Kernel: Push missing IP and SP to mcontext in signal handler

I was missing these two registers, messing up the whole siginfo_t
structure. This fixes libc's stack trace dump crashing :D

kernel/arch/i686/Signal.S

@@ -1,7 +1,7 @@
 .section .userspace, "ax"
 
 // stack contains
-//    (4 bytes)  return address
+//    (4 bytes)  return address (on return stack)
 //    (4 bytes)  return stack
 //    (4 bytes)  return rflags
 //    (8 bytes)  restore sigmask
@@ -19,6 +19,10 @@ signal_trampoline:
 	pushl %eax
 	pushl %ebp
 
+	movl 80(%esp), %eax
+	pushl %eax; addl $4, (%esp)
+	pushl (%eax)
+
 	// FIXME: populate these
 	xorl %eax, %eax
 	pushl %eax // stack
@@ -29,9 +33,9 @@ signal_trampoline:
 	pushl %eax // link
 
 	movl    %esp,  %edx // ucontext
-	leal 60(%esp), %esi // siginfo
-	movl 56(%esp), %edi // signal number
-	movl 52(%esp), %eax // handlers
+	leal 68(%esp), %esi // siginfo
+	movl 64(%esp), %edi // signal number
+	movl 60(%esp), %eax // handlers
 
 	// align stack to 16 bytes
 	movl %esp, %ebp
@@ -62,6 +66,7 @@ signal_trampoline:
 	int $0xF0
 
 	// restore registers
+	addl $8, %esp
 	popl %ebp
 	popl %eax
 	popl %ebx

kernel/arch/x86_64/Signal.S

@@ -1,7 +1,7 @@
 .section .userspace, "ax"
 
 // stack contains
-//    (8 bytes)  return address
+//    (8 bytes)  return address (on return stack)
 //    (8 bytes)  return stack
 //    (8 bytes)  return rflags
 //    (8 bytes)  restore sigmask
@@ -27,6 +27,10 @@ signal_trampoline:
 	pushq %rax
 	pushq %rbp
 
+	movq 208(%rsp), %rax
+	pushq %rax; addq $(128 + 8), (%rsp)
+	pushq (%rax)
+
 	// FIXME: populate these
 	xorq %rax, %rax
 	pushq %rax // stack
@@ -36,9 +40,9 @@ signal_trampoline:
 	pushq %rax // link
 
 	movq  %rsp,     %rdx // ucontext
-	leaq 176(%rsp), %rsi // siginfo
-	movq 168(%rsp), %rdi // signal number
-	movq 160(%rsp), %rax // handler
+	leaq 192(%rsp), %rsi // siginfo
+	movq 184(%rsp), %rdi // signal number
+	movq 176(%rsp), %rax // handler
 
 	// align stack to 16 bytes
 	movq %rsp, %rbp
@@ -64,6 +68,7 @@ signal_trampoline:
 	syscall
 
 	// restore registers
+	addq $16, %rsp
 	popq %rbp
 	popq %rax
 	popq %rbx