Use stable #[naked] instead of global_asm!() fallback

#[naked] is stable since Rust 1.79, and origin already requires 1.88.
This removes the global_asm!() fallback and the naked_fn! macro entirely,
inlining #[naked] directly at each call site.

Signal handlers don't need #[no_mangle] since they're passed by address.

Author: walruscraft

src/arch/aarch64.rs

@@ -22,28 +22,28 @@ use {
     rustix::thread::RawPid,
 };
 
+/// The program entry point.
+///
+/// # Safety
+///
+/// This function must never be called explicitly. It is the first thing
+/// executed in the program, and it assumes that memory is laid out according
+/// to the operating system convention for starting a new program.
 #[cfg(feature = "origin-start")]
-naked_fn!(
-    "
-    The program entry point.
-
-    # Safety
-
-    This function must never be called explicitly. It is the first thing
-    executed in the program, and it assumes that memory is laid out according
-    to the operating system convention for starting a new program.
-    ";
-    pub(super) fn _start() -> !;
-
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+pub(super) unsafe extern "C" fn _start() -> ! {
     // Jump to `entry`, passing it the initial stack pointer value as an
     // argument, a null return address, a null frame pointer, and an aligned
     // stack pointer. On many architectures, the incoming frame pointer is
     // already null.
-    "mov x0, sp",   // Pass the incoming `sp` as the arg to `entry`.
-    "mov x30, xzr", // Set the return address to zero.
-    "b {entry}";    // Jump to `entry`.
-    entry = sym super::program::entry
-);
+    core::arch::naked_asm!(
+        "mov x0, sp",   // Pass the incoming `sp` as the arg to `entry`.
+        "mov x30, xzr", // Set the return address to zero.
+        "b {entry}",    // Jump to `entry`.
+        entry = sym super::program::entry
+    )
+}
 
 /// Execute a trap instruction.
 ///
@@ -300,25 +300,24 @@ pub(super) unsafe fn munmap_and_exit_thread(map_addr: *mut c_void, map_len: usiz
     }
 }
 
+/// Invoke the `__NR_rt_sigreturn` system call to return control from a signal
+/// handler.
+///
+/// # Safety
+///
+/// This function must never be called other than by the `sa_restorer`
+/// mechanism.
 #[cfg(feature = "take-charge")]
 #[cfg(feature = "signal")]
-naked_fn!(
-    "
-    Invoke the `__NR_rt_sigreturn` system call to return control from a signal
-    handler.
-
-    # Safety
-
-    This function must never be called other than by the `sa_restorer`
-    mechanism.
-    ";
-    pub(super) fn return_from_signal_handler() -> ();
-
-    "mov x8, {__NR_rt_sigreturn}",
-    "svc 0",
-    "udf #16";
-    __NR_rt_sigreturn = const __NR_rt_sigreturn
-);
+#[unsafe(naked)]
+pub(super) unsafe extern "C" fn return_from_signal_handler() {
+    core::arch::naked_asm!(
+        "mov x8, {__NR_rt_sigreturn}",
+        "svc 0",
+        "udf #16",
+        __NR_rt_sigreturn = const __NR_rt_sigreturn
+    )
+}
 
 /// Invoke the appropriate system call to return control from a signal
 /// handler that does not use `SA_SIGINFO`. On aarch64, this uses the same

src/arch/arm.rs

@@ -22,28 +22,28 @@ use {
     rustix::thread::RawPid,
 };
 
+/// The program entry point.
+///
+/// # Safety
+///
+/// This function must never be called explicitly. It is the first thing
+/// executed in the program, and it assumes that memory is laid out according
+/// to the operating system convention for starting a new program.
 #[cfg(feature = "origin-start")]
-naked_fn!(
-    "
-    The program entry point.
-
-    # Safety
-
-    This function must never be called explicitly. It is the first thing
-    executed in the program, and it assumes that memory is laid out according
-    to the operating system convention for starting a new program.
-    ";
-    pub(super) fn _start() -> !;
-
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+pub(super) unsafe extern "C" fn _start() -> ! {
     // Jump to `entry`, passing it the initial stack pointer value as an
     // argument, a null return address, a null frame pointer, and an aligned
     // stack pointer. On many architectures, the incoming frame pointer is
     // already null.
-    "mov r0, sp",   // Pass the incoming `sp` as the arg to `entry`.
-    "mov lr, #0",   // Set the return address to zero.
-    "b {entry}";    // Jump to `entry`.
-    entry = sym super::program::entry
-);
+    core::arch::naked_asm!(
+        "mov r0, sp",   // Pass the incoming `sp` as the arg to `entry`.
+        "mov lr, #0",   // Set the return address to zero.
+        "b {entry}",    // Jump to `entry`.
+        entry = sym super::program::entry
+    )
+}
 
