Merge pull request #422 from Egggggg/master

Change Star::write() to use checked subtractions
rust-osdev · Jun 11, 2023 · 486c2a4 · 486c2a4
2 parents 22066fa + 3222b10
commit 486c2a4
Showing 1 changed file with 16 additions and 2 deletions.
diff --git a/src/registers/model_specific.rs b/src/registers/model_specific.rs
@@ -425,11 +425,25 @@ mod x86_64 {
             cs_syscall: SegmentSelector,
             ss_syscall: SegmentSelector,
         ) -> Result<(), &'static str> {
-            if cs_sysret.0 - 16 != ss_sysret.0 - 8 {
+            let cs_sysret_cmp = cs_sysret
+                .0
+                .checked_sub(16)
+                .ok_or("Sysret CS is not at least 16.")?;
+            let ss_sysret_cmp = ss_sysret
+                .0
+                .checked_sub(8)
+                .ok_or("Sysret SS is not at least 8.")?;
+            let cs_syscall_cmp = cs_syscall.0;
+            let ss_syscall_cmp = ss_syscall
+                .0
+                .checked_sub(8)
+                .ok_or("Syscall SS is not at least 8.")?;
+
+            if cs_sysret_cmp != ss_sysret_cmp {
                 return Err("Sysret CS and SS is not offset by 8.");
             }
 
-            if cs_syscall.0 != ss_syscall.0 - 8 {
+            if cs_syscall_cmp != ss_syscall_cmp {
                 return Err("Syscall CS and SS is not offset by 8.");
             }