Revert "Merge branch 'bob' of https://repo.or.cz/RPi-MMU-example into alice"

This reverts commit 5662aacc5688bba4873367ed9ab51fb83fbd1feb, reversing
changes made to b0a6351d52af8bdf6fa9cca0d313df323249a520.

8 files changed, 33 insertions, 162 deletions

diff --git a/Makefile b/Makefile
index f07bced..ce29a19 100644
--- a/Makefile
+++ b/Makefile
@@ -3,10 +3,6 @@ ELFFLAGS=-ffreestanding -O2 -nostdlib -lgcc -I.
 
 ARM_OBJECTS=kernel.o paging.o demo_functionality.o PL0_test.o uart.o loader_stage1.o loader_stage2.o
 
-EMBEDDABLE_OBJECTS=PL_0_test_embeddable.o loader_stage2_embeddable.o
-
-RENAME_FLAGS=--rename-section .data=.renamed_data --rename-section .rodata=.renamed_rodata --rename-section .text=.renamed_text --rename-section .bss=.renamed_bss
-
 all : kernel7.img
 
 %.o : %.c
@@ -21,16 +17,10 @@ all : kernel7.img
 %_embeddable.o : %.img
 	arm-none-eabi-objcopy -I binary -O elf32-littlearm -B arm --rename-section .data=.rodata $^ $@
 
-libkernel.o : libkernel.c
-	arm-none-eabi-gcc $(CFLAGS) -fPIC -c $^ -o $@
-
-libkernel_renamed.o : libkernel.o
-	arm-none-eabi-objcopy $(RENAME_FLAGS) $^ $@
-
 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
 	arm-none-eabi-gcc -T linker.ld -o $@ $(ELFFLAGS) $^
 
 loader_stage2.elf : loader_stage2.o uart.o
diff --git a/PL0_test.c b/PL0_test.c
index 1b93024..2216436 100644
--- a/PL0_test.c
+++ b/PL0_test.c
@@ -5,6 +5,9 @@ void PL0_main(void)
 {
   uart_puts("hello PL0! Switching to user mode!\n\r");
 
+  asm("cps #0b10000\n\r"
+      "isb" ::: "memory");
+
   // if all went correct, Success! gets printed
   uart_puts("Success!\n\r");
 
diff --git a/PL0_test.ld b/PL0_test.ld
index 45bee5e..430e098 100644
--- a/PL0_test.ld
+++ b/PL0_test.ld
@@ -4,11 +4,6 @@ SECTIONS
 {
     /* 0b10101010101000000000000000000000 */
     . = 0xaaa00000;
-    
-    /* For some reason ld warns when _start is not defined. */
-    /* Other .elf files link ok - only PL0_test.elf seems to */
-    /* expect _start to be deifned. */
-    _start = .;
     __start = .;
     __text_start = .;
     .text :
diff --git a/demo_functionality.c b/demo_functionality.c
index fbf5eb4..7bba6a6 100644
--- a/demo_functionality.c
+++ b/demo_functionality.c
@@ -2,7 +2,6 @@
 #include "psr.h"
 #include "memory.h"
 #include "translation_table_descriptors.h"
-#include "libkernel.h"
 
 void demo_paging_support(void)
 {
@@ -56,73 +55,35 @@ void demo_mode_to_system(void)
   set_system_mode();
 }
 
-#define TRANSLATION_TABLE						\
-  ((short_section_descriptor_t volatile*) TRANSLATION_TABLE_BASE)
-
-extern char
-  __renamed_start,
-  __renamed_end,
-  __renamed_size;
-
-void demo_setup_libkernel(void) {
-  short_section_descriptor_t volatile *libkernel_section_entry =
-    &TRANSLATION_TABLE[LIBKERNEL_SECTION_NUMBER];
-
-  short_section_descriptor_t
-    libkernel_section = *libkernel_section_entry;
-
-  // make libkernel section executable and read-only for
-  // unprivileged code
-  libkernel_section.ACCESS_PERMISSIONS_2 =
-    AP_2_0_MODEL_RW_PL1_RO_PL0 >> 2;
-  libkernel_section.ACCESS_PERMISSIONS_1_0 =
-    AP_2_0_MODEL_RW_PL1_RO_PL0 & 0b011;
-
-  *libkernel_section_entry = libkernel_section;  
-
-  // invalidate main Translation Lookup Buffer (just in case)
-  asm("mcr p15, 0, %0, c8, c7, 0\n\r"
-      "isb" :: "r" (0) : "memory");
-  
-  // copy libkernel code to libkernel section
-  for (size_t i = 0; i < (size_t) &__renamed_size; i++)
-    ((volatile char*) LIBKERNEL_SECTION_START)[i] =
-      (&__renamed_start)[i];  
-}
-
 extern char
   _binary_PL_0_test_img_start,
   _binary_PL_0_test_img_end,
   _binary_PL_0_test_img_size;
 
