kern/ldr: add support for --x executables

libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_page_table.hpp

@@ -109,6 +109,9 @@ namespace ams::kern::arch::arm64 {
             KPageTableManager &GetPageTableManager() const { return *m_manager; }
         private:
             constexpr PageTableEntry GetEntryTemplate(const KPageProperties properties) const {
+                /* Check that the property is not kernel execute. */
+                MESOSPHERE_ABORT_UNLESS((properties.perm & KMemoryPermission_KernelExecute) == 0);
+
                 /* Set basic attributes. */
                 PageTableEntry entry{PageTableEntry::ExtensionFlag_Valid};
                 entry.SetPrivilegedExecuteNever(true);
@@ -122,22 +125,24 @@ namespace ams::kern::arch::arm64 {
                 /* Set page attribute. */
                 if (properties.io) {
                     MESOSPHERE_ABORT_UNLESS(!properties.uncached);
-                    MESOSPHERE_ABORT_UNLESS((properties.perm & (KMemoryPermission_KernelExecute | KMemoryPermission_UserExecute)) == 0);
+                    MESOSPHERE_ABORT_UNLESS((properties.perm & KMemoryPermission_UserExecute) == 0);
 
                     entry.SetPageAttribute(PageTableEntry::PageAttribute_Device_nGnRnE)
                          .SetUserExecuteNever(true);
                 } else if (properties.uncached) {
-                    MESOSPHERE_ABORT_UNLESS((properties.perm & (KMemoryPermission_KernelExecute | KMemoryPermission_UserExecute)) == 0);
+                    MESOSPHERE_ABORT_UNLESS((properties.perm & KMemoryPermission_UserExecute) == 0);
 
-                    entry.SetPageAttribute(PageTableEntry::PageAttribute_NormalMemoryNotCacheable);
+                    entry.SetPageAttribute(PageTableEntry::PageAttribute_NormalMemoryNotCacheable)
+                         .SetUserExecuteNever(true);
                 } else {
                     entry.SetPageAttribute(PageTableEntry::PageAttribute_NormalMemory);
-                }
 
-                /* Set user execute never bit. */
+                    if ((properties.perm & KMemoryPermission_UserExecute) != 0) {
-                if (properties.perm != KMemoryPermission_UserReadExecute) {
+                        /* Check that the permission is either r--/--x or r--/r-x. */
-                    MESOSPHERE_ABORT_UNLESS((properties.perm & (KMemoryPermission_KernelExecute | KMemoryPermission_UserExecute)) == 0);
+                        MESOSPHERE_ABORT_UNLESS((properties.perm & ~ams::svc::MemoryPermission_Read) == (KMemoryPermission_KernelRead | KMemoryPermission_UserExecute));
-                    entry.SetUserExecuteNever(true);
+                    } else {
+                        entry.SetUserExecuteNever(true);
+                    }
                 }
 
                 /* Set AP[1] based on perm. */

libraries/libmesosphere/include/mesosphere/arch/arm64/kern_userspace_memory_access.hpp

@@ -21,7 +21,18 @@ namespace ams::kern::arch::arm64 {
     void UserspaceAccessFunctionAreaBegin();
 
     class UserspaceAccess {
+        private:
+            static bool CopyMemoryFromUserSize32BitWithSupervisorAccessImpl(void *dst, const void *src);
         public:
+            static bool CopyMemoryFromUserSize32BitWithSupervisorAccess(void *dst, const void *src) {
+                /* Check that the address is within the valid userspace range. */
+                if (const uintptr_t src_uptr = reinterpret_cast<uintptr_t>(src); src_uptr < ams::svc::AddressNullGuard32Size || (src_uptr + sizeof(u32) - 1) >= ams::svc::AddressMemoryRegion39Size) {
+                    return false;
+                }
+
+                return CopyMemoryFromUserSize32BitWithSupervisorAccessImpl(dst, src);
+            }
+
             static bool CopyMemoryFromUser(void *dst, const void *src, size_t size);
             static bool CopyMemoryFromUserAligned32Bit(void *dst, const void *src, size_t size);
             static bool CopyMemoryFromUserAligned64Bit(void *dst, const void *src, size_t size);

libraries/libmesosphere/source/arch/arm64/kern_exception_handlers.cpp

@@ -100,6 +100,8 @@ namespace ams::kern::arch::arm64 {
                 u32 insn_value = 0;
                 if (UserspaceAccess::CopyMemoryFromUser(std::addressof(insn_value), reinterpret_cast<u32 *>(context->pc), sizeof(insn_value))) {
                     insn = insn_value;
+                } else if (KTargetSystem::IsDebugMode() && (context->pc & 3) == 0 && UserspaceAccess::CopyMemoryFromUserSize32BitWithSupervisorAccess(std::addressof(insn_value), reinterpret_cast<u32 *>(context->pc))) {
+                    insn = insn_value;
                 } else {
                     insn = 0;
                 }
@@ -112,33 +114,6 @@ namespace ams::kern::arch::arm64 {
             bool should_process_user_exception = KTargetSystem::IsUserExceptionHandlersEnabled();
 
             const u64 ec = (esr >> 26) & 0x3F;
-            switch (ec) {
-                case EsrEc_Unknown:
-                case EsrEc_IllegalExecution:
-                case EsrEc_Svc32:
-                case EsrEc_Svc64:
-                case EsrEc_PcAlignmentFault:
-                case EsrEc_SpAlignmentFault:
-                case EsrEc_SErrorInterrupt:
-                case EsrEc_BreakPointEl0:
-                case EsrEc_SoftwareStepEl0:
-                case EsrEc_WatchPointEl0:
-                case EsrEc_BkptInstruction:
-                case EsrEc_BrkInstruction:
-                    break;
-                default:
-                    {
-                        /* If the fault address's state is KMemoryState_Code and the user can't read the address, force processing exception. */
-                        KMemoryInfo info;
-                        ams::svc::PageInfo pi;
-                        if (R_SUCCEEDED(cur_process.GetPageTable().QueryInfo(std::addressof(info), std::addressof(pi), far))) {
-                            if (info.GetState() == KMemoryState_Code && ((info.GetPermission() & KMemoryPermission_UserRead) != KMemoryPermission_UserRead)) {
-                                should_process_user_exception = true;
-                            }
-                        }
-                    }
-                    break;
-            }
 
             /* In the event that we return from this exception, we want SPSR.SS set so that we advance an instruction if single-stepping. */
             #if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)

libraries/libmesosphere/source/arch/arm64/kern_userspace_memory_access_asm.s

@@ -154,6 +154,21 @@ _ZN3ams4kern4arch5arm6415UserspaceAccess27CopyMemoryFromUserSize32BitEPvPKv:
     mov     x0, #1
     ret
 
+/* ams::kern::arch::arm64::UserspaceAccess::CopyMemoryFromUserSize32BitWithSupervisorAccessImpl(void *dst, const void *src) */
+.section    .text._ZN3ams4kern4arch5arm6415UserspaceAccess51CopyMemoryFromUserSize32BitWithSupervisorAccessImplEPvPKv, "ax", %progbits
+.global     _ZN3ams4kern4arch5arm6415UserspaceAccess51CopyMemoryFromUserSize32BitWithSupervisorAccessImplEPvPKv
+.type       _ZN3ams4kern4arch5arm6415UserspaceAccess51CopyMemoryFromUserSize32BitWithSupervisorAccessImplEPvPKv, %function
+.balign 0x10
+_ZN3ams4kern4arch5arm6415UserspaceAccess51CopyMemoryFromUserSize32BitWithSupervisorAccessImplEPvPKv:
+    /* Just load and store a u32. */
+    /* NOTE: This is done with supervisor access permissions. */
+    ldr     w2, [x1]
+    str     w2, [x0]
+
+    /* We're done. */
+    mov     x0, #1
+    ret
+
 /* ams::kern::arch::arm64::UserspaceAccess::CopyStringFromUser(void *dst, const void *src, size_t size) */
 .section    .text._ZN3ams4kern4arch5arm6415UserspaceAccess18CopyStringFromUserEPvPKvm, "ax", %progbits
 .global     _ZN3ams4kern4arch5arm6415UserspaceAccess18CopyStringFromUserEPvPKvm

libraries/libmesosphere/source/kern_k_page_table_base.cpp

@@ -1787,6 +1787,11 @@ namespace ams::kern {
         /* We're going to perform an update, so create a helper. */
         KScopedPageTableUpdater updater(this);
 
+        /* If we're creating an executable mapping, take and immediately release the scheduler lock. This will force a reschedule. */
+        if (is_x) {
+            KScopedSchedulerLock sl;
+        }
+
         /* Perform mapping operation. */
         const KPageProperties properties = { new_perm, false, false, DisableMergeAttribute_None };
         const auto operation = was_x ? OperationType_ChangePermissionsAndRefreshAndFlush : OperationType_ChangePermissions;

libraries/libmesosphere/source/svc/kern_svc_process_memory.cpp

@@ -27,6 +27,7 @@ namespace ams::kern::svc {
                 case ams::svc::MemoryPermission_Read:
                 case ams::svc::MemoryPermission_ReadWrite:
                 case ams::svc::MemoryPermission_ReadExecute:
+                case ams::svc::MemoryPermission_Execute:
                     return true;
                 default:
                     return false;

libraries/libstratosphere/include/stratosphere/ldr/ldr_types.hpp

@@ -226,6 +226,7 @@ namespace ams::ldr {
             MetaFlag_OptimizeMemoryAllocation       = (1 << 4),
             MetaFlag_DisableDeviceAddressSpaceMerge = (1 << 5),
             MetaFlag_EnableAliasRegionExtraSize     = (1 << 6),
+            MetaFlag_PreventCodeReads               = (1 << 7),
         };
 
         enum AddressSpaceType {

libraries/libstratosphere/source/os/impl/os_process_memory_impl.os.horizon.cpp

@@ -27,6 +27,7 @@ namespace ams::os::impl {
                 case os::MemoryPermission_ReadOnly:    return svc::MemoryPermission_Read;
                 case os::MemoryPermission_ReadWrite:   return svc::MemoryPermission_ReadWrite;
                 case os::MemoryPermission_ReadExecute: return svc::MemoryPermission_ReadExecute;
+                case os::MemoryPermission_ExecuteOnly: return svc::MemoryPermission_Execute;
                 AMS_UNREACHABLE_DEFAULT_CASE();
             }
         }

stratosphere/loader/source/ldr_process_creation.cpp

@@ -555,7 +555,7 @@ namespace ams::ldr {
             R_SUCCEED();
         }
 
-        Result LoadAutoLoadModule(os::NativeHandle process_handle, fs::FileHandle file, const NsoHeader *nso_header, uintptr_t nso_address, size_t nso_size) {
+        Result LoadAutoLoadModule(os::NativeHandle process_handle, fs::FileHandle file, const NsoHeader *nso_header, uintptr_t nso_address, size_t nso_size, bool prevent_code_reads) {
             /* Map and read data from file. */
             {
                 /* Map the process memory. */
@@ -594,7 +594,7 @@ namespace ams::ldr {
             const size_t ro_size   = util::AlignUp(nso_header->ro_size, os::MemoryPageSize);
             const size_t rw_size   = util::AlignUp(nso_header->rw_size + nso_header->bss_size, os::MemoryPageSize);
             if (text_size) {
-                R_TRY(os::SetProcessMemoryPermission(process_handle, nso_address + nso_header->text_dst_offset, text_size, os::MemoryPermission_ReadExecute));
+                R_TRY(os::SetProcessMemoryPermission(process_handle, nso_address + nso_header->text_dst_offset, text_size, prevent_code_reads ? os::MemoryPermission_ExecuteOnly : os::MemoryPermission_ReadExecute));
             }
             if (ro_size) {
                 R_TRY(os::SetProcessMemoryPermission(process_handle, nso_address + nso_header->ro_dst_offset,   ro_size,   os::MemoryPermission_ReadOnly));
@@ -606,7 +606,7 @@ namespace ams::ldr {
             R_SUCCEED();
         }
 
-        Result LoadAutoLoadModules(const ProcessInfo *process_info, const NsoHeader *nso_headers, const bool *has_nso, const ArgumentStore::Entry *argument) {
+        Result LoadAutoLoadModules(const ProcessInfo *process_info, const NsoHeader *nso_headers, const bool *has_nso, const ArgumentStore::Entry *argument, bool prevent_code_reads) {
             /* Load each NSO. */
             for (size_t i = 0; i < Nso_Count; i++) {
                 if (has_nso[i]) {
@@ -614,7 +614,7 @@ namespace ams::ldr {
                     R_TRY(fs::OpenFile(std::addressof(file), GetNsoPath(i), fs::OpenMode_Read));
                     ON_SCOPE_EXIT { fs::CloseFile(file); };
 
-                    R_TRY(LoadAutoLoadModule(process_info->process_handle, file, nso_headers + i, process_info->nso_address[i], process_info->nso_size[i]));
+                    R_TRY(LoadAutoLoadModule(process_info->process_handle, file, nso_headers + i, process_info->nso_address[i], process_info->nso_size[i], prevent_code_reads));
                 }
             }
 
@@ -658,7 +658,7 @@ namespace ams::ldr {
             ON_RESULT_FAILURE { svc::CloseHandle(process_handle); };
 
             /* Load all auto load modules. */
-            R_RETURN(LoadAutoLoadModules(out, nso_headers, has_nso, argument));
+            R_RETURN(LoadAutoLoadModules(out, nso_headers, has_nso, argument, (meta->npdm->flags & ldr::Npdm::MetaFlag_PreventCodeReads) != 0));
         }
 
     }