Interrupt Vector Table, first tests

Populated a relocated IVT, and tested SWI (Software Interrupt)

Makefile

@@ -1,6 +1,6 @@
 .POSIX:
 CCX=arm-none-eabi-g++
-CCFLAGS=-c -Wall -fno-stack-protector -ffreestanding -fno-exceptions -march=armv7-a -nostdlib -Iinclude -g
+CCFLAGS=-c -Wall -fno-stack-protector -ffreestanding -fno-exceptions -march=armv7-a -mno-unaligned-access -nostdlib -Iinclude -g
 
 C_HDR=$(wildcard include/*.h)
 C_SRC=$(wildcard src/*.cpp)

include/dbg.h

@@ -1,8 +1,10 @@
 #ifndef DBG_H
 #define DBG_H
+#include <stdint.h>
 
 extern "C" int printk(const char* msg);
 extern "C" int printkl(const char* msg);
+extern "C" const char* itoa(uint32_t n);
 
 namespace dbg {
 

include/interrupt.h

@@ -0,0 +1,12 @@
+#ifndef INTERRUPT_H
+#define INTERRUPT_H
+
+#include <stdint.h>
+
+extern "C" void setVectorBAR(void);
+extern "C" address_t* getVectorBAR(void);
+
+extern "C" void fireswi(void);
+
+
+#endif

include/stdint.h

@@ -0,0 +1,81 @@
+/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/*
+ *	ISO C99: 7.18 Integer types <stdint.h>
+ */
+
+/* Exact integral types.  */
+
+/* Signed.  */
+
+/* There is some amount of overlap with <sys/types.h> as known by inet code */
+#ifndef __int8_t_defined
+# define __int8_t_defined
+typedef signed char		int8_t;
+typedef short int		int16_t;
+typedef int			int32_t;
+# if __WORDSIZE == 64
+typedef long int		int64_t;
+# else
+__extension__
+typedef long long int		int64_t;
+# endif
+#endif
+
+/* Unsigned.  */
+typedef unsigned char		uint8_t;
+typedef unsigned short int	uint16_t;
+#ifndef __uint32_t_defined
+typedef unsigned int		uint32_t;
+# define __uint32_t_defined
+#endif
+#if __WORDSIZE == 64
+typedef unsigned long int	uint64_t;
+#else
+__extension__
+typedef unsigned long long int	uint64_t;
+#endif
+
+
+/* Small types.  */
+
+/* Signed.  */
+typedef signed char		int_least8_t;
+typedef short int		int_least16_t;
+typedef int			int_least32_t;
+#if __WORDSIZE == 64
+typedef long int		int_least64_t;
+#else
+__extension__
+typedef long long int		int_least64_t;
+#endif
+
+/* Unsigned.  */
+typedef unsigned char		uint_least8_t;
+typedef unsigned short int	uint_least16_t;
+typedef unsigned int		uint_least32_t;
+#if __WORDSIZE == 64
+typedef unsigned long int	uint_least64_t;
+#else
+__extension__
+typedef unsigned long long int	uint_least64_t;
+#endif
+
+/* Pointers */
+/* Suggested use address_t* only */
+typedef char address_t;

src/dbg.cpp

@@ -1,4 +1,5 @@
 #include <dbg.h>
+#include <stdint.h>
 
 /* Never call this function directly: always use the printk,
  * which disables and reenables interrupts */
@@ -17,3 +18,17 @@ extern "C" int printkl(const char* msg) {
     return 0;
 }
 
+static char string[11];
+/* TODO: WARNING: this is not thread safe!! */
+extern "C" const char* itoa(uint32_t n) {
+    string[10] = '\0';
+    string[0] = '0'; string[1] = 'x';
+
+    for (short i = 0; i < 8; ++i) {
+        string[9 - i] = "0123456789abcdef"[n & 0xF];
+        n = n >> 4;
+    }
+
+    return &string[0];
+}
+

src/fireswi.s

@@ -0,0 +1,24 @@
+/*
+    Example SWI (Software Interrupt)
+    also known as SVC (go to SuperVisor)
+*/
+.data
+calledme:
+.string "fireswi() has been called\0"
+doneme:
+.string "fireswi() has done\0"
+
+.text
+.global fireswi
+fireswi:
+    push {lr}
+
+    ldr r0, =calledme
+    bl printkl
+    swi #8
+    ldr r0, =doneme
+    bl printkl
+
+    pop {lr}
+    mov pc, lr
+

