Auto merge of #38401 - redox-os:redox_cross, r=brson

Redox Cross Compilation

I will admit - there are things here that I wish I did not have to do. This completes the ability to create a cross compiler from the rust repository for `x86_64-unknown-redox`. I will document this PR with inline comments explaining some things.

[View this gist to see how a cross compiler is built](https://gist.github.com/jackpot51/6680ad973986e84d69c79854249f2b7e)

Prior discussion of a smaller change is here: https://github.com/rust-lang/rust/pull/38366

15 files changed, 95 insertions, 0 deletions

diff --git a/src/librustc_back/target/apple_base.rs b/src/librustc_back/target/apple_base.rs
index 70c7ea99e13..21a2d4293df 100644
--- a/src/librustc_back/target/apple_base.rs
+++ b/src/librustc_back/target/apple_base.rs
@@ -37,6 +37,7 @@ pub fn opts() -> TargetOptions {
         function_sections: false,
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         is_like_osx: true,
         has_rpath: true,
         dll_prefix: "lib".to_string(),
diff --git a/src/librustc_back/target/bitrig_base.rs b/src/librustc_back/target/bitrig_base.rs
index 7baf80066b2..62418e68d43 100644
--- a/src/librustc_back/target/bitrig_base.rs
+++ b/src/librustc_back/target/bitrig_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         position_independent_executables: true,
diff --git a/src/librustc_back/target/dragonfly_base.rs b/src/librustc_back/target/dragonfly_base.rs
index 7555181a15c..dca33e45af7 100644
--- a/src/librustc_back/target/dragonfly_base.rs
+++ b/src/librustc_back/target/dragonfly_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/freebsd_base.rs b/src/librustc_back/target/freebsd_base.rs
index 7555181a15c..dca33e45af7 100644
--- a/src/librustc_back/target/freebsd_base.rs
+++ b/src/librustc_back/target/freebsd_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/fuchsia_base.rs b/src/librustc_back/target/fuchsia_base.rs
index 69546684cb7..8c517224201 100644
--- a/src/librustc_back/target/fuchsia_base.rs
+++ b/src/librustc_back/target/fuchsia_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/haiku_base.rs b/src/librustc_back/target/haiku_base.rs
index 5e319ba1838..bfdc9faaa8a 100644
--- a/src/librustc_back/target/haiku_base.rs
+++ b/src/librustc_back/target/haiku_base.rs
@@ -17,6 +17,7 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         has_rpath: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         .. Default::default()
     }
diff --git a/src/librustc_back/target/linux_base.rs b/src/librustc_back/target/linux_base.rs
index d1ab71e4140..4b2ae9c8e69 100644
--- a/src/librustc_back/target/linux_base.rs
+++ b/src/librustc_back/target/linux_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/mod.rs b/src/librustc_back/target/mod.rs
index 13333be66f5..8c37eb6986a 100644
--- a/src/librustc_back/target/mod.rs
+++ b/src/librustc_back/target/mod.rs
@@ -69,6 +69,7 @@ mod windows_base;
 mod windows_msvc_base;
 mod thumb_base;
 mod fuchsia_base;
+mod redox_base;
 
 pub type TargetResult = Result<Target, String>;
 
@@ -184,6 +185,8 @@ supported_targets! {
     ("aarch64-unknown-fuchsia", aarch64_unknown_fuchsia),
     ("x86_64-unknown-fuchsia", x86_64_unknown_fuchsia),
 
