Fine tuned syscall permission checking

CMakeLists.txt

@@ -35,6 +35,7 @@ endif()
 set (OUTPUT_DIR ${CMAKE_SOURCE_DIR}/out CACHE STRING "The output directory.")
 set (OBOS_PAGE_REPLACEMENT_ALGORITHM "Aging" CACHE STRING "(Kernel developers only) The page replacement algorithm used by the MM.")
 set (OBOS_DEV_PREFIX "/dev" CACHE STRING "Directory where the kernel places devices.")
+set (OBOS_PERM_PREFIX "/sys/perm" CACHE STRING "Directory where the kernel checks for capabilities")
 set (OBOS_CLANG_SUFFIX "" CACHE STRING "Some Linux distributions add a suffix to various clang and LLVM commands, such as the version used. Specify that suffix, if needed")
 
 file (TO_CMAKE_PATH "${OUTPUT_DIR}" OUTPUT_DIR)
@@ -249,6 +250,7 @@ configure_file(${CMAKE_SOURCE_DIR}/src/inc/dev_prefix.h.in ${CMAKE_SOURCE_DIR}/s
 add_compile_definitions(
 	OBOS_ARCHITECTURE_HAS_ACPI=${OBOS_ARCHITECTURE_HAS_ACPI}
 	OBOS_ARCHITECTURE_HAS_PCI=${OBOS_ARCHITECTURE_HAS_PCI}
+	OBOS_PERM_PREFIX="${OBOS_PERM_PREFIX}"
 )
 
 if (OBOS_USE_OBOS_GCC AND OBOS_COMPILE_USER_UTILS)

src/oboskrnl/CMakeLists.txt

@@ -22,7 +22,7 @@ list (APPEND oboskrnl_sources
 	"init_proc.c" "vfs/create.c" "net/route.c" "net/eth.c"
 	"net/ip.c" "net/arp.c" "power/event.c" "net/udp.c"
 	"net/icmp.c" "net/tcp.c" "vfs/socket.c" "net/lo.c"
-	"kinit.c" "vfs/local_socket.c"
+	"kinit.c" "vfs/local_socket.c" "perm.c"
 )
 
 add_executable(oboskrnl)

src/oboskrnl/driver_interface/drv_sys.c

@@ -9,6 +9,7 @@
 #include <handle.h>
 #include <memmanip.h>
 #include <syscall.h>
+#include <perm.h>
 
 #include <driver_interface/drv_sys.h>
 #include <driver_interface/loader.h>
@@ -23,15 +24,11 @@
 #include <allocators/base.h>
 
 handle Sys_LoadDriver(const void* file, size_t szFile, obos_status* ustatus)
-{
-    if (Core_GetCurrentThread()->proc->euid != ROOT_UID)
-    {
-        obos_status status = OBOS_STATUS_ACCESS_DENIED;
-        if (ustatus) memcpy_k_to_usr(ustatus, &status, sizeof(obos_status));
-        return HANDLE_INVALID;
-    }
+{        
+    obos_status status = OBOS_CapabilityCheck("drv/load", false);
+    if (obos_is_error(status))
+        return status;
 
-    obos_status status = OBOS_STATUS_SUCCESS;
     if (!szFile)
     {
         status = OBOS_STATUS_INVALID_ARGUMENT;
@@ -62,19 +59,13 @@ handle Sys_LoadDriver(const void* file, size_t szFile, obos_status* ustatus)
     return ret;
 }
 
-#define perm_check_impl(ret) do {\
-    if (Core_GetCurrentThread()->proc->euid != ROOT_UID)\
-        return (ret);\
-} while(0)
-#define perm_check() perm_check_impl(OBOS_STATUS_ACCESS_DENIED)
-#define perm_check_hnd() perm_check_impl(HANDLE_INVALID)
-
 obos_status Sys_StartDriver(handle driver, handle* mainThread)
 {
-    perm_check();
+    obos_status status = OBOS_CapabilityCheck("drv/start", false);
+    if (obos_is_error(status))
+        return status;
 
