x86/signal/compat: Move sigaction_compat_abi() to signal_64.c

Also remove the now-empty signal_compat.c.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20221219193904.190220-3-brgerst@gmail.com
Cc: Al Viro <viro@zeniv.linux.org.uk>

Author: Brian Gerst

arch/x86/kernel/Makefile

@@ -45,7 +45,6 @@ obj-y			+= head$(BITS).o
 obj-y			+= ebda.o
 obj-y			+= platform-quirks.o
 obj-y			+= process_$(BITS).o signal.o signal_$(BITS).o
-obj-$(CONFIG_COMPAT)	+= signal_compat.o
 obj-y			+= traps.o idt.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
 obj-y			+= time.o ioport.o dumpstack.o nmi.o
 obj-$(CONFIG_MODIFY_LDT_SYSCALL)	+= ldt.o

arch/x86/kernel/signal_64.c

@@ -382,6 +382,19 @@ COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
 }
 #endif /* CONFIG_X86_X32_ABI */
 
+#ifdef CONFIG_COMPAT
+void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
+{
+	if (!act)
+		return;
+
+	if (in_ia32_syscall())
+		act->sa.sa_flags |= SA_IA32_ABI;
+	if (in_x32_syscall())
+		act->sa.sa_flags |= SA_X32_ABI;
+}
+#endif /* CONFIG_COMPAT */
+
 /*
 * If adding a new si_code, there is probably new data in
 * the siginfo.  Make sure folks bumping the si_code