From a63fb971d42b33c25829068bb085d68add3818a4 Mon Sep 17 00:00:00 2001
From: TuxSH <tuxsh@sfr.fr>
Date: Fri, 6 May 2016 20:22:43 +0200
Subject: [PATCH] Add support for k9/p9 exception handling on all FIRMs

---
 source/firm.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
 source/fs.c   |  6 +-----
 source/fs.h   |  2 +-
 3 files changed, 45 insertions(+), 8 deletions(-)

diff --git a/source/firm.c b/source/firm.c
index 37ebef4..4b8245e 100755
--- a/source/firm.c
+++ b/source/firm.c
@@ -24,6 +24,41 @@ u32 config,
     firmSource,
     emuOffset;
 
+static inline void patchExceptionHandlersInstall(u8 *arm9Section)
+{
+    static const u8 pattern[] = {
+        0x18, 0x10, 0x80, 0xE5, 
+        0x10, 0x10, 0x80, 0xE5, 
+        0x20, 0x10, 0x80, 0xE5, 
+        0x28, 0x10, 0x80, 0xE5,
+    }; //i.e when it stores ldr pc, [pc, #-4]
+    
+    u32* off = (u32 *)(memsearch(arm9Section, pattern, section[2].size, sizeof(pattern)));
+    if(off == NULL) return;
+    off += sizeof(pattern)/4;
+    
+    u32 r0 = 0x08000000;
+    
+    for(; *off != 0xE3A01040; off++) //until mov r1, #0x40
+    {
+        if((*off >> 26) != 0x39 || ((*off >> 16) & 0xf) != 0 || ((*off >> 25) & 1) != 0 || ((*off >> 20) & 5) != 0)
+            continue; //discard everything that's not str rX, [r0, #imm](!)
+        
+        int rD = (*off >> 12) & 0xf;
+        int offset = (*off & 0xfff) * ((((*off >> 23) & 1) == 0) ? -1 : 1);
+        int writeback = (*off >> 21) & 1, pre = (*off >> 24) & 1;
+        
+        u32 addr = r0 + ((pre || !writeback) ? offset : 0);
+        if(addr != 0x08000014 && addr != 0x08000004)
+            *off = 0xE1A00000; //nop
+        else
+            *off = 0xE5800000 | (rD << 12) | (addr & 0xfff); //preserve IRQ and svc handlers
+        
+        if(!pre) addr += offset;
+        if(writeback) r0 = addr;
+    }
+}
+
 void main(void)
 {
     u32 bootType,
@@ -72,7 +107,11 @@ void main(void)
 
         u32 devMode = CONFIG(5);
 
-        if(devMode) detectAndProcessExceptionDumps();
+        if(devMode) 
+        { 
+            detectAndProcessExceptionDumps();
+            installArm9Handlers(); 
+        }
 
         bootType = 0;
         firmType = 0;
@@ -139,7 +178,7 @@ void main(void)
             /* If L and R/A/Select or one of the single payload buttons are pressed,
                chainload an external payload */
             if(devMode || (pressed & SINGLE_PAYLOAD_BUTTONS) || ((pressed & BUTTON_L1) && (pressed & L_PAYLOAD_BUTTONS)))
-                loadPayload(pressed, devMode);
+                loadPayload(pressed);
 
             //If screens are inited or the corresponding option is set, load splash screen
             if(PDN_GPU_CNT != 1 || CONFIG(8)) loadSplash();
@@ -193,6 +232,8 @@ void main(void)
 
     loadFirm(firmType, !firmType && updatedSys == !firmSource);
 
+    patchExceptionHandlersInstall((u8 *)firm + section[2].offset);
+    
     switch(firmType)
     {
         case 0:
diff --git a/source/fs.c b/source/fs.c
index 5030ae3..13212a3 100644
--- a/source/fs.c
+++ b/source/fs.c
@@ -5,7 +5,6 @@
 #include "fs.h"
 #include "memory.h"
 #include "screeninit.h"
-#include "exceptions.h"
 #include "fatfs/ff.h"
 #include "buttons.h"
 #include "../build/loader.h"
@@ -50,7 +49,7 @@ void fileWrite(const void *buffer, const char *path, u32 size)
     }
 }
 
-void loadPayload(u32 pressed, u32 devMode)
+void loadPayload(u32 pressed)
 {
     const char *pattern;
 
@@ -76,9 +75,6 @@ void loadPayload(u32 pressed, u32 devMode)
 
     if(result == FR_OK && info.fname[0])
     {
-        //Only when "Enable developer features" is set
-        if(devMode) installArm9Handlers();
-
         initScreens();
 
         u32 *const loaderAddress = (u32 *)0x24FFFB00;
diff --git a/source/fs.h b/source/fs.h
index 065d440..6956148 100644
--- a/source/fs.h
+++ b/source/fs.h
@@ -12,5 +12,5 @@ u32 mountFs(void);
 u32 fileRead(void *dest, const char *path);
 void fileWrite(const void *buffer, const char *path, u32 size);
 void findDumpFile(const char *path, char *fileName);
-void loadPayload(u32 pressed, u32 devMode);
+void loadPayload(u32 pressed);
 void firmRead(void *dest, const char *firmFolder);
\ No newline at end of file