netbsd adding mcontext related data for riscv64

ref: https://github.com/NetBSD/src/blob/0465e5c825effb130eca95499f5ac6454fe0d5ab/sys/arch/riscv/include/mcontext.h#L44

src/unix/bsd/netbsdlike/netbsd/riscv64.rs

@@ -3,11 +3,77 @@ use PT_FIRSTMACH;
 pub type c_long = i64;
 pub type c_ulong = u64;
 pub type c_char = u8;
+pub type __greg_t = u64;
 pub type __cpu_simple_lock_nv_t = ::c_int;
+pub type __gregset = [__greg_t; _NGREG];
+pub type __fregset = [__freg; _NFREG];
+
+s! {
+    pub struct mcontext_t {
+        pub __gregs: __gregset,
+        pub __fregs: __fpregset,
+        __spare: [::__greg_t; 7],
+    }
+}
+
+s_no_extra_traits! {
+    #[cfg_attr(feature = "extra_traits", allow(missing_debug_implementations))]
+    pub union __fpreg {
+        pub u_u64: u64,
+        pub u_d: ::c_double,
+    }
+}
 
 pub(crate) const _ALIGNBYTES: usize = ::mem::size_of::<::c_long>() - 1;
 
 pub const PT_GETREGS: ::c_int = PT_FIRSTMACH + 0;
 pub const PT_SETREGS: ::c_int = PT_FIRSTMACH + 1;
 pub const PT_GETFPREGS: ::c_int = PT_FIRSTMACH + 2;
 pub const PT_SETFPREGS: ::c_int = PT_FIRSTMACH + 3;
+
+pub const _NGREG: usize = 32;
+pub const _NFREG: usize = 33;
+
+pub const _REG_X1: ::c_int = 0;
+pub const _REG_X2: ::c_int = 1;
+pub const _REG_X3: ::c_int = 2;
+pub const _REG_X4: ::c_int = 3;
+pub const _REG_X5: ::c_int = 4;
+pub const _REG_X6: ::c_int = 5;
+pub const _REG_X7: ::c_int = 6;
+pub const _REG_X8: ::c_int = 7;
+pub const _REG_X9: ::c_int = 8;
+pub const _REG_X10: ::c_int = 9;
+pub const _REG_X11: ::c_int = 10;
+pub const _REG_X12: ::c_int = 11;
+pub const _REG_X13: ::c_int = 12;
+pub const _REG_X14: ::c_int = 13;
+pub const _REG_X15: ::c_int = 14;
+pub const _REG_X16: ::c_int = 15;
+pub const _REG_X17: ::c_int = 16;
+pub const _REG_X18: ::c_int = 17;
+pub const _REG_X19: ::c_int = 18;
+pub const _REG_X20: ::c_int = 19;
+pub const _REG_X21: ::c_int = 20;
+pub const _REG_X22: ::c_int = 21;
+pub const _REG_X23: ::c_int = 22;
+pub const _REG_X24: ::c_int = 23;
+pub const _REG_X25: ::c_int = 24;
+pub const _REG_X26: ::c_int = 25;
+pub const _REG_X27: ::c_int = 26;
+pub const _REG_X28: ::c_int = 27;
+pub const _REG_X29: ::c_int = 28;
+pub const _REG_X30: ::c_int = 29;
+pub const _REG_X31: ::c_int = 30;
+pub const _REG_PC: ::c_int = 31;
+
+pub const _REG_RA: ::c_int = _REG_X1;
+pub const _REG_SP: ::c_int = _REG_X2;
+pub const _REG_GP: ::c_int = _REG_X3;
+pub const _REG_TP: ::c_int = _REG_X4;
+pub const _REG_S0: ::c_int = _REG_X8;
+pub const _REG_RV: ::c_int = _REG_X10;
+pub const _REG_A0: ::c_int = _REG_X10;
+
+pub const _REG_F0: ::c_int = 0;
+pub const _REG_FPCSR: ::c_int = 32;