Primitive ability to call kernel code from userspace.

15 files changed, 249 insertions, 224 deletions

diff --git a/Makefile.preamble b/Makefile.preamble
index b338833..f6e1370 100644
--- a/Makefile.preamble
+++ b/Makefile.preamble
@@ -2,7 +2,7 @@ OPT?=-O
 PREFIX?=arm-unknown-eabi-
 CC=$(PREFIX)gcc
 LD=$(PREFIX)ld
-CFLAGS?=$(OPT) -mcpu=cortex-m4 -mthumb -mimplicit-it  -g -lgcc -static -nostartfiles -Iinclude -Iinclude/arch/arm
+CFLAGS?=$(OPT) -mcpu=cortex-m4 -mthumb -g -lgcc -static -nostartfiles -Iinclude -Iinclude/arch/arm
 LD_FLAGS?=-T linker/linker_script.ld -nostdlib --cref -Map linker/main.map -static
 
 TEST_PREFIX=x86_64-pc-linux-gnu-
diff --git a/include/kern/mpu/mpu_manager.h b/include/kern/mpu/mpu_manager.h
index 7c47722..5a0904c 100644
--- a/include/kern/mpu/mpu_manager.h
+++ b/include/kern/mpu/mpu_manager.h
@@ -55,7 +55,7 @@ typedef enum {
 
   /* Both privileged and non-privileged users can access this memory, but only
      as Read-only.*/
-  ACCESS_PERMS_BOTH_RO = 5,
+  ACCESS_PERMS_BOTH_RO = 6,
 } access_perms_t;
 
 typedef struct {
@@ -81,4 +81,28 @@ void mpu_set_enabled(bool enabled);
  */
 void mpu_configure_region(int region_number, memory_region_opts_t* opts);
 
+typedef enum {
+  PRIVILEGED,
+  NOT_PRIVILEGED,
+} privilege_t;
+
+
+/** Configure a peripheral region with default peripheral attributes. */
+void configure_peripheral_region(
+    void* peripheral_base,
+    region_size_t region_size,
+    privilege_t priv);
+
+/** Configure a flash region with default flash attributes. */
+void configure_flash_region(
+    void* flash_base,
+    region_size_t region_size,
+    privilege_t priv);
+
+/** Configure a ram region with default ram attributes. */
+void configure_ram_region(
+    void* ram_base,
+    region_size_t region_size,
+    privilege_t priv);
+
 #endif /* KERN_MPU_MPU_MANAGER_H_ */
diff --git a/include/kern/priv.h b/include/kern/priv.h
index 8940b23..35404f4 100644
--- a/include/kern/priv.h
+++ b/include/kern/priv.h
@@ -10,5 +10,7 @@ void set_control_register(uint32_t reg);
 /* Enters user mode from privilieged mode. */
 void enter_user_mode();
 
+void jump_to_user_mode();
+
 
 #endif /* _KERN_PRIV_H_ */
diff --git a/include/kern/syscall.h b/include/kern/syscall.h
new file mode 100644
index 0000000..d39b620
--- /dev/null
+++ b/include/kern/syscall.h
@@ -0,0 +1,8 @@
+#ifndef KERN_SYSCALL_H_
+#define KERN_SYSCALL_H_
+
+#define SYSCALL(id, fn, kernfn, argt) void kernfn(argt arg);
+#include "kern/syscall/syscall_tbl.inc"
+#undef SYSCALL
+
+#endif
diff --git a/include/kern/syscall/syscall_tbl.inc b/include/kern/syscall/syscall_tbl.inc
new file mode 100644
index 0000000..6c4be57
--- /dev/null
+++ b/include/kern/syscall/syscall_tbl.inc
@@ -0,0 +1,5 @@
+/*
+ * Defines a table of SYSCALLS. The syscalls need to be void functions that
+ * a single 32-bit integer as their argument.
+ */
+SYSCALL(25, logs, kern_logs, const char*)
diff --git a/include/user/syscall.h b/include/user/syscall.h
new file mode 100644
index 0000000..c420a3b
--- /dev/null
+++ b/include/user/syscall.h
@@ -0,0 +1,10 @@
+#ifndef USER_SYSCALL_H_
+#define USER_SYSCALL_H_
+
+/* This defines the full set of system calls accessible from usermode. */
+
+#define SYSCALL(id, fn, kernfn, argt) void fn(argt arg);
+#include "kern/syscall/syscall_tbl.inc"
+#undef SYSCALL
+
+#endif
diff --git a/src/kern/init.c b/src/kern/init.c
index 8885c09..c776b4a 100644
--- a/src/kern/init.c
+++ b/src/kern/init.c
@@ -66,9 +66,6 @@ init1()
 
