Kernel: Implement signal trampoline for i386

kernel/CMakeLists.txt

@@ -125,6 +125,7 @@ elseif("${BANAN_ARCH}" STREQUAL "i386")
 		${KERNEL_SOURCES}
 		arch/i386/boot.S
 		arch/i386/PageTable.cpp
+		arch/i386/Signal.S
 		arch/i386/Syscall.S
 		arch/i386/Thread.S
 	)

kernel/arch/i386/Signal.S

@@ -0,0 +1,29 @@
+.section .userspace, "aw"
+
+// stack contains
+//    return address
+//    signal number
+//    signal handler
+
+.global signal_trampoline
+signal_trampoline:
+	pushl %ebp
+	movl %esp, %ebp
+	subl $8, %esp
+
+	pusha
+
+	movl 40(%esp), %edi
+	movl 36(%esp), %eax
+
+	subl $12, %esp
+	pushl %edi
+	call *%eax
+	addl $16, %esp
+
+	popa
+
+	leave
+	addl $8, %esp
+
+	ret