services from the kernel, such as file operations, process
management, and network communication.
Quick Syscall Reference Table
First here is a basic syscall table for x86_64 Linux with the most commonly used
syscalls. I have also had to abbreviate some of the types and parameters to fit 
them in the table, so I have also included a key for the abbreviations used in the table.
These abbreviations are not used anywhere else in this manual

uns = unsigned
con = const
fn = filename
fd = file descriptor
fp = file path
buf = buffer
s_t = size_t
ch = char
st = struct
lg = long
off = offset
__old_kernel_stat = __okst
__kernel_old_stat = _kost
__kernel_old_itimerval = _koitv
__kernel_old_timeval = _kotv
__kernel_old_timespec = _kots
__kernel_timespec = _kts

| syscall name | rax | 0-rdi | 1-rsi | 2-rdx | 3-r10 | 4-r8 | 5-r9 |
|---|---|---|---|---|---|---|---|
| read | 0x00 | uns int fd | ch buf | s_t count | - | - | - |
| write | 0x01 | uns int fd | con ch buf | s_t count | - | - | - |
| open | 0x02 | con ch fn | int flags | umode_t mode | - | - | - |
| close | 0x03 | uns int fd | - | - | - | - | - |
| stat | 0x04 | con ch fn | st __okst statbuf | - | - | - | - |
| fstat | 0x05 | uns int fd | st __okst statbuf | - | - | - | - |
| lstat | 0x06 | con ch fn | st __okst statbuf | - | - | - | - |
| poll | 0x07 | st pollfd ufds | uns int nfds | int timeout | - | - | - |
| lseek | 0x08 | uns int fd | off_t off | uns int whence | - | - | - |
| mmap | 0x09 | ? | ? | ? | ? | ? | ? |
| mprotect | 0x0a | uns lg start | s_t len | uns lg prot | - | - | - |
| munmap | 0x0b | uns lg addr | s_t len | - | - | - | - |
| brk | 0x0c | uns lg brk | - | - | - | - | - |
| rt_sigaction | 0x0d | int | con st sigaction * | st sigaction * | s_t | - | - |
| rt_sigprocmask | 0x0e | int how | sigset_t set | sigset_t oset | s_t sigsetsize | - | - |
| rt_sigreturn | 0x0f | ? | ? | ? | ? | ? | ? |
| ioctl | 0x10 | uns int fd | uns int cmd | uns lg arg | - | - | - |
| pread64 | 0x11 | uns int fd | ch buf | s_t count | loff_t pos | - | - |
| pwrite64 | 0x12 | uns int fd | con ch buf | s_t count | loff_t pos | - | - |
| readv | 0x13 | uns lg fd | con st iovec vec | uns lg vlen | - | - | - |
| writev | 0x14 | uns lg fd | con st iovec vec | uns lg vlen | - | - | - |
| access | 0x15 | con ch fn | int mode | - | - | - | - |
| pipe | 0x16 | int fildes | - | - | - | - | - |
| select | 0x17 | int n | fd_set inp | fd_set outp | fd_set exp | st _kotv tvp | - |
| sched_yield | 0x18 | - | - | - | - | - | - |
| mremap | 0x19 | uns lg addr | uns lg old_len | uns lg new_len | uns lg flags | uns lg new_addr | - |
| msync | 0x1a | uns lg start | s_t len | int flags | - | - | - |
| mincore | 0x1b | uns lg start | s_t len | uns ch * vec | - | - | - |
| madvise | 0x1c | uns lg start | s_t len | int behavior | - | - | - |
| shmget | 0x1d | key_t key | s_t size | int flag | - | - | - |
| shmat | 0x1e | int shmid | ch shmaddr | int shmflg | - | - | - |
| shmctl | 0x1f | int shmid | int cmd | st shmid_ds buf | - | - | - |
| dup | 0x20 | uns int fildes | - | - | - | - | - |
| dup2 | 0x21 | uns int oldfd | uns int newfd | - | - | - | - |
| pause | 0x22 | - | - | - | - | - | - |
| nanosleep | 0x23 | st _kts rqtp | st _kts rmtp | - | - | - | - |
| getitimer | 0x24 | int which | st _koitv value | - | - | - | - |
| alarm | 0x25 | uns int seconds | - | - | - | - | - |