 /// Execute a trap instruction.
 ///
@@ -314,42 +314,40 @@ pub(super) unsafe fn munmap_and_exit_thread(map_addr: *mut c_void, map_len: usiz
     }
 }
 
+/// Invoke the `__NR_rt_sigreturn` system call to return control from a signal
+/// handler.
+///
+/// # Safety
+///
+/// This function must never be called other than by the `sa_restorer`
+/// mechanism.
 #[cfg(feature = "take-charge")]
 #[cfg(feature = "signal")]
-naked_fn!(
-    "
-    Invoke the `__NR_rt_sigreturn` system call to return control from a signal
-    handler.
-
-    # Safety
-
-    This function must never be called other than by the `sa_restorer`
-    mechanism.
-    ";
-    pub(super) fn return_from_signal_handler() -> ();
-
-    "mov r7, {__NR_rt_sigreturn}",
-    "swi 0",
-    "udf #16";
-    __NR_rt_sigreturn = const __NR_rt_sigreturn
-);
+#[unsafe(naked)]
+pub(super) unsafe extern "C" fn return_from_signal_handler() {
+    core::arch::naked_asm!(
+        "mov r7, {__NR_rt_sigreturn}",
+        "swi 0",
+        "udf #16",
+        __NR_rt_sigreturn = const __NR_rt_sigreturn
+    )
+}
 
+/// Invoke the appropriate system call to return control from a signal
+/// handler that does not use `SA_SIGINFO`.
+///
+/// # Safety
+///
+/// This function must never be called other than by the `sa_restorer`
+/// mechanism.
 #[cfg(feature = "take-charge")]
 #[cfg(feature = "signal")]
-naked_fn!(
-    "
-    Invoke the appropriate system call to return control from a signal
-    handler that does not use `SA_SIGINFO`.
-
-    # Safety
-
-    This function must never be called other than by the `sa_restorer`
-    mechanism.
-    ";
-    pub(super) fn return_from_signal_handler_noinfo() -> ();
-
-    "mov r7, {__NR_sigreturn}",
-    "swi 0",
-    "udf #16";
-    __NR_sigreturn = const __NR_sigreturn
-);
+#[unsafe(naked)]
+pub(super) unsafe extern "C" fn return_from_signal_handler_noinfo() {
+    core::arch::naked_asm!(
+        "mov r7, {__NR_sigreturn}",
+        "swi 0",
+        "udf #16",
+        __NR_sigreturn = const __NR_sigreturn
+    )
+}

src/arch/riscv64.rs

@@ -19,29 +19,29 @@ use {
     rustix::thread::RawPid,
 };
 
+/// The program entry point.
+///
+/// # Safety
+///
+/// This function must never be called explicitly. It is the first thing
+/// executed in the program, and it assumes that memory is laid out according
+/// to the operating system convention for starting a new program.
 #[cfg(feature = "origin-start")]
-naked_fn!(
-    "
-    The program entry point.
-
-    # Safety
-
-    This function must never be called explicitly. It is the first thing
-    executed in the program, and it assumes that memory is laid out according
-    to the operating system convention for starting a new program.
-    ";
-    pub(super) fn _start() -> !;
-
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+pub(super) unsafe extern "C" fn _start() -> ! {
     // Jump to `entry`, passing it the initial stack pointer value as an
     // argument, a null return address, a null frame pointer, and an aligned
     // stack pointer. On many architectures, the incoming frame pointer is
     // already null.
-    "mv a0, sp",    // Pass the incoming `sp` as the arg to `entry`.
-    "mv ra, zero",  // Set the return address to zero.
-    "mv fp, zero",  // Set the frame address to zero.
-    "tail {entry}"; // Jump to `entry`.
-    entry = sym super::program::entry
-);
+    core::arch::naked_asm!(
+        "mv a0, sp",    // Pass the incoming `sp` as the arg to `entry`.
+        "mv ra, zero",  // Set the return address to zero.
+        "mv fp, zero",  // Set the frame address to zero.
+        "tail {entry}", // Jump to `entry`.
+        entry = sym super::program::entry
+    )
+}
 
 /// Execute a trap instruction.
 ///

src/arch/x86.rs

@@ -25,32 +25,32 @@ use {
     rustix::thread::RawPid,
 };
 