-void demo_setup_PL0(void)
+void demo_go_unprivileged(void)
 {
-  short_section_descriptor_t volatile *PL0_section_entry =
-    &TRANSLATION_TABLE[PL0_SECTION_NUMBER];
-  short_section_descriptor_t volatile *UART_memory_section_entry =
-    &TRANSLATION_TABLE[((uint32_t) GPIO_BASE) >> 20];
+  short_section_descriptor_t *translation_table =
+    (short_section_descriptor_t*) TRANSLATION_TABLE_BASE;
 
-  short_section_descriptor_t
-    PL0_section = *PL0_section_entry,
-    UART_memory_section = *UART_memory_section_entry;
+  volatile short_section_descriptor_t *PL0_section =
+    &translation_table[PL0_SECTION_NUMBER];
+  volatile short_section_descriptor_t *UART_memory_section =
+    &translation_table[((uint32_t) GPIO_BASE) >> 20];
 
-  // set up address of PL0 section
-  PL0_section.SECTION_BASE_ADDRESS_31_20 =
+  PL0_section->SECTION_BASE_ADDRESS_31_20 =
     UNPRIVILEGED_MEMORY_START >> 20;
 
   // make the selected section and uart section available for PL0
-  PL0_section.ACCESS_PERMISSIONS_2 =
+  PL0_section->ACCESS_PERMISSIONS_2 =
     AP_2_0_MODEL_RW_ALL >> 2;
-  PL0_section.ACCESS_PERMISSIONS_1_0 =
+  PL0_section->ACCESS_PERMISSIONS_1_0 =
     AP_2_0_MODEL_RW_ALL & 0b011;
 
-  UART_memory_section.ACCESS_PERMISSIONS_2 =
+  UART_memory_section->ACCESS_PERMISSIONS_2 =
     AP_2_0_MODEL_RW_ALL >> 2;
-  UART_memory_section.ACCESS_PERMISSIONS_1_0 =
+  UART_memory_section->ACCESS_PERMISSIONS_1_0 =
     AP_2_0_MODEL_RW_ALL & 0b011;
-
-  *PL0_section_entry = PL0_section;
-  *UART_memory_section_entry = UART_memory_section;
+  
 
   // invalidate main Translation Lookup Buffer (just in case)
   asm("mcr p15, 0, %0, c8, c7, 0\n\r"
@@ -138,30 +99,17 @@ void demo_setup_PL0(void)
   
   uart_puts((char*) VIRTUAL_PL0_MEMORY_START);
 
-  // now paste a userspace program to that section
+  // now paste a userspace program to that section, jump to it and
+  // switch to PL0
   for (size_t i = 0; i < (size_t) &_binary_PL_0_test_img_size; i++)
     ((volatile char*) VIRTUAL_PL0_MEMORY_START)[i] =
       (&_binary_PL_0_test_img_start)[i];
 
-  uart_puts("copied PL0 and libkernel code to their sections");
-}
-
-void demo_go_unprivileged(void)
-{
-  size_t call_unprivileged_offset =
-    (size_t) &call_unprivileged - (size_t) &__renamed_start;
-
-  void *call_unprivileged_new_location =
-    (void*) (LIBKERNEL_SECTION_START + call_unprivileged_offset);
-  
-  // call call_unprivileged from libkernel
-  asm volatile("mov  r5, %0\n\r"
-	       "mov  r0, %1\n\r"
-	       "mov  r4, #0\n\r"
-  	       "movt r4, #"PL0_SECTION_NUMBER_STR"1111\n\r"
-  	       "mov  sp, r4\n\r" // setting stack is important :D
-  	       "blx  r5\n\r" ::
-	       "r" (call_unprivileged_new_location),
-	       "r" (VIRTUAL_PL0_MEMORY_START)
-	       : "memory", "r4", "r5", "r0");
+  // jump to that copied code (switch to PL0 is done by that code)
+  asm volatile("mov  r5, #0\n\r"
+  	       "movt r5, #"PL0_SECTION_NUMBER_STR"1111\n\r"
+  	       "mov  sp, r5\n\r" // setting stack is important :D
+  	       "mov  r5, #0\n\r"
+  	       "movt r5, #"PL0_SECTION_NUMBER_STR"0000\n\r"
+  	       "blx  r5\n\r");
 }
diff --git a/demo_functionality.h b/demo_functionality.h
index 5d6e659..c8b163f 100644
--- a/demo_functionality.h
+++ b/demo_functionality.h
@@ -5,10 +5,6 @@ void demo_paging_support(void);
 
 void demo_mode_to_system(void);
 