 init3()
 {
-  klogf("--- System Restart ---\n");
-  klogf("Setting the vector offset table to point to the start of flash.\n");
-
   /* Set the vector offset table to be at the start
    * of FLASH memory. */
   SCB.vto_r = 0x08000000;
@@ -92,10 +89,6 @@ void run_init_routines()
        ++initfn) {
     while (initfn == init_boundaries[initlevel] && initlevel < INIT_LEVEL_7) {
       ++initlevel;
-
-      if (initlevel > 2) {
-        klogf("[init%d]\n", initlevel);
-      }
     }
 
     (*initfn)();
@@ -103,11 +96,7 @@ void run_init_routines()
 
   while (initlevel < INIT_LEVEL_7) {
     ++initlevel;
-
-    klogf("[init%d]\n", initlevel);
   }
-
-  klogf("Initialization Routines Complete. Onto main()\n");
 }
 
 /*
diff --git a/src/kern/log.c b/src/kern/log.c
index 3331249..e9bd424 100644
--- a/src/kern/log.c
+++ b/src/kern/log.c
@@ -18,8 +18,6 @@ init2()
   regset(USART2.c_r1, usart_txeie, 1);
   regset(USART2.c_r1, usart_rxneie, 1);
   usart_set_enabled(&USART2, USART_ENABLE_TX | USART_ENABLE_RX);
-
-  klogf("klog() enabled on USART2\n");
 }
 
 void klogf(const char* fmt, ...)
diff --git a/src/kern/main.c b/src/kern/main.c
index 4ed67be..3af8beb 100644
--- a/src/kern/main.c
+++ b/src/kern/main.c
@@ -8,6 +8,7 @@
 #include "kern/mpu/mpu_manager.h"
 #include "kern/panic.h"
 #include "kern/priv.h"
+#include "user/syscall.h"
 
 void on_hard_fault()
 {
@@ -19,139 +20,34 @@ void on_systick() /* Overrides weak-symbol on_systick. */
   klogf("Systick\n");
 }
 
-#ifdef ARCH_STM32L4
+void configure_mpu()
+{
+  configure_flash_region((void*)0x08000000, REGION_SIZE_256Kb, NOT_PRIVILEGED);
+  configure_ram_region((void*)SRAM1_BASE, REGION_SIZE_64Kb, NOT_PRIVILEGED);
+  configure_ram_region((void*)SRAM2_BASE, REGION_SIZE_16Kb, NOT_PRIVILEGED);
+  configure_peripheral_region((void*)0x40000000, REGION_SIZE_512Mb, PRIVILEGED);
+  mpu_set_enabled(1);
+}
 