src/interrupt.s

@@ -0,0 +1,27 @@
+.text
+
+.global setVectorBAR
+setVectorBAR:
+    /* Disable interrupts */
+    cpsid if
+
+    /* Enable BAR remapping (clears bit 13 of SCTLR) */
+    mrc p15, 0, r0, c1, c0, 0
+    and r0, #0xffffdfff
+    mcr p15, 0, r0, c1, c0, 0
+
+    /* Sets VBAR with custom vector table's address */
+    ldr r0, =vectab
+    mcr p15, 0, r0, c12, c0, 0
+
+    /* Re-Enables interrupts */
+    cpsie if
+
+    mov pc, lr
+
+.global getVectorBAR
+getVectorBAR:
+    mrc p15, 0, r0, c12, c0, 0
+    mov pc, lr
+
+

src/kernel.cpp

@@ -1,10 +1,29 @@
 #include <dbg.h>
+#include <stdint.h>
+#include <interrupt.h>
 
 /* KERNEL MAIN */
 extern "C" int main(int argc, char** argv) {
     printkl("Welcome to STKARM -- Simple and Trivial Kernel for Advanced Reduced Instruction Set Computer Machines");
 
+    setVectorBAR();
+    uint32_t bar = (uint32_t)getVectorBAR();
+    printk("BAR is now at ");
+    printkl(itoa(bar));
+
+    uint32_t* table = (uint32_t*)(bar);
+    printkl("Vector table content:");
+    for (short i = 0; i < 8; ++i) {
+        printk(itoa(i)); printk("\t");
+        printkl(itoa(table[i]));
+    }
+
+    printkl("Now firing software interrupt...");
+    fireswi();
+
     printkl("EOK -- End of Kernel");
+    printkl("Now waiting for Godot in an endless loop");
+    while(true);
     return 0;
 }
 

src/kernel.s

@@ -1,10 +1,31 @@
 .text
+
 .align 4
 .global _start
 _start:
+    /* Initialize stack pointers */
+
+    ldr sp, =stack_svc
+
+    cps #0x1b
+    ldr sp, =stack_und
+    cps #0x17
+    ldr sp, =stack_abt
+    cps #0x12
+    ldr sp, =stack_irq
+    cps #0x11
+    ldr sp, =stack_fiq
+
+    // Leave in sys mode
+    cps #0x1f
+    ldr sp, =stack_sys
+
+// Leave in usr mode
+//    cps #0x10
+//    ldr sp, =stack_usr
+
+    /* C-Main */
     bl main
 
-endless_busy_loop:
-    cpsid if
-    b endless_busy_loop
-
+    /* Endless busy loop */
+    b .

src/linker.ld

@@ -1,15 +1,32 @@
 ENTRY(_start)
 
+MEMORY {
+    m_text  (RX) : ORIGIN = 0x40000000, LENGTH = 16M
+    m_data  (RW) : ORIGIN = 0x41000000, LENGTH = 16M
+    m_stack (RW) : ORIGIN = 0x42000000, LENGTH = 16M
+}
+
 SECTIONS
 {
-	. = 0x10000;
-	.text : {
+	. = 0x40000000;
+	.text : ALIGN(0x1000) {
+        obj/s_vectab.o (.text)
 		*(.text)
-	}
+	} > m_text
 	.data : ALIGN(0x1000) {
 		*(.data)
-	}
+	} > m_data
 	.bss : ALIGN(0x1000) {
 		*(.bss)
-	}
+	} > m_data
+
+    . = ALIGN(0x100);   stack_svc = .;
+    . = . + 0x100;      stack_und = .;
+    . = . + 0x100;      stack_abt = .;
+    . = . + 0x100;      stack_irq = .;
+    . = . + 0x100;      stack_fiq = .;
+    . = . + 0x100;      stack_sys = .;
+    . = . + 0x100;      stack_usr = .;
+
 }
+

src/vectab.s

@@ -0,0 +1,26 @@
+.data
+swimsg:
+.string "Hello. I am the sample SWI handler! =)\0"
+
+.text
+.align 4
+.global vectab
+vectab:
+    b _start
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+    ldr pc, =swi_handler
+
+swi_handler:
+    stmfd sp!, {lr}
+
+    ldr r0, =swimsg
+    bl printkl
+
+    ldmfd sp!, {pc}^
+
+