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authorAlex Bennée <alex.bennee@linaro.org>2021-07-21 00:26:54 +0100
committerAlex Bennée <alex.bennee@linaro.org>2021-07-23 17:22:16 +0100
commitf7e68c9c99ad94f23d3ba3af1642c805b11c71c1 (patch)
tree0a1141f57b680499f943b37beee3093c6cfa8514 /plugins
parent094d278547dcb66ad222047ab9c325c452fe31e3 (diff)
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tcg/plugins: implement a qemu_plugin_user_exit helper
In user-mode emulation there is a small race between preexit_cleanup and exit_group() which means we may end up calling instrumented instructions before the kernel reaps child threads. To solve this we implement a new helper which ensures the callbacks are flushed along with any translations before we let the host do it's a thing. While we are at it make the documentation of qemu_plugin_register_atexit_cb clearer as to what the user can expect. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Mahmoud Mandour <ma.mandourr@gmail.com> Acked-by: Warner Losh <imp@bsdimp.com> Message-Id: <20210720232703.10650-21-alex.bennee@linaro.org>
Diffstat (limited to 'plugins')
-rw-r--r--plugins/core.c39
1 files changed, 39 insertions, 0 deletions
diff --git a/plugins/core.c b/plugins/core.c
index 474db28..6b2490f 100644
--- a/plugins/core.c
+++ b/plugins/core.c
@@ -488,6 +488,45 @@ void qemu_plugin_register_atexit_cb(qemu_plugin_id_t id,
}
/*
+ * Handle exit from linux-user. Unlike the normal atexit() mechanism
+ * we need to handle the clean-up manually as it's possible threads
+ * are still running. We need to remove all callbacks from code
+ * generation, flush the current translations and then we can safely
+ * trigger the exit callbacks.
+ */
+
+void qemu_plugin_user_exit(void)
+{
+ enum qemu_plugin_event ev;
+ CPUState *cpu;
+
+ QEMU_LOCK_GUARD(&plugin.lock);
+
+ start_exclusive();
+
+ /* un-register all callbacks except the final AT_EXIT one */
+ for (ev = 0; ev < QEMU_PLUGIN_EV_MAX; ev++) {
+ if (ev != QEMU_PLUGIN_EV_ATEXIT) {
+ struct qemu_plugin_ctx *ctx;
+ QTAILQ_FOREACH(ctx, &plugin.ctxs, entry) {
+ plugin_unregister_cb__locked(ctx, ev);
+ }
+ }
+ }
+
+ tb_flush(current_cpu);
+
+ CPU_FOREACH(cpu) {
+ qemu_plugin_disable_mem_helpers(cpu);
+ }
+
+ end_exclusive();
+
+ /* now it's safe to handle the exit case */
+ qemu_plugin_atexit_cb();
+}
+
+/*
* Call this function after longjmp'ing to the main loop. It's possible that the
* last instruction of a TB might have used helpers, and therefore the
* "disable" instruction will never execute because it ended up as dead code.