From ec08a449adf13f26579de0be4571b1783feabf2e Mon Sep 17 00:00:00 2001
From: sup39 <sms@sup39.dev>
Date: Fri, 11 Nov 2022 17:14:11 +0900
Subject: [PATCH] add gecko-jump.s

---
 ReadFile.c   |  2 +-
 gecko-jump.s | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 gecko-jump.s

diff --git a/ReadFile.c b/ReadFile.c
index cae9a25..c354433 100644
--- a/ReadFile.c
+++ b/ReadFile.c
@@ -44,7 +44,7 @@ int onReadOptionBlock(TCardManager *this, CARDFileInfo *fileInfo) {
   } else {
     // everything is good => apply gecko code
     // TODO entry
-    ((void(*)())0x817f0000)();
+    ((void(*)())0x817f4000)();
   }
 
   // close file
diff --git a/gecko-jump.s b/gecko-jump.s
new file mode 100644
index 0000000..5e049f5
--- /dev/null
+++ b/gecko-jump.s
@@ -0,0 +1,29 @@
+.set gpApplication, 0x803e6000 # TODO version
+.set dst, 0x817fb000
+
+## TODO prevent softlock: check app state >= 4
+  lis r5, gpApplication+8@ha
+  lbz r5, gpApplication+8@l(r5)
+  cmplwi r5, 4
+  bltlr
+## r5 = 00D0C0DE
+  lis r5, 0x00D0
+  ori r5, r5, 0xC0DE
+## check if code is loaded (check header)
+  lis r3, dst@ha
+### first 00D0C0DE
+### r3 = &dst
+  lwzu r0, dst@l(r3)
+  cmplw r0, r5
+  bnelr
+### second 00D0C0DE
+  lwz r0, 4(r3)
+  cmplw r0, r5
+  bnelr
+## backup r15 (pointer to current gecko instruction) at dst-4
+  add r0, r15, r4
+  stw r0, -4(r3)
+## update r15 = dst + 8(header) - r4(this C0 code size)
+  addi r15, r3, 8
+  sub r15, r15, r4
+  blr