ntdll: Ensure CONTEXT_EX on exception stack is initialized.

On non-AVX CPUs, CONTEXT_EX is not being initialized. In WOW64 mode, this results in invalid exception records when dispatch_wow_exception() uses RtlCopyContext(). Signed-off-by: Brendan Shanks <bshanks@codeweavers.com> Signed-off-by: Alexandre Julliard <julliard@winehq.org>

ntdll: Ensure CONTEXT_EX on exception stack is initialized.
a906f13f · Brendan Shanks · Alexandre Julliard · b73e3102 · a906f13f · a906f13f
Commit a906f13f authored Mar 03, 2022 by Brendan Shanks Committed by Alexandre Julliard Mar 04, 2022
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signal_i386.c dlls/ntdll/unix/signal_i386.c +16 -1

signal_x86_64.c dlls/ntdll/unix/signal_x86_64.c +16 -1

No files found.
--- a/dlls/ntdll/unix/signal_i386.c
+++ b/dlls/ntdll/unix/signal_i386.c
@@ -581,12 +581,23 @@ static inline void context_init_xstate( CONTEXT *context, void *xstate_buffer )
    xctx->Legacy.Length = sizeof(CONTEXT);
    xctx->Legacy.Offset = -(LONG)sizeof(CONTEXT);

+    if (xstate_buffer)
+    {
        xctx->XState.Length = sizeof(XSTATE);
        xctx->XState.Offset = (BYTE *)xstate_buffer - (BYTE *)xctx;
+        context->ContextFlags |= CONTEXT_XSTATE;

        xctx->All.Length = sizeof(CONTEXT) + xctx->XState.Offset + xctx->XState.Length;
+    }
+    else
+    {
+        xctx->XState.Length = 25;
+        xctx->XState.Offset = 0;
+
+        xctx->All.Length = sizeof(CONTEXT) + 24; /* sizeof(CONTEXT_EX) minus 8 alignment bytes on x64. */
+    }
+
    xctx->All.Offset = -(LONG)sizeof(CONTEXT);
-    context->ContextFlags |= CONTEXT_XSTATE;
 }


@@ -1456,6 +1467,10 @@ C_ASSERT( (offsetof(struct stack_layout, xstate) == sizeof(struct stack_layout))
            memcpy( &dst_xs->YmmContext, &src_xs->YmmContext, sizeof(dst_xs->YmmContext) );
        }
    }
+    else
+    {
+        context_init_xstate( &stack->context, NULL );
+    }

    stack->rec_ptr      = &stack->rec;
    stack->context_ptr  = &stack->context;

--- a/dlls/ntdll/unix/signal_x86_64.c
+++ b/dlls/ntdll/unix/signal_x86_64.c
@@ -411,12 +411,23 @@ static inline void context_init_xstate( CONTEXT *context, void *xstate_buffer )
    xctx->Legacy.Length = sizeof(CONTEXT);
    xctx->Legacy.Offset = -(LONG)sizeof(CONTEXT);

+    if (xstate_buffer)
+    {
        xctx->XState.Length = sizeof(XSTATE);
        xctx->XState.Offset = (BYTE *)xstate_buffer - (BYTE *)xctx;
+        context->ContextFlags |= CONTEXT_XSTATE;

        xctx->All.Length = sizeof(CONTEXT) + xctx->XState.Offset + xctx->XState.Length;
+    }
+    else
+    {
+        xctx->XState.Length = 25;
+        xctx->XState.Offset = 0;
+
+        xctx->All.Length = sizeof(CONTEXT) + 24; /* sizeof(CONTEXT_EX) minus 8 alignment bytes on x64. */
+    }
+
    xctx->All.Offset = -(LONG)sizeof(CONTEXT);
-    context->ContextFlags |= CONTEXT_XSTATE;
 }

 static USHORT cs32_sel;  /* selector for %cs in 32-bit mode */
@@ -2195,6 +2206,10 @@ static void setup_raise_exception( ucontext_t *sigcontext, EXCEPTION_RECORD *rec
            memcpy( &dst_xs->YmmContext, &src_xs->YmmContext, sizeof(dst_xs->YmmContext) );
        }
    }
+    else
+    {
+        context_init_xstate( &stack->context, NULL );
+    }

    CS_sig(sigcontext)  = cs64_sel;
    RIP_sig(sigcontext) = (ULONG_PTR)pKiUserExceptionDispatcher;