Auto merge of #3437 - SteveLauC:eventfd_read, r=JohnTitor

feat: eventfd_read/write for Android/FreeBSD/Linux

Add

```c
int eventfd_read(int fd, eventfd_t *value);
int eventfd_write(int fd, eventfd_t value);
```

for

* Android
* [FreeBSD](https://man.freebsd.org/cgi/man.cgi?query=eventfd&apropos=0&sektion=2&manpath=FreeBSD+13.2-RELEASE&arch=default&format=html)
* [Linux](https://man7.org/linux/man-pages/man2/eventfd.2.html)

libc-test/build.rs

@@ -2417,6 +2417,8 @@ fn test_freebsd(target: &str) {
             // the struct "__kvm" is quite tricky to bind so since we only use a pointer to it
             // for now, it doesn't matter too much...
             "kvm_t" => true,
+            // `eventfd(2)` and things come with it are added in FreeBSD 13
+            "eventfd_t" if Some(13) > freebsd_ver => true,
 
             _ => false,
         }
@@ -2494,6 +2496,8 @@ fn test_freebsd(target: &str) {
             | "aio_readv"
             | "aio_writev"
             | "copy_file_range"
+            | "eventfd_read"
+            | "eventfd_write"
                 if Some(13) > freebsd_ver =>
             {
                 true

libc-test/semver/android.txt

@@ -3756,3 +3756,5 @@ write
 writev
 dirname
 basename
+eventfd_read
+eventfd_write

libc-test/semver/freebsd.txt

@@ -2245,3 +2245,5 @@ dirname
 basename
 closefrom
 close_range
+eventfd_read
+eventfd_write

libc-test/semver/linux.txt

@@ -3842,3 +3842,5 @@ vhangup
 vmsplice
 wait4
 waitid
+eventfd_read
+eventfd_write

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -48,6 +48,8 @@ pub type cpusetid_t = ::c_int;
 
 pub type sctp_assoc_t = u32;
 
+pub type eventfd_t = u64;
+
 #[cfg_attr(feature = "extra_traits", derive(Debug, Hash, PartialEq, Eq))]
 #[repr(u32)]
 pub enum devstat_support_flags {
@@ -5383,6 +5385,8 @@ extern "C" {
     pub fn setaudit(auditinfo: *const auditinfo_t) -> ::c_int;
 
     pub fn eventfd(init: ::c_uint, flags: ::c_int) -> ::c_int;
+    pub fn eventfd_read(fd: ::c_int, value: *mut eventfd_t) -> ::c_int;
+    pub fn eventfd_write(fd: ::c_int, value: eventfd_t) -> ::c_int;
 
     pub fn fdatasync(fd: ::c_int) -> ::c_int;
 

src/unix/linux_like/android/mod.rs

@@ -46,6 +46,8 @@ pub type Elf64_Off = u64;
 pub type Elf64_Word = u32;
 pub type Elf64_Xword = u64;
 
+pub type eventfd_t = u64;
+
 s! {
     pub struct stack_t {
         pub ss_sp: *mut ::c_void,
@@ -3566,6 +3568,8 @@ extern "C" {
         flags: ::c_uint,
     ) -> ::ssize_t;
     pub fn eventfd(init: ::c_uint, flags: ::c_int) -> ::c_int;
+    pub fn eventfd_read(fd: ::c_int, value: *mut eventfd_t) -> ::c_int;
+    pub fn eventfd_write(fd: ::c_int, value: eventfd_t) -> ::c_int;
     pub fn sched_rr_get_interval(pid: ::pid_t, tp: *mut ::timespec) -> ::c_int;
     pub fn sem_timedwait(sem: *mut sem_t, abstime: *const ::timespec) -> ::c_int;
     pub fn sem_getvalue(sem: *mut sem_t, sval: *mut ::c_int) -> ::c_int;

src/unix/linux_like/linux/mod.rs

@@ -52,6 +52,7 @@ pub type iconv_t = *mut ::c_void;
 // linux/sctp.h
 pub type sctp_assoc_t = ::__s32;
 
+pub type eventfd_t = u64;
 #[cfg_attr(feature = "extra_traits", derive(Debug))]
 pub enum fpos64_t {} // FIXME: fill this out with a struct
 impl ::Copy for fpos64_t {}
@@ -5092,6 +5093,9 @@ extern "C" {
         flags: ::c_uint,
     ) -> ::ssize_t;
     pub fn eventfd(init: ::c_uint, flags: ::c_int) -> ::c_int;
+    pub fn eventfd_read(fd: ::c_int, value: *mut eventfd_t) -> ::c_int;
+    pub fn eventfd_write(fd: ::c_int, value: eventfd_t) -> ::c_int;
+
     pub fn sched_rr_get_interval(pid: ::pid_t, tp: *mut ::timespec) -> ::c_int;
     pub fn sem_timedwait(sem: *mut sem_t, abstime: *const ::timespec) -> ::c_int;
     pub fn sem_getvalue(sem: *mut sem_t, sval: *mut ::c_int) -> ::c_int;