Auto merge of #2355 - semarie:openbsd-sigcontext, r=JohnTitor

openbsd: export `struct sigcontext` for x86_64

based on initial work from `@devnexen` (see #2189)

tested on OpenBSD (7.0-beta) with rustc 1.54.0

libc-test/build.rs

@@ -387,6 +387,8 @@ fn test_openbsd(target: &str) {
     let mut cfg = ctest_cfg();
     cfg.flag("-Wno-deprecated-declarations");
 
+    let x86_64 = target.contains("x86_64");
+
     headers! { cfg:
         "elf.h",
         "errno.h",
@@ -405,6 +407,7 @@ fn test_openbsd(target: &str) {
         "ctype.h",
         "dirent.h",
         "sys/socket.h",
+        [x86_64]:"machine/fpu.h",
         "net/if.h",
         "net/route.h",
         "net/if_arp.h",

src/unix/bsd/netbsdlike/openbsd/x86_64.rs

@@ -3,6 +3,112 @@ use PT_FIRSTMACH;
 pub type c_long = i64;
 pub type c_ulong = u64;
 pub type c_char = i8;
+pub type ucontext_t = sigcontext;
+
+s! {
+    pub struct sigcontext {
+        pub sc_rdi: ::c_long,
+        pub sc_rsi: ::c_long,
+        pub sc_rdx: ::c_long,
+        pub sc_rcx: ::c_long,
+        pub sc_r8: ::c_long,
+        pub sc_r9: ::c_long,
+        pub sc_r10: ::c_long,
+        pub sc_r11: ::c_long,
+        pub sc_r12: ::c_long,
+        pub sc_r13: ::c_long,
+        pub sc_r14: ::c_long,
+        pub sc_r15: ::c_long,
+        pub sc_rbp: ::c_long,
+        pub sc_rbx: ::c_long,
+        pub sc_rax: ::c_long,
+        pub sc_gs: ::c_long,
+        pub sc_fs: ::c_long,
+        pub sc_es: ::c_long,
+        pub sc_ds: ::c_long,
+        pub sc_trapno: ::c_long,
+        pub sc_err: ::c_long,
+        pub sc_rip: ::c_long,
+        pub sc_cs: ::c_long,
+        pub sc_rflags: ::c_long,
+        pub sc_rsp: ::c_long,
+        pub sc_ss: ::c_long,
+        pub sc_fpstate: *mut fxsave64,
+        __sc_unused: ::c_int,
+        pub sc_mask: ::c_int,
+        pub sc_cookie: ::c_long,
+    }
+}
+
+s_no_extra_traits! {
+    #[repr(packed)]
+    pub struct fxsave64 {
+        pub fx_fcw: u16,
+        pub fx_fsw: u16,
+        pub fx_ftw: u8,
+        __fx_unused1: u8,
+        pub fx_fop: u16,
+        pub fx_rip: u64,
+        pub fx_rdp: u64,
+        pub fx_mxcsr: u32,
+        pub fx_mxcsr_mask: u32,
+        pub fx_st: [[u64; 2]; 8],
+        pub fx_xmm: [[u64; 2]; 16],
+        __fx_unused3: [u8; 96],
+    }
+}
+
+cfg_if! {
+    if #[cfg(feature = "extra_traits")] {
+        // `fxsave64` is packed, so field access is unaligned.
+        // use {x} to create temporary storage, copy field to it, and do aligned access.
+        impl PartialEq for fxsave64 {
+            fn eq(&self, other: &fxsave64) -> bool {
+                return {self.fx_fcw} == {other.fx_fcw} &&
+                    {self.fx_fsw} == {other.fx_fsw} &&
+                    {self.fx_ftw} == {other.fx_ftw} &&
+                    {self.fx_fop} == {other.fx_fop} &&
+                    {self.fx_rip} == {other.fx_rip} &&
+                    {self.fx_rdp} == {other.fx_rdp} &&
+                    {self.fx_mxcsr} == {other.fx_mxcsr} &&
+                    {self.fx_mxcsr_mask} == {other.fx_mxcsr_mask} &&
+                    {self.fx_st}.iter().zip({other.fx_st}.iter()).all(|(a,b)| a == b) &&
+                    {self.fx_xmm}.iter().zip({other.fx_xmm}.iter()).all(|(a,b)| a == b)
+            }
+        }
+        impl Eq for fxsave64 {}
+        impl ::fmt::Debug for fxsave64 {
+            fn fmt(&self, f: &mut ::fmt::Formatter) -> ::fmt::Result {
+                f.debug_struct("fxsave64")
+                    .field("fx_fcw", &{self.fx_fcw})
+                    .field("fx_fsw", &{self.fx_fsw})
+                    .field("fx_ftw", &{self.fx_ftw})
+                    .field("fx_fop", &{self.fx_fop})
+                    .field("fx_rip", &{self.fx_rip})
+                    .field("fx_rdp", &{self.fx_rdp})
+                    .field("fx_mxcsr", &{self.fx_mxcsr})
+                    .field("fx_mxcsr_mask", &{self.fx_mxcsr_mask})
+                    // FIXME: .field("fx_st", &{self.fx_st})
+                    // FIXME: .field("fx_xmm", &{self.fx_xmm})
+                    .finish()
+            }
+        }
+        impl ::hash::Hash for fxsave64 {
+            fn hash<H: ::hash::Hasher>(&self, state: &mut H) {
+                {self.fx_fcw}.hash(state);
+                {self.fx_fsw}.hash(state);
+                {self.fx_ftw}.hash(state);
+                {self.fx_fop}.hash(state);
+                {self.fx_rip}.hash(state);
+                {self.fx_rdp}.hash(state);
+                {self.fx_mxcsr}.hash(state);
+                {self.fx_mxcsr_mask}.hash(state);
+                {self.fx_st}.hash(state);
+                {self.fx_xmm}.hash(state);
+            }
+        }
+    }
+}
 
 // should be pub(crate), but that requires Rust 1.18.0
 cfg_if! {