| setitimer | 0x26 | int which | st _koitv value | st _koitv ovalue | - | - | - |
| getpid | 0x27 | - | - | - | - | - | - |
| sendfile | 0x28 | int out_fd | int in_fd | off_t off | s_t count | - | - |
| socket | 0x29 | int | int | int | - | - | - |
| connect | 0x2a | int | st sockaddr * | int | - | - | - |
| accept | 0x2b | int | st sockaddr * | int * | - | - | - |
| sendto | 0x2c | int | void * | s_t | uns | st sockaddr * | int |
| recvfrom | 0x2d | int | void * | s_t | uns | st sockaddr * | int * |
| sendmsg | 0x2e | int fd | st user_msghdr msg | uns flags | - | - | - |
| recvmsg | 0x2f | int fd | st user_msghdr msg | uns flags | - | - | - |
| shutdown | 0x30 | int | int | - | - | - | - |
| bind | 0x31 | int | st sockaddr * | int | - | - | - |
| listen | 0x32 | int | int | - | - | - | - |
| getsockname | 0x33 | int | st sockaddr * | int * | - | - | - |
| getpeername | 0x34 | int | st sockaddr * | int * | - | - | - |
| socketpair | 0x35 | int | int | int | int * | - | - |
| setsockopt | 0x36 | int fd | int level | int optname | ch optval | int optlen | - |
| getsockopt | 0x37 | int fd | int level | int optname | ch optval | int optlen | - |
| clone | 0x38 | uns lg | uns lg | int * | int * | uns lg | - |
| fork | 0x39 | - | - | - | - | - | - |
| vfork | 0x3a | - | - | - | - | - | - |
| execve | 0x3b | con ch fn | con ch con argv | con ch con envp | - | - | - |
| exit | 0x3c | int error_code | - | - | - | - | - |
| wait4 | 0x3d | pid_t pid | int stat_addr | int options | st rusage ru | - | - |
| kill | 0x3e | pid_t pid | int sig | - | - | - | - |
| uname | 0x3f | st old_utsname * | - | - | - | - | - |
| semget | 0x40 | key_t key | int nsems | int semflg | - | - | - |
| semop | 0x41 | int semid | st sembuf sops | uns nsops | - | - | - |
| semctl | 0x42 | int semid | int semnum | int cmd | uns lg arg | - | - |
| shmdt | 0x43 | ch shmaddr | - | - | - | - | - |
| msgget | 0x44 | key_t key | int msgflg | - | - | - | - |
| msgsnd | 0x45 | int msqid | st msgbuf msgp | s_t msgsz | int msgflg | - | - |
| msgrcv | 0x46 | int msqid | st msgbuf msgp | s_t msgsz | lg msgtyp | int msgflg | - |
| msgctl | 0x47 | int msqid | int cmd | st msqid_ds buf | - | - | - |
| fcntl | 0x48 | uns int fd | uns int cmd | uns lg arg | - | - | - |
| flock | 0x49 | uns int fd | uns int cmd | - | - | - | - |
| fsync | 0x4a | uns int fd | - | - | - | - | - |
| fdatasync | 0x4b | uns int fd | - | - | - | - | - |
| truncate | 0x4c | con ch path | lg length | - | - | - | - |
| ftruncate | 0x4d | uns int fd | off_t length | - | - | - | - |
| getdents | 0x4e | uns int fd | st linux_dirent dirent | uns int count | - | - | - |
| getcwd | 0x4f | ch buf | uns lg size | - | - | - | - |
| chdir | 0x50 | con ch fn | - | - | - | - | - |
| fchdir | 0x51 | uns int fd | - | - | - | - | - |
| rename | 0x52 | con ch oldname | con ch newname | - | - | - | - |
| mkdir | 0x53 | con ch pathname | umode_t mode | - | - | - | - |
| rmdir | 0x54 | con ch pathname | - | - | - | - | - |
| creat | 0x55 | con ch pathname | umode_t mode | - | - | - | - |
| link | 0x56 | con ch oldname | con ch newname | - | - | - | - |
| unlink | 0x57 | con ch pathname | - | - | - | - | - |
| symlink | 0x58 | con ch old | con ch new | - | - | - | - |
| readlink | 0x59 | con ch path | ch buf | int bufsiz | - | - | - |
| chmod | 0x5a | con ch fn | umode_t mode | - | - | - | - |
