Macros for fs/gs deref.

3 files changed, 44 insertions, 13 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index af5cdc1..ccc665e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [unreleased]
 
+## [0.49.0] - 2022-06-03
+
+- Removed `bits64::segmentation::fs_deref()`: Users should replace calls to
+  `fs_deref` with the more general `fbits64::segmentation::s_deref!` macro.
+  `fs_deref!(0)` is equivalent to `fs_deref()`.
+- Removed `bits64::segmentation::gs_deref()`: Users should replace calls to
+  `gs_deref` with the more general `bits64::segmentation::gs_deref!` macro.
+  `fs_deref!(0)` is equivalent to `fs_deref()`.
+
 ## [0.48.0] - 2022-05-23
 
 - Added `const new` constructor for X2APIC struct
diff --git a/Cargo.toml b/Cargo.toml
index e7f128d..f49ca40 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "x86"
-version = "0.48.0"
+version = "0.49.0"
 authors = [
   "Gerd Zellweger <mail@gerdzellweger.com>",
   "Eric Kidd <git@randomhacks.net>",
diff --git a/src/bits64/segmentation.rs b/src/bits64/segmentation.rs
index 36e3171..78c39a8 100644
--- a/src/bits64/segmentation.rs
+++ b/src/bits64/segmentation.rs
@@ -191,28 +191,50 @@ pub unsafe fn rdfsbase() -> u64 {
     fs_base
 }
 
-/// "Dereferences" the fs register at offset 0.
+/// "Dereferences" the fs register at `offset`.
 ///
 /// # Safety
-/// fs needs to point to valid address.
+/// - Offset needs to be within valid memory relative to what the fs register
+///   points to.
 #[cfg(target_arch = "x86_64")]
-pub unsafe fn fs_deref() -> u64 {
-    let fs: u64;
-    asm!("movq %fs:0x0, {0}", out(reg) fs, options(att_syntax));
-    fs
+#[macro_export]
+macro_rules! fs_deref {
+    ($offset:expr) => {{
+        let fs: u64;
+        core::arch::asm!("movq %fs:{offset}, {result}",
+                offset = const ($offset),
+                result = out(reg) fs,
+                options(att_syntax)
+        );
+        fs
+    }};
 }
 
-/// "Dereferences" the gs register at offset 0.
+#[cfg(target_arch = "x86_64")]
+pub use fs_deref;
+
+/// "Dereferences" the gs register at `offset`.
 ///
 /// # Safety
-/// gs needs to point to valid address.
+/// - Offset needs to be within valid memory relative to what the gs register
+///   points to.
 #[cfg(target_arch = "x86_64")]
-pub unsafe fn gs_deref() -> u64 {
-    let gs: u64;
-    asm!("movq %gs:0x0, {0}", out(reg) gs, options(att_syntax));
-    gs
+#[macro_export]
+macro_rules! gs_deref {
+    ($offset:expr) => {{
+        let gs: u64;
+        core::arch::asm!("movq %gs:{offset}, {result}",
+                offset = const ($offset),
+                result = out(reg) gs,
+                options(att_syntax)
+        );
+        gs
+    }};
 }
 
+#[cfg(target_arch = "x86_64")]
+pub use gs_deref;
+
 /// Swap the GS register.
 ///
 /// Exchanges the current GS base register value with the value contained