core/stdarch/crates/core_arch/src/x86/
cpuid.rs

1//! `cpuid` intrinsics
2#![allow(clippy::module_name_repetitions)]
3
4use crate::arch::asm;
5#[cfg(test)]
6use stdarch_test::assert_instr;
7
8/// Result of the `cpuid` instruction.
9#[allow(clippy::missing_inline_in_public_items)]
10// ^^ the derived impl of Debug for CpuidResult is not #[inline] and that's OK.
11#[derive(Copy, Clone, Debug, Eq, Ord, PartialEq, PartialOrd)]
12#[stable(feature = "simd_x86", since = "1.27.0")]
13pub struct CpuidResult {
14    /// EAX register.
15    #[stable(feature = "simd_x86", since = "1.27.0")]
16    pub eax: u32,
17    /// EBX register.
18    #[stable(feature = "simd_x86", since = "1.27.0")]
19    pub ebx: u32,
20    /// ECX register.
21    #[stable(feature = "simd_x86", since = "1.27.0")]
22    pub ecx: u32,
23    /// EDX register.
24    #[stable(feature = "simd_x86", since = "1.27.0")]
25    pub edx: u32,
26}
27
28/// Returns the result of the `cpuid` instruction for a given `leaf` (`EAX`)
29/// and `sub_leaf` (`ECX`).
30///
31/// There are two types of information leaves - basic leaves (with `leaf < 0x8000000`)
32/// and extended leaves (with `leaf >= 0x80000000`). The highest supported basic and
33/// extended leaves can be obtained by calling CPUID with `0` and `0x80000000`,
34/// respectively, and reading the value in the `EAX` register. If the leaf supports
35/// more than one sub-leaf, then the procedure of obtaining the highest supported
36/// sub-leaf, as well as the behavior if a invalid sub-leaf value is passed, depends
37/// on the specific leaf.
38///
39/// If the `leaf` value is higher than the maximum supported basic or extended leaf
40/// for the processor, this returns the information for the highest supported basic
41/// information leaf (with the passed `sub_leaf` value). If the `leaf` value is less
42/// than or equal to the highest basic or extended leaf value, but the leaf is not
43/// supported on the processor, all zeros are returned.
44///
45/// The [CPUID Wikipedia page][wiki_cpuid] contains information on how to query which
46/// information using the `EAX` and `ECX` registers, and the interpretation of
47/// the results returned in `EAX`, `EBX`, `ECX`, and `EDX`.
48///
49/// The references are:
50/// - [Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2:
51///   Instruction Set Reference, A-Z][intel64_ref].
52/// - [AMD64 Architecture Programmer's Manual, Volume 3: General-Purpose and
53///   System Instructions][amd64_ref].
54///
55/// [wiki_cpuid]: https://en.wikipedia.org/wiki/CPUID
56/// [intel64_ref]: https://cdrdv2-public.intel.com/671110/325383-sdm-vol-2abcd.pdf
57/// [amd64_ref]: https://docs.amd.com/v/u/en-US/24594_3.37
58#[inline]
59#[cfg_attr(test, assert_instr(cpuid))]
60#[stable(feature = "simd_x86", since = "1.27.0")]
61pub fn __cpuid_count(leaf: u32, sub_leaf: u32) -> CpuidResult {
62    if cfg!(target_env = "sgx") {
63        panic!("`__cpuid` cannot be used in SGX");
64    }
65
66    let eax;
67    let ebx;
68    let ecx;
69    let edx;
70
71    // LLVM sometimes reserves `ebx` for its internal use, we so we need to use
72    // a scratch register for it instead.
73    #[cfg(target_arch = "x86")]
74    unsafe {
75        asm!(
76            "mov {0}, ebx",
77            "cpuid",
78            "xchg {0}, ebx",
79            out(reg) ebx,
80            inout("eax") leaf => eax,
81            inout("ecx") sub_leaf => ecx,
82            out("edx") edx,
83            options(nostack, preserves_flags),
84        );
85    }
86    #[cfg(target_arch = "x86_64")]
87    unsafe {
88        asm!(
89            "mov {0:r}, rbx",
90            "cpuid",
91            "xchg {0:r}, rbx",
92            out(reg) ebx,
93            inout("eax") leaf => eax,
94            inout("ecx") sub_leaf => ecx,
95            out("edx") edx,
96            options(nostack, preserves_flags),
97        );
98    }
99    CpuidResult { eax, ebx, ecx, edx }
100}
101
102/// Calls CPUID with the provided `leaf` value, with `sub_leaf` set to 0.
103/// See [`__cpuid_count`](fn.__cpuid_count.html).
104#[inline]
105#[cfg_attr(test, assert_instr(cpuid))]
106#[stable(feature = "simd_x86", since = "1.27.0")]
107pub fn __cpuid(leaf: u32) -> CpuidResult {
108    __cpuid_count(leaf, 0)
109}
110
111/// Returns the EAX and EBX register after calling CPUID with the provided `leaf`,
112/// with `sub_leaf` set to 0.
113///
114/// If `leaf` if 0 or `0x80000000`, the first tuple argument contains the maximum
115/// supported basic or extended leaf, respectively.
116///
117/// See also [`__cpuid`](fn.__cpuid.html) and
118/// [`__cpuid_count`](fn.__cpuid_count.html).
119#[inline]
120#[stable(feature = "simd_x86", since = "1.27.0")]
121pub fn __get_cpuid_max(leaf: u32) -> (u32, u32) {
122    let CpuidResult { eax, ebx, .. } = __cpuid(leaf);
123    (eax, ebx)
124}
core/stdarch/crates/core_arch/src/x86/cpuid.rs

core/stdarch/crates/core_arch/src/x86/
cpuid.rs
