wow64: Directly use CPU area in Wow64KiUserCallbackDispatcher for I386_CONTEXT.

NtSetInformationThread for i386 causes WOW64_CPURESERVED_FLAG_RESET_STATE to be set, which makes subsequent syscall to restore the state instead of returning its result.

wow64: Directly use CPU area in Wow64KiUserCallbackDispatcher for I386_CONTEXT.
de5f640a · Jacek Caban · Alexandre Julliard · 8e27f6c2 · de5f640a
Commit de5f640a authored Aug 11, 2022 by Jacek Caban Committed by Alexandre Julliard Aug 11, 2022
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Showing with 7 additions and 9 deletions

syscall.c dlls/wow64/syscall.c +7 -9

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--- a/dlls/wow64/syscall.c
+++ b/dlls/wow64/syscall.c
@@ -865,13 +865,14 @@ NTSTATUS WINAPI Wow64KiUserCallbackDispatcher( ULONG id, void *args, ULONG len,
    {
    case IMAGE_FILE_MACHINE_I386:
        {
-            I386_CONTEXT orig_ctx, ctx = { CONTEXT_I386_FULL };
+            I386_CONTEXT orig_ctx, *ctx;
            void *args_data;
            ULONG *stack;

-            NtQueryInformationThread( GetCurrentThread(), ThreadWow64Context, &ctx, sizeof(ctx), NULL );
+            RtlWow64GetCurrentCpuArea( NULL, (void **)&ctx, NULL );
+            orig_ctx = *ctx;

-            stack = args_data = ULongToPtr( (ctx.Esp - len) & ~15 );
+            stack = args_data = ULongToPtr( (ctx->Esp - len) & ~15 );
            memcpy( args_data, args, len );
            *(--stack) = 0;
            *(--stack) = len;
@@ -879,16 +880,13 @@ NTSTATUS WINAPI Wow64KiUserCallbackDispatcher( ULONG id, void *args, ULONG len,
            *(--stack) = id;
            *(--stack) = 0xdeadbabe;

-            orig_ctx = ctx;
-            ctx.Esp = PtrToUlong( stack );
-            ctx.Eip = pLdrSystemDllInitBlock->pKiUserCallbackDispatcher;
-            NtSetInformationThread( GetCurrentThread(), ThreadWow64Context, &ctx, sizeof(ctx) );
+            ctx->Esp = PtrToUlong( stack );
+            ctx->Eip = pLdrSystemDllInitBlock->pKiUserCallbackDispatcher;

            if (!__wine_setjmpex( &frame.jmpbuf, NULL ))
                cpu_simulate();
            else
-                NtSetInformationThread( GetCurrentThread(), ThreadWow64Context,
-                                        &orig_ctx, sizeof(orig_ctx) );
+                *ctx = orig_ctx;
        }
        break;