mmap(), mprotect(), munmap(): Check more stuff

README.md

@@ -11,6 +11,7 @@ Not so much at the moment.
 - Can [load userspace ELF programs](kernel/src/sys/elf/) from the initial ramdisk as user tasks.
 - [System call](kernel/src/sys/) interface and bare-bones [C Library](libs/libc/).
 - Some very simple [example programs](apps/), written in C, that the kernel then loads from the initial ramdisk.
+- UNIX-like [multitasking primitives](kernel/src/sys/exec.cpp).
 
 ## Setup
 To build and run Luna, you will need to build a [GCC Cross-Compiler](https://wiki.osdev.org/Why_do_I_need_a_Cross_Compiler%3F) and cross-binutils for `x86_64-luna`. (Yes, Luna is advanced enough that it can use its own [OS-Specific Toolchain](https://wiki.osdev.org/OS_Specific_Toolchain), instead of a bare metal target like `x86_64-elf`. It is the first of my OS projects to be able to do so. The patches for Binutils and GCC are [binutils.patch](tools/binutils.patch) and [gcc.patch](tools/gcc.patch)).

kernel/src/sys/mem.cpp

@@ -3,6 +3,7 @@
 #include "errno.h"
 #include "interrupts/Context.h"
 #include "log/Log.h"
+#include "memory/Memory.h"
 #include "memory/MemoryManager.h"
 #include "memory/VMM.h"
 #include "misc/utils.h"
@@ -50,6 +51,12 @@ void sys_mmap(Context* context, void* address, size_t size, int prot)
     if (address)
     {
         kdbgln("mmap(): %ld pages at address %p, %s", size / PAGE_SIZE, address, format_prot(prot));
+        if (Memory::is_kernel_address((uintptr_t)address))
+        {
+            kwarnln("munmap() failed: attempted to unmap a kernel page");
+            context->rax = MAP_FAIL(ENOMEM);
+            return;
+        }
         if (VMM::get_physical((uint64_t)address) != (uint64_t)-1) // Address is already used.
         {
             kwarnln("attempt to map an already mapped address");
@@ -67,7 +74,7 @@ void sys_mmap(Context* context, void* address, size_t size, int prot)
         }
         else
         {
-            kwarnln("mmap() failed");
+            kwarnln("mmap() failed: failed to allocate physical memory");
             context->rax = MAP_FAIL(ENOMEM);
             return;
         }
@@ -75,6 +82,12 @@ void sys_mmap(Context* context, void* address, size_t size, int prot)
     kdbgln("mmap(): %ld pages at any address, %s", Utilities::get_blocks_from_size(PAGE_SIZE, size), format_prot(prot));
     uint64_t ptr =
         Scheduler::current_task()->allocator.request_virtual_pages(Utilities::get_blocks_from_size(PAGE_SIZE, size));
+    if (!ptr)
+    {
+        kwarnln("mmap() failed: failed to allocate virtual address");
+        context->rax = MAP_FAIL(ENOMEM);
+        return;
+    }
     void* result = MemoryManager::get_pages_at(ptr, Utilities::get_blocks_from_size(PAGE_SIZE, size), real_flags);
     if (result)
     {
@@ -84,7 +97,7 @@ void sys_mmap(Context* context, void* address, size_t size, int prot)
     }
     else
     {
-        kwarnln("mmap() failed");
+        kwarnln("mmap() failed: failed to allocate physical memory");
         context->rax = MAP_FAIL(ENOMEM);
         return;
     }
@@ -111,10 +124,16 @@ void sys_munmap(Context* context, void* address, size_t size)
         context->rax = -EINVAL;
         return;
     }
-    uint64_t flags = VMM::get_flags((uint64_t)address);
-    if (!(flags & MAP_USER))
+    if (Memory::is_kernel_address((uintptr_t)address))
     {
-        kwarnln("munmap() failed: attempted to unmap a non-existent or kernel page");
+        kwarnln("munmap() failed: attempted to unmap a kernel page");
+        context->rax = -EINVAL;
+        return;
+    }
+    uint64_t phys = VMM::get_physical((uint64_t)address);
+    if (phys == (uint64_t)-1)
+    {
+        kwarnln("munmap() failed: attempted to unmap a non-existent page");
         context->rax = -EINVAL;
         return;
     }
@@ -145,15 +164,20 @@ void sys_mprotect(Context* context, void* address, size_t size, int prot)
     }
     if (!address)
     {
-        kwarnln("mprotect() failed: attempted to unmap page 0");
+        kwarnln("mprotect() failed: attempted to protect page 0");
         context->rax = -EINVAL;
         return;
     }
-
-    uint64_t flags = VMM::get_flags((uint64_t)address);
-    if (!(flags & MAP_USER))
+    if (Memory::is_kernel_address((uintptr_t)address))
     {
-        kwarnln("mprotect() failed: attempted to protect a non-existent or kernel page");
+        kwarnln("mprotect() failed: attempted to protect a kernel page");
+        context->rax = -EINVAL;
+        return;
+    }
+    uint64_t phys = VMM::get_physical((uint64_t)address);
+    if (phys == (uint64_t)-1)
+    {
+        kwarnln("mprotect() failed: attempted to protect a non-existent page");
         context->rax = -EINVAL;
         return;
     }