From 6efcfa6018ba3f02c5855952034a23048495b863 Mon Sep 17 00:00:00 2001
From: redoste <redoste@redoste.xyz>
Date: Sun, 4 Jun 2023 17:57:49 +0200
Subject: [PATCH] ubc: panic when trying to break in code using register bank 1

---
 src/kernel/exch.c |  2 ++
 src/ubc/ubc.S     | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/src/kernel/exch.c b/src/kernel/exch.c
index 1efcfbc..c061f21 100644
--- a/src/kernel/exch.c
+++ b/src/kernel/exch.c
@@ -78,6 +78,7 @@ GNORETURN static void gint_default_panic(GUNUSED uint32_t code)
 	if(code == 0x1040) name = "Add-in too large";
 	if(code == 0x1060) name = "Memory init failed";
 	if(code == 0x1080) name = "Stack overflow";
+	if(code == 0x10a0) name = "UBC in bank 1 code";
 
 	if(name[0]) dtext(1, 9, name);
 	else dprint(1, 9, "%03x", code);
@@ -118,6 +119,7 @@ GNORETURN static void gint_default_panic(GUNUSED uint32_t code)
 	if(code == 0x1040) name = "Add-in not fully mapped (too large)";
 	if(code == 0x1060) name = "Memory initialization failed (heap)";
 	if(code == 0x1080) name = "Stack overflow during world switch";
+	if(code == 0x10a0) name = "UBC break in register bank 1 code";
 
 	dprint(6, 25, "%03x %s", code, name);
 
diff --git a/src/ubc/ubc.S b/src/ubc/ubc.S
index fc956f6..734bdb3 100644
--- a/src/ubc/ubc.S
+++ b/src/ubc/ubc.S
@@ -14,6 +14,12 @@ _ubc_getDBR:
 
 .global _ubc_dbh
 _ubc_dbh:
+	/* We don't support breaking in a context where register bank 1 is used */
+	stc	ssr, r0
+	mov.l	.sr_rb1_mask, r1
+	tst	r0, r1
+	bf	.dbh_panic
+
 	/* We backup registers in the correct order to build gdb_cpu_state_t */
 	stc.l	ssr,  @-r15
 	sts.l	macl, @-r15
@@ -92,9 +98,25 @@ _ubc_dbh:
 	rte
 	nop
 
+.dbh_panic:
+	stc	sr, r1
+	mov.l	.sr_mask, r0
+	and	r0, r1
+	ldc	r1, sr
+
+	mov.l	.panic_code, r4
+
+	mov.l	.panic, r0
+	mov.l	@r0, r0
+	jmp	@r0
+	nop
+
 .align 4
 .handler:	.long _ubc_debug_handler
 .ubc_dbh_lock:	.long _ubc_dbh_lock
+.panic_code:	.long 0x10a0
+.panic:		.long _gint_exc_panic
+.sr_rb1_mask:	.long (1 << 29)
 .sr_mask:	.long ~0x300000f0  /* IMASK = 0 : mask no interrupts
                                       BL = 0    : do not block interrupts
                                       RB = 0    : use register BANK0