Fix warnings after updating rustc

Couple of features got stabilized, cpuid was made safe and there is a
new lint for function item to integer casts.

src/acpi/madt/arch/x86.rs

@@ -105,7 +105,7 @@ pub(super) fn init(madt: Madt) {
                     ap_args_ptr.write(&args as *const _ as u64);
                     ap_page_table.write(page_table_physaddr as u64);
                     #[expect(clippy::fn_to_numeric_cast)]
-                    ap_code.write(kstart_ap as u64);
+                    ap_code.write(kstart_ap as *const () as u64);
 
                     // TODO: Is this necessary (this fence)?
                     core::arch::asm!("");

src/arch/x86_64/interrupt/syscall.rs

@@ -27,7 +27,7 @@ pub unsafe fn init() {
 
         msr::wrmsr(msr::IA32_STAR, u64::from(star_high) << 32);
         #[expect(clippy::fn_to_numeric_cast)]
-        msr::wrmsr(msr::IA32_LSTAR, syscall_instruction as u64);
+        msr::wrmsr(msr::IA32_LSTAR, syscall_instruction as *const () as u64);
 
         // DF needs to be cleared, required by the compiler ABI. If DF were not part of FMASK,
         // userspace would be able to reverse the direction of in-kernel REP MOVS/STOS/(CMPS/SCAS), and

src/arch/x86_shared/cpuid.rs

@@ -4,9 +4,9 @@ pub fn cpuid() -> CpuId {
     // FIXME check for cpuid availability during early boot and error out if it doesn't exist.
     CpuId::with_cpuid_fn(|a, c| {
         #[cfg(target_arch = "x86")]
-        let result = unsafe { core::arch::x86::__cpuid_count(a, c) };
+        let result = core::arch::x86::__cpuid_count(a, c);
         #[cfg(target_arch = "x86_64")]
-        let result = unsafe { core::arch::x86_64::__cpuid_count(a, c) };
+        let result = core::arch::x86_64::__cpuid_count(a, c);
         CpuIdResult {
             eax: result.eax,
             ebx: result.ebx,

src/arch/x86_shared/device/tsc.rs

@@ -99,7 +99,7 @@ pub fn get_kvm_support() -> &'static Option<KvmSupport> {
     static KVM_SUPPORT: Once<Option<KvmSupport>> = Once::new();
 
     KVM_SUPPORT.call_once(|| {
-        let res = unsafe { __cpuid(0x4000_0000) };
+        let res = __cpuid(0x4000_0000);
         if [res.ebx, res.ecx, res.edx].map(u32::to_le_bytes) != [*b"KVMK", *b"VMKV", *b"M\0\0\0"] {
             return None;
         }
@@ -107,7 +107,7 @@ pub fn get_kvm_support() -> &'static Option<KvmSupport> {
         if max_leaf < 0x4000_0001 {
             return None;
         }
-        let res = unsafe { __cpuid(0x4000_0001) };
+        let res = __cpuid(0x4000_0001);
 
         let supp_feats = KvmFeatureBits::from_bits_retain(res.eax);
 

src/arch/x86_shared/idt.rs

@@ -196,14 +196,15 @@ fn init_generic(cpu_id: LogicalCpuId, idt: &mut Idt, backup_stack_end: usize) {
     current_idt[18].set_ist(BACKUP_IST);
 
     assert_eq!(
-        __generic_interrupts_end as usize - __generic_interrupts_start as usize,
+        __generic_interrupts_end as *const () as usize
+            - __generic_interrupts_start as *const () as usize,
         224 * 8
     );
 
     for i in 0..224 {
         current_idt[i + 32].set_func(unsafe {
             mem::transmute::<usize, unsafe extern "C" fn()>(
-                __generic_interrupts_start as usize + i * 8,
+                __generic_interrupts_start as *const () as usize + i * 8,
             )
         });
     }

src/context/arch/x86_64.rs

@@ -107,7 +107,7 @@ impl Context {
                 stack_top = stack_top.sub(size_of::<usize>());
                 stack_top
                     .cast::<usize>()
-                    .write(crate::arch::interrupt::syscall::enter_usermode as usize);
+                    .write(crate::arch::interrupt::syscall::enter_usermode as *const () as usize);
             }
 
             stack_top = stack_top.sub(size_of::<usize>());

src/main.rs

@@ -3,10 +3,8 @@
 //! The Redox OS Kernel is a microkernel that supports `x86_64` systems and
 //! provides Unix-like syscalls for primarily Rust applications
 
-#![feature(asm_cfg)] // Stabilized in 1.93
-#![feature(if_let_guard)]
 #![feature(int_roundings)]
-#![feature(iter_next_chunk)]
+#![cfg_attr(dtb, feature(iter_next_chunk))]
 #![feature(sync_unsafe_cell)]
 #![feature(btree_cursors)]
 #![cfg_attr(not(test), no_std)]

src/scheme/sys/mod.rs

@@ -113,7 +113,7 @@ impl KernelScheme for SysScheme {
     }
     fn kopenat(
         &self,
-        id: usize,
+        _id: usize,
         user_buf: StrOrBytes,
         _flags: usize,
         _fcntl_flags: u32,