     OBOS_LockHandleTable(OBOS_CurrentHandleTable());
-    obos_status status = OBOS_STATUS_SUCCESS;
     handle_desc* drv = OBOS_HandleLookup(OBOS_CurrentHandleTable(), driver, HANDLE_TYPE_DRIVER_ID, false, &status);
     if (!drv)
     {
@@ -105,10 +96,11 @@ obos_status Sys_StartDriver(handle driver, handle* mainThread)
 
 obos_status Sys_UnloadDriver(handle driver)
 {
-    perm_check();
+    obos_status status = OBOS_CapabilityCheck("drv/unload", false);
+    if (obos_is_error(status))
+        return status;
 
     OBOS_LockHandleTable(OBOS_CurrentHandleTable());
-    obos_status status = OBOS_STATUS_SUCCESS;
     handle_desc* drv = OBOS_HandleLookup(OBOS_CurrentHandleTable(), driver, HANDLE_TYPE_DRIVER_ID, false, &status);
     if (!drv)
     {
@@ -127,10 +119,11 @@ obos_status Sys_UnloadDriver(handle driver)
 
 obos_status Sys_PnpLoadDriversAt(handle dent, bool wait)
 {
-    perm_check();
+    obos_status status = OBOS_CapabilityCheck("drv/load-pnp", false);
+    if (obos_is_error(status))
+        return status;
 
     OBOS_LockHandleTable(OBOS_CurrentHandleTable());
-    obos_status status = OBOS_STATUS_SUCCESS;
     handle_desc* dirent = OBOS_HandleLookup(OBOS_CurrentHandleTable(), dent, HANDLE_TYPE_DIRENT, false, &status);
     if (!dirent)
     {
@@ -145,11 +138,13 @@ obos_status Sys_PnpLoadDriversAt(handle dent, bool wait)
 // Finds a loaded driver by its name, and returns a handle to it.
 handle Sys_FindDriverByName(const char* uname /* assumed to be 64-bytes at max */)
 {
-    perm_check_hnd();
+    obos_status status = OBOS_CapabilityCheck("drv/open-name", false);
+    if (obos_is_error(status))
+        return HANDLE_INVALID;
 
     char* name = nullptr;
     size_t sz_name = 0;
-    obos_status status = OBOSH_ReadUserString(uname, nullptr, &sz_name);
+    status = OBOSH_ReadUserString(uname, nullptr, &sz_name);
     if (obos_is_error(status))
         return HANDLE_INVALID;
     if (sz_name >= 64)
@@ -187,7 +182,9 @@ handle Sys_FindDriverByName(const char* uname /* assumed to be 64-bytes at max *
 // If 'curr' is HANDLE_INVALID, the first item in the list is returned.
 handle Sys_EnumerateLoadedDrivers(handle curr)
 {
-    perm_check_hnd();
+    obos_status status = OBOS_CapabilityCheck("drv/enumerate", false);
+    if (obos_is_error(status))
+        return HANDLE_INVALID;
 
     driver_id* id = nullptr;
 
@@ -222,13 +219,14 @@ handle Sys_EnumerateLoadedDrivers(handle curr)
 // Queries the name of the driver in 'drv'.
 obos_status Sys_QueryDriverName(handle driver, char* namebuf, size_t *sznamebuf /* need not be over 64 */)
 {
-    perm_check();
+    obos_status status = OBOS_CapabilityCheck("drv/query-name", false);
+    if (obos_is_error(status))
+        return status;
 
     if (!sznamebuf)
         return OBOS_STATUS_INVALID_ARGUMENT; 
 
     OBOS_LockHandleTable(OBOS_CurrentHandleTable());
-    obos_status status = OBOS_STATUS_SUCCESS;
     handle_desc* drv = OBOS_HandleLookup(OBOS_CurrentHandleTable(), driver, HANDLE_TYPE_DRIVER_ID, false, &status);
     if (!drv)
     {

src/oboskrnl/mm/mm_sys.c

@@ -4,10 +4,10 @@
  * Copyright (c) 2024-2025 Omar Berrow
  */
 
-#include "mm/swap.h"
 #include <int.h>
 #include <memmanip.h>
 #include <klog.h>
+#include <perm.h>
 #include <error.h>
 #include <syscall.h>
 #include <handle.h>
@@ -23,6 +23,7 @@
 #include <mm/mm_sys.h>
 #include <mm/disk_swap.h>
 #include <mm/fork.h>
+#include <mm/swap.h>
 
