[PATCH v2 2/8] Windows gdb: Use allocated buffer for CONTEXT

[Hannes Domani <ssbssa@yahoo.de>]

This is done in preparation for the XState functions, because the
extended registers are stored directly after the CONTEXT, and its actual
size depends on the available XState features.
---
 gdb/aarch64-windows-nat.c      | 16 ++++++++--------
 gdb/nat/windows-nat.c          | 19 +++++++++++++++++++
 gdb/nat/windows-nat.h          | 16 ++++++++++++----
 gdb/windows-nat.c              |  1 +
 gdbserver/win32-aarch64-low.cc | 10 +++++-----
 gdbserver/win32-low.cc         |  1 +
 6 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/gdb/aarch64-windows-nat.c b/gdb/aarch64-windows-nat.c
index ff2c9762467..630704a8caf 100644
--- a/gdb/aarch64-windows-nat.c
+++ b/gdb/aarch64-windows-nat.c
@@ -185,7 +185,7 @@ aarch64_windows_nat_target::cleanup_windows_arch ()
 void
 aarch64_windows_per_inferior::fill_thread_context (windows_thread_info *th)
 {
-  CONTEXT *context = &th->context;
+  CONTEXT *context = th->context;
 
   if (context->ContextFlags == 0)
     {
@@ -199,7 +199,7 @@ aarch64_windows_per_inferior::fill_thread_context (windows_thread_info *th)
 void
 aarch64_windows_per_inferior::invalidate_thread_context (windows_thread_info *th)
 {
-  CONTEXT *context = &th->context;
+  CONTEXT *context = th->context;
   context->ContextFlags = 0;
 }
 
@@ -209,7 +209,7 @@ void
 aarch64_windows_nat_target::thread_context_continue (windows_thread_info *th,
 						     int killed)
 {
-  CONTEXT *context = &th->context;
+  CONTEXT *context = th->context;
 
   if (th->debug_registers_changed)
     {
@@ -250,9 +250,9 @@ aarch64_windows_nat_target::thread_context_step (windows_thread_info *th,
 						 bool enable)
 {
   if (enable)
-    th->context.Cpsr |= 0x200000;
+    th->context->Cpsr |= 0x200000;
   else
-    th->context.Cpsr &= ~0x200000;
+    th->context->Cpsr &= ~0x200000;
 }
 
 /* See windows-nat.h.  */
@@ -263,7 +263,7 @@ aarch64_windows_nat_target::fetch_one_register (struct regcache *regcache,
 {
   gdb_assert (r >= 0);
 
-  char *context_ptr = (char *) &th->context;
+  char *context_ptr = (char *) th->context;
   char *context_offset = context_ptr + aarch64_windows_process.mappings[r];
   struct gdbarch *gdbarch = regcache->arch ();
 
@@ -292,9 +292,9 @@ aarch64_windows_nat_target::store_one_register (const struct regcache *regcache,
 						windows_thread_info *th, int r)
 {
   gdb_assert (r >= 0);
-  gdb_assert (th->context.ContextFlags != 0);
+  gdb_assert (th->context->ContextFlags != 0);
 
-  char *context_ptr = (char *) &th->context;
+  char *context_ptr = (char *) th->context;
 
   regcache->raw_collect (r, context_ptr + aarch64_windows_process.mappings[r]);
 }
diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index e975892f487..689601f3a82 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -291,6 +291,25 @@ windows_process_info::pid_to_exec_file (int pid)
   return path;
 }
 
+/* See windows-nat.h.  */
+
+void windows_process_info::initialize_context (windows_thread_info *th)
+{
+#ifdef __x86_64__
+  if (wow64_process)
+    {
+      th->context_buffer.reset (xmalloc (sizeof (WOW64_CONTEXT)));
+      th->wow64_context = (WOW64_CONTEXT *) th->context_buffer.get ();
+    }
+  else
+#endif
+    {
+      th->context_buffer.reset (xmalloc (sizeof (CONTEXT)));
+      th->context = (CONTEXT *) th->context_buffer.get ();
+    }
+  *context_flags_ptr (th) = 0;
+}
+
 /* Return the name of the DLL referenced by H at ADDRESS.  UNICODE
    determines what sort of string is read from the inferior.  Returns
    the name of the DLL, or NULL on error.  If a name is returned, it
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 44b628c9bd1..76688fa90da 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -183,9 +183,9 @@ struct windows_thread_info
   /* The context of the thread, including any manipulations.  */
   union
   {
-    CONTEXT context {};
+    CONTEXT *context = nullptr;
 #ifdef __x86_64__
-    WOW64_CONTEXT wow64_context;
+    WOW64_CONTEXT *wow64_context;
 #endif
   };
 
