常见系统调用

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# epoll_pwait

wait for an I/O event on an epoll file descriptor.

#include <sys/epoll.h>

int epoll_wait(int epfd, struct epoll_event *events, int maxevents, int timeout);
int epoll_pwait(int epfd, struct epoll_event *events, int maxevents, int timeout, const sigset_t *sigmask);

typedef union epoll_data {
    void    *ptr;
    int      fd;
    uint32_t u32;
    uint64_t u64;
} epoll_data_t;

struct epoll_event {
    uint32_t     events;    /* Epoll events */
    epoll_data_t data;      /* User data variable */
};

epoll_pwait(3, [{EPOLLIN, {u32=18, u64=18}}], 1024, 11749, NULL, 8)

epoll_pwait

# epoll_ctl

control interface for an epoll descriptor

#include <sys/epoll.h>

int epoll_ctl(int epfd, int op, int fd, struct epoll_event *event);

epoll_ctl(3, EPOLL_CTL_ADD, 22, {EPOLLOUT, {u32=22, u64=7575752952099373078}}) // 0
epoll_ctl(3, EPOLL_CTL_ADD, 25, {EPOLLIN, {u32=25, u64=7575752952099373081}})  // -1 EEXIST (File exists)

# accept_4

accept a connection on a socket.

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/socket.h>
int accept4(int sockfd, struct sockaddr *addr, socklen_t *addrlen, int flags);

accept4(18, NULL, NULL, SOCK_CLOEXEC|SOCK_NONBLOCK)

accept4

# write

write to a file descriptor.

也包括标准输出

#include <unistd.h>
ssize_t write(int fd, const void *buf, size_t count);

write(21, "Q\0\0\0\372SELECT \"users\".\"id\" FROM \"u"..., 251)  // 251
write(26, "HTTP/1.1 200 OK\r\nX-Powered-By: E"..., 30514)         // 30514

# read

read from a file descriptor.

#include <unistd.h>
ssize_t read(int fd, void *buf, size_t count);

read(26, "POST /graphql?query=ME HTTP/1"..., 65536)    // 1435

# futex

#include <linux/futex.h>
#include <sys/time.h>

int futex(int *uaddr, int op, int val, const struct timespec *timeout,
          int *uaddr2, int val3);

futex(0x7f3804ef39a4, FUTEX_WAKE_PRIVATE, 1)        // = 1

# mprotect

set protection on a region of memory

#include <sys/mman.h>

int mprotect(void *addr, size_t len, int prot);

mprotect(0x38ae4f980000, 524288, PROT_READ|PROT_WRITE) // = 0

# getpid

get process identification

#include <sys/types.h>
#include <unistd.h>

pid_t getpid(void);
pid_t getppid(void);
getpid()                        // 122

# mmap/munmap

map or unmap files or devices into memory.

mmap creates a new mapping in the virtual address space of the calling process.

#include <sys/mman.h>
void *mmap(void *addr, size_t lengthint, int prot, int flags,
           int fd, off_t offset);
int munmap(void *addr, size_t length);

// 如果 addr 是 NULL，将会开辟一片空间
// MAP_PRIVATE: 私有的 copy-on-write 的映射
// MAP_ANONYMOUS: The mapping is not backed by any file; its contents are initialized to zero.
mmap(NULL, 286720, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) // 0x7f38076a8000

# brk

change data segment size.

#include <unistd.h>

int brk(void *addr);

void *sbrk(intptr_t increment);

brk(NULL)                           // 0x36df000

# execve

execute program.

#include <unistd.h>

int execve(const char *filename, char *const argv[], char *const envp[]);

execve("/usr/bin/node", ["node", "index.js"], [/* 27 vars */]) // = 0