 #include <vfs/dirent.h>
 
@@ -81,6 +82,16 @@ void* Sys_VirtualMemoryAlloc(handle ctx, void* base, size_t size, struct vma_all
     prot &= ~OBOS_PROTECTION_CACHE_DISABLE;
     flags &= ~VMA_FLAGS_32BITPHYS; // userspace doesn't need this as much as kernel mode
 
+    if (flags & VMA_FLAGS_NON_PAGED)
+    {
+        obos_status status = OBOS_CapabilityCheck("mm/allocate-non-paged", false);
+        if (obos_is_error(status))
+        {
+            if (pstatus) memcpy_k_to_usr(pstatus, &status, sizeof(status));
+            return nullptr;
+        }
+    }
+
     void* ret = Mm_VirtualMemoryAllocEx(vmm_ctx, base, size, prot, flags, file, args.offset, &status);
     if (pstatus)
         memcpy_k_to_usr(pstatus, &status, sizeof(status));
@@ -99,10 +110,12 @@ obos_status Sys_VirtualMemoryProtect(handle ctx, void* base, size_t size, prot_f
 }
 obos_status Sys_VirtualMemoryLock(handle ctx, void* base, size_t size)
 {
+    OBOS_UNUSED(ctx && base && size);
     return OBOS_STATUS_UNIMPLEMENTED;
 }
 obos_status Sys_VirtualMemoryUnlock(handle ctx, void* base, size_t size)
 {
+    OBOS_UNUSED(ctx && base && size);
     return OBOS_STATUS_UNIMPLEMENTED;
 }
 
@@ -157,6 +170,10 @@ size_t Sys_GetUsedPhysicalMemoryCount()
 
 obos_status Sys_QueryPageInfo(handle ctx, void* base, page_info* info)
 {
+    obos_status status = OBOS_CapabilityCheck("mm/query-page-info", false);
+    if (obos_is_error(status))
+        return status;
+
     context* vmm_ctx = context_from_handle(ctx, false, 0, true);
     // Search the page in the RB-Tree.
     irql oldIrql = Core_SpinlockAcquire(&vmm_ctx->lock);
@@ -198,9 +215,13 @@ obos_status Sys_MakeDiskSwap(const char* upath)
 
 obos_status Sys_SwitchSwap(const char* upath)
 {
+    obos_status status = OBOS_CapabilityCheck("mm/switch-swap", false);
+    if (obos_is_error(status))
+        return status;
+
     char* path = nullptr;
     size_t sz_path = 0;
-    obos_status status = OBOSH_ReadUserString(upath, nullptr, &sz_path);
+    status = OBOSH_ReadUserString(upath, nullptr, &sz_path);
     if (obos_is_error(status))
         return status;
     path = ZeroAllocate(OBOS_KernelAllocator, sz_path+1, sizeof(char), nullptr);
@@ -236,6 +257,26 @@ obos_status Sys_SwitchSwap(const char* upath)
 
 void Sys_SyncAnonPages()
 {
+    obos_status status = OBOS_CapabilityCheck("mm/sync-anon", true);
+    if (obos_is_error(status))
+        return;
     Mm_PageWriterOperation = PAGE_WRITER_SYNC_ANON;
     Mm_WakePageWriter(true);
 }
+
+handle Sys_MmFork()
+{
+    // Zeroed in Mm_ConstructContext
+    context* ctx = Allocate(Mm_Allocator, sizeof(context), nullptr);
+    Mm_ConstructContext(ctx);
+    Mm_ForkContext(ctx, Core_GetCurrentThread()->proc->ctx);
+    ctx->workingSet.capacity = Core_GetCurrentThread()->proc->ctx->workingSet.capacity;
+
+    OBOS_LockHandleTable(OBOS_CurrentHandleTable());
+    handle_desc* desc = nullptr;
+    handle hnd = OBOS_HandleAllocate(OBOS_CurrentHandleTable(), HANDLE_TYPE_VMM_CONTEXT, &desc);
+    desc->un.vmm_context = ctx;
+    OBOS_UnlockHandleTable(OBOS_CurrentHandleTable());
+
+    return hnd;
+}

src/oboskrnl/mm/mm_sys.h

@@ -38,3 +38,5 @@ obos_status Sys_QueryPageInfo(handle ctx, void* base, page_info* info);
 obos_status Sys_MakeDiskSwap(const char* path);
 obos_status Sys_SwitchSwap(const char* path);
 void Sys_SyncAnonPages();
+
+handle Sys_MmFork();