3 files changed, 38 insertions, 7 deletions
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index 3c1249f8de4..7698ff62880 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -10,6 +10,7 @@ use std::ffi::OsString;
 use std::fmt;
 use std::fs;
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 
 use crate::cache::{Interned, INTERNER};
 use crate::flags::Flags;
@@ -65,7 +66,7 @@ pub struct Config {
     pub rustc_error_format: Option<String>,
     pub json_output: bool,
     pub test_compare_mode: bool,
-    pub llvm_libunwind: bool,
+    pub llvm_libunwind: Option<LlvmLibunwind>,
 
     pub on_fail: Option<String>,
     pub stage: u32,
@@ -177,6 +178,32 @@ pub struct Config {
     pub out: PathBuf,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum LlvmLibunwind {
+    No,
+    InTree,
+    System,
+}
+
+impl Default for LlvmLibunwind {
+    fn default() -> Self {
+        Self::No
+    }
+}
+
+impl FromStr for LlvmLibunwind {
+    type Err = String;
+
+    fn from_str(value: &str) -> Result<Self, Self::Err> {
+        match value {
+            "no" => Ok(Self::No),
+            "in-tree" => Ok(Self::InTree),
+            "system" => Ok(Self::System),
+            invalid => Err(format!("Invalid value '{}' for rust.llvm-libunwind config.", invalid)),
+        }
+    }
+}
+
 #[derive(Debug, Copy, Clone, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct TargetSelection {
     pub triple: Interned<String>,
@@ -457,7 +484,7 @@ struct Rust {
     remap_debuginfo: Option<bool>,
     jemalloc: Option<bool>,
     test_compare_mode: Option<bool>,
-    llvm_libunwind: Option<bool>,
+    llvm_libunwind: Option<String>,
     control_flow_guard: Option<bool>,
     new_symbol_mangling: Option<bool>,
 }
@@ -799,7 +826,9 @@ impl Config {
             set(&mut config.rust_rpath, rust.rpath);
             set(&mut config.jemalloc, rust.jemalloc);
             set(&mut config.test_compare_mode, rust.test_compare_mode);
-            set(&mut config.llvm_libunwind, rust.llvm_libunwind);
+            config.llvm_libunwind = rust
+                .llvm_libunwind
+                .map(|v| v.parse().expect("failed to parse rust.llvm-libunwind"));
             set(&mut config.backtrace, rust.backtrace);
             set(&mut config.channel, rust.channel);
             set(&mut config.rust_dist_src, rust.dist_src);
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index 47673ce1e87..e156952d56f 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -65,7 +65,7 @@ v("llvm-cflags", "llvm.cflags", "build LLVM with these extra compiler flags")
 v("llvm-cxxflags", "llvm.cxxflags", "build LLVM with these extra compiler flags")
 v("llvm-ldflags", "llvm.ldflags", "build LLVM with these extra linker flags")
 
-o("llvm-libunwind", "rust.llvm-libunwind", "use LLVM libunwind")
+v("llvm-libunwind", "rust.llvm-libunwind", "use LLVM libunwind")
 
 # Optimization and debugging options. These may be overridden by the release
 # channel, etc.
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 6880f6e816a..593d1c4ae88 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -121,7 +121,7 @@ use std::os::windows::fs::symlink_file;
 use build_helper::{mtime, output, run, run_suppressed, t, try_run, try_run_suppressed};
 use filetime::FileTime;
 
-use crate::config::TargetSelection;
+use crate::config::{LlvmLibunwind, TargetSelection};
 use crate::util::{exe, libdir, CiEnv};
 
 mod builder;
@@ -540,8 +540,10 @@ impl Build {
     fn std_features(&self) -> String {
         let mut features = "panic-unwind".to_string();
 
-        if self.config.llvm_libunwind {
-            features.push_str(" llvm-libunwind");
+        match self.config.llvm_libunwind.unwrap_or_default() {
+            LlvmLibunwind::InTree => features.push_str(" llvm-libunwind"),
+            LlvmLibunwind::System => features.push_str(" system-llvm-libunwind"),
+            LlvmLibunwind::No => {}
         }
         if self.config.backtrace {
             features.push_str(" backtrace");