Entrypoint detection stuff (untested)

common/entrypoints.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#define ENTRY_UNKNOWN  (0)
+#define ENTRY_B9S      (1)
+#define ENTRY_NTRBOOT  (2)
+#define ENTRY_NANDBOOT (3)
+#define ENTRY_SPIBOOT  (4)

source/main.c

@@ -3,7 +3,7 @@
 #include "pxi.h"
 #include "i2c.h"
 
-void main(int argc, char** argv)
+void main(int argc, char** argv, int entrypoint)
 {
     (void) argv; // unused for now
 

source/start.s

@@ -4,6 +4,7 @@
 
 #include <arm.h>
 #include <brf.h>
+#include <entrypoints.h>
 
 .global _start
 _start:
@@ -13,9 +14,10 @@ _start:
     msr cpsr_c, r4
 
     @ Preserve boot registers
-    mov r9, r0
+    mov r8, r0
-    mov r10, r1
+    mov r9, r1
-    mov r11, r2
+    mov r10, r2
+    mov r11, r3
 
     @ Clear bss
     ldr r0, =__bss_start
@@ -46,33 +48,29 @@ _start:
     mcr p15, 0, r0, c5, c0, 3 @ write instruction access
 
     @ Set MPU regions and cache settings
-    adr r0, __mpu_regions
+    ldr lr, =__mpu_regions
-    ldmia r0, {r1-r8}
+    ldmia lr, {r0-r7}
-    mov r0, #0b00101000
+    mov lr, #0b00101000
-    mcr p15, 0, r1, c6, c0, 0
+    mcr p15, 0, r0, c6, c0, 0
-    mcr p15, 0, r2, c6, c1, 0
+    mcr p15, 0, r1, c6, c1, 0
-    mcr p15, 0, r3, c6, c2, 0
+    mcr p15, 0, r2, c6, c2, 0
-    mcr p15, 0, r4, c6, c3, 0
+    mcr p15, 0, r3, c6, c3, 0
-    mcr p15, 0, r5, c6, c4, 0
+    mcr p15, 0, r4, c6, c4, 0
-    mcr p15, 0, r6, c6, c5, 0
+    mcr p15, 0, r5, c6, c5, 0
-    mcr p15, 0, r7, c6, c6, 0
+    mcr p15, 0, r6, c6, c6, 0
-    mcr p15, 0, r8, c6, c7, 0
+    mcr p15, 0, r7, c6, c7, 0
-    mcr p15, 0, r0, c3, c0, 0	@ Write bufferable
+    mcr p15, 0, lr, c3, c0, 0	@ Write bufferable
-    mcr p15, 0, r0, c2, c0, 0	@ Data cacheable
+    mcr p15, 0, lr, c2, c0, 0	@ Data cacheable
-    mcr p15, 0, r0, c2, c0, 1	@ Inst cacheable
+    mcr p15, 0, lr, c2, c0, 1	@ Inst cacheable
 
-    @ Enable dctm
+    @ Enable DTCM
     ldr r0, =0x3000800A
     mcr p15, 0, r0, c9, c1, 0  @ set the DTCM Region Register
 
-    @ Enable caches / select low exception vectors
+    @ Fix SDMC mounting
-    ldr r1, =(CR_ALT_VECTORS | CR_DISABLE_TBIT)
+    mov r0, #0x10000000
-    ldr r2, =(CR_ENABLE_MPU  | CR_ENABLE_DCACHE | CR_ENABLE_ICACHE | \
+    mov r1, #0x340
-              CR_ENABLE_DTCM | CR_CACHE_RROBIN)
+    str r1, [r0, #0x20]
-    mrc p15, 0, r0, c1, c0, 0
-    bic r0, r1
-    orr r0, r2
-    mcr p15, 0, r0, c1, c0, 0
 
     @ Install exception handlers
     ldr r0, =XRQ_Start
@@ -84,31 +82,78 @@ _start:
         strlo r3, [r2], #4
         blo .LXRQ_Install
 
-    @ Fix SDMC mounting
+    @ Enable caches / DTCM / select low exception vectors
-    mov r0, #0x10000000
+    ldr r1, =(CR_ALT_VECTORS | CR_DISABLE_TBIT)
-    mov r1, #0x340
+    ldr r2, =(CR_ENABLE_MPU  | CR_ENABLE_DCACHE | CR_ENABLE_ICACHE | \
-    str r1, [r0, #0x20]
+              CR_ENABLE_DTCM | CR_CACHE_RROBIN)
-
+    mrc p15, 0, r0, c1, c0, 0
-    @ Check arguments
+    bic r0, r1
-    lsl r2, r11, #16
+    orr r0, r2
-    lsr r2, r2, #16
+    mcr p15, 0, r0, c1, c0, 0
-
-    ldr r3, =0xBEEF
-    cmp r2, r3
-
-    moveq r0, r9
-    moveq r1, r10
-    movne r0, #0
 
     @ Switch to system mode, disable interrupts, setup application stack
     msr cpsr_c, #(SR_SYS_MODE | SR_IRQ | SR_FIQ)
     ldr sp, =__stack_top
-    b main
+
+    @ Check entrypoints
+
+    @ b9s
+    ldr r3, =0xBEEF
+    lsl r2, r10, #16
+    lsr r2, r2, #16
+    cmp r2, r3
+
+    moveq r0, r8
+    moveq r1, r9
+    moveq r2, #(ENTRY_B9S)
+    beq .Lboot_main
+
+    @ ntrboot
+    ldr r4, =0x1FFFE00C
+    ldr r5, =0x1FFFE010
+
+    ldrd r6, r7, [r5]
+    orr r6, r6, r7
+    cmp r6, #0
+    ldreqb r6, [r4, #1]
+    ldreqb r7, [r4, #3]
+    cmpeq r6, #0
+    cmpeq r7, #2
+
+    moveq r0, #0
+    moveq r1, #0
+    moveq r2, #(ENTRY_NTRBOOT)
+    beq .Lboot_main
+
+    @ nandboot
+    ldrd r6, r7, [r5]
+    orr r6, r6, r7
+    cmp r6, #0
+    beq .Lentrycheck_firmboot_end
+    ldrb r6, [r4, #0]
+    cmp r6, #0
+    moveq r0, #0
+    moveq r1, #0
+    moveq r2, #(ENTRY_NANDBOOT)
+    beq .Lboot_main
+.Lentrycheck_firmboot_end:
+
+    @ Unknown
+    mov r0, #0
+    mov r1, #0
+    mov r2, #(ENTRY_UNKNOWN)
+
+
+.Lboot_main:
+    ldr r3, =main
+    mov lr, #0
+    bx r3
+
 
 __mpu_regions:
     .word 0xFFFF001F @ FFFF0000 64k  | bootrom (unprotected / protected)
     .word 0x3000801B @ 30008000 16k  | dtcm
-    .word 0x00000035 @ 00000000 128M | itcm
+    .word 0x00000035 @ 00000000 128M | itcm (+ mirrors)
     .word 0x08000029 @ 08000000 2M   | arm9 mem (O3DS / N3DS)
     .word 0x10000029 @ 10000000 2M   | io mem (ARM9 / first 2MB)
     .word 0x20000037 @ 20000000 256M | fcram (O3DS / N3DS)