From 39145f6d1b8c57abe2bc0167b2b413970d0dfdb6 Mon Sep 17 00:00:00 2001
From: Wojtek Kosior <kwojtus@protonmail.com>
Date: Tue, 19 Nov 2019 17:49:20 +0100
Subject: split kernel into more files

---
 demo_functionality.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 demo_functionality.c

(limited to 'demo_functionality.c')

diff --git a/demo_functionality.c b/demo_functionality.c
new file mode 100644
index 0000000..53035b7
--- /dev/null
+++ b/demo_functionality.c
@@ -0,0 +1,115 @@
+#include "uart.h"
+#include "psr.h"
+#include "memory.h"
+#include "translation_table_descriptors.h"
+
+void demo_paging_support(void)
+{
+  uint32_t ID_MMFR0;
+  // get contents of coprocessor register to check for paging support
+  asm("mrc p15, 0, %0, c0, c1, 4" : "=r" (ID_MMFR0));
+  
+  char *paging;
+  
+  switch(ID_MMFR0 & 0xf) /* lowest 4 bits indicate VMSA support */
+    {
+    case 0 : paging = "no paging\n\r"; break;
+    case 1 : paging = "implementation defined paging\n\r"; break;
+    case 2 : paging = "VMSAv6, with cache and TLB type registers\n\r"; break;
+    case 3 : paging = "VMSAv7, with support for remapping and access flag\n\r"; break;
+    case 4 : paging = "VMSAv7 with PXN bit supported\n\r"; break;
+    case 5 : paging = "VMSAv7, PXN and long format descriptors. EPAE is supported.\n\r"; break;
+    default : paging = "?_? unknown paging ?_?\n\r";
+    }
+  
+  uart_puts(paging);
+}
+
+void demo_mode_to_system(void)
+{
+
+  // get content of current program status register to check the current
+  // processor mode
+  PSR_t CPSR = read_CPSR();
+
+  char *mode_name;
+  
+  switch(CPSR.fields.PSR_MODE_4_0)
+    {
+    case MODE_USER       : mode_name = "User (PL0)\r\n"; break;
+    case MODE_FIQ        : mode_name = "FIQ (PL1)\r\n"; break;
+    case MODE_IRQ        : mode_name = "IRQ (PL1)\r\n"; break;
+    case MODE_SUPERVISOR : mode_name = "Supervisor (PL1)\r\n"; break;
+    case MODE_MONITOR    : mode_name = "Monitor (PL1)\r\n"; break;
+    case MODE_ABORT      : mode_name = "Abort (PL1)\r\n"; break;
+    case MODE_HYPERVISOR : mode_name = "Hyp (PL2)\r\n"; break;
+    case MODE_UNDEFINED  : mode_name = "Undefined (PL1)\r\n"; break;
+    case MODE_SYSTEM     : mode_name = "System (PL1)\r\n"; break;
+    default : mode_name = "Unknown mode\r\n"; break;
+    }
+
+  uart_puts("current mode: ");
+  uart_puts(mode_name);
+
+  uart_puts("setting mode to system (PL1)...\r\n");
+  set_system_mode();
+}
+
+extern char
+  _binary_PL_0_test_img_start,
+  _binary_PL_0_test_img_end,
+  _binary_PL_0_test_img_size;
+
+void demo_go_unprivileged(void)
+{
+  short_section_descriptor_t *translation_table =
+    (short_section_descriptor_t*) TRANSLATION_TABLE_BASE;
+
+  volatile short_section_descriptor_t *PL0_code_section =
+    &translation_table[PL0_SECTION_NUMBER];
+  volatile short_section_descriptor_t *UART_memory_section =
+    &translation_table[((uint32_t) GPIO_BASE) >> 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*) VIRTUAL_PL0_MEMORY_START);
+
+  // 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];
+
+  // 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");
+}
-- 
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