From 3d75856d1a9c8d187d91066d0747de7a0d1ce3d5 Mon Sep 17 00:00:00 2001
From: Richard Henderson <richard.henderson@linaro.org>
Date: Tue, 9 Jul 2024 12:52:40 -0700
Subject: [PATCH] accel/tcg: Move {set,clear}_helper_retaddr to cpu_ldst.h

Use of these in helpers goes hand-in-hand with tlb_vaddr_to_host
and other probing functions.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/cpu-exec.c     |  3 ---
 accel/tcg/user-exec.c    |  1 -
 accel/tcg/user-retaddr.h | 28 ----------------------------
 include/exec/cpu_ldst.h  | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 34 insertions(+), 32 deletions(-)
 delete mode 100644 accel/tcg/user-retaddr.h

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 9010dad073..8163295f34 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -41,9 +41,6 @@
 #include "tb-context.h"
 #include "internal-common.h"
 #include "internal-target.h"
-#if defined(CONFIG_USER_ONLY)
-#include "user-retaddr.h"
-#endif
 
 /* -icount align implementation. */
 
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index 80d24540ed..7ddc47b0ba 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -33,7 +33,6 @@
 #include "tcg/tcg-ldst.h"
 #include "internal-common.h"
 #include "internal-target.h"
-#include "user-retaddr.h"
 
 __thread uintptr_t helper_retaddr;
 
diff --git a/accel/tcg/user-retaddr.h b/accel/tcg/user-retaddr.h
deleted file mode 100644
index e0f57e1994..0000000000
--- a/accel/tcg/user-retaddr.h
+++ /dev/null
@@ -1,28 +0,0 @@
-#ifndef ACCEL_TCG_USER_RETADDR_H
-#define ACCEL_TCG_USER_RETADDR_H
-
-#include "qemu/atomic.h"
-
-extern __thread uintptr_t helper_retaddr;
-
-static inline void set_helper_retaddr(uintptr_t ra)
-{
-    helper_retaddr = ra;
-    /*
-     * Ensure that this write is visible to the SIGSEGV handler that
-     * may be invoked due to a subsequent invalid memory operation.
-     */
-    signal_barrier();
-}
-
-static inline void clear_helper_retaddr(void)
-{
-    /*
-     * Ensure that previous memory operations have succeeded before
-     * removing the data visible to the signal handler.
-     */
-    signal_barrier();
-    helper_retaddr = 0;
-}
-
-#endif
diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
index 71009f84f5..dac12bd8eb 100644
--- a/include/exec/cpu_ldst.h
+++ b/include/exec/cpu_ldst.h
@@ -379,4 +379,38 @@ void *tlb_vaddr_to_host(CPUArchState *env, abi_ptr addr,
                         MMUAccessType access_type, int mmu_idx);
 #endif
 
+/*
+ * For user-only, helpers that use guest to host address translation
+ * must protect the actual host memory access by recording 'retaddr'
+ * for the signal handler.  This is required for a race condition in
+ * which another thread unmaps the page between a probe and the
+ * actual access.
+ */
+#ifdef CONFIG_USER_ONLY
+extern __thread uintptr_t helper_retaddr;
+
+static inline void set_helper_retaddr(uintptr_t ra)
+{
+    helper_retaddr = ra;
+    /*
+     * Ensure that this write is visible to the SIGSEGV handler that
+     * may be invoked due to a subsequent invalid memory operation.
+     */
+    signal_barrier();
+}
+
+static inline void clear_helper_retaddr(void)
+{
+    /*
+     * Ensure that previous memory operations have succeeded before
+     * removing the data visible to the signal handler.
+     */
+    signal_barrier();
+    helper_retaddr = 0;
+}
+#else
+#define set_helper_retaddr(ra)   do { } while (0)
+#define clear_helper_retaddr()   do { } while (0)
+#endif
+
 #endif /* CPU_LDST_H */