Use config.toml instead of x86_* Cargo feature.

Cargo.toml

@@ -45,7 +45,7 @@ raw-cpuid = "10.2.0"
 x86 = { version = "0.47.0", default-features = false }
 
 [features]
-default = ["acpi", "multi_core", "graphical_debug", "serial_debug", "x86_smap"]
+default = ["acpi", "multi_core", "graphical_debug", "serial_debug"]
 acpi = []
 doc = []
 graphical_debug = []
@@ -58,12 +58,6 @@ serial_debug = []
 system76_ec_debug = []
 slab = ["slab_allocator"]
 
-# TODO: Either wait for LLVM 12 and use target_feature, or use another system for cpu features
-x86_fsgsbase = []
-
-# Enables SMAP if available, on x86_64. Ignored on other architectures.
-x86_smap = []
-
 [profile.dev]
 # Avoids having to define the eh_personality lang item and reduces kernel size
 panic = "abort"

src/arch/x86_64/gdt.rs

@@ -206,7 +206,7 @@ pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
         })
     });
 
-    if cfg!(feature = "x86_fsgsbase") {
+    if cfg!(cpu_feature_always = "fsgsbase") {
         assert!(cpu_supports_fsgsbase, "running kernel with features not supported by the current CPU");
 
         x86::controlregs::cr4_write(x86::controlregs::cr4() | x86::controlregs::Cr4::CR4_ENABLE_FSGSBASE);

src/arch/x86_64/misc.rs

@@ -23,7 +23,7 @@ pub unsafe fn init(cpu_id: LogicalCpuId) {
         // obvious reasons.
         x86::controlregs::cr4_write(x86::controlregs::cr4() | Cr4::CR4_ENABLE_SMEP);
     }
-    if has_ext_feat(|feat| feat.has_smap()) && cfg!(feature = "x86_smap") {
+    if has_ext_feat(|feat| feat.has_smap()) && cfg!(cpu_feature_always = "smap") {
         // SMAP (Supervisor-Mode Access Prevention) forbids the kernel from accessing any
         // userspace-accessible pages, with the necessary exception of RFLAGS.AC = 1. This limits
         // user-memory accesses to the UserSlice wrapper, so that no code outside of usercopy

src/arch/x86_64/mod.rs

@@ -64,7 +64,7 @@ pub mod flags {
 pub unsafe extern "C" fn arch_copy_to_user(dst: usize, src: usize, len: usize) -> u8 {
     // TODO: LFENCE (spectre_v1 mitigation)?
 
-    #[cfg(not(feature = "x86_smap"))]
+    #[cfg(cpu_feature_never = "smap")]
     core::arch::asm!("
         xor eax, eax
         mov rcx, rdx
@@ -72,7 +72,7 @@ pub unsafe extern "C" fn arch_copy_to_user(dst: usize, src: usize, len: usize) -
         ret
     ", options(noreturn));
 
-    #[cfg(feature = "x86_smap")]
+    #[cfg(cpu_feature_always = "smap")]
     core::arch::asm!("
         xor eax, eax
         mov rcx, rdx

src/arch/x86_64/start.rs

@@ -285,7 +285,7 @@ macro_rules! inner_pit_unmap(
     }
 );
 
-#[cfg(not(feature = "x86_fsgsbase"))]
+#[cfg(cpu_feature_never = "fsgsbase")]
 macro_rules! save_fsgsbase(
     () => {
         "
@@ -303,7 +303,7 @@ macro_rules! save_fsgsbase(
         "
     }
 );
-#[cfg(feature = "x86_fsgsbase")]
+#[cfg(cpu_feature_always = "fsgsbase")]
 macro_rules! save_fsgsbase(
     () => {
         "
@@ -314,7 +314,7 @@ macro_rules! save_fsgsbase(
     }
 );
 
-#[cfg(feature = "x86_fsgsbase")]
+#[cfg(cpu_feature_always = "fsgsbase")]
 macro_rules! restore_fsgsbase(
     () => {
         "
@@ -324,7 +324,7 @@ macro_rules! restore_fsgsbase(
     }
 );
 
-#[cfg(not(feature = "x86_fsgsbase"))]
+#[cfg(cpu_feature_never = "fsgsbase")]
 macro_rules! restore_fsgsbase(
     () => {
         "

src/context/arch/x86_64.rs

@@ -146,7 +146,7 @@ pub unsafe fn switch_to(prev: &mut super::Context, next: &mut super::Context) {
 
         // This is so much shorter in Rust!
 
-        if cfg!(feature = "x86_fsgsbase") {
+        if cfg!(cpu_feature_always = "fsgsbase") {
             prev.arch.fsbase = rdfsbase() as usize;
             wrfsbase(next.arch.fsbase as u64);
             swapgs();

src/scheme/proc.rs

@@ -421,14 +421,14 @@ impl ProcScheme {
     #[cfg(target_arch = "x86_64")]
     fn read_env_regs(&self, info: &Info) -> Result<EnvRegisters> {
         let (fsbase, gsbase) = if info.pid == context::context_id() {
-            #[cfg(not(feature = "x86_fsgsbase"))]
+            #[cfg(cpu_feature_never = "fsgsbase")]
             unsafe {
                 (
                     x86::msr::rdmsr(x86::msr::IA32_FS_BASE),
                     x86::msr::rdmsr(x86::msr::IA32_KERNEL_GSBASE),
                 )
             }
-            #[cfg(feature = "x86_fsgsbase")]
+            #[cfg(cpu_feature_always = "fsgsbase")]
             unsafe {
                 use x86::bits64::segmentation::*;
 
@@ -504,7 +504,7 @@ impl ProcScheme {
         }
 
         if info.pid == context::context_id() {
-            #[cfg(not(feature = "x86_fsgsbase"))]
+            #[cfg(cpu_feature_never = "fsgsbase")]
             unsafe {
                 x86::msr::wrmsr(x86::msr::IA32_FS_BASE, regs.fsbase as u64);
                 // We have to write to KERNEL_GSBASE, because when the kernel returns to
@@ -518,7 +518,7 @@ impl ProcScheme {
                     }
                 }
             }
-            #[cfg(feature = "x86_fsgsbase")]
+            #[cfg(cpu_feature_always = "fsgsbase")]
             unsafe {
                 use x86::bits64::segmentation::*;