1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
// Copyright 2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

/// A witness indicating that CPU features have been detected and cached.
///
/// TODO: Eventually all feature detection logic should be done through
/// functions that accept a `Features` parameter, to guarantee that nothing
/// tries to read the cached values before they are written.
///
/// This is a zero-sized type so that it can be "stored" wherever convenient.
#[derive(Copy, Clone)]
pub(crate) struct Features(());

#[inline(always)]
pub(crate) fn features() -> Features {
    // We don't do runtime feature detection on aarch64-apple-* as all AAarch64
    // features we use are available on every device since the first devices.
    #[cfg(any(
        target_arch = "x86",
        target_arch = "x86_64",
        all(
            any(target_arch = "aarch64", target_arch = "arm"),
            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
        )
    ))]
    {
        static INIT: spin::Once<()> = spin::Once::new();
        let () = INIT.call_once(|| {
            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
            {
                extern "C" {
                    fn GFp_cpuid_setup();
                }
                unsafe {
                    GFp_cpuid_setup();
                }
            }

            #[cfg(all(
                any(target_arch = "aarch64", target_arch = "arm"),
                any(target_os = "android", target_os = "fuchsia", target_os = "linux")
            ))]
            {
                arm::setup();
            }
        });
    }

    Features(())
}

pub(crate) mod arm {
    #[cfg(all(
        any(target_os = "android", target_os = "linux"),
        any(target_arch = "aarch64", target_arch = "arm")
    ))]
    pub fn setup() {
        use libc::c_ulong;

        // XXX: The `libc` crate doesn't provide `libc::getauxval` consistently
        // across all Android/Linux targets, e.g. musl.
        extern "C" {
            fn getauxval(type_: c_ulong) -> c_ulong;
        }

        const AT_HWCAP: c_ulong = 16;

        #[cfg(target_arch = "aarch64")]
        const HWCAP_NEON: c_ulong = 1 << 1;

        #[cfg(target_arch = "arm")]
        const HWCAP_NEON: c_ulong = 1 << 12;

        let caps = unsafe { getauxval(AT_HWCAP) };

        // We assume NEON is available on AARCH64 because it is a required
        // feature.
        #[cfg(target_arch = "aarch64")]
        debug_assert!(caps & HWCAP_NEON == HWCAP_NEON);

        // OpenSSL and BoringSSL don't enable any other features if NEON isn't
        // available.
        if caps & HWCAP_NEON == HWCAP_NEON {
            let mut features = NEON.mask;

            #[cfg(target_arch = "aarch64")]
            const OFFSET: c_ulong = 3;

            #[cfg(target_arch = "arm")]
            const OFFSET: c_ulong = 0;

            #[cfg(target_arch = "arm")]
            let caps = {
                const AT_HWCAP2: c_ulong = 26;
                unsafe { getauxval(AT_HWCAP2) }
            };

            const HWCAP_AES: c_ulong = 1 << 0 + OFFSET;
            const HWCAP_PMULL: c_ulong = 1 << 1 + OFFSET;
            const HWCAP_SHA2: c_ulong = 1 << 3 + OFFSET;

            if caps & HWCAP_AES == HWCAP_AES {
                features |= AES.mask;
            }
            if caps & HWCAP_PMULL == HWCAP_PMULL {
                features |= PMULL.mask;
            }
            if caps & HWCAP_SHA2 == HWCAP_SHA2 {
                features |= SHA256.mask;
            }

            unsafe { GFp_armcap_P = features };
        }
    }

    #[cfg(all(target_os = "fuchsia", target_arch = "aarch64"))]
    pub fn setup() {
        type zx_status_t = i32;

        #[link(name = "zircon")]
        extern "C" {
            fn zx_system_get_features(kind: u32, features: *mut u32) -> zx_status_t;
        }

        const ZX_OK: i32 = 0;
        const ZX_FEATURE_KIND_CPU: u32 = 0;
        const ZX_ARM64_FEATURE_ISA_ASIMD: u32 = 1 << 2;
        const ZX_ARM64_FEATURE_ISA_AES: u32 = 1 << 3;
        const ZX_ARM64_FEATURE_ISA_PMULL: u32 = 1 << 4;
        const ZX_ARM64_FEATURE_ISA_SHA2: u32 = 1 << 6;

        let mut caps = 0;
        let rc = unsafe { zx_system_get_features(ZX_FEATURE_KIND_CPU, &mut caps) };

        // OpenSSL and BoringSSL don't enable any other features if NEON isn't
        // available.
        if rc == ZX_OK && (caps & ZX_ARM64_FEATURE_ISA_ASIMD == ZX_ARM64_FEATURE_ISA_ASIMD) {
            let mut features = NEON.mask;

            if caps & ZX_ARM64_FEATURE_ISA_AES == ZX_ARM64_FEATURE_ISA_AES {
                features |= AES.mask;
            }
            if caps & ZX_ARM64_FEATURE_ISA_PMULL == ZX_ARM64_FEATURE_ISA_PMULL {
                features |= PMULL.mask;
            }
            if caps & ZX_ARM64_FEATURE_ISA_SHA2 == ZX_ARM64_FEATURE_ISA_SHA2 {
                features |= 1 << 4;
            }

            unsafe { GFp_armcap_P = features };
        }
    }

    macro_rules! features {
        {
            $(
                $name:ident {
                    mask: $mask:expr,

