CM: Pre-checks added before process syscalls

Library functions must validate user input before making a system call.
Kernel functions assumes valid input from user.

Also includes:
* New system call to get OS errors
* Process functions moved to cm/process.c & cm.h
* New functions to set library mode errors.

include/cm/cm.h

@@ -10,6 +10,13 @@
 
 #include <types.h>
 #include <stdarg.h>
+#ifdef KERNEL
+    #include <cm/osif.h>
+    #include <cm/syscall.h>
+#else
+    #include <osif.h>
+    #include <syscall.h>
+#endif
 
 #define INVALID_HANDLE (-1)
 #define HALT()         for (;;)
@@ -23,3 +30,30 @@ INT vsnprintf (CHAR* dest, size_t size, const CHAR* fmt, va_list l);
  * @return      Nothing
  **************************************************************************************************/
 void cm_delay (UINT ms);
+
+/***************************************************************************************************
+ * Process management
+ ***************************************************************************************************/
+INT cm_thread_create (void (*startLocation)(), bool isKernelMode);
+INT cm_process_create (void* startLocation, SIZE binaryLengthBytes, bool isKernelMode);
+bool cm_process_is_yield_requested();
+
+static inline void cm_process_yield()
+{
+    syscall (OSIF_SYSCALL_YIELD_PROCESS, 0, 0, 0, 0, 0);
+}
+
+static inline void cm_process_kill (UINT code)
+{
+    syscall (OSIF_SYSCALL_KILL_PROCESS, code, 0, 0, 0, 0);
+}
+
+static inline U32 cm_process_get_pid()
+{
+    return (U32)syscall (OSIF_SYSCALL_PROCESS_GETPID, 0, 0, 0, 0, 0);
+}
+
+static inline void* cm_process_get_datamem_start()
+{
+    return (void*)syscall (OSIF_SYSCALL_PROCESS_GET_DATAMEM_START, 0, 0, 0, 0, 0);
+}

include/cm/err.h

@@ -0,0 +1,44 @@
+/*
+ * ---------------------------------------------------------------------------
+ * Megha Operating System V2 - C MOS App library - Library errors
+ * ---------------------------------------------------------------------------
+ */
+
+#include <stdint.h>
+#ifdef KERNEL
+    #include <cm/debug.h>
+    #include <cm/syscall.h>
+    #include <cm/osif.h>
+#else
+    #include <debug.h>
+    #include <syscall.h>
+    #include <osif.h>
+#endif
+
+#define CM_FAILURE (-1)
+
+typedef enum CMErrors {
+    // OS Errors start from 0 and must end before the start of library errors
+    LIBRARY_ERRORS_START = 100,
+    CM_ERR_INVALID_INPUT = 100,
+} CMErrors;
+
+extern uint32_t cm_error_num__;
+
+static inline uint32_t cm_get_lib_error()
+{
+    return cm_error_num__;
+}
+
+static inline uint32_t cm_get_os_error()
+{
+    return (uint32_t)syscall (OSIF_SYSCALL_GET_OS_ERROR, 0, 0, 0, 0, 0);
+}
+
+/* Can be used to store an error code and return from a function */
+#define CM_RETURN_ERROR__(errno, rval) \
+    do {                               \
+        ERROR ("Error %x.", errno);    \
+        cm_error_num__ = errno;        \
+        return rval;                   \
+    } while (0)

include/cm/osif.h

@@ -31,6 +31,7 @@ typedef enum OSIF_SYSCALLS {
     OSIF_SYSCALL_WINDOW_DESTORY            = 11,
     OSIF_SYSCALL_WINDOW_GET_WINDOW_FB      = 12,
     OSIF_SYSCALL_WINDOW_FLUSH_GRAPHICS     = 13,
+    OSIF_SYSCALL_GET_OS_ERROR              = 14,
 } OSIF_SYSCALLS;
 
 typedef enum OSIF_ProcessEvents {

include/cm/syscall.h

@@ -17,37 +17,18 @@
 #endif
 
 S32 syscall (OSIF_SYSCALLS fn, U32 arg1, U32 arg2, U32 arg3, U32 arg4, U32 arg5);
-INT cm_thread_create (void (*startLocation)(), bool isKernelMode);
-INT cm_process_create (void* startLocation, SIZE binaryLengthBytes, bool isKernelMode);
 UINT cm_get_tick_period_us();
-bool cm_process_is_yield_requested();
-bool cm_process_is_child_exited (UINT* exitCode);
 
 static inline UINT cm_tickcount_to_microsec(UINT tick)
 {
     return ((tick)*cm_get_tick_period_us());
 }
 
