Merge tag 'pull-tcg-20240723' of https://gitlab.com/rth7680/qemu into staging

accel/tcg: Export set/clear_helper_retaddr
target/arm: Use set_helper_retaddr for dc_zva, sve and sme
target/ppc: Tidy dcbz helpers
target/ppc: Use set_helper_retaddr for dcbz
target/s390x: Use set_helper_retaddr in mem_helper.c

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# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [ultimate]

* tag 'pull-tcg-20240723' of https://gitlab.com/rth7680/qemu:
  target/riscv: Simplify probing in vext_ldff
  target/s390x: Use set/clear_helper_retaddr in mem_helper.c
  target/s390x: Use user_or_likely in access_memmove
  target/s390x: Use user_or_likely in do_access_memset
  target/ppc: Improve helper_dcbz for user-only
  target/ppc: Merge helper_{dcbz,dcbzep}
  target/ppc: Split out helper_dbczl for 970
  target/ppc: Hoist dcbz_size out of dcbz_common
  target/ppc/mem_helper.c: Remove a conditional from dcbz_common()
  target/arm: Use set/clear_helper_retaddr in SVE and SME helpers
  target/arm: Use set/clear_helper_retaddr in helper-a64.c
  accel/tcg: Move {set,clear}_helper_retaddr to cpu_ldst.h

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 34 insertions, 0 deletions

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 */