@@ -204,6 +204,10 @@ struct windows_thread_info
 
   /* The name of the thread.  */
   gdb::unique_xmalloc_ptr<char> name;
+
+  /* The buffer for the thread context, including any XState registers if
+     available.  */
+  gdb::unique_xmalloc_ptr<void> context_buffer;
 };
 
 enum handle_exception_result
@@ -313,15 +317,19 @@ struct windows_process_info
 
   const char *pid_to_exec_file (int);
 
+  /* Allocate the context buffer for this thread.  */
+
+  void initialize_context (windows_thread_info *th);
+
   template<typename Function>
   auto with_context (windows_thread_info *th, Function function)
   {
 #ifdef __x86_64__
     if (wow64_process)
-      return function (th != nullptr ? &th->wow64_context : nullptr);
+      return function (th != nullptr ? th->wow64_context : nullptr);
     else
 #endif
-      return function (th != nullptr ? &th->context : nullptr);
+      return function (th != nullptr ? th->context : nullptr);
   }
 
   DWORD *context_flags_ptr (windows_thread_info *th)
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index def8fa606f4..4cd301d4959 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -515,6 +515,7 @@ windows_nat_target::add_thread (ptid_t ptid, HANDLE h, void *tlb,
 #endif
   windows_private_thread_info *th
     = new windows_private_thread_info (windows_process, ptid.lwp (), h, base);
+  windows_process->initialize_context (th);
 
   /* Add this new thread to the list of threads.
 
diff --git a/gdbserver/win32-aarch64-low.cc b/gdbserver/win32-aarch64-low.cc
index 5a7b72155db..e94548b6fef 100644
--- a/gdbserver/win32-aarch64-low.cc
+++ b/gdbserver/win32-aarch64-low.cc
@@ -169,7 +169,7 @@ aarch64_initial_stuff (process_info *proc)
 static void
 aarch64_get_thread_context (windows_thread_info *th)
 {
-  CONTEXT *context = &th->context;
+  CONTEXT *context = th->context;
 
   context->ContextFlags = (WindowsContext<decltype(context)>::full
 			   | WindowsContext<decltype(context)>::floating
@@ -193,7 +193,7 @@ aarch64_prepare_to_resume (windows_thread_info *th)
     {
       win32_require_context (th);
 
-      CONTEXT *context = &th->context;
+      CONTEXT *context = th->context;
 
       for (int i = 0; i < aarch64_num_bp_regs; i++)
 	{
@@ -223,7 +223,7 @@ aarch64_thread_added (windows_thread_info *th)
 static void
 aarch64_single_step (windows_thread_info *th)
 {
-  th->context.Cpsr |= 0x200000;
+  th->context->Cpsr |= 0x200000;
 }
 
 /* An array of offset mappings into a Win32 Context structure.
@@ -322,7 +322,7 @@ aarch64_fetch_inferior_register (struct regcache *regcache,
   int mappings_count;
   get_mappings (mappings, mappings_count);
 
-  char *context_ptr = (char *) &th->context;
+  char *context_ptr = (char *) th->context;
   char *context_offset;
   if (r < mappings_count)
     context_offset = context_ptr + mappings[r];
@@ -341,7 +341,7 @@ aarch64_store_inferior_register (struct regcache *regcache,
   int mappings_count;
   get_mappings (mappings, mappings_count);
 
-  char *context_ptr = (char *) &th->context;
+  char *context_ptr = (char *) th->context;
   char *context_offset;
   if (r < mappings_count)
     context_offset = context_ptr + mappings[r];
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 7629beca213..3d85faf0785 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -152,6 +152,7 @@ child_add_thread (DWORD pid, DWORD tid, HANDLE h, void *tlb)
     base += 2 * 4096; /* page size = 4096 */
 #endif
   th = new windows_thread_info (&windows_process, tid, h, base);
+  windows_process.initialize_context (th);
 
   find_process_pid (pid)->add_thread (ptid, th);
 
-- 
2.54.0