[PATCH v7 4/4] ntdll: Add thread_get_register_pointer_values-based fast path for NtFlushProcessWriteBuffers.

[Torge Matthies]

From: Torge Matthies

---
 dlls/ntdll/unix/virtual.c | 62 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/dlls/ntdll/unix/virtual.c b/dlls/ntdll/unix/virtual.c
index 3c7a4c9f800..91c84508f44 100644
--- a/dlls/ntdll/unix/virtual.c
+++ b/dlls/ntdll/unix/virtual.c
@@ -65,6 +65,9 @@
 #if defined(__APPLE__)
 # include <mach/mach_init.h>
 # include <mach/mach_vm.h>
+# include <mach/task.h>
+# include <mach/thread_state.h>
+# include <mach/vm_map.h>
 #endif

#include "ntstatus.h"
@@ -218,6 +221,11 @@ struct range_entry
 static struct range_entry *free_ranges;
 static struct range_entry *free_ranges_end;

+#ifdef __APPLE__
+static kern_return_t (*p_thread_get_register_pointer_values)( thread_t, uintptr_t*, size_t*, uintptr_t* );
+static pthread_once_t tgrpvs_init_once = PTHREAD_ONCE_INIT;
+#endif
+
 #ifdef __linux__
 #ifdef __NR_membarrier
 static BOOL membarrier_exp_available;
@@ -5190,6 +5198,58 @@ NTSTATUS WINAPI NtFlushInstructionCache( HANDLE handle, const void *addr, SIZE_T
 }

+#ifdef __APPLE__
+
+static void tgrpvs_init( void )
+{
+    p_thread_get_register_pointer_values = dlsym( RTLD_DEFAULT, "thread_get_register_pointer_values" );
+}
+
+static int try_mach_tgrpvs( void )
+{
+    /* Taken from https://github.com/dotnet/runtime/blob/7be37908e5a1cbb83b1062768c1649827eeac... */
+    mach_msg_type_number_t count, i;
+    thread_act_array_t threads;
+    kern_return_t kret;
+    int ret = 0;
+
+    pthread_once(&tgrpvs_init_once, tgrpvs_init);
+    if (!p_thread_get_register_pointer_values)
+        return 0;
+
+    kret = task_threads( mach_task_self(), &threads, &count );
+    if (kret)
+        return 0;
+
+    for (i = 0; i < count; i++)
+    {
+        uintptr_t reg_values[128];
+        size_t reg_count = ARRAY_SIZE( reg_values );
+        uintptr_t sp;
+
+        /* This function always fails when querying Rosetta's exception handling thread, so we will only handle
+           KERN_INSUFFICIENT_BUFFER_SIZE as an error, like .NET core does. */
+        kret = p_thread_get_register_pointer_values( threads[i], &sp, &reg_count, reg_values );
+        if (kret == KERN_INSUFFICIENT_BUFFER_SIZE)
+            goto fail;
+
+        kret = mach_port_deallocate( mach_task_self(), threads[i] );
+        if (kret)
+            goto fail;
+    }
+    ret = 1;
+fail:
+    for (; i < count; i++)
+        mach_port_deallocate( mach_task_self(), threads[i] );
+    vm_deallocate( mach_task_self(), (vm_address_t)threads, count * sizeof(threads[0]) );
+    return ret;
+}
+
+#else
+static int try_mach_tgrpvs( void ) { return 0; }
+#endif
+
+
 #if defined(__linux__) && defined(__NR_membarrier)
 #define MEMBARRIER_CMD_QUERY                        0x00
 #define MEMBARRIER_CMD_PRIVATE_EXPEDITED            0x08
@@ -5294,6 +5354,8 @@ static void do_apc_memorybarrier( void )
  */
 void WINAPI NtFlushProcessWriteBuffers(void)
 {
+    if (try_mach_tgrpvs())
+        return;
     if (try_exp_membarrier())
         return;
     if (try_madvise())