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[Qemu-devel] [PATCH] accel/tcg/translate-all: expand cpu_restore_state r

From: Alex Bennée
Subject: [Qemu-devel] [PATCH] accel/tcg/translate-all: expand cpu_restore_state retaddr check
Date: Tue, 7 Nov 2017 16:52:26 +0000

We are still seeing signals during translation time when we walk over
a page protection boundary. This expands the check to ensure the
retaddr is inside the code generation buffer. The original suggestion
was to check versus tcg_ctx.code_gen_ptr but as we now segment the
translation buffer we have to settle for just a general check for
being inside.

Signed-off-by: Alex Bennée <address@hidden>
Reported-by: Peter Maydell <address@hidden>
Suggested-by: Paolo Bonzini <address@hidden>
Cc: Richard Henderson <address@hidden>
 accel/tcg/translate-all.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 34c5e28d07..eb255af402 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -357,16 +357,20 @@ bool cpu_restore_state(CPUState *cpu, uintptr_t retaddr)
     TranslationBlock *tb;
     bool r = false;
-    /* A retaddr of zero is invalid so we really shouldn't have ended
-     * up here. The target code has likely forgotten to check retaddr
-     * != 0 before attempting to restore state. We return early to
-     * avoid blowing up on a recursive tb_lock(). The target must have
-     * previously survived a failed cpu_restore_state because
-     * tb_find_pc(0) would have failed anyway. It still should be
-     * fixed though.
+    /* The retaddr has to be in the region of current code buffer. If
+     * it's not we will not be able to resolve it here. If it is zero
+     * the calling code has likely forgotten to check retaddr before
+     * calling here. If it is not in the translated code we could be
+     * faulting during translation itself.
+     *
+     * Either way we need return early to avoid blowing up on a
+     * recursive tb_lock() as we can't resolve it here.
-    if (!retaddr) {
+    if (!retaddr ||
+        (retaddr < (uintptr_t) tcg_init_ctx.code_gen_buffer) ||
+        (retaddr > (uintptr_t) (tcg_init_ctx.code_gen_buffer +
+                                tcg_init_ctx.code_gen_buffer_size))) {
         return r;

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