-int thing_in_sram_1;
+#ifdef ARCH_STM32L4
 
 /* Main function. This gets executed from the interrupt vector defined above. */
 int main()
 {
-  klogf("Hello, World! Clock Mhz: %d\n", (uint32_t)get_clock_mhz());
-  klogf("Heap Start: %p\n", &HEAP_START);
-  klogf("Heap End  : %p\n", &HEAP_STOP);
-
-  klogf("mpu: %p\n", &MPU);
-  klogf("mpu.type_r: %p\n", MPU.type_r);
-  klogf("mpu.ctrl_r: %p\n", MPU.ctrl_r);
-  klogf("mpu.rn_r: %p\n", MPU.rn_r);
-
-  thing_in_sram_1 = 0xdeadbeef;
-
-  uint32_t control;
-  asm volatile("mrs %0, control" : "=r"(control) :);
-
-  /* Set the countdown to start from 10,000,0000. */
-  SCB.strv_r = 10000000 / 20;
-
-  /* Enable interrupts. */
-  // regset(SCB.stcs_r, scb_tickint, 1);
-
-  /* Start the systick. */
-  regset(SCB.stcs_r, scb_enable, 1);
-
-
-  klogf("&thing_in_sram_1: %p\n", &thing_in_sram_1);
-  klogf(" thing_in_sram_1: %p\n", thing_in_sram_1);
-  mpu_set_enabled(0);
-
-  memory_region_opts_t memopts = { 0 };
-  memopts.region = (void*) 0x08000000 /* Flash base */ ;
-  memopts.bufferable = 0;
-  memopts.cacheable = 1;
-  memopts.sharable = 0;
-  memopts.tex = 0;
-  memopts.size = REGION_SIZE_256Kb;
-  memopts.perms = ACCESS_PERMS_ONLY_PRIV_RO;
-  memopts.subregion_disable = 0;
-  memopts.executable = 1;
-  memopts.enable = 1;
+  configure_mpu();
 
-  mpu_configure_region(0, &memopts);
+  klogf("Outside of usermode, I can still log stuff using klogf()\n");
 
-  memopts.region = (void*) SRAM1_BASE;
-  memopts.bufferable = 0;
-  memopts.cacheable = 1;
-  memopts.sharable = 0;
-  memopts.tex = 0;
-  memopts.size = REGION_SIZE_64Kb;
-  memopts.perms = ACCESS_PERMS_FULL;
-  memopts.subregion_disable = 0;
-  memopts.executable = 1;
-  memopts.enable = 1;
-
-  mpu_configure_region(1, &memopts);
-
-  memopts.region = (void*) SRAM2_BASE;
-  memopts.bufferable = 0;
-  memopts.cacheable = 1;
-  memopts.sharable = 0;
-  memopts.tex = 0;
-  memopts.size = REGION_SIZE_16Kb;
-  memopts.perms = ACCESS_PERMS_FULL;
-  memopts.subregion_disable = 0;
-  memopts.executable = 1;
-  memopts.enable = 1;
-
-  mpu_configure_region(2, &memopts);
-
-  memopts.region = (void*) 0x40000000 /* Peripheral base. */;
-  memopts.bufferable = 1;
-  memopts.cacheable = 0;
-  memopts.sharable = 1;
-  memopts.tex = 0;
-  memopts.size = REGION_SIZE_512Mb;
-  memopts.perms = ACCESS_PERMS_ONLY_PRIV;
-  memopts.subregion_disable = 0;
-  memopts.executable = 0;
-  memopts.enable = 1;
-
-  mpu_configure_region(3, &memopts);
-
-  for (uint32_t i = 0; i < 8; ++ i) {
-    MPU.rn_r = i;
-    klogf("--- %d ---\n", i);
-    klogf("mpu: %p\n", &MPU);
-    klogf("mpu.type_r: %p\n", MPU.type_r);
-    klogf("mpu.ctrl_r: %p\n", MPU.ctrl_r);
-    klogf("mpu.rn_r: %p\n", MPU.rn_r);
-    klogf("mpu.ras_r: %p\n", MPU.ras_r);
-    klogf("mpu.rba_r: %p\n", MPU.rba_r);
-  }
-
-  // memopts.region = (void*) (SRAM1_BASE);
-  // memopts.bufferable = 0;
-  // memopts.cacheable = 1;
-  // memopts.sharable = 1;
-  // memopts.tex = 0;
-  // memopts.size = REGION_SIZE_16Kb;
-  // memopts.perms = ACCESS_PERMS_NO_ACCESS;
-
-  klogf("CONTROL: %p\n", get_control_register());
-  klogf("CONTROL: %p\n", get_control_register());
-  klogf("MPU not enabled\n");
-
-  volatile int x;
-  klogf("x location: %p\n", &x);
-
-  // mpu_set_enabled(1);
-
-  x = 5;
-  klogf("Still alive?\n");
-
-  klogf("Entering User Mode\n");
   enter_user_mode();
 
