Linux sandbox: Allow restricting sched_* on other processes.

sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h

Index: sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
index 4e855c59ef3bd583eed8edae1710f25a34b669af..099bc227aa68b258a30c06f06c6451305b3200eb 100644
--- a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h
@@ -47,6 +47,12 @@ SANDBOX_EXPORT intptr_t
 // argument.
 SANDBOX_EXPORT intptr_t
     SIGSYSFutexFailure(const struct arch_seccomp_data& args, void* aux);
+// If the syscall is not being called on the current tid, crashes in the same
+// way as CrashSIGSYS_Handler.  Otherwise, returns the result of calling the
+// syscall with the pid argument set to 0 (which for these calls means the
+// current thread).
+SANDBOX_EXPORT intptr_t
+    SIGSYSSchedHandler(const struct arch_seccomp_data& args, void* aux);
 
 // Variants of the above functions for use with bpf_dsl.
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYS();
@@ -55,6 +61,7 @@ SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSPrctl();
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSIoctl();
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSKill();
 SANDBOX_EXPORT bpf_dsl::ResultExpr CrashSIGSYSFutex();
+SANDBOX_EXPORT bpf_dsl::ResultExpr RewriteSchedSIGSYS();
 
 // Following four functions return substrings of error messages used
 // in the above four functions. They are useful in death tests.