FreeBSD support (#315)

Fix FreeBSD support

### Checklist
- [x] I've run tests to see all new and existing tests pass
- [x] I've followed the code style of the rest of the project
- [x] I've read the [Contribution Guidelines](CONTRIBUTING.md)
- [x] I've updated the documentation if necessary

### Motivation:
To add FreeBSD support to Swift, we must ensure that swift crypto builds
on FreeBSD since it's a dependency of swiftpm and several essential
packages.

### Modifications:
- `Package.swift` - Ideally FreeBSD should use `.when(platforms:)` to
set the corresponding swift settings and dependencies. However,
`Platform.freebsd` is not yet available on swiftpm and therefore use
guard the settings behind a `isFreeBSD` boolean flag. This is chosen
because it minimize the diff and maintains the maximum readability.
- `cmake/modules/SwiftSupport.cmake` - add `amd64` arch support, maps to
`x86_64`.
- `**/CMakeLists.txt` - Use the Linux assembly files for FreeBSD. Both
Linux and FreeBSD uses SysV ABI, and there're no syscalls involved
(after all, they're supposed to be "pure") so there are no ABI
compatibility problem. After all, all the tests are passing on FreeBSD
with this PR.

### Result:
All the tests (via `swift test`) passed on x86_64 FreeBSD 14.1-p6, and
passed on aarch64 macOS.

Test log available here:
[swift-test-result.txt](https://github.com/user-attachments/files/18147920/swift-test-result.txt)

Package.swift

@@ -27,9 +27,18 @@ import PackageDescription
 // To develop this on Apple platforms, set this to true
 let development = false
 
+// Ideally, we should use `.when(platforms:)` to set `swiftSettings` and
+// `dependencies` like on other platforms. However, `Platform.freebsd` is not
+// yet available, and therefore we guard the settings behind this boolean.
+#if os(FreeBSD)
+let isFreeBSD = true
+#else
+let isFreeBSD = false
+#endif
+
 let swiftSettings: [SwiftSetting]
 let dependencies: [Target.Dependency]
-if development {
+if development || isFreeBSD {
     swiftSettings = [
         .define("CRYPTO_IN_SWIFTPM"),
         .define("CRYPTO_IN_SWIFTPM_FORCE_BUILD_API"),
@@ -44,7 +53,7 @@ if development {
         Platform.linux,
         Platform.android,
         Platform.windows,
-        Platform.wasi,
+        Platform.wasi
     ]
     swiftSettings = [
         .define("CRYPTO_IN_SWIFTPM"),

Sources/CCryptoBoringSSL/CMakeLists.txt

@@ -276,7 +276,7 @@ if(CMAKE_SYSTEM_NAME STREQUAL Darwin AND CMAKE_SYSTEM_PROCESSOR MATCHES "amd64|x
     gen/crypto/chacha-x86_64-apple.S
     gen/crypto/chacha20_poly1305_x86_64-apple.S
     gen/crypto/md5-x86_64-apple.S)
-elseif(CMAKE_SYSTEM_NAME MATCHES "Linux|Android" AND CMAKE_SYSTEM_PROCESSOR MATCHES "amd64|x86_64")
+elseif(CMAKE_SYSTEM_NAME MATCHES "Linux|Android|FreeBSD" AND CMAKE_SYSTEM_PROCESSOR MATCHES "amd64|x86_64")
   target_sources(CCryptoBoringSSL PRIVATE
     gen/bcm/aes-gcm-avx10-x86_64-linux.S
     gen/bcm/aesni-gcm-x86_64-linux.S
@@ -313,7 +313,7 @@ elseif(CMAKE_SYSTEM_NAME STREQUAL Darwin AND CMAKE_SYSTEM_PROCESSOR MATCHES "arm
     gen/bcm/vpaes-armv8-apple.S
     gen/crypto/chacha-armv8-apple.S
     gen/crypto/chacha20_poly1305_armv8-apple.S)
-elseif(CMAKE_SYSTEM_NAME MATCHES "Linux|Android" AND CMAKE_SYSTEM_PROCESSOR MATCHES "arm64|aarch64")
+elseif(CMAKE_SYSTEM_NAME MATCHES "Linux|Android|FreeBSD" AND CMAKE_SYSTEM_PROCESSOR MATCHES "arm64|aarch64")
   target_sources(CCryptoBoringSSL PRIVATE
     gen/bcm/aesv8-armv8-linux.S
     gen/bcm/aesv8-gcm-armv8-linux.S

Sources/Crypto/CMakeLists.txt

@@ -96,7 +96,7 @@ add_library(Crypto
 target_compile_definitions(Crypto PRIVATE
   "$<$<COMPILE_LANGUAGE:Swift>:CRYPTO_IN_SWIFTPM>")
 
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Windows" OR CMAKE_SYSTEM_NAME STREQUAL "Android" OR CMAKE_SYSTEM_NAME STREQUAL "WASI")
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux" OR CMAKE_SYSTEM_NAME STREQUAL "Windows" OR CMAKE_SYSTEM_NAME STREQUAL "Android" OR CMAKE_SYSTEM_NAME STREQUAL "WASI" OR CMAKE_SYSTEM_NAME STREQUAL FreeBSD)
   target_compile_definitions(Crypto PRIVATE
     "$<$<COMPILE_LANGUAGE:Swift>:CRYPTO_IN_SWIFTPM_FORCE_BUILD_API>")
 endif()

Sources/CryptoBoringWrapper/Util/RandomBytes.swift

@@ -19,7 +19,7 @@ extension UnsafeMutableRawBufferPointer {
             return
         }
 
-        #if canImport(Darwin) || os(Linux) || os(Android) || os(Windows)
+        #if canImport(Darwin) || os(Linux) || os(Android) || os(Windows) || os(FreeBSD)
         var rng = SystemRandomNumberGenerator()
         precondition(count <= self.count)
 

Tests/CryptoTests/Encodings/DERTests.swift

@@ -49,7 +49,7 @@ class DERTests: XCTestCase {
     }
 
     func randomBytes(count: Int) -> [UInt8] {
-        #if canImport(Darwin) || os(Linux) || os(Android) || os(Windows)
+        #if canImport(Darwin) || os(Linux) || os(Android) || os(Windows) || os(FreeBSD)
         var rng = SystemRandomNumberGenerator()
         return (0..<count).map { _ in rng.next() }
         #else

cmake/modules/SwiftSupport.cmake

@@ -42,6 +42,8 @@ function(get_swift_host_arch result_var_name)
     set("${result_var_name}" "armv7" PARENT_SCOPE)
   elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "AMD64")
     set("${result_var_name}" "x86_64" PARENT_SCOPE)
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "amd64")
+    set("${result_var_name}" "x86_64" PARENT_SCOPE)
   elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "IA64")
     set("${result_var_name}" "itanium" PARENT_SCOPE)
   elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86")