-  asm volatile (
-      "svc #21\n"
-      );
-
-  klogf("Should Kernel Panic\n");
+  logs("Now that I'm in user mode, I have to log stuff using a system call\n");
+  logs(
+      "because I no longer have direct accss to USART2 and cannot use\n"
+      "klogf()\n");
 
-  for(;;);
-  // klogf("MPU enabled\n");
 
-  // klogf("&thing_in_sram_1: %p\n", &thing_in_sram_1);
-  // klogf(" thing_in_sram_1: %p\n", thing_in_sram_1);
+  for (;;)
+    ;
 }
 
 #endif
diff --git a/src/kern/mpu/mpu_manager.c b/src/kern/mpu/mpu_manager.c
index 614766a..0d03c39 100644
--- a/src/kern/mpu/mpu_manager.c
+++ b/src/kern/mpu/mpu_manager.c
@@ -1,6 +1,6 @@
-#include "arch.h"
 #include "kern/mpu/mpu_manager.h"
 
+#include "arch.h"
 #include "arch/arm/cortex-m4/mpu.h"
 #include "kern/common.h"
 #include "kern/log.h"
@@ -40,8 +40,6 @@ void mpu_configure_region(int region_number, memory_region_opts_t* opts)
   uint32_t rbar = region;
   regset(rbar, mpu_region, region_number);
   regset(rbar, mpu_valid, 1);
-  
-  klogf("Writing RBAR: %p\n", rbar);
 
   uint32_t rasr = 0;
   regset(rasr, mpu_en, opts->enable);
@@ -56,8 +54,103 @@ void mpu_configure_region(int region_number, memory_region_opts_t* opts)
   regset(rasr, mpu_ap, opts->perms);
   regset(rasr, mpu_xn, !opts->executable);
 
-  klogf("Writing RASR: %p\n", rasr);
-
   MPU.rba_r = rbar;
   MPU.ras_r = rasr;
 }
+
+static int find_unused_region_slot()
+{
+  // memory_region_opts_t memory_regions[8];
+
+  int i;
+  for (i = 0; i < sizeof(memory_regions) / sizeof(memory_region_opts_t);
+       ++i) {
+    if (!memory_regions[i].enable) {
+      return i;
+    }
+  }
+
+  return i;
+}
+
+void configure_peripheral_region(
+    void* peripheral_base, region_size_t region_size, privilege_t priv)
+{
+  int idx = find_unused_region_slot();
+
+  memory_region_opts_t memopts = {0};
+
+  memopts.region = peripheral_base;
+  memopts.bufferable = 1;
+  memopts.cacheable = 0;
+  memopts.sharable = 1;
+  memopts.tex = 0;
+  memopts.size = region_size;
+  switch (priv) {
+    case NOT_PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_FULL;
+      break;
+    case PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_ONLY_PRIV;
+      break;
+  }
+  memopts.subregion_disable = 0;
+  memopts.executable = 0;
+  memopts.enable = 1;
+
+  mpu_configure_region(idx, &memopts);
+}
+
+void configure_flash_region(
+    void* flash_base, region_size_t region_size, privilege_t priv)
+{
+  int idx = find_unused_region_slot();
+
+  memory_region_opts_t memopts = {0};
+  memopts.region = flash_base;
+  memopts.bufferable = 0;
+  memopts.cacheable = 1;
+  memopts.sharable = 0;
+  memopts.tex = 0;
+  memopts.size = region_size;
+  switch (priv) {
+    case NOT_PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_BOTH_RO;
+      break;
+    case PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_ONLY_PRIV_RO;
+      break;
+  }
+  memopts.subregion_disable = 0;
+  memopts.executable = 1;
+  memopts.enable = 1;
+
+  mpu_configure_region(idx, &memopts);
+}
+
+void configure_ram_region(
+    void* ram_base, region_size_t region_size, privilege_t priv)
+{
+  int idx = find_unused_region_slot();
+
+  memory_region_opts_t memopts = {0};
+  memopts.region = ram_base;
+  memopts.bufferable = 0;
+  memopts.cacheable = 1;
+  memopts.sharable = 0;
+  memopts.tex = 0;
+  memopts.size = region_size;
+  switch (priv) {
+    case NOT_PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_FULL;
+      break;
+    case PRIVILEGED:
+      memopts.perms = ACCESS_PERMS_ONLY_PRIV;
+      break;
+  }
+  memopts.subregion_disable = 0;
+  memopts.executable = 0;
+  memopts.enable = 1;
+
+  mpu_configure_region(idx, &memopts);
+}
diff --git a/src/kern/panic.c b/src/kern/panic.c
index 3e67b90..de1d143 100644
--- a/src/kern/panic.c
+++ b/src/kern/panic.c
@@ -28,7 +28,6 @@ _Noreturn void panic(const char* fmt, ...)
       kerr_logf(" (%p) %p\n", &base[i], base[i]);
     }
 
