Auto merge of #2788 - semio-ai:master, r=Amanieu

Complete i686-unknown-linux-musl ucontext_t #2787

Fix for #2787

src/unix/linux_like/linux/musl/b32/x86/mod.rs

@@ -1,5 +1,6 @@
 pub type c_char = i8;
 pub type wchar_t = i32;
+pub type greg_t = i32;
 
 s! {
     pub struct stat {
@@ -112,8 +113,28 @@ s! {
         pub f_spare: [::c_ulong; 4],
     }
 
+    pub struct _libc_fpreg {
+        pub significand: [u16; 4],
+        pub exponent: u16,
+    }
+
+    pub struct _libc_fpstate {
+        pub cw: ::c_ulong,
+        pub sw: ::c_ulong,
+        pub tag: ::c_ulong,
+        pub ipoff: ::c_ulong,
+        pub cssel: ::c_ulong,
+        pub dataoff: ::c_ulong,
+        pub datasel: ::c_ulong,
+        pub _st: [_libc_fpreg; 8],
+        pub status: ::c_ulong,
+    }
+
     pub struct mcontext_t {
-        __private: [u32; 22]
+        pub gregs: [greg_t; 19],
+        pub fpregs: *mut _libc_fpstate,
+        pub oldmask: ::c_ulong,
+        pub cr2: ::c_ulong,
     }
 
     pub struct siginfo_t {
@@ -876,6 +897,27 @@ pub const EFL: ::c_int = 14;
 pub const UESP: ::c_int = 15;
 pub const SS: ::c_int = 16;
 
+// offsets in mcontext_t.gregs from sys/ucontext.h
+pub const REG_GS: ::c_int = 0;
+pub const REG_FS: ::c_int = 1;
+pub const REG_ES: ::c_int = 2;
+pub const REG_DS: ::c_int = 3;
+pub const REG_EDI: ::c_int = 4;
+pub const REG_ESI: ::c_int = 5;
+pub const REG_EBP: ::c_int = 6;
+pub const REG_ESP: ::c_int = 7;
+pub const REG_EBX: ::c_int = 8;
+pub const REG_EDX: ::c_int = 9;
+pub const REG_ECX: ::c_int = 10;
+pub const REG_EAX: ::c_int = 11;
+pub const REG_TRAPNO: ::c_int = 12;
+pub const REG_ERR: ::c_int = 13;
+pub const REG_EIP: ::c_int = 14;
+pub const REG_CS: ::c_int = 15;
+pub const REG_EFL: ::c_int = 16;
+pub const REG_UESP: ::c_int = 17;
+pub const REG_SS: ::c_int = 18;
+
 extern "C" {
     pub fn getrandom(buf: *mut ::c_void, buflen: ::size_t, flags: ::c_uint) -> ::ssize_t;
 }