TEST CODE: prepare for switching to PL0

1 files changed, 56 insertions, 1 deletions

diff --git a/kernel.c b/kernel.c
index 7a10b24..bd4426d 100644
--- a/kernel.c
+++ b/kernel.c
@@ -6,6 +6,11 @@
 
 extern char __end;
 
+extern char
+  _binary_PL_0_test_img_start,
+  _binary_PL_0_test_img_end,
+  _binary_PL_0_test_img_size;
+
 void enabling_code_from_the_net(void);
   
 void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
@@ -85,7 +90,7 @@ void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
  
   // flat map all memory
   uart_puts("preparing translation table\n\r");
-  short_descriptor_lvl1_t *translation_table =
+  short_descriptor_lvl1_t volatile *translation_table =
     (short_descriptor_lvl1_t*) translation_table_base;
   
   for (uint32_t i = 0; i < 4096; i++)
@@ -178,6 +183,56 @@ void kernel_main(uint32_t r0, uint32_t r1, uint32_t atags)
   asm("mcr p15, 0, %0, c1, c0, 0\n\r"
       "isb" :: "r" (SCTLR.raw) : "memory");
 
+  volatile short_section_descriptor_t *PL0_code_section =
+    &translation_table[0b101010101010].section_fields;
+  volatile short_section_descriptor_t *UART_memory_section =
+    &translation_table[((uint32_t) GPIO_BASE) >> 20].section_fields;
+
+  // map code section to the memory right after out kernel
+  uint32_t kernel_memory_end = (uint32_t) (translation_table + 4096);
+  uint32_t unprivileged_memory_start =
+    (((kernel_memory_end - 1) >> 20) + 1) << 20;
+  
+  PL0_code_section->SECTION_BASE_ADDRESS_31_20 =
+    unprivileged_memory_start >> 20;
+
+  // make the selected section and uart section available for PL0
+  PL0_code_section->ACCESS_PERMISSIONS_2   =
+    AP_2_0_MODEL_RW_ALL >> 2;
+  PL0_code_section->ACCESS_PERMISSIONS_1_0 =
+    AP_2_0_MODEL_RW_ALL & 0b011;
+
+  UART_memory_section->ACCESS_PERMISSIONS_2   =
+    AP_2_0_MODEL_RW_ALL >> 2;
+  UART_memory_section->ACCESS_PERMISSIONS_1_0 =
+    AP_2_0_MODEL_RW_ALL & 0b011;
+  
+
+  // invalidate main Translation Lookup Buffer (just in case)
+  asm("mcr p15, 0, %0, c8, c7, 0\n\r"
+      "isb" :: "r" (0) : "memory");
+
+  // check that translation works... by copying a string using one
+  // mapping and reading it using other :D
+  char message[] = "mapped sections for PL0 code\n\r";
+
+  unsigned int i;
+  for (i = 0; i < sizeof(message); i++)
+    ((volatile char*) unprivileged_memory_start)[i] =  message[i];
+  
+  uart_puts((char*) (((uint32_t) 0b101010101010) << 20));
+
+  // 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++)
+    ((char*) (((uint32_t) 0b101010101010) << 20))[i] =
+      (&_binary_PL_0_test_img_start)[i];
+
+  // jump to that copied code (no switch to PL0 yet, just testing)
+  ((void(*)(void)) (((uint32_t) 0b101010101010) << 20))();
+  
+  while(1);
+  
   while (1)
     {
       char c;