diff --git a/Cargo.lock b/Cargo.lock
index 80acf227698..b5a6c942079 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1915,9 +1915,8 @@ checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
 
 [[package]]
 name = "libc"
-version = "0.2.99"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a7f823d141fe0a24df1e23b4af4e3c7ba9e5966ec514ea068c93024aa7deb765"
+version = "0.2.101"
+source = "git+file:///Users/Jess/Git/rust-crate-libc/.git?rev=0b6604ff2c8e5555782c3b2c5c3b488bf8394ab3#0b6604ff2c8e5555782c3b2c5c3b488bf8394ab3"
 dependencies = [
  "rustc-std-workspace-core",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 3822da2ccd5..ff94189337e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -113,5 +113,7 @@ rustc-std-workspace-core = { path = 'library/rustc-std-workspace-core' }
 rustc-std-workspace-alloc = { path = 'library/rustc-std-workspace-alloc' }
 rustc-std-workspace-std = { path = 'library/rustc-std-workspace-std' }
 
+libc = { git = "file:///Users/Jess/Git/rust-crate-libc/.git", rev = "0b6604ff2c8e5555782c3b2c5c3b488bf8394ab3" }
+
 [patch."https://github.com/rust-lang/rust-clippy"]
 clippy_lints = { path = "src/tools/clippy/clippy_lints" }
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index 964b7cace9c..d7f14b72f46 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -275,8 +275,10 @@ fn main() {
         "stdc++"
     };
 
-    // RISC-V requires libatomic for sub-word atomic operations
-    if target.starts_with("riscv") {
+    // RISC-V GCC erroneously requires libatomic for sub-word atomic operations.
+    // FreeBSD uses Clang as its system compiler and provides no libatomic in
+    // its base system so does not want this.
+    if target.starts_with("riscv") && !target.contains("freebsd") {
         println!("cargo:rustc-link-lib=atomic");
     }
 
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 273221360b8..e65d2ea6961 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -805,6 +805,7 @@ fn $module() {
     ("powerpc-unknown-freebsd", powerpc_unknown_freebsd),
     ("powerpc64-unknown-freebsd", powerpc64_unknown_freebsd),
     ("powerpc64le-unknown-freebsd", powerpc64le_unknown_freebsd),
+    ("riscv64gc-unknown-freebsd", riscv64gc_unknown_freebsd),
     ("x86_64-unknown-freebsd", x86_64_unknown_freebsd),
 
     ("x86_64-unknown-dragonfly", x86_64_unknown_dragonfly),
diff --git a/library/std/build.rs b/library/std/build.rs
index 726157c1f1a..b46968f4d97 100644
--- a/library/std/build.rs
+++ b/library/std/build.rs
@@ -4,7 +4,8 @@ fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     let target = env::var("TARGET").expect("TARGET was not set");
     if target.contains("freebsd") {
-        if env::var("RUST_STD_FREEBSD_12_ABI").is_ok() {
+        // RISC-V first appeared in FreeBSD 12 so lacks FreeBSD 11's syscalls.
+        if env::var("RUST_STD_FREEBSD_12_ABI").is_ok() || target.starts_with("riscv64") {
             println!("cargo:rustc-cfg=freebsd12");
         }
     } else if target.contains("linux")
diff --git a/library/std/src/os/raw/mod.rs b/library/std/src/os/raw/mod.rs
index 1e220ea30ab..3ce7a048536 100644
--- a/library/std/src/os/raw/mod.rs
+++ b/library/std/src/os/raw/mod.rs
@@ -68,7 +68,8 @@ macro_rules! type_alias {
             target_arch = "aarch64",
             target_arch = "arm",
             target_arch = "powerpc",
-            target_arch = "powerpc64"
+            target_arch = "powerpc64",
+            target_arch = "riscv64"
         )
     ),
     all(
@@ -110,7 +111,8 @@ macro_rules! type_alias {
             target_arch = "aarch64",
             target_arch = "arm",
             target_arch = "powerpc",
-            target_arch = "powerpc64"
+            target_arch = "powerpc64",
+            target_arch = "riscv64"
         )
     ),
     all(
diff --git a/library/stdarch b/library/stdarch
--- a/library/stdarch
+++ b/library/stdarch
@@ -1 +1 @@
-Subproject commit 89b0e355bc3cff5cddec2290c84f36eb3a026aad
+Subproject commit 89b0e355bc3cff5cddec2290c84f36eb3a026aad-dirty
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index 0e306cb7211..5f513786ebb 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -248,9 +248,11 @@ fn run(self, builder: &Builder<'_>) -> PathBuf {
             }
         }
 
-        if target.starts_with("riscv") {
-            // In RISC-V, using C++ atomics require linking to `libatomic` but the LLVM build
-            // system check cannot detect this. Therefore it is set manually here.
+        if target.starts_with("riscv") && !target.contains("freebsd") {
+            // RISC-V GCC erroneously requires linking against `libatomic` when using 1-byte and
+            // 2-byte C++ atomics but the LLVM build system check cannot detect this. Therefore it
+            // is set manually here. FreeBSD uses Clang as its system compiler and provides no
+            // libatomic in its base system so does not want this.
             if !builder.config.llvm_tools_enabled {
                 cfg.define("CMAKE_EXE_LINKER_FLAGS", "-latomic");
             } else {