Implement errno in LibC.

This also meant I had to implement BSS (SHT_NOBITS) sections in ELFLoader.
I also added an strerror() so we can print out what the errors are.

Kernel/Task.cpp

@@ -9,6 +9,7 @@
 #include <VirtualFileSystem/VirtualFileSystem.h>
 #include <ELFLoader/ExecSpace.h>
 #include "MemoryManager.h"
+#include "errno.h"
 
 //#define DEBUG_IO
 //#define TASK_DEBUG
@@ -166,25 +167,32 @@ int Task::sys$munmap(void* addr, size_t size)
 
 int Task::sys$spawn(const char* path)
 {
-    auto* child = Task::createUserTask(path, m_uid, m_gid, m_pid);
+    int error = 0;
+    auto* child = Task::createUserTask(path, m_uid, m_gid, m_pid, error);
     if (child)
         return child->pid();
-    return -1;
+    return error;
 }
 
-Task* Task::createUserTask(const String& path, uid_t uid, gid_t gid, pid_t parentPID)
+Task* Task::createUserTask(const String& path, uid_t uid, gid_t gid, pid_t parentPID, int& error)
 {
     auto parts = path.split('/');
-    if (parts.isEmpty())
+    if (parts.isEmpty()) {
+        error = -ENOENT;
         return nullptr;
+    }
 
     auto handle = VirtualFileSystem::the().open(path);
-    if (!handle)
+    if (!handle) {
+        error = -ENOENT; // FIXME: Get a more detailed error from VFS.
         return nullptr;
+    }
 
     auto elfData = handle->readEntireFile();
-    if (!elfData)
+    if (!elfData) {
+        error = -EIO; // FIXME: Get a more detailed error from VFS.
         return nullptr;
+    }
 
     InterruptDisabler disabler; // FIXME: Get rid of this, jesus christ. This "critical" section is HUGE.
     Task* t = new Task(parts.takeLast(), uid, gid, parentPID, Ring3);
@@ -203,12 +211,14 @@ Task* Task::createUserTask(const String& path, uid_t uid, gid_t gid, pid_t paren
     if (!success) {
         delete t;
         kprintf("Failure loading ELF %s\n", path.characters());
+        error = -ENOEXEC;
         return nullptr;
     }
 
     t->m_tss.eip = (dword)space.symbolPtr("_start");
     if (!t->m_tss.eip) {
         delete t;
+        error = -ENOEXEC;
         return nullptr;
     }
 
@@ -221,6 +231,7 @@ Task* Task::createUserTask(const String& path, uid_t uid, gid_t gid, pid_t paren
     kprintf("Task %u (%s) spawned @ %p\n", t->pid(), t->name().characters(), t->m_tss.eip);
 #endif
 
+    error = 0;
     return t;
 }
 
@@ -758,11 +769,6 @@ Task* Task::kernelTask()
     return s_kernelTask;
 }
 
-void Task::setError(int error)
-{
-    m_error = error;
-}
-
 Task::Region::Region(LinearAddress a, size_t s, RetainPtr<Zone>&& z, String&& n)
     : linearAddress(a)
     , size(s)

Kernel/Task.h

@@ -16,7 +16,7 @@ class Task : public InlineLinkedListNode<Task> {
     friend class InlineLinkedListNode<Task>;
 public:
     static Task* createKernelTask(void (*entry)(), String&& name);
-    static Task* createUserTask(const String& path, uid_t, gid_t, pid_t parentPID);
+    static Task* createUserTask(const String& path, uid_t, gid_t, pid_t parentPID, int& error);
     ~Task();
 
     static Vector<Task*> allTasks();
@@ -100,7 +100,6 @@ public:
     int sys$getcwd(char*, size_t);
 
     static void initialize();
-    void setError(int);
 
     static void taskDidCrash(Task*);
 

Kernel/errno.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#define EPERM      1    // Operation not permitted
+#define ENOENT     2    // No such file or directory
+#define ESRCH      3    // No such process
+#define EINTR      4    // Interrupted system call
+#define EIO        5    // I/O error
+#define ENXIO      6    // No such device or address
+#define E2BIG      7    // Argument list too long
+#define ENOEXEC    8    // Exec format error
+#define EBADF      9    // Bad file number
+#define ECHILD    10    // No child processes
+#define EAGAIN    11    // Try again
+#define ENOMEM    12    // Out of memory
+#define EACCES    13    // Permission denied
+#define EFAULT    14    // Bad address
+#define ENOTBLK   15    // Block device required
+#define EBUSY     16    // Device or resource busy
+#define EEXIST    17    // File exists
+#define EXDEV     18    // Cross-device link
+#define ENODEV    19    // No such device
+#define ENOTDIR   20    // Not a directory
+#define EISDIR    21    // Is a directory
+#define EINVAL    22    // Invalid argument
+#define ENFILE    23    // File table overflow
+#define EMFILE    24    // Too many open files
+#define ENOTTY    25    // Not a typewriter
+#define ETXTBSY   26    // Text file busy
+#define EFBIG     27    // File too large
+#define ENOSPC    28    // No space left on device
+#define ESPIPE    29    // Illegal seek
+#define EROFS     30    // Read-only file system
+#define EMLINK    31    // Too many links
+#define EPIPE     32    // Broken pipe
+#define EDOM      33    // Math argument out of domain of func
+#define ERANGE    34    // Math result not representable
+
+#define EOVERFLOW 75    // Value too large for defined data type 

Kernel/init.cpp

@@ -140,7 +140,8 @@ static void init_stage2()
     dword lastAlloc = sum_alloc;
 
     for (unsigned i = 0; i < 100; ++i) {
-        auto* shTask = Task::createUserTask("/bin/id", (uid_t)100, (gid_t)100, (pid_t)0);
+        int error;
+        auto* shTask = Task::createUserTask("/bin/id", (uid_t)100, (gid_t)100, (pid_t)0, error);
         kprintf("malloc stats: alloc:%u free:%u\n", sum_alloc, sum_free);
         kprintf("sizeof(Task):%u\n", sizeof(Task));
         kprintf("delta:%u\n",sum_alloc - lastAlloc);
@@ -149,7 +150,8 @@ static void init_stage2()
     }
 #endif
 
-    auto* shTask = Task::createUserTask("/bin/sh", (uid_t)100, (gid_t)100, (pid_t)0);
+    int error;
+    auto* shTask = Task::createUserTask("/bin/sh", (uid_t)100, (gid_t)100, (pid_t)0, error);
 
     banner();