-
     set_system_clock_MHz(4); /* reduce power usage while we do nothing. */
     for(;;);
   } else {
diff --git a/src/kern/priv.c b/src/kern/priv.c
index 085de85..3162639 100644
--- a/src/kern/priv.c
+++ b/src/kern/priv.c
@@ -3,87 +3,6 @@
 #include "arch.h"
 #include "kern/log.h"
 
-void handle_svc_call(uint32_t svc_number)
-{
-  klogf("Handle SVC: %p\n", svc_number);
-  for (;;)
-    ;
-}
-
-asm("	.align	2\n"
-    "	.global	on_svc\n"
-    "	.syntax unified\n"
-    "	.fpu softvfp\n"
-    "	.type	on_svc, %function\n"
-    "on_svc:\n"
-    "	tst   lr,#4\n"
-    " ite   eq\n"
-    "	moveq r12,sp\n"
-    "	mrsne r12,psp\n"
-    "	ldr   r12, [r12, #24]\n"
-    "	ldrh  r12, [r12, #-2]\n"
-    "	bics  r12, r12, #0xff00\n"
-    "	push  {r4, lr}\n"
-    "	mov   r0 , r12\n"
-    "	bl    handle_svc_call\n"
-    "	pop   {r4, lr}\n"
-    "	tst   lr, #4\n"
-    " ite   eq\n"
-    "	moveq r12,sp\n"
-    "	mrsne r12,psp\n"
-    "	stm   r12,{r0-r3}\n"
-    "	bx    lr\n");
-
-// void on_svc()  // ISR handler. Override from weak symbol.
-// {
-// asm volatile(
-//     "push {r0-r12, lr}\n\t"
-//     "ldr  r0, [lr, #-4]\n\t"
-//     "bic  r0, r0, #0xff000000\n\t"
-//     );
-
-// TST     LR,#4                   ; Called from Handler Mode?
-// MRSNE   R12,PSP                 ; Yes, use PSP
-// MOVEQ   R12,SP                  ; No, use MSP
-// LDR     R12,[R12,#24]           ; Read Saved PC from Stack
-// LDRH    R12,[R12,#-2]           ; Load Halfword
-// BICS    R12,R12,#0xFF00         ; Extract SVC Number
-// uint32_t reg;
-// asm volatile(
-//     "mov  r12, sp\n\t"
-//     "ldr  r12, [r12,#24]\n\t"
-//     // "ldrh r12,[r12, #-2]\n\t"
-//     // "bics r12, r12, #0xff00\n\t"
-//     "mov  %0, r12\n\t": "=r"(reg));
-
-//   uint32_t base[0];
-//   uint32_t reg;
-//
-//
-//   asm volatile("mov  %0, sp\n\t" : "=r"(reg));
-//   uint32_t* at = (uint32_t*) (reg + 44); /* Does GCC set up 5 stack frame
-//   words? */
-//
-//   klogf("Stack pointer: %p\n", reg);
-//   klogf("Stack pointer +44: %p\n", (reg + 44));
-//   klogf("At_: %p: %p\n\n", 0x80009f6, *(uint32_t*)0x80009f6);
-//   klogf("At: %p: %p\n\n", at, *at);
-//
-//
-//   int i = 0;
-//   for (; i < 20 && &base[i] != (void*)STACK_TOP; ++ i) {
-//     kerr_logf(" (%p) %p\n", &base[i], base[i]);
-//   }
-//
-//   // klogf("TEST %p\n", reg);
-//
-//   for(;;);
-
-// register int svc_number asm ("r0");
-
-// klogf("SVC #: %p\n", svc_number);
-// }
-
