[Qemu-devel] [PATCH v3 05/11] linux-user: arm: handle CPSR.E correctly in strex emulation

[Paolo Bonzini <pbonzini@redhat.com>]

Now that CPSR.E is set correctly, prepare for when setend will be able
to change it; bswap data in and out of strex manually by comparing
SCTLR.B, CPSR.E and TARGET_WORDS_BIGENDIAN (we do not have the luxury
of using TCGMemOps).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 linux-user/main.c | 50 +++++++++++++++++++++++++++++++++++++++++++-------
 target-arm/cpu.h  | 28 ++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 7 deletions(-)

diff --git a/linux-user/main.c b/linux-user/main.c
index 795a407..9782c13 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -449,6 +449,38 @@ void cpu_loop(CPUX86State *env)
         __r;                                            \
     })
 
+#define get_user_data_u32(x, gaddr, env)                \
+    ({ abi_long __r = get_user_u32((x), (gaddr));       \
+        if (!__r && arm_cpu_bswap_data(env)) {          \
+            (x) = bswap32(x);                           \
+        }                                               \
+        __r;                                            \
+    })
+
+#define get_user_data_u16(x, gaddr, env)                \
+    ({ abi_long __r = get_user_u16((x), (gaddr));       \
+        if (!__r && arm_cpu_bswap_data(env)) {          \
+            (x) = bswap16(x);                           \
+        }                                               \
+        __r;                                            \
+    })
+
+#define put_user_data_u32(x, gaddr, env)                \
+    ({ typeof(x) __x = (x);                             \
+        if (arm_cpu_bswap_data(env)) {                  \
+            __x = bswap32(__x);                         \
+        }                                               \
+        put_user_u32(__x, (gaddr));                     \
+    })
+
+#define put_user_data_u16(x, gaddr, env)                \
+    ({ typeof(x) __x = (x);                             \
+        if (arm_cpu_bswap_data(env)) {                  \
+            __x = bswap16(__x);                         \
+        }                                               \
+        put_user_u16(__x, (gaddr));                     \
+    })
+
 #ifdef TARGET_ABI32
 /* Commpage handling -- there is no commpage for AArch64 */
 
@@ -610,11 +642,11 @@ static int do_strex(CPUARMState *env)
         segv = get_user_u8(val, addr);
         break;
     case 1:
-        segv = get_user_u16(val, addr);
+        segv = get_user_data_u16(val, addr, env);
         break;
     case 2:
     case 3:
-        segv = get_user_u32(val, addr);
+        segv = get_user_data_u32(val, addr, env);
         break;
     default:
         abort();
@@ -625,12 +657,16 @@ static int do_strex(CPUARMState *env)
     }
     if (size == 3) {
         uint32_t valhi;
-        segv = get_user_u32(valhi, addr + 4);
+        segv = get_user_data_u32(valhi, addr + 4, env);
         if (segv) {
             env->exception.vaddress = addr + 4;
             goto done;
         }
-        val = deposit64(val, 32, 32, valhi);
+        if (arm_cpu_bswap_data(env)) {
+            val = deposit64((uint64_t)valhi, 32, 32, val);
+        } else {
+            val = deposit64(val, 32, 32, valhi);
+        }
     }
     if (val != env->exclusive_val) {
         goto fail;
@@ -642,11 +678,11 @@ static int do_strex(CPUARMState *env)
         segv = put_user_u8(val, addr);
         break;
     case 1:
-        segv = put_user_u16(val, addr);
+        segv = put_user_data_u16(val, addr, env);
         break;
     case 2:
     case 3:
-        segv = put_user_u32(val, addr);
+        segv = put_user_data_u32(val, addr, env);
         break;
     }
     if (segv) {
@@ -655,7 +691,7 @@ static int do_strex(CPUARMState *env)
     }
     if (size == 3) {
         val = env->regs[(env->exclusive_info >> 12) & 0xf];
-        segv = put_user_u32(val, addr + 4);
+        segv = put_user_data_u32(val, addr + 4, env);
         if (segv) {
             env->exception.vaddress = addr + 4;
             goto done;
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index cb5be84..defd65e 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -1192,6 +1192,34 @@ static inline bool bswap_code(bool sctlr_b)
 #endif
 }
 
+#ifdef CONFIG_USER_ONLY
+/* get_user and put_user respectivaly return and expect data according
+ * to TARGET_WORDS_BIGENDIAN, but ldrex/strex emulation needs to take
+ * into account CPSR.E.  Similar to bwap_code, a XOR gives exactly the
+ * required result, we just throw CPSR.E into the mix too:
+ *
+ *            TARGET_WORDS_BIGENDIAN  SCTLR.B  CPSR.E    need swap?
+ *   LE/LE                 no             0      0          no
+ *   LE/BE                 no             0      1          yes
+ *   BE8/LE                yes            0      0          yes
+ *   BE8/BE                yes            0      1          no
+ *   BE32/BE               yes            1      0          no
+ *  (BE32/LE)              yes            1      1          yes
+ *
+ * Officially, BE32 with CPSR.E=1 has "unpredictable" results.  We
+ * implement it as big-endian code, little-endian data.
+ */
+static inline bool arm_cpu_bswap_data(CPUARMState *env)
+{
+    return
+#ifdef TARGET_WORDS_BIGENDIAN
+       1 ^
+#endif
+       arm_sctlr_b(env) ^
+       !!(env->uncached_cpsr & CPSR_E);
+}
+#endif
+
 static inline void cpu_get_tb_cpu_state(CPUARMState *env, target_ulong *pc,
                                         target_ulong *cs_base, int *flags)
 {
-- 
1.9.3