[PATCH 2/4] translator: always pair plugin_gen_insn_{start, end} calls

From: Emilio Cota <cota@braap.org>
To: qemu-devel@nongnu.org
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"Aaron Lindsay" <aaron@os.amperecomputing.com>,
	"Emilio Cota" <cota@braap.org>
Subject: [PATCH 2/4] translator: always pair plugin_gen_insn_{start, end} calls
Date: Sun,  8 Jan 2023 11:47:29 -0500	[thread overview]
Message-ID: <20230108164731.61469-3-cota@braap.org> (raw)
In-Reply-To: <20230108164731.61469-1-cota@braap.org>

Related: #1381

Signed-off-by: Emilio Cota <cota@braap.org>
---
 accel/tcg/translator.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
index 061519691f..ef5193c67e 100644
--- a/accel/tcg/translator.c
+++ b/accel/tcg/translator.c
@@ -100,19 +100,24 @@ void translator_loop(CPUState *cpu, TranslationBlock *tb, int max_insns,
             ops->translate_insn(db, cpu);
         }
 
-        /* Stop translation if translate_insn so indicated.  */
-        if (db->is_jmp != DISAS_NEXT) {
-            break;
-        }
-
         /*
          * We can't instrument after instructions that change control
          * flow although this only really affects post-load operations.
+         *
+         * Calling plugin_gen_insn_end() before we possibly stop translation
+         * is important. Even if this ends up as dead code, plugin generation
+         * needs to see a matching plugin_gen_insn_{start,end}() pair in order
+         * to accurately track instrumented helpers that might access memory.
          */
         if (plugin_enabled) {
             plugin_gen_insn_end();
         }
 
+        /* Stop translation if translate_insn so indicated.  */
+        if (db->is_jmp != DISAS_NEXT) {
+            break;
+        }
+
         /* Stop translation if the output buffer is full,
            or we have executed all of the allowed instructions.  */
         if (tcg_op_buf_full() || db->num_insns >= db->max_insns) {
-- 
2.34.1


