From: Richard Henderson <richard.henderson@linaro.org>

If the host does not support swapped-endian loads and stores,
then we emulate those within the tcg expanders with explicit
bswap operations.

However, we were passing values to the plugin interface in
the middle of those bswap operations, which meant that we
would pass values of the wrong endianness to plugins when
running on hosts without swapped-endian loads and stores.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3351
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Tested-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 tcg/tcg-op-ldst.c | 52 ++++++++++++++++++++++++-----------------------
 1 file changed, 27 insertions(+), 25 deletions(-)

diff --git a/tcg/tcg-op-ldst.c b/tcg/tcg-op-ldst.c
index 354d9968f92..22211ccb452 100644
--- a/tcg/tcg-op-ldst.c
+++ b/tcg/tcg-op-ldst.c
@@ -262,9 +262,6 @@ static void tcg_gen_qemu_ld_i32_int(TCGv_i32 val, TCGTemp *addr,
     addr_new = tci_extend_addr(addr);
     copy_addr = plugin_maybe_preserve_addr(addr);
     gen_ldst1(INDEX_op_qemu_ld, TCG_TYPE_I32, tcgv_i32_temp(val), addr_new, oi);
-    plugin_gen_mem_callbacks_i32(val, copy_addr, addr, orig_oi,
-                                 QEMU_PLUGIN_MEM_R);
-    maybe_free_addr(addr, addr_new);
 
     if ((orig_memop ^ memop) & MO_BSWAP) {
         switch (orig_memop & MO_SIZE) {
@@ -280,6 +277,10 @@ static void tcg_gen_qemu_ld_i32_int(TCGv_i32 val, TCGTemp *addr,
             g_assert_not_reached();
         }
     }
+
+    plugin_gen_mem_callbacks_i32(val, copy_addr, addr, orig_oi,
+                                 QEMU_PLUGIN_MEM_R);
+    maybe_free_addr(addr, addr_new);
 }
 
 void tcg_gen_qemu_ld_i32_chk(TCGv_i32 val, TCGTemp *addr, TCGArg idx,
@@ -290,10 +291,10 @@ void tcg_gen_qemu_ld_i32_chk(TCGv_i32 val, TCGTemp *addr, TCGArg idx,
     tcg_gen_qemu_ld_i32_int(val, addr, idx, memop);
 }
 
-static void tcg_gen_qemu_st_i32_int(TCGv_i32 val, TCGTemp *addr,
+static void tcg_gen_qemu_st_i32_int(TCGv_i32 orig_val, TCGTemp *addr,
                                     TCGArg idx, MemOp memop)
 {
-    TCGv_i32 swap = NULL;
+    TCGv_i32 val = orig_val;
     MemOpIdx orig_oi, oi;
     TCGTemp *addr_new;
 
@@ -302,29 +303,29 @@ static void tcg_gen_qemu_st_i32_int(TCGv_i32 val, TCGTemp *addr,
     orig_oi = oi = make_memop_idx(memop, idx);
 
     if ((memop & MO_BSWAP) && !tcg_target_has_memory_bswap(memop)) {
-        swap = tcg_temp_ebb_new_i32();
+        val = tcg_temp_ebb_new_i32();
         switch (memop & MO_SIZE) {
         case MO_16:
-            tcg_gen_bswap16_i32(swap, val, 0);
+            tcg_gen_bswap16_i32(val, orig_val, 0);
             break;
         case MO_32:
-            tcg_gen_bswap32_i32(swap, val);
+            tcg_gen_bswap32_i32(val, orig_val);
             break;
         default:
             g_assert_not_reached();
         }
-        val = swap;
         memop &= ~MO_BSWAP;
         oi = make_memop_idx(memop, idx);
     }
 
     addr_new = tci_extend_addr(addr);
     gen_ldst1(INDEX_op_qemu_st, TCG_TYPE_I32, tcgv_i32_temp(val), addr_new, oi);
-    plugin_gen_mem_callbacks_i32(val, NULL, addr, orig_oi, QEMU_PLUGIN_MEM_W);
+    plugin_gen_mem_callbacks_i32(orig_val, NULL, addr, orig_oi,
+                                 QEMU_PLUGIN_MEM_W);
     maybe_free_addr(addr, addr_new);
 
-    if (swap) {
-        tcg_temp_free_i32(swap);
+    if (val != orig_val) {
+        tcg_temp_free_i32(val);
     }
 }
 
@@ -360,9 +361,6 @@ static void tcg_gen_qemu_ld_i64_int(TCGv_i64 val, TCGTemp *addr,
     addr_new = tci_extend_addr(addr);
     copy_addr = plugin_maybe_preserve_addr(addr);
     gen_ld_i64(val, addr_new, oi);
-    plugin_gen_mem_callbacks_i64(val, copy_addr, addr, orig_oi,
-                                 QEMU_PLUGIN_MEM_R);
-    maybe_free_addr(addr, addr_new);
 
     if ((orig_memop ^ memop) & MO_BSWAP) {
         int flags = (orig_memop & MO_SIGN
@@ -382,6 +380,10 @@ static void tcg_gen_qemu_ld_i64_int(TCGv_i64 val, TCGTemp *addr,
             g_assert_not_reached();