| fchmod | 0x5b | uns int fd | umode_t mode | - | - | - | - |
| chown | 0x5c | con ch fn | uid_t user | gid_t group | - | - | - |
| fchown | 0x5d | uns int fd | uid_t user | gid_t group | - | - | - |
| lchown | 0x5e | con ch fn | uid_t user | gid_t group | - | - | - |
| umask | 0x5f | int mask | - | - | - | - | - |
| gettimeofday | 0x60 | st _kotv tv | st timezone tz | - | - | - | - |
| getrlimit | 0x61 | uns int resource | st rlimit rlim | - | - | - | - |
| getrusage | 0x62 | int who | st rusage ru | - | - | - | - |
| sysinfo | 0x63 | st sysinfo info | - | - | - | - | - |
| times | 0x64 | st tms tbuf | - | - | - | - | - |
| ptrace | 0x65 | lg request | lg pid | uns lg addr | uns lg data | - | - |
| getuid | 0x66 | - | - | - | - | - | - |
| syslog | 0x67 | int type | ch buf | int len | - | - | - |
| getgid | 0x68 | - | - | - | - | - | - |
| setuid | 0x69 | uid_t uid | - | - | - | - | - |
| setgid | 0x6a | gid_t gid | - | - | - | - | - |
| geteuid | 0x6b | - | - | - | - | - | - |
| getegid | 0x6c | - | - | - | - | - | - |
| setpgid | 0x6d | pid_t pid | pid_t pgid | - | - | - | - |
| getppid | 0x6e | - | - | - | - | - | - |
| getpgrp | 0x6f | - | - | - | - | - | - |
| setsid | 0x70 | - | - | - | - | - | - |
| setreuid | 0x71 | uid_t ruid | uid_t euid | - | - | - | - |
| setregid | 0x72 | gid_t rgid | gid_t egid | - | - | - | - |
| getgroups | 0x73 | int gidsetsize | gid_t grouplist | - | - | - | - |
| setgroups | 0x74 | int gidsetsize | gid_t grouplist | - | - | - | - |
| setresuid | 0x75 | uid_t ruid | uid_t euid | uid_t suid | - | - | - |
Syscall Details
Now we are going to go over some of the details of the syscalls and document 
the parameters and return values and its behavior. This is not going to be an 
exhaustive list of all the syscalls, but I am slowly adding to this section.
0x00 - read
The read syscall reads data from a file descriptor into a buffer.
Synopsis
```c
include 
ssize_t read(int fd, void *buf, size_t count);
```
Example
c
int fd = open("example.txt", O_RDONLY);
char buf[100];
ssize_t bytes_read = read(fd, buf, sizeof(buf));
if (bytes_read < 0) {
    // handle error
}
Parameters

fd: The file descriptor to read from.
buf: The buffer to read the data into.
count: The number of bytes to read.

Return Value
The number of bytes read on success, or -1 on error. errno is set to indicate 
the error.
Error values

EAGAIN: The file descriptor is non-blocking and no data is available to read.
EBADF: The file descriptor is not valid or is not open for reading.
EFAULT: The buffer is outside the accessible address space.
EINTR: The call was interrupted by a signal before any data was read.
EINVAL: The file descriptor cannot be read from, or the buffer is not valid.
EIO: An I/O error occurred while reading from the file descriptor.
EISDIR: The file descriptor refers to a directory.

0x01 - write
The write syscall writes data from a buffer to a file descriptor.
Synopsis
```c
include 
ssize_t write(int fd, const void *buf, size_t count);
```
Example
c
int fd = open("example.txt", O_WRONLY | O_CREAT, 0644);
const char *buf = "Hello, world!";
ssize_t bytes_written = write(fd, buf, strlen(buf));
if (bytes_written < 0) {
    // handle error
}
Parameters

fd: The file descriptor to write to.
buf: The buffer containing the data to write.
count: The number of bytes to write.

Return Value
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