 void set_control_register(uint32_t reg)
 {
   asm volatile("msr control, %0" : "=r"(reg) :);
@@ -102,3 +21,10 @@ void enter_user_mode()
       "mov r0, #1\n\t"
       "msr control, r0\n\t");
 }
+
+void jump_to_user_mode()
+{
+  asm volatile(
+      "mov r0, #1\n\t"
+      "msr control, r0\n\t");
+}
diff --git a/src/kern/svc.c b/src/kern/svc.c
new file mode 100644
index 0000000..5527364
--- /dev/null
+++ b/src/kern/svc.c
@@ -0,0 +1,51 @@
+#include "arch.h"
+#include "kern/common.h"
+#include "kern/log.h"
+#include "kern/syscall.h"
+
+void handle_svc_call(
+    uint32_t syscall_id, uint32_t syscall_arg, uint32_t svc_number)
+{
+  switch (svc_number) {
+    case 0x04:
+      switch (syscall_id) {
+#define SYSCALL(id, fn, kernfn, argt) \
+  case id:                    \
+    kernfn((argt)syscall_arg);    \
+    break;
+#include "kern/syscall/syscall_tbl.inc"
+#undef SYSCALL
+      }
+      break;
+
+    default:
+      /* An illegal syscall. TODO kill whatever is happening. */
+      break;
+  }
+}
+
+/* The actual handling for the svc call. Overrides the weak
+ * symbol on_svc in irq.h */
+asm("	.align	2\n"
+    "	.global	on_svc\n"
+    "	.syntax unified\n"
+    "	.fpu softvfp\n"
+    "	.type	on_svc, %function\n"
+    "on_svc:\n"
+    "	tst   lr,#4\n"
+    " ite   eq\n"
+    "	moveq r12,sp\n"
+    "	mrsne r12,psp\n"
+    "	ldr   r12, [r12, #24]\n"
+    "	ldrh  r12, [r12, #-2]\n"
+    "	bics  r12, r12, #0xff00\n"
+    "	push  {r4, lr}\n"
+    "	mov   r2 , r12\n"
+    "	bl    handle_svc_call\n"
+    "	pop   {r4, lr}\n"
+    "	tst   lr, #4\n"
+    " ite   eq\n"
+    "	moveq r12,sp\n"
+    "	mrsne r12,psp\n"
+    "	stm   r12,{r0-r3}\n"
+    "	bx    lr\n");
diff --git a/src/kern/syscalls/logs.c b/src/kern/syscalls/logs.c
new file mode 100644
index 0000000..855672c
--- /dev/null
+++ b/src/kern/syscalls/logs.c
@@ -0,0 +1,7 @@
+#include "kern/syscall.h"
+#include "kern/log.h"
+
+void kern_logs(const char* str)
+{
+  klogf("[Log] - %s", str);
+}
diff --git a/src/user/syscall.c b/src/user/syscall.c
new file mode 100644
index 0000000..3aa0707
--- /dev/null
+++ b/src/user/syscall.c
@@ -0,0 +1,17 @@
+#include "user/syscall.h"
+
+#include <stdint.h>
+
+void __attribute__ ((noinline)) do_syscall(
+    volatile uint32_t id,
+    volatile uint32_t arg)
+{
+  asm volatile("svc #0x04");
+}
+
+#define SYSCALL(id, fn, kernfn, argt) \
+  void fn(argt arg) \
+{ \
+  do_syscall(id, (uint32_t) arg); \
+}
+#include "kern/syscall/syscall_tbl.inc"