Make Wes' inner mathematician happy.

_posts/2024-06-26-sentries-cfi.markdown

@@ -45,12 +45,12 @@ RISC-V has a single instruction for both jump to a register and jump-and-link to
 The non-linking version just uses the zero register (`cnull` on a CHERI system) as the link register.
 Murali's proposal ended up with the following interpretations of the instruction depending on the operands:
 
-cs1 | cd | Used for | Valid sentry types
--- | -- | -- | --
-`cra` | `cnull` | Function return | Return sentries
-≠`cra` | `cnull` | Tail call | Unsealed or interrupt inheriting forward sentry
-any | ≠`cnull` | Function call | Unsealed or interrupt inheriting forward sentry
-any | `cra` | Function call | Unsealed or forward sentries
+cs1 | cd  | Used for | Valid sentry types
+-- | --  | -- | --
+`cra` | `cnull`  | Function return | Return sentries
+≠`cra` | `cnull`  | Tail call | Unsealed or interrupt inheriting forward sentry
+any | ∉{`cnull`,`cra`} | Function call | Unsealed or interrupt inheriting forward sentry
+any | `cra`  | Function call | Unsealed or forward sentries
 
 We are treating `cjr cra` as a return instruction, so it must have a return.