-void demo_setup_libkernel(void);
-
-void demo_setup_PL0(void);
-
 void demo_go_unprivileged(void);
 
 #endif // DEMO_FUNCTIONALITY_H
diff --git a/kernel.c b/kernel.c
index 67c32dd..95d803d 100644
--- a/kernel.c
+++ b/kernel.c
@@ -29,12 +29,6 @@ void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
   // prints some info and sets upp translation table, turns on MMU
   setup_flat_map();
 
-  demo_setup_libkernel();
-
-  demo_setup_PL0();
-
-  demo_go_unprivileged();
-  
   // prints some info and sets up a section for PL0 code, loads a blob
   // there and jumps to it... never, ever, ever returns
   demo_go_unprivileged();
diff --git a/linker.ld b/linker.ld
index 199cc0f..e7bfdb8 100644
--- a/linker.ld
+++ b/linker.ld
@@ -49,46 +49,5 @@ SECTIONS
     . = ALIGN(4096); /* align to page size */
     __bss_end = .;
     __bss_size = __bss_end - __bss_start;
-
-
-
-    /* Here come the definitions for renamed sections */
-    __renamed_start = .;
-    __renamed_text_start = .;
-    .renamed_text :
-    {
-        *(.renamed_text)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __renamed_text_end = .;
- 
-    __renamed_rodata_start = .;
-    .renamed_rodata :
-    {
-        *(.renamed_rodata)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __renamed_rodata_end = .;
- 
-    __renamed_data_start = .;
-    .renamed_data :
-    {
-        *(.renamed_data)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __renamed_data_end = .;
- 
-    __renamed_bss_start = .;
-    .renamed_bss :
-    {
-        renamed_bss = .;
-        *(.renamed_bss)
-    }
-    . = ALIGN(4096); /* align to page size */
-    __renamed_bss_end = .;
-    __renamed_bss_size = __renamed_bss_end - __renamed_bss_start;
-    __renamed_end = .;
-    __renamed_size = __renamed_end - __renamed_start;
-    
     __end = .;
 }
diff --git a/memory.h b/memory.h
index 1c9ae35..1472a8b 100644
--- a/memory.h
+++ b/memory.h
@@ -1,17 +1,13 @@
 #ifndef MEMORY_H
 #define MEMORY_H
 
-#include "paging.h"
-
-#define SECTION_SIZE (((uint32_t) 1) << 20)
-
 #define INTERRUPT_VECTOR_TABLE_START ((uint32_t) 0x0)
 
 #define STACK_START ((uint32_t) 0x4000)
 #define STACK_END   ((uint32_t) 0x8000)
 
-extern const char __end;
-extern const char __start;
+extern char __end;
+extern char __start;
 
 #define KERNEL_START ((uint32_t) &__start)
 #define KERNEL_END   ((uint32_t) &__end)
@@ -24,21 +20,11 @@ extern const char __start;
 #define TRANSLATION_TABLE_END				\
   (TRANSLATION_TABLE_BASE + (uint32_t) (4096 * 4))
 
-#define LIBKERNEL_SECTION_START					\
-  (((TRANSLATION_TABLE_END - (uint32_t) 1) & ~((uint32_t) 0xfffff))	\
-   + SECTION_SIZE)
-
-#define LIBKERNEL_SECTION_END			\
-  (LIBKERNEL_SECTION_START + SECTION_SIZE)
+#define PRIVILEGED_MEMORY_END TRANSLATION_TABLE_END
 
-// section for libkernel is flat-mapped
-#define LIBKERNEL_SECTION_NUMBER (LIBKERNEL_SECTION_START >> 20)
-
-#define PRIVILEGED_MEMORY_END LIBKERNEL_SECTION_END
-
-#define UNPRIVILEGED_MEMORY_START PRIVILEGED_MEMORY_END
-#define UNPRIVILEGED_MEMORY_END			\
-  (UNPRIVILEGED_MEMORY_START + SECTION_SIZE)
+#define UNPRIVILEGED_MEMORY_START					\
+  (((PRIVILEGED_MEMORY_END - (uint32_t) 1) & ~((uint32_t) 0xfffff))	\
+   + (uint32_t) 0x100000)
 
 #define PL0_SECTION_NUMBER     ((uint32_t) 0b101010101010)
 #define PL0_SECTION_NUMBER_STR "0b101010101010"
@@ -46,4 +32,4 @@ extern const char __start;
 #define VIRTUAL_PL0_MEMORY_START (PL0_SECTION_NUMBER << 20)
 
 #endif // MEMORY_H
-
+