diff --git a/libc/config/linux/api.td b/libc/config/linux/api.td
--- a/libc/config/linux/api.td
+++ b/libc/config/linux/api.td
@@ -270,9 +270,11 @@
   let Functions = [
     "raise",
     "sigaction",
+    "sigdelset",
     "sigprocmask",
     "sigemptyset",
     "sigaddset",
+    "sigfillset",
     "signal",
   ];
 }
diff --git a/libc/spec/posix.td b/libc/spec/posix.td
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -157,6 +157,12 @@
            ArgSpec<ConstRestrictStructSigactionPtr>,
            ArgSpec<RestrictStructSigactionPtr>]
         >,
+        FunctionSpec<
+          "sigdelset",
+          RetValSpec<IntType>,
+          [ArgSpec<SigSetPtrType>,
+           ArgSpec<IntType>]
+        >,
         FunctionSpec<
           "sigprocmask",
           RetValSpec<IntType>,
@@ -170,6 +176,12 @@
         FunctionSpec<
           "sigaddset",
           RetValSpec<IntType>,
+          [ArgSpec<SigSetPtrType>,
+           ArgSpec<IntType>]
+        >,
+        FunctionSpec<
+          "sigfillset",
+          RetValSpec<IntType>,
           [ArgSpec<SigSetPtrType>]
         >,
       ]