[PATCH 0/2] MR123: Fix interaction between RtlWow64SetThreadContext and NtSetThreadContext

[Jinoh Kang (＠iamahuman)]

If a Wow64 process is in emulation mode (e.g. CS points to 32-bit compat
segment on x86-64), the Wow64 register context is synonymous to the
native register context.  The client should indicate this condition by
omitting the Wow64 context when issuing a select request.  Then, the
wineserver automatically redirects Wow64 context writes to the native
context.

[PATCH 1/2] server: Discard existing Wow64 context when the client does not provide a new one.

[Jinoh Kang]

From: Jinoh Kang

Today, the wineserver does not discard the stale Wow64 context when the
client sends its new register context via the select request.

If a Wow64 process is in emulation mode (e.g. CS points to 32-bit compat
segment on x86-64), the Wow64 register context is synonymous to the
native register context.  The client can indicate this condition by
omitting the Wow64 context when issuing a select request.

If the client does omit the Wow64 context, the server shall discard the
old Wow64 context which has now become stale; however, the server
leaves the Wow64 context slot unchanged.  This becomes an issue if the
Wow64 context slot has already been populated by a prior select request
(e.g. a debug event).

Fix this by clearing the 'machine' and 'flags' fields of the Wow64
context slot unless a new Wow64 context is provided by the client.

Signed-off-by: Jinoh Kang 
---
 server/thread.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/server/thread.c b/server/thread.c
index 467ccd1f0db..c795df8ffa1 100644
--- a/server/thread.c
+++ b/server/thread.c
@@ -1616,11 +1616,16 @@ DECL_HANDLER(select)
             ctx->regs[CTX_WOW].machine = current->process->machine;
             copy_context( &ctx->regs[CTX_WOW], wow_context, wow_context->flags & ~ctx->regs[CTX_WOW].flags );
         }
-        else if (ctx->regs[CTX_PENDING].flags)
+        else
         {
-            unsigned int flags = ctx->regs[CTX_PENDING].flags & ~ctx->regs[CTX_NATIVE].flags;
-            copy_context( &ctx->regs[CTX_NATIVE], &ctx->regs[CTX_PENDING], flags );
-            ctx->regs[CTX_NATIVE].flags |= flags;
+            ctx->regs[CTX_WOW].machine = 0;
+            ctx->regs[CTX_WOW].flags = 0;
+            if (ctx->regs[CTX_PENDING].flags)
+            {
+                unsigned int flags = ctx->regs[CTX_PENDING].flags & ~ctx->regs[CTX_NATIVE].flags;
+                copy_context( &ctx->regs[CTX_NATIVE], &ctx->regs[CTX_PENDING], flags );
+                ctx->regs[CTX_NATIVE].flags |= flags;
+            }
         }
         ctx->regs[CTX_PENDING].flags = 0;
         ctx->status = STATUS_SUCCESS;

[PATCH 2/2] Revert "ntdll: Always send a Wow context to the server for Wow64 processes."

[Jinoh Kang]

From: Jinoh Kang

This reverts commit ee99bd4bc1b7ef4c18d5254a76d72d3bd38f41e8.

If a Wow64 process is in emulation mode (e.g. CS points to 32-bit compat
segment on x86-64), the Wow64 register context is synonymous to the
native register context.  The client should indicate this condition by
omitting the Wow64 context when issuing a select request.  Then, the
wineserver automatically redirects Wow64 context writes to the native
context.

Signed-off-by: Jinoh Kang 
---
 dlls/ntdll/unix/thread.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/dlls/ntdll/unix/thread.c b/dlls/ntdll/unix/thread.c
index 6d937675bcb..8de8e68a8e7 100644
--- a/dlls/ntdll/unix/thread.c
+++ b/dlls/ntdll/unix/thread.c
@@ -1011,9 +1011,6 @@ static void contexts_to_server( context_t server_contexts[2], CONTEXT *context )
         context_to_server( &server_contexts[count++], native_machine, native_context, native_machine );
         if (wow_context) context_to_server( &server_contexts[count++], main_image_info.Machine,
                                             wow_context, main_image_info.Machine );
-        else if (native_machine != main_image_info.Machine)
-            context_to_server( &server_contexts[count++], main_image_info.Machine,
-                               native_context, native_machine );
     }
     else
         context_to_server( &server_contexts[count++], native_machine,