                    /// Should we assume that the feature is always available
                    /// for aarch64-apple-* targets? The first AArch64 iOS
                    /// device used the Apple A7 chip.
                    // TODO: When we can use `if` in const expressions:
                    // ```
                    // aarch64_apple: $aarch64_apple,
                    // ```
                    aarch64_apple: true,
                }
            ),+
            , // trailing comma is required.
        } => {
            $(
                #[allow(dead_code)]
                pub(crate) const $name: Feature = Feature {
                    mask: $mask,
                };
            )+

            // TODO: When we can use `if` in const expressions, do this:
            // ```
            // const ARMCAP_STATIC: u32 = 0
            //    $(
            //        | ( if $aarch64_apple &&
            //               cfg!(all(target_arch = "aarch64",
            //                        target_vendor = "apple")) {
            //                $name.mask
            //            } else {
            //                0
            //            }
            //          )
            //    )+;
            // ```
            //
            // TODO: Add static feature detection to other targets.
            // TODO: Combine static feature detection with runtime feature
            //       detection.
            #[cfg(all(target_arch = "aarch64", target_vendor = "apple"))]
            const ARMCAP_STATIC: u32 = 0
                $(  | $name.mask
                )+;
            #[cfg(not(all(target_arch = "aarch64", target_vendor = "apple")))]
            const ARMCAP_STATIC: u32 = 0;

            #[cfg(all(target_arch = "aarch64", target_vendor = "apple"))]
            #[test]
            fn test_armcap_static_available() {
                let features = crate::cpu::features();
                $(
                    assert!($name.available(features));
                )+
            }
        }
    }

    #[allow(dead_code)]
    pub(crate) struct Feature {
        mask: u32,
    }

    impl Feature {
        #[allow(dead_code)]
        #[inline(always)]
        pub fn available(&self, _: super::Features) -> bool {
            if self.mask == self.mask & ARMCAP_STATIC {
                return true;
            }

            #[cfg(all(
                any(target_os = "android", target_os = "fuchsia", target_os = "linux"),
                any(target_arch = "arm", target_arch = "aarch64")
            ))]
            {
                if self.mask == self.mask & unsafe { GFp_armcap_P } {
                    return true;
                }
            }

            false
        }
    }

    features! {
        // Keep in sync with `ARMV7_NEON`.
        NEON {
            mask: 1 << 0,
            aarch64_apple: true,
        },

        // Keep in sync with `ARMV8_AES`.
        AES {
            mask: 1 << 2,
            aarch64_apple: true,
        },

        // Keep in sync with `ARMV8_SHA256`.
        SHA256 {
            mask: 1 << 4,
            aarch64_apple: true,
        },

        // Keep in sync with `ARMV8_PMULL`.
        PMULL {
            mask: 1 << 5,
            aarch64_apple: true,
        },
    }

    // Some non-Rust code still checks this even when it is statically known
    // the given feature is available, so we have to ensure that this is
    // initialized properly. Keep this in sync with the initialization in
    // BoringSSL's crypto.c.
    //
    // TODO: This should have "hidden" visibility but we don't have a way of
    // controlling that yet: https://github.com/rust-lang/rust/issues/73958.
    #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
    #[no_mangle]
    static mut GFp_armcap_P: u32 = ARMCAP_STATIC;

    #[cfg(all(
        any(target_arch = "arm", target_arch = "aarch64"),
        target_vendor = "apple"
    ))]
    #[test]
    fn test_armcap_static_matches_armcap_dynamic() {
        assert_eq!(ARMCAP_STATIC, 1 | 4 | 16 | 32);
        assert_eq!(ARMCAP_STATIC, unsafe { GFp_armcap_P });
    }
}

#[cfg_attr(
    not(any(target_arch = "x86", target_arch = "x86_64")),
    allow(dead_code)
)]
pub(crate) mod intel {
    pub(crate) struct Feature {
        word: usize,
        mask: u32,
    }

    impl Feature {
        #[allow(clippy::needless_return)]
        #[inline(always)]
        pub fn available(&self, _: super::Features) -> bool {
            #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
            {
                extern "C" {
                    static mut GFp_ia32cap_P: [u32; 4];
                }
                return self.mask == self.mask & unsafe { GFp_ia32cap_P[self.word] };
            }

            #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
            {
                return false;
            }
        }
    }

    pub(crate) const FXSR: Feature = Feature {
        word: 0,
        mask: 1 << 24,
    };

    pub(crate) const PCLMULQDQ: Feature = Feature {
        word: 1,
        mask: 1 << 1,
    };

    pub(crate) const SSSE3: Feature = Feature {
        word: 1,
        mask: 1 << 9,
    };

    #[cfg(target_arch = "x86_64")]
    pub(crate) const SSE41: Feature = Feature {
        word: 1,
        mask: 1 << 19,
    };

    #[cfg(target_arch = "x86_64")]
    pub(crate) const MOVBE: Feature = Feature {
        word: 1,
        mask: 1 << 22,
    };

    pub(crate) const AES: Feature = Feature {
        word: 1,
        mask: 1 << 25,
    };

    #[cfg(target_arch = "x86_64")]
    pub(crate) const AVX: Feature = Feature {
        word: 1,
        mask: 1 << 28,
    };

    #[cfg(all(target_arch = "x86_64", test))]
    mod x86_64_tests {
        use super::*;

        #[test]
        fn test_avx_movbe_mask() {
            // This is the OpenSSL style of testing these bits.
            assert_eq!((AVX.mask | MOVBE.mask) >> 22, 0x41);
        }
    }
}