-static inline void cm_process_yield()
-{
-    syscall (OSIF_SYSCALL_YIELD_PROCESS, 0, 0, 0, 0, 0);
-}
-
-static inline void cm_process_kill(UINT code)
-{
-    syscall (OSIF_SYSCALL_KILL_PROCESS, code, 0, 0, 0, 0);
-}
-
 static inline void cm_putstr (char* text)
 {
     syscall (OSIF_SYSCALL_CONSOLE_WRITELN, (PTR)text, 0, 0, 0, 0);
 }
 
-static inline U32 cm_process_get_pid()
-{
-    return (U32)syscall (OSIF_SYSCALL_PROCESS_GETPID, 0, 0, 0, 0, 0);
-}
-
 static inline U32 cm_get_tickcount()
 {
     return (U32)syscall (OSIF_SYSCALL_TIMER_GET_TICKCOUNT, 0, 0, 0, 0, 0);
@@ -63,11 +44,6 @@ static inline U32 cm_window_destory (Handle h)
     return (U32)syscall (OSIF_SYSCALL_WINDOW_DESTORY, (U32)h, 0, 0, 0, 0);
 }
 
-static inline void* cm_process_get_datamem_start()
-{
-    return (void*)syscall (OSIF_SYSCALL_PROCESS_GET_DATAMEM_START, 0, 0, 0, 0, 0);
-}
-
 static inline void* cm_window_flush_graphics()
 {
     return (void*)syscall (OSIF_SYSCALL_WINDOW_FLUSH_GRAPHICS, 0, 0, 0, 0, 0);

src/cm/CMakeLists.txt

@@ -21,6 +21,7 @@ compile_lib(
 # C library to talk to the OS and helpful/common functions for use by application programs.
 # ------------------------------------------------------------------------
 set(APPLIB_SOURCES
+        ${CMAKE_CURRENT_SOURCE_DIR}/process.c
         ${CMAKE_CURRENT_SOURCE_DIR}/syscalls.c
         ${CMAKE_CURRENT_SOURCE_DIR}/printf.c
         ${CMAKE_CURRENT_SOURCE_DIR}/debug.c

src/cm/cm.c

@@ -9,6 +9,9 @@
 #include <cm/syscall.h>
 #include <cm/debug.h>
 
+/* Variable to store Library error*/
+uint32_t cm_error_num__;
+
 #define cm_MICRODEC_TO_TICK_COUNT(us) ((us) / cm_get_tick_period_us())
 
 void event_handler_NDU_()

src/cm/process.c

@@ -0,0 +1,53 @@
+/*
+ * -------------------------------------------------------------------------------------------------
+ * Megha Operating System V2 - C MOS App Library - Process management
+ * -------------------------------------------------------------------------------------------------
+ */
+
+#include <process.h>
+#include <cm/syscall.h>
+#include <cm/err.h>
+
+INT cm_process_create (void* startLocation, SIZE binaryLengthBytes, bool isKernelMode)
+{
+    if (!startLocation || binaryLengthBytes == 0) {
+        CM_RETURN_ERROR__ (CM_ERR_INVALID_INPUT, CM_FAILURE);
+    }
+
+    KProcessFlags flags = PROCESS_FLAGS_NONE;
+    if (isKernelMode) {
+        flags |= PROCESS_FLAGS_KERNEL_PROCESS;
+    }
+
+    INT pid = syscall (OSIF_SYSCALL_CREATE_PROCESS, (U32)startLocation, binaryLengthBytes,
+                       (U32)flags, 0, 0);
+    if (pid < 0) {
+        CM_RETURN_ERROR__ (cm_get_os_error(), CM_FAILURE);
+    }
+    return pid;
+}
+
+INT cm_thread_create (void (*startLocation)(), bool isKernelMode)
+{
+    if (!startLocation) {
+        CM_RETURN_ERROR__ (CM_ERR_INVALID_INPUT, CM_FAILURE);
+    }
+
+    KProcessFlags flags = PROCESS_FLAGS_THREAD;
+    if (isKernelMode) {
+        flags |= PROCESS_FLAGS_KERNEL_PROCESS;
+    }
+
+    INT pid = syscall (OSIF_SYSCALL_CREATE_PROCESS, (U32)startLocation, 0, (U32)flags, 0, 0);
+    if (pid < 0) {
+        CM_RETURN_ERROR__ (cm_get_os_error(), CM_FAILURE);
+    }
+    return pid;
+}
+
+bool cm_process_is_yield_requested()
+{
+    volatile OSIF_ProcessEvent e = { 0 };
+    cm_process_pop_event ((OSIF_ProcessEvent*)&e);
+    return (e.event == OSIF_PROCESS_EVENT_PROCCESS_YIELD_REQ);
+}

src/cm/syscalls.c

@@ -16,8 +16,6 @@
 
 #include <cm/syscall.h>
 #include <config.h>
-#include <kernel.h>
-#include <process.h>
 
