[PATCH v2 10/47] Windows gdb: Eliminate reload_context

Pedro Alves
2025-05-19T13:29:09Z

We don't need reload_context, because we can get the same information
out of th->context.ContextFlags. If ContextFlags is zero, then we
need to fetch the context out of the inferior thread. This is what
gdbserver does too.

Approved-By: Tom Tromey <tom@tromey.com>
Change-Id: Ied566037c81383414c46c77713bdd1aec6377b23
---
gdb/nat/windows-nat.h | 4 ----
gdb/windows-nat.c | 49 +++++++++++++++++++++++--------------------
2 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 902508b0aea..71560930e84 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -90,10 +90,6 @@ struct windows_thread_info
the thread. */
bool debug_registers_changed = false;

- /* Nonzero if CONTEXT is invalidated and must be re-read from the
- inferior thread. */
- bool reload_context = false;
-
/* True if this thread is currently stopped at a software
breakpoint. This is used to offset the PC when needed. */
bool stopped_at_software_breakpoint = false;
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index e9389169ab3..4a10cf962a9 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -101,6 +101,8 @@ struct windows_per_inferior : public windows_process_info
void handle_unload_dll () override;
bool handle_access_violation (const EXCEPTION_RECORD *rec) override;

+ void invalidate_context (windows_thread_info *th);
+
int windows_initialization_done = 0;

std::vector<std::unique_ptr<windows_thread_info>> thread_list;
@@ -516,7 +518,18 @@ windows_per_inferior::find_thread (ptid_t ptid)
return nullptr;
}

-/* See nat/windows-nat.h. */
+/* Invalidate TH's context. */
+
+void
+windows_per_inferior::invalidate_context (windows_thread_info *th)
+{
+#ifdef __x86_64__
+ if (windows_process.wow64_process)
+ th->wow64_context.ContextFlags = 0;
+ else
+#endif
+ th->context.ContextFlags = 0;
+}

windows_thread_info *
windows_per_inferior::thread_rec (ptid_t ptid,
@@ -531,11 +544,11 @@ windows_per_inferior::thread_rec (ptid_t ptid,
case INVALIDATE_CONTEXT:
if (ptid.lwp () != current_event.dwThreadId)
th->suspend ();
- th->reload_context = true;
+ invalidate_context (th);
break;
case DONT_SUSPEND:
- th->reload_context = true;
th->suspended = -1;
+ invalidate_context (th);
break;
}
}
@@ -637,18 +650,13 @@ windows_nat_target::delete_thread (ptid_t ptid, DWORD exit_code,
and supplies its value to the given regcache.

This function assumes that R is non-negative. A failed assertion
- is raised if that is not true.
-
- This function assumes that TH->RELOAD_CONTEXT is not set, meaning
- that the windows_thread_info has an up-to-date context. A failed
- assertion is raised if that assumption is violated. */
+ is raised if that is not true. */

static void
windows_fetch_one_register (struct regcache *regcache,
windows_thread_info *th, int r)
{
gdb_assert (r >= 0);
- gdb_assert (!th->reload_context);

char *context_ptr = windows_process.with_context (th, [] (auto *context)
{
@@ -717,16 +725,14 @@ windows_nat_target::fetch_registers (struct regcache *regcache, int r)
if (th == NULL)
return;

- if (th->reload_context)
- {
- windows_process.with_context (th, [&] (auto *context)
- {
- context->ContextFlags = WindowsContext<decltype(context)>::all;
- CHECK (get_thread_context (th->h, context));
- });
-
- th->reload_context = false;
- }
+ windows_process.with_context (th, [&] (auto *context)
+ {
+ if (context->ContextFlags == 0)
+ {
+ context->ContextFlags = WindowsContext<decltype(context)>::all;
+ CHECK (get_thread_context (th->h, context));
+ }
+ });

if (r < 0)
for (r = 0; r < gdbarch_num_regs (regcache->arch()); r++)
@@ -1446,10 +1452,7 @@ windows_nat_target::get_windows_debug_event
*ourstatus = stop->status;

ptid_t ptid (windows_process.current_event.dwProcessId, thread_id);
- windows_thread_info *th
- = windows_process.thread_rec (ptid, INVALIDATE_CONTEXT);
- th->reload_context = true;
-
+ windows_process.thread_rec (ptid, INVALIDATE_CONTEXT);
return ptid;
}

--
2.49.0