[clang] [Clang][attr] Add 'kcfi_salt' attribute (PR #141846)

[Miguel Ojeda via cfe-commits]

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@@ -3643,6 +3643,64 @@ make the function's CFI jump table canonical. See :ref:`the CFI documentation
   }];
 }
 
+def KCFISaltDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Use ``__attribute__((kcfi_salt("<salt>")))`` on a function declaration, function
+definition, or typedef to help distinguish CFI hashes between functions with
+the same type signature.
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ojeda wrote:

Like in the kernel patch, it would be nice to summarize the use case, i.e. in what cases we would want to apply this.

https://github.com/llvm/llvm-project/pull/141846