 S32 syscall (OSIF_SYSCALLS fn, U32 arg1, U32 arg2, U32 arg3, U32 arg4, U32 arg5)
 {
@@ -30,33 +28,6 @@ S32 syscall (OSIF_SYSCALLS fn, U32 arg1, U32 arg2, U32 arg3, U32 arg4, U32 arg5)
     return retval;
 }
 
-INT cm_process_create (void* startLocation, SIZE binaryLengthBytes, bool isKernelMode)
-{
-    KProcessFlags flags = PROCESS_FLAGS_NONE;
-    if (isKernelMode) {
-        flags |= PROCESS_FLAGS_KERNEL_PROCESS;
-    }
-
-    return syscall (OSIF_SYSCALL_CREATE_PROCESS, (U32)startLocation, binaryLengthBytes, (U32)flags,
-                    0, 0);
-}
-
-INT cm_thread_create (void (*startLocation)(), bool isKernelMode)
-{
-    KProcessFlags flags = PROCESS_FLAGS_THREAD;
-    if (isKernelMode) {
-        flags |= PROCESS_FLAGS_KERNEL_PROCESS;
-    }
-    return syscall (OSIF_SYSCALL_CREATE_PROCESS, (U32)startLocation, 0, (U32)flags, 0, 0);
-}
-
-bool cm_process_is_yield_requested()
-{
-    volatile OSIF_ProcessEvent e = { 0 };
-    cm_process_pop_event ((OSIF_ProcessEvent*)&e);
-    return (e.event == OSIF_PROCESS_EVENT_PROCCESS_YIELD_REQ);
-}
-
 UINT cm_get_tick_period_us()
 {
     return CONFIG_TICK_PERIOD_MICROSEC;

src/kernel/x86/syscalls.c

@@ -42,6 +42,7 @@ bool ksys_processPopEvent (SystemcallFrame frame, OSIF_ProcessEvent* const e);
 U32 ksys_process_getPID (SystemcallFrame frame);
 U32 ksys_get_tickcount (SystemcallFrame frame);
 PTR ksys_process_getDataMemoryStart (SystemcallFrame frame);
+U32 sys_get_os_error (SystemcallFrame frame);
 
 #ifdef GRAPHICS_MODE_ENABLED
 Handle ksys_window_createWindow (SystemcallFrame frame, const char* winTitle);
@@ -57,25 +58,30 @@ static INT s_handleInvalidSystemCall();
 #pragma GCC diagnostic ignored "-Wincompatible-pointer-types"
 #pragma GCC diagnostic ignored "-Wpedantic"
 void* g_syscall_table[] = {
+    //---------------------------
 #if defined(DEBUG)
     &ksys_console_writeln,            // 0
 #else
     &s_handleInvalidSystemCall,       // 0
 #endif
+    //---------------------------
     &ksys_createProcess,              // 1
     &ksys_yieldProcess,               // 2
     &ksys_killProcess,                // 3
+    //---------------------------
 #if defined(DEBUG) && !defined(GRAPHICS_MODE_ENABLED)
     &ksys_console_setcolor,           // 4
     &ksys_console_setposition,        // 5
 #else
     &s_handleInvalidSystemCall,       // 4
     &s_handleInvalidSystemCall,       // 5
 #endif
+    //---------------------------
     &ksys_processPopEvent,            // 6
     &ksys_process_getPID,             // 7
     &ksys_get_tickcount,              // 8
     &ksys_process_getDataMemoryStart, // 9
+    //---------------------------
 #ifdef GRAPHICS_MODE_ENABLED
     &ksys_window_createWindow,        // 10
     &ksys_window_destoryWindow,       // 11
@@ -87,6 +93,8 @@ void* g_syscall_table[] = {
     &s_handleInvalidSystemCall,      // 12
     &s_handleInvalidSystemCall,      // 13
 #endif
+    //---------------------------
+    &sys_get_os_error,               // 14
 };
 #pragma GCC diagnostic pop