Kernel: Use copy_from_user() and copy_to_user() in read/write

This is huge. Finally, we can do proper reads/writes with invalid addresses, or big buffers.

kernel/include/fs/FileDescriptor.h

@@ -32,6 +32,9 @@ struct Descriptor
     ssize_t read(size_t size, char* buffer);
     ssize_t write(size_t size, const char* buffer);
 
+    ssize_t user_read(size_t size, char* buffer);
+    ssize_t user_write(size_t size, const char* buffer);
+
     uintptr_t mmap(uintptr_t addr, size_t size, int prot, off_t offset);
 
     long ioctl(int cmd, uintptr_t arg);

kernel/src/fs/FileDescriptor.cpp

@@ -1,5 +1,7 @@
 #include "fs/FileDescriptor.h"
 #include "std/errno.h"
+#include "std/stdlib.h"
+#include "sys/UserMemory.h"
 
 Descriptor::Descriptor() : m_is_open(false)
 {
@@ -37,6 +39,28 @@ ssize_t Descriptor::write(size_t size, const char* buffer)
     return result;
 }
 
+ssize_t Descriptor::user_read(size_t size, char* buffer)
+{
+    char* buf = (char*)kmalloc(size);
+    if (!buf) return -ENOMEM;
+    ssize_t result = read(size, buf);
+    if (!copy_to_user(buffer, buf, size)) result = -EFAULT;
+    kfree(buf);
+    return result;
+}
+
+ssize_t Descriptor::user_write(size_t size, const char* buffer)
+{
+    char* buf = (char*)kmalloc(size);
+    if (!buf) return -ENOMEM;
+    ssize_t result;
+    if (!copy_from_user(buffer, buf, size)) result = -EFAULT;
+    else
+        result = write(size, buf);
+    kfree(buf);
+    return result;
+}
+
 #define MAP_FAIL(errno) 0xffffffffffffff00 | (unsigned char)(errno)
 
 uintptr_t Descriptor::mmap(uintptr_t addr, size_t size, int prot, off_t offset)

kernel/src/sys/stdio.cpp

@@ -155,9 +155,7 @@ void sys_write(Context* context, int fd, size_t size, const char* addr)
         context->rax = -EBADF;
         return;
     }
-    ssize_t result = file->write(
-        size, (const char*)VMM::get_physical((uint64_t)addr)); // FIXME: Handle buffers bigger than one page, which may
-                                                               // not be contiguous in physical memory.
+    ssize_t result = file->user_write(size, addr);
     context->rax = (size_t)result;
     return;
 }
@@ -298,13 +296,11 @@ void sys_read(Context* context, int fd, size_t size, char* buffer)
         current_task->state = current_task->Blocking;
         current_task->block_reason = BlockReason::Reading;
         current_task->blocking_read_info.fd = fd;
-        current_task->blocking_read_info.buf = (char*)VMM::get_physical((uint64_t)buffer); // FIXME: Handle errors.
+        current_task->blocking_read_info.buf = buffer;
         current_task->blocking_read_info.size = size;
         return Scheduler::task_yield(context);
     }
-    ssize_t result =
-        file->read(size, (char*)VMM::get_physical((uint64_t)buffer)); // FIXME: Handle big buffers which may
-                                                                      // not be across continuous physical pages.
+    ssize_t result = file->user_read(size, buffer);
     context->rax = (size_t)result;
     return;
 }

kernel/src/thread/Task.cpp

@@ -74,7 +74,7 @@ bool Task::has_died()
 
 void Task::resume_read()
 {
-    regs.rax = files[blocking_read_info.fd].read(blocking_read_info.size, blocking_read_info.buf);
+    regs.rax = files[blocking_read_info.fd].user_read(blocking_read_info.size, blocking_read_info.buf);
 }
 
 bool Task::is_read_still_blocking()
@@ -86,7 +86,7 @@ void Task::resume()
 {
     VMM::switch_back_to_kernel_address_space();
     VMM::apply_address_space();
-    VMM::switch_to_previous_user_address_space();
+    VMM::switch_to_user_address_space(address_space);
     switch (block_reason)
     {
     case BlockReason::None: return;