futex: split backend into val2 and timespec versions, reorganize new …

…functions

src/backend/libc/thread/futex.rs

@@ -3,7 +3,7 @@ use crate::backend::c;
 bitflags::bitflags! {
     /// `FUTEX_*` flags for use with [`futex`].
     ///
-    /// [`futex`]: crate::thread::futex
+    /// [`futex`]: mod@crate::thread::futex
     #[repr(transparent)]
     #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
     pub struct FutexFlags: u32 {
@@ -16,7 +16,7 @@ bitflags::bitflags! {
 
 /// `FUTEX_*` operations for use with [`futex`].
 ///
-/// [`futex`]: crate::thread::futex
+/// [`futex`]: mod@crate::thread::futex
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[repr(u32)]
 pub enum FutexOperation {

src/backend/libc/thread/syscalls.rs

@@ -417,9 +417,81 @@ pub(crate) fn setresgid_thread(
     unsafe { ret(setresgid(rgid.as_raw(), egid.as_raw(), sgid.as_raw())) }
 }
 
-// TODO: This could be de-multiplexed.
 #[cfg(linux_kernel)]
-pub(crate) unsafe fn futex(
+pub(crate) unsafe fn futex_val2(
+    uaddr: *const AtomicU32,
+    op: FutexOperation,
+    flags: FutexFlags,
+    val: u32,
+    val2: u32,
+    uaddr2: *const AtomicU32,
+    val3: u32,
+) -> io::Result<usize> {
+    // the least significant four bytes of the timeout pointer are used as `val2`.
+    // ["the kernel casts the timeout value first to unsigned long, then to uint32_t"](https://man7.org/linux/man-pages/man2/futex.2.html),
+    // so we perform that exact conversion in reverse to create the pointer.
+    let utime = val2 as usize as *const Timespec;
+
+    #[cfg(all(
+        target_pointer_width = "32",
+        not(any(target_arch = "aarch64", target_arch = "x86_64"))
+    ))]
+    {
+        // TODO: Upstream this to the libc crate.
+        #[allow(non_upper_case_globals)]
+        const SYS_futex_time64: i32 = linux_raw_sys::general::__NR_futex_time64 as i32;
+
+        syscall! {
+            fn futex_time64(
+                uaddr: *const AtomicU32,
+                futex_op: c::c_int,
+                val: u32,
+                timeout: *const Timespec,
+                uaddr2: *const AtomicU32,
+                val3: u32
+            ) via SYS_futex_time64 -> c::ssize_t
+        }
+
+        ret_usize(futex_time64(
+            uaddr,
+            op as i32 | flags.bits() as i32,
+            val,
+            utime,
+            uaddr2,
+            val3,
+        ))
+    }
+
+    #[cfg(any(
+        target_pointer_width = "64",
+        target_arch = "aarch64",
+        target_arch = "x86_64"
+    ))]
+    {
+        syscall! {
+            fn futex(
+                uaddr: *const AtomicU32,
+                futex_op: c::c_int,
+                val: u32,
+                timeout: *const linux_raw_sys::general::__kernel_timespec,
+                uaddr2: *const AtomicU32,
+                val3: u32
+            ) via SYS_futex -> c::c_long
+        }
+
+        ret_usize(futex(
+            uaddr,
+            op as i32 | flags.bits() as i32,
+            val,
+            utime.cast(),
+            uaddr2,
+            val3,
+        ) as isize)
+    }
+}
+
+#[cfg(linux_kernel)]
+pub(crate) unsafe fn futex_timespec(
     uaddr: *const AtomicU32,
     op: FutexOperation,
     flags: FutexFlags,
@@ -460,7 +532,7 @@ pub(crate) unsafe fn futex(
             // See the comments in `rustix_clock_gettime_via_syscall` about
             // emulation.
             if err == io::Errno::NOSYS {
-                futex_old(uaddr, op, flags, val, utime, uaddr2, val3)
+                futex_old_timespec(uaddr, op, flags, val, utime, uaddr2, val3)
             } else {
                 Err(err)
             }
@@ -500,7 +572,7 @@ pub(crate) unsafe fn futex(
     target_pointer_width = "32",
     not(any(target_arch = "aarch64", target_arch = "x86_64"))
 ))]
-unsafe fn futex_old(
+unsafe fn futex_old_timespec(
     uaddr: *const AtomicU32,
     op: FutexOperation,
     flags: FutexFlags,
@@ -520,15 +592,22 @@ unsafe fn futex_old(
         ) via SYS_futex -> c::c_long
     }
 
-    let old_utime = linux_raw_sys::general::__kernel_old_timespec {
-        tv_sec: (*utime).tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
-        tv_nsec: (*utime).tv_nsec.try_into().map_err(|_| io::Errno::INVAL)?,
+    let old_utime = if utime.is_null() {
+        None
+    } else {
+        Some(linux_raw_sys::general::__kernel_old_timespec {
+            tv_sec: (*utime).tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
+            tv_nsec: (*utime).tv_nsec.try_into().map_err(|_| io::Errno::INVAL)?,
+        })
     };
     ret_usize(futex(
         uaddr,
         op as i32 | flags.bits() as i32,
         val,
-        &old_utime,
+        old_utime
+            .as_ref()
+            .map(|r| r as *const linux_raw_sys::general::__kernel_old_timespec)
+            .unwrap_or(core::ptr::null()),
         uaddr2,
         val3,
     ) as isize)

src/backend/linux_raw/thread/futex.rs

@@ -1,7 +1,7 @@
 bitflags::bitflags! {
     /// `FUTEX_*` flags for use with [`futex`].
     ///
-    /// [`futex`]: crate::thread::futex
+    /// [`futex`]: mod@crate::thread::futex
     #[repr(transparent)]
     #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
     pub struct FutexFlags: u32 {
@@ -18,7 +18,7 @@ bitflags::bitflags! {
 
 /// `FUTEX_*` operations for use with [`futex`].
 ///
-/// [`futex`]: crate::thread::futex
+/// [`futex`]: mod@crate::thread::futex
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[repr(u32)]
 pub enum FutexOperation {

src/backend/linux_raw/thread/syscalls.rs

@@ -205,9 +205,47 @@ pub(crate) fn gettid() -> Pid {
     }
 }
 
-// TODO: This could be de-multiplexed.
 #[inline]
-pub(crate) unsafe fn futex(
+pub(crate) unsafe fn futex_val2(
+    uaddr: *const AtomicU32,
+    op: FutexOperation,
+    flags: FutexFlags,
+    val: u32,
+    val2: u32,
+    uaddr2: *const AtomicU32,
+    val3: u32,
+) -> io::Result<usize> {
+    // the least significant four bytes of the timeout pointer are used as `val2`.
+    // ["the kernel casts the timeout value first to unsigned long, then to uint32_t"](https://man7.org/linux/man-pages/man2/futex.2.html),
+    // so we perform that exact conversion in reverse to create the pointer.
+    let utime = val2 as usize as *const Timespec;
+
+    #[cfg(target_pointer_width = "32")]
+    {
+        ret_usize(syscall!(
+            __NR_futex_time64,
+            uaddr,
+            (op, flags),
+            c_uint(val),
+            utime,
+            uaddr2,
+            c_uint(val3)
+        ))
+    }
+    #[cfg(target_pointer_width = "64")]
+    ret_usize(syscall!(
+        __NR_futex,
+        uaddr,
+        (op, flags),
+        c_uint(val),
+        utime,
+        uaddr2,
+        c_uint(val3)
+    ))
+}
+
+#[inline]
+pub(crate) unsafe fn futex_timespec(
     uaddr: *const AtomicU32,
     op: FutexOperation,
     flags: FutexFlags,
@@ -231,7 +269,7 @@ pub(crate) unsafe fn futex(
             // See the comments in `rustix_clock_gettime_via_syscall` about
             // emulation.
             if err == io::Errno::NOSYS {
-                futex_old(uaddr, op, flags, val, utime, uaddr2, val3)
+                futex_old_timespec(uaddr, op, flags, val, utime, uaddr2, val3)
             } else {
                 Err(err)
             }
@@ -250,7 +288,7 @@ pub(crate) unsafe fn futex(
 }
 
 #[cfg(target_pointer_width = "32")]
-unsafe fn futex_old(
+unsafe fn futex_old_timespec(
     uaddr: *const AtomicU32,
     op: FutexOperation,
     flags: FutexFlags,
@@ -259,16 +297,23 @@ unsafe fn futex_old(
     uaddr2: *const AtomicU32,
     val3: u32,
 ) -> io::Result<usize> {
-    let old_utime = __kernel_old_timespec {
-        tv_sec: (*utime).tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
-        tv_nsec: (*utime).tv_nsec.try_into().map_err(|_| io::Errno::INVAL)?,
+    let old_utime = if utime.is_null() {
+        None
+    } else {
+        Some(__kernel_old_timespec {
+            tv_sec: (*utime).tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
+            tv_nsec: (*utime).tv_nsec.try_into().map_err(|_| io::Errno::INVAL)?,
+        })
     };
     ret_usize(syscall!(
         __NR_futex,
         uaddr,
         (op, flags),
         c_uint(val),
-        by_ref(&old_utime),
+        old_utime
+            .as_ref()
+            .map(|r| r as *const __kernel_old_timespec)
+            .unwrap_or(core::ptr::null()),
         uaddr2,
         c_uint(val3)
     ))