re-enter system mode on invalid data access from PL0 code

7 files changed, 71 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index f07bced..377ba18 100644
--- a/Makefile
+++ b/Makefile
@@ -30,7 +30,7 @@ libkernel_renamed.o : libkernel.o
 PL_0_test.elf : PL0_test.o uart.o
 	arm-none-eabi-gcc -T PL0_test.ld -o $@ $(ELFFLAGS) $^
 
-kernel.elf : boot.o kernel.o uart.o PL_0_test_embeddable.o demo_functionality.o paging.o libkernel_renamed.o
+kernel.elf : boot.o kernel.o uart.o PL_0_test_embeddable.o demo_functionality.o paging.o libkernel_renamed.o interrupt_vector.o interrupts.o
 	arm-none-eabi-gcc -T linker.ld -o $@ $(ELFFLAGS) $^
 
 loader_stage2.elf : loader_stage2.o uart.o
diff --git a/demo_functionality.c b/demo_functionality.c
index fbf5eb4..60b0bfa 100644
--- a/demo_functionality.c
+++ b/demo_functionality.c
@@ -165,3 +165,25 @@ void demo_go_unprivileged(void)
 	       "r" (VIRTUAL_PL0_MEMORY_START)
 	       : "memory", "r4", "r5", "r0");
 }
+
+extern char
+  __interrupt_vectors_start,
+  __interrupt_vectors_end,
+  __interrupt_vectors_size;
+
+extern void (*volatile system_reentry_point)(void);
+
+void system_reentry(void)
+{
+  uart_puts("re-entered system");
+  while(1);
+}
+
+void demo_setup_interrupts(void)
+{
+  system_reentry_point = system_reentry;
+
+  for (size_t i = 0; i < (size_t) &__interrupt_vectors_size; i++)
+    ((volatile char*) 0)[i] =
+      (&__interrupt_vectors_start)[i];
+}
diff --git a/demo_functionality.h b/demo_functionality.h
index 5d6e659..73a284b 100644
--- a/demo_functionality.h
+++ b/demo_functionality.h
@@ -11,4 +11,6 @@ void demo_setup_PL0(void);
 
 void demo_go_unprivileged(void);
 
+void demo_setup_interrupts(void);
+
 #endif // DEMO_FUNCTIONALITY_H
diff --git a/interrupt_vector.S b/interrupt_vector.S
new file mode 100644
index 0000000..f71330b
--- /dev/null
+++ b/interrupt_vector.S
@@ -0,0 +1,20 @@
+.section ".interrupt_vectors.text"
+
+.global abort_handler
+.local generic_handler	
+.global _interrupt_vectors
+_interrupt_vectors:
+	b generic_handler
+	b generic_handler
+	b generic_handler
+	b abort_handler_caller
+	b abort_handler_caller
+	b generic_handler
+	b generic_handler
+
+generic_handler:
+	b generic_handler
+abort_handler_caller:
+	mov sp, #0x8000
+	ldr r5, =abort_handler
+	bx r5
diff --git a/interrupts.c b/interrupts.c
index 3dc3d6f..191ce40 100644
--- a/interrupts.c
+++ b/interrupts.c
@@ -12,4 +12,15 @@ void __attribute__((interrupt("UNDEF"))) undefined_instruction_vector(void)
     {
         /* Do Nothing! */
     }
-}
\ No newline at end of file
+}
+
+void __attribute__((section(".interrupt_vectors.data")))
+(*system_reentry_point) (void);
+
+void
+__attribute__((interrupt("ABORT")))
+__attribute__((section(".interrupt_vectors.text")))
+abort_handler(void)
+{
+  system_reentry_point();
+}
diff --git a/kernel.c b/kernel.c
index 1a3b87d..eb3e811 100644
--- a/kernel.c
+++ b/kernel.c
@@ -31,7 +31,7 @@ void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
 
   demo_setup_PL0();
 
-  demo_go_unprivileged();
+  demo_setup_interrupts();
   
   // prints some info and sets up a section for PL0 code, loads a blob
   // there and jumps to it... never, ever, ever returns
diff --git a/linker.ld b/linker.ld
index 199cc0f..01eda35 100644
--- a/linker.ld
+++ b/linker.ld
@@ -89,6 +89,19 @@ SECTIONS
     __renamed_bss_size = __renamed_bss_end - __renamed_bss_start;
     __renamed_end = .;
     __renamed_size = __renamed_end - __renamed_start;
+
+
+    . = ALIGN(4096); /* align to page size */
+    __interrupt_vectors_start = .;
+    .interrupt_vectors :
+    {
+	interrupt_vectors = .;
+	*(.interrupt_vectors.text)
+	*(.interrupt_vectors.data)
+    }
+    . = ALIGN(4096); /* align to page size */
+    __interrupt_vectors_end = .;
+    __interrupt_vectors_size = __interrupt_vectors_end - __interrupt_vectors_start;
     
     __end = .;
 }