+    ("x86_64-unknown-redox", x86_64_unknown_redox),
+
     ("i386-apple-ios", i386_apple_ios),
     ("x86_64-apple-ios", x86_64_apple_ios),
     ("aarch64-apple-ios", aarch64_apple_ios),
diff --git a/src/librustc_back/target/netbsd_base.rs b/src/librustc_back/target/netbsd_base.rs
index 6e038a7ed56..57179a68afd 100644
--- a/src/librustc_back/target/netbsd_base.rs
+++ b/src/librustc_back/target/netbsd_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/openbsd_base.rs b/src/librustc_back/target/openbsd_base.rs
index 1f74170e399..12b8e8bdc88 100644
--- a/src/librustc_back/target/openbsd_base.rs
+++ b/src/librustc_back/target/openbsd_base.rs
@@ -15,6 +15,7 @@ pub fn opts() -> TargetOptions {
     TargetOptions {
         dynamic_linking: true,
         executables: true,
+        target_family: Some("unix".to_string()),
         linker_is_gnu: true,
         has_rpath: true,
         is_like_openbsd: true,
diff --git a/src/librustc_back/target/redox_base.rs b/src/librustc_back/target/redox_base.rs
new file mode 100644
index 00000000000..1dffff59809
--- /dev/null
+++ b/src/librustc_back/target/redox_base.rs
@@ -0,0 +1,50 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use PanicStrategy;
+use target::TargetOptions;
+use std::default::Default;
+
+pub fn opts() -> TargetOptions {
+    TargetOptions {
+        pre_link_args: vec![
+            // We want to be able to strip as much executable code as possible
+            // from the linker command line, and this flag indicates to the
+            // linker that it can avoid linking in dynamic libraries that don't
+            // actually satisfy any symbols up to that point (as with many other
+            // resolutions the linker does). This option only applies to all
+            // following libraries so we're sure to pass it as one of the first
+            // arguments.
+            "-Wl,--as-needed".to_string(),
+
+            // Always enable NX protection when it is available
+            "-Wl,-z,noexecstack".to_string(),
+
+            // Static link
+            "-static".to_string()
+        ],
+        late_link_args: vec![
+            "-lc".to_string(),
+            "-lm".to_string()
+        ],
+        executables: true,
+        relocation_model: "static".to_string(),
+        disable_redzone: true,
+        eliminate_frame_pointer: false,
+        target_family: None,
+        linker_is_gnu: true,
+        no_default_libraries: true,
+        lib_allocation_crate: "alloc_system".to_string(),
+        exe_allocation_crate: "alloc_system".to_string(),
+        has_elf_tls: true,
+        panic_strategy: PanicStrategy::Abort,
+        .. Default::default()
+    }
+}
diff --git a/src/librustc_back/target/solaris_base.rs b/src/librustc_back/target/solaris_base.rs
index a7af0462e57..41323c9c26b 100644
--- a/src/librustc_back/target/solaris_base.rs
+++ b/src/librustc_back/target/solaris_base.rs
@@ -16,6 +16,7 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         has_rpath: true,
+        target_family: Some("unix".to_string()),
         is_like_solaris: true,
         exe_allocation_crate: super::maybe_jemalloc(),
 
diff --git a/src/librustc_back/target/windows_base.rs b/src/librustc_back/target/windows_base.rs
index 19ca0df51b9..db02e142fcc 100644
--- a/src/librustc_back/target/windows_base.rs
+++ b/src/librustc_back/target/windows_base.rs
@@ -24,6 +24,7 @@ pub fn opts() -> TargetOptions {
         staticlib_prefix: "".to_string(),
         staticlib_suffix: ".lib".to_string(),
         no_default_libraries: true,
+        target_family: Some("windows".to_string()),
         is_like_windows: true,
         allows_weak_linkage: false,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/windows_msvc_base.rs b/src/librustc_back/target/windows_msvc_base.rs
index 84e22e84fdb..efa215b419d 100644
--- a/src/librustc_back/target/windows_msvc_base.rs
+++ b/src/librustc_back/target/windows_msvc_base.rs
@@ -53,6 +53,7 @@ pub fn opts() -> TargetOptions {
         exe_suffix: ".exe".to_string(),
         staticlib_prefix: "".to_string(),
         staticlib_suffix: ".lib".to_string(),
+        target_family: Some("windows".to_string()),
         is_like_windows: true,
         is_like_msvc: true,
         pre_link_args: vec![
diff --git a/src/librustc_back/target/x86_64_unknown_redox.rs b/src/librustc_back/target/x86_64_unknown_redox.rs
new file mode 100644
index 00000000000..cecac06b235
--- /dev/null
+++ b/src/librustc_back/target/x86_64_unknown_redox.rs
@@ -0,0 +1,30 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use target::{Target, TargetResult};
+
+pub fn target() -> TargetResult {
+    let mut base = super::redox_base::opts();
+    base.cpu = "x86-64".to_string();
+    base.max_atomic_width = Some(64);
+    base.pre_link_args.push("-m64".to_string());
+
+    Ok(Target {
+        llvm_target: "x86_64-unknown-redox".to_string(),
+        target_endian: "little".to_string(),
+        target_pointer_width: "64".to_string(),
+        data_layout: "e-m:e-i64:64-f80:128-n8:16:32:64-S128".to_string(),
+        arch: "x86_64".to_string(),
+        target_os: "redox".to_string(),
+        target_env: "".to_string(),
+        target_vendor: "unknown".to_string(),
+        options: base,
+    })
+}