From 395250b5a9dea16f9303363509036b976bc2e272 Mon Sep 17 00:00:00 2001
From: Lephenixnoir <sebastien.michelland@protonmail.com>
Date: Sat, 13 Jul 2024 10:10:38 +0200
Subject: [PATCH] exch: add trapa #31 handler

---
 CMakeLists.txt       |  1 +
 include/gint/intc.h  |  7 +++----
 src/kernel/exch.s    | 35 ++++++++++++++++++++++++++++++++++-
 src/kernel/syscall.c | 13 +++++++++++++
 src/tmu/inth-tmu.s   |  3 +--
 5 files changed, 52 insertions(+), 7 deletions(-)
 create mode 100644 src/kernel/syscall.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94c7fcf..eafed97 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,6 +125,7 @@ set(SOURCES
   src/kernel/osmenu.c
   src/kernel/start.c
   src/kernel/start.S
+  src/kernel/syscall.c
   src/kernel/syscalls.S
   src/kernel/tlbh.S
   src/kernel/world.c
diff --git a/include/gint/intc.h b/include/gint/intc.h
index 7af58aa..1f43ae2 100644
--- a/include/gint/intc.h
+++ b/include/gint/intc.h
@@ -132,10 +132,9 @@ void *intc_handler(int event_code, void const *handler, size_t size);
    the numerous constraints of intc_handler(), at the cost of always going back
    to userspace and a small time overhead.
 
-   Since gint_inth_callback is used to do the heavy lifting of setting up a sane
-   context for C code, the gint_call_t object can be built with GINT_CALL_FLAG
-   if the called function expects a gint_inth_callback_context_t structure as its
-   first argument.
+   gint_inth_callback does the heavy lifting of setting up a sane context for C
+   code. If the gint_call_t object is built with GINT_CALL_FLAG, the function
+   is called with a gint_inth_callback_context_t * as its first argument.
 
    @event_code  Identifier of the interrupt block
    @function    Function to use as a handler
diff --git a/src/kernel/exch.s b/src/kernel/exch.s
index ccd97d5..70d876c 100644
--- a/src/kernel/exch.s
+++ b/src/kernel/exch.s
@@ -16,8 +16,31 @@ _gint_exch:
 	mov.l	@r0, r0
 	tst	#1, r0
 	mov.l	.expevt_sh4, r8
-	bt	catch
+	mov.l	.tra_sh4, r9
+	bt	syscall
 	mov.l	.expevt_sh3, r8
+	mov.l	.tra_sh3, r9
+
+syscall:
+	/* If this is trapa #31, save context and run the syscall interface. */
+	mov.l	@r8, r4
+	mov.w	.expevt_trapa, r5
+	mov.l	@r9, r0
+	cmp/eq	r4, r5
+	bf	catch
+	cmp/eq	#31*4, r0
+	bf	catch
+
+	add	#-20, r15
+	mov.l	.syscall_entry_plus1, r0
+	mov	r15, r4
+	mov.l	.callback, r1
+	mov.l	@r1, r1
+	jsr	@r1
+	mov.l	r0, @r4
+
+	bra	end
+	add	#20, r15
 
 catch:
 	/* Panic if the catcher is NULL */
@@ -89,3 +112,13 @@ end:
 	.long	(0xf << 4)
 .SR_clear_BL:
 	.long	~(1 << 28)
+.callback:
+	.long	_gint_inth_callback
+.syscall_entry_plus1:
+	.long	_syscall_entry + 1
+.tra_sh3:
+	.long	0xffffffd0
+.tra_sh4:
+	.long	0xff000020
+.expevt_trapa:
+	.word	0x160
diff --git a/src/kernel/syscall.c b/src/kernel/syscall.c
new file mode 100644
index 0000000..2929cef
--- /dev/null
+++ b/src/kernel/syscall.c
@@ -0,0 +1,13 @@
+#include <gint/gint.h>
+
+int debug_syscall_count = 0;
+int debug_syscall_lastnr = 0;
+
+void syscall_entry(gint_inth_callback_context_t *ptr)
+{
+	/* TODO: Currently, only user's r0...r7, spc, and ssr are saved here */
+	(void)ptr;
+
+	++debug_syscall_count;
+	debug_syscall_lastnr = ptr->r3;
+}
diff --git a/src/tmu/inth-tmu.s b/src/tmu/inth-tmu.s
index 3344f9c..46bf5c3 100644
--- a/src/tmu/inth-tmu.s
+++ b/src/tmu/inth-tmu.s
@@ -32,8 +32,7 @@ _inth_tmu:
 	sts.l	pr, @-r15
 	mov.l	r5, @-r15
 
-	/* Clear the interrupt flag. Because r5 contains 0, 1 or 2 the 16 top
-	   bits are 0 so we can compare without extending */
+	/* Clear the interrupt flag */
 1:	mov.w	@r1, r5
 	extu.b	r5, r3
 	cmp/eq	r5, r3