From ebcbcc8b73cb6fa8aad42e258ca0382db68e7876 Mon Sep 17 00:00:00 2001
From: Cathal Mullan <contact@cathal.dev>
Date: Wed, 13 Aug 2025 13:18:06 +0100
Subject: [PATCH] bootstrap: Fix jemalloc 64K page support for aarch64 tools

---
 src/bootstrap/src/core/build_steps/compile.rs | 1 +
 src/bootstrap/src/core/build_steps/tool.rs    | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/src/bootstrap/src/core/build_steps/compile.rs b/src/bootstrap/src/core/build_steps/compile.rs
index 4519731ada7f3..edd9492225a98 100644
--- a/src/bootstrap/src/core/build_steps/compile.rs
+++ b/src/bootstrap/src/core/build_steps/compile.rs
@@ -1391,6 +1391,7 @@ pub fn rustc_cargo_env(builder: &Builder<'_>, cargo: &mut Cargo, target: TargetS
 
     // Build jemalloc on AArch64 with support for page sizes up to 64K
     // See: https://github.com/rust-lang/rust/pull/135081
+    // See also the "JEMALLOC_SYS_WITH_LG_PAGE" setting in the tool build step.
     if builder.config.jemalloc(target)
         && target.starts_with("aarch64")
         && env::var_os("JEMALLOC_SYS_WITH_LG_PAGE").is_none()
diff --git a/src/bootstrap/src/core/build_steps/tool.rs b/src/bootstrap/src/core/build_steps/tool.rs
index aa00cd03c5bb7..0c263120eeec9 100644
--- a/src/bootstrap/src/core/build_steps/tool.rs
+++ b/src/bootstrap/src/core/build_steps/tool.rs
@@ -257,6 +257,14 @@ pub fn prepare_tool_cargo(
     // own copy
     cargo.env("LZMA_API_STATIC", "1");
 
+    // Build jemalloc on AArch64 with support for page sizes up to 64K
+    // See: https://github.com/rust-lang/rust/pull/135081
+    // Note that `miri` always uses jemalloc. As such, there is no checking of the jemalloc build flag.
+    // See also the "JEMALLOC_SYS_WITH_LG_PAGE" setting in the compile build step.
+    if target.starts_with("aarch64") && env::var_os("JEMALLOC_SYS_WITH_LG_PAGE").is_none() {
+        cargo.env("JEMALLOC_SYS_WITH_LG_PAGE", "16");
+    }
+
     // CFG_RELEASE is needed by rustfmt (and possibly other tools) which
     // import rustc-ap-rustc_attr which requires this to be set for the
     // `#[cfg(version(...))]` attribute.