tcg: Introduce set/clear_helper_retaddr

At present we have a potential error in that helper_retaddr contains
data for handle_cpu_signal, but we have not ensured that those stores
will be scheduled properly before the operation that may fault.

It might be that these races are not in practice observable, due to
our use of -fno-strict-aliasing, but better safe than sorry.

Adjust all of the setters of helper_retaddr.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

2 files changed, 25 insertions, 26 deletions

diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
index 44e45a8037..060699b901 100644
--- a/target/arm/helper-a64.c
+++ b/target/arm/helper-a64.c
@@ -554,7 +554,7 @@ uint64_t HELPER(paired_cmpxchg64_le)(CPUARMState *env, uint64_t addr,
     /* ??? Enforce alignment.  */
     uint64_t *haddr = g2h(addr);
 
-    helper_retaddr = ra;
+    set_helper_retaddr(ra);
     o0 = ldq_le_p(haddr + 0);
     o1 = ldq_le_p(haddr + 1);
     oldv = int128_make128(o0, o1);
@@ -564,7 +564,7 @@ uint64_t HELPER(paired_cmpxchg64_le)(CPUARMState *env, uint64_t addr,
         stq_le_p(haddr + 0, int128_getlo(newv));
         stq_le_p(haddr + 1, int128_gethi(newv));
     }
-    helper_retaddr = 0;
+    clear_helper_retaddr();
 #else
     int mem_idx = cpu_mmu_index(env, false);
     TCGMemOpIdx oi0 = make_memop_idx(MO_LEQ | MO_ALIGN_16, mem_idx);
@@ -624,7 +624,7 @@ uint64_t HELPER(paired_cmpxchg64_be)(CPUARMState *env, uint64_t addr,
     /* ??? Enforce alignment.  */
     uint64_t *haddr = g2h(addr);
 
-    helper_retaddr = ra;
+    set_helper_retaddr(ra);
     o1 = ldq_be_p(haddr + 0);
     o0 = ldq_be_p(haddr + 1);
     oldv = int128_make128(o0, o1);
@@ -634,7 +634,7 @@ uint64_t HELPER(paired_cmpxchg64_be)(CPUARMState *env, uint64_t addr,
         stq_be_p(haddr + 0, int128_gethi(newv));
         stq_be_p(haddr + 1, int128_getlo(newv));
     }
-    helper_retaddr = 0;
+    clear_helper_retaddr();
 #else
     int mem_idx = cpu_mmu_index(env, false);
     TCGMemOpIdx oi0 = make_memop_idx(MO_BEQ | MO_ALIGN_16, mem_idx);
diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
index fd434c66ea..fc0c1755d2 100644
--- a/target/arm/sve_helper.c
+++ b/target/arm/sve_helper.c
@@ -4125,12 +4125,11 @@ static intptr_t max_for_page(target_ulong base, intptr_t mem_off,
     return MIN(split, mem_max - mem_off) + mem_off;
 }
 
-static inline void set_helper_retaddr(uintptr_t ra)
-{
-#ifdef CONFIG_USER_ONLY
-    helper_retaddr = ra;
+#ifndef CONFIG_USER_ONLY
+/* These are normally defined only for CONFIG_USER_ONLY in <exec/cpu_ldst.h> */
+static inline void set_helper_retaddr(uintptr_t ra) { }
+static inline void clear_helper_retaddr(void) { }
 #endif
-}
 
 /*
  * The result of tlb_vaddr_to_host for user-only is just g2h(x),
@@ -4188,7 +4187,7 @@ static void sve_ld1_r(CPUARMState *env, void *vg, const target_ulong addr,
         if (test_host_page(host)) {
             mem_off = host_fn(vd, vg, host - mem_off, mem_off, mem_max);
             tcg_debug_assert(mem_off == mem_max);
-            set_helper_retaddr(0);
+            clear_helper_retaddr();
             /* After having taken any fault, zero leading inactive elements. */
             swap_memzero(vd, reg_off);
             return;
@@ -4239,7 +4238,7 @@ static void sve_ld1_r(CPUARMState *env, void *vg, const target_ulong addr,
     }
 #endif
 
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
     memcpy(vd, &scratch, reg_max);
 }
 
@@ -4312,7 +4311,7 @@ static void sve_ld2_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 2 * size;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 
     /* Wait until all exceptions have been raised to write back.  */
     memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4341,7 +4340,7 @@ static void sve_ld3_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 3 * size;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 
     /* Wait until all exceptions have been raised to write back.  */
     memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4372,7 +4371,7 @@ static void sve_ld4_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 4 * size;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 
     /* Wait until all exceptions have been raised to write back.  */
     memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4494,7 +4493,7 @@ static void sve_ldff1_r(CPUARMState *env, void *vg, const target_ulong addr,
         if (test_host_page(host)) {
             mem_off = host_fn(vd, vg, host - mem_off, mem_off, mem_max);
             tcg_debug_assert(mem_off == mem_max);
-            set_helper_retaddr(0);
+            clear_helper_retaddr();
             /* After any fault, zero any leading inactive elements.  */
             swap_memzero(vd, reg_off);
             return;
@@ -4537,7 +4536,7 @@ static void sve_ldff1_r(CPUARMState *env, void *vg, const target_ulong addr,
     }
 #endif
 
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
     record_fault(env, reg_off, reg_max);
 }
 
@@ -4740,7 +4739,7 @@ static void sve_st1_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += msize;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 static void sve_st2_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4766,7 +4765,7 @@ static void sve_st2_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 2 * msize;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 static void sve_st3_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4794,7 +4793,7 @@ static void sve_st3_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 3 * msize;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 static void sve_st4_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4824,7 +4823,7 @@ static void sve_st4_r(CPUARMState *env, void *vg, target_ulong addr,
             addr += 4 * msize;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 #define DO_STN_1(N, NAME, ESIZE) \
@@ -4932,7 +4931,7 @@ static void sve_ld1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
             i += 4, pg >>= 4;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 
     /* Wait until all exceptions have been raised to write back.  */
     memcpy(vd, &scratch, oprsz);
@@ -4955,7 +4954,7 @@ static void sve_ld1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
             tlb_fn(env, &scratch, i * 8, base + (off << scale), oi, ra);
         }
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 
     /* Wait until all exceptions have been raised to write back.  */
     memcpy(vd, &scratch, oprsz * 8);
@@ -5133,7 +5132,7 @@ static inline void sve_ldff1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
         tlb_fn(env, vd, reg_off, addr, oi, ra);
 
         /* The rest of the reads will be non-faulting.  */
-        set_helper_retaddr(0);
+        clear_helper_retaddr();
     }
 
     /* After any fault, zero the leading predicated false elements.  */
@@ -5175,7 +5174,7 @@ static inline void sve_ldff1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
         tlb_fn(env, vd, reg_off, addr, oi, ra);
 
         /* The rest of the reads will be non-faulting.  */
-        set_helper_retaddr(0);
+        clear_helper_retaddr();
     }
 
     /* After any fault, zero the leading predicated false elements.  */
@@ -5299,7 +5298,7 @@ static void sve_st1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
             i += 4, pg >>= 4;
         } while (i & 15);
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 static void sve_st1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
@@ -5318,7 +5317,7 @@ static void sve_st1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
             tlb_fn(env, vd, i * 8, base + (off << scale), oi, ra);
         }
     }
-    set_helper_retaddr(0);
+    clear_helper_retaddr();
 }
 
 #define DO_ST1_ZPZ_S(MEM, OFS) \