+/// The program entry point.
+///
+/// # Safety
+///
+/// This function must never be called explicitly. It is the first thing
+/// executed in the program, and it assumes that memory is laid out according
+/// to the operating system convention for starting a new program.
 #[cfg(feature = "origin-start")]
-naked_fn!(
-    "
-    The program entry point.
-
-    # Safety
-
-    This function must never be called explicitly. It is the first thing
-    executed in the program, and it assumes that memory is laid out according
-    to the operating system convention for starting a new program.
-    ";
-    pub(super) fn _start() -> !;
-
+#[unsafe(naked)]
+#[unsafe(no_mangle)]
+pub(super) unsafe extern "C" fn _start() -> ! {
     // Jump to `entry`, passing it the initial stack pointer value as an
     // argument, a null return address, a null frame pointer, and an aligned
     // stack pointer. On many architectures, the incoming frame pointer is
     // already null.
-    "mov eax, esp", // Save the incoming `esp` value.
-    "push ebp",     // Pad for stack pointer alignment.
-    "push ebp",     // Pad for stack pointer alignment.
-    "push ebp",     // Pad for stack pointer alignment.
-    "push eax",     // Pass saved the incoming `esp` as the arg to `entry`.
-    "push ebp",     // Set the return address to zero.
-    "jmp {entry}";  // Jump to `entry`.
-    entry = sym super::program::entry
-);
+    core::arch::naked_asm!(
+        "mov eax, esp", // Save the incoming `esp` value.
+        "push ebp",     // Pad for stack pointer alignment.
+        "push ebp",     // Pad for stack pointer alignment.
+        "push ebp",     // Pad for stack pointer alignment.
+        "push eax",     // Pass saved the incoming `esp` as the arg to `entry`.
+        "push ebp",     // Set the return address to zero.
+        "jmp {entry}",  // Jump to `entry`.
+        entry = sym super::program::entry
+    )
+}
 
 /// Execute a trap instruction.
 ///
@@ -398,43 +398,41 @@ pub(super) unsafe fn munmap_and_exit_thread(map_addr: *mut c_void, map_len: usiz
     }
 }
 
+/// Invoke the `__NR_rt_sigreturn` system call to return control from a signal
+/// handler.
+///
+/// # Safety
+///
+/// This function must never be called other than by the `sa_restorer`
+/// mechanism.
 #[cfg(feature = "take-charge")]
 #[cfg(feature = "signal")]
-naked_fn!(
-    "
-    Invoke the `__NR_rt_sigreturn` system call to return control from a signal
-    handler.
-
-    # Safety
-
-    This function must never be called other than by the `sa_restorer`
-    mechanism.
-    ";
-    pub(super) fn return_from_signal_handler() -> ();
-
-    "mov eax,  {__NR_rt_sigreturn}",
-    "int 0x80",
-    "ud2";
-    __NR_rt_sigreturn = const __NR_rt_sigreturn
-);
+#[unsafe(naked)]
+pub(super) unsafe extern "C" fn return_from_signal_handler() {
+    core::arch::naked_asm!(
+        "mov eax,  {__NR_rt_sigreturn}",
+        "int 0x80",
+        "ud2",
+        __NR_rt_sigreturn = const __NR_rt_sigreturn
+    )
+}
 
+/// Invoke the appropriate system call to return control from a signal
+/// handler that does not use `SA_SIGINFO`.
+///
+/// # Safety
+///
+/// This function must never be called other than by the `sa_restorer`
+/// mechanism.
 #[cfg(feature = "take-charge")]
 #[cfg(feature = "signal")]
-naked_fn!(
-    "
-    Invoke the appropriate system call to return control from a signal
-    handler that does not use `SA_SIGINFO`.
-
-    # Safety
-
-    This function must never be called other than by the `sa_restorer`
-    mechanism.
-    ";
-    pub(super) fn return_from_signal_handler_noinfo() -> ();
-
-    "pop eax",
-    "mov eax, {__NR_sigreturn}",
-    "int 0x80",
-    "ud2";
-    __NR_sigreturn = const __NR_sigreturn
-);
+#[unsafe(naked)]
+pub(super) unsafe extern "C" fn return_from_signal_handler_noinfo() {
+    core::arch::naked_asm!(
+        "pop eax",
+        "mov eax, {__NR_sigreturn}",
+        "int 0x80",
+        "ud2",
+        __NR_sigreturn = const __NR_sigreturn
+    )
+}