implement detour_transaction_begin

mach_detours.c

@@ -1,8 +1,104 @@
+// Copyright (c) Microsoft Corporation.  All rights reserved.
+// Copyright (c) Lysann Tranvouez.  All rights reserved.
+
 #include "mach_detours.h"
 
-#include <stdio.h>
+#include "detours_internal.h"
+#include "arm64/detours_arm64.h"
 
-void hello(void)
+#include <stdatomic.h>
+#include <stdint.h>
+
+#include <mach/mach_init.h>
+#include <mach/mach_vm.h>
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Trampoline Memory Management
+
+typedef struct detour_region
 {
-    printf("Hello, World!\n");
-}
+    uint32_t signature;
+    struct detour_region* next;  // Next region in list of regions.
+    detour_trampoline* free_list_head;  // List of free trampolines in this region.
+} detour_region;
+
+static const uint32_t DETOUR_REGION_SIGNATURE = 'Rrtd';
+static const uint32_t DETOUR_REGION_SIZE = 0x10000;
+static const uint32_t DETOUR_TRAMPOLINES_PER_REGION = (DETOUR_REGION_SIZE / sizeof(detour_trampoline)) - 1;
+static detour_region* s_regions_head = nullptr;
+static detour_region* s_default_region = nullptr;
+
+static mach_error_t internal_detour_writable_trampoline_regions()
+{
+    // Mark all the regions as writable.
+    const mach_port_t port = mach_task_self();
+    for (detour_region* pRegion = s_regions_head; pRegion != NULL; pRegion = pRegion->next) {
+        const mach_error_t error = mach_vm_protect(port, (mach_vm_address_t)pRegion, DETOUR_REGION_SIZE, false, VM_PROT_READ | VM_PROT_WRITE);
+        if (error != err_none) {
+            return error;
+        }
+    }
+    return err_none;
+}
+
+static void internal_detour_runnable_trampoline_regions()
+{
+    // Mark all the regions as executable.
+    const mach_port_t port = mach_task_self();
+    for (detour_region* pRegion = s_regions_head; pRegion != NULL; pRegion = pRegion->next) {
+        const mach_error_t error = mach_vm_protect(port, (mach_vm_address_t)pRegion, DETOUR_REGION_SIZE, false, VM_PROT_READ | VM_PROT_EXECUTE);
+        if (error != err_none) {
+            DETOUR_BREAK();
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+// Transactions
+
+typedef enum detour_operation_kind {
+    attach,
+    detach,
+} detour_operation_kind;
+
+typedef struct detour_operation
+{
+    struct detour_operation* next;
+    detour_operation_kind kind;
+    uint8_t** pointer;
+    uint8_t* target;
+    struct detour_trampoline* trampoline;
+    vm_prot_t perm;
+} detour_operation;
+
+typedef struct detour_pending_thread
+{
+    struct detour_pending_thread* next;
+    thread_t thread;
+} detour_pending_thread;
+
+static _Atomic(thread_t) s_transaction_thread = THREAD_NULL;
+static detour_operation* s_pending_operations_head = nullptr;
+static detour_pending_thread* s_pending_threads_head = nullptr;
+
+static mach_error_t s_pending_error = err_none;
+static void** s_pending_error_pointer = nullptr;
+
+mach_error_t detour_transaction_begin()
+{
+    // Make sure only one thread can start a transaction.
+    thread_t expected = THREAD_NULL;
+    // ReSharper disable once CppIncompatiblePointerConversion
+    if (!atomic_compare_exchange_strong(&s_transaction_thread, &expected, mach_thread_self())) {
+        return detour_err_in_progress;
+    }
+
+    s_pending_operations_head = nullptr;
+    s_pending_threads_head = nullptr;
+    s_pending_error_pointer = nullptr;
+
+    // Make sure the trampoline pages are writable.
+    s_pending_error = internal_detour_writable_trampoline_regions();
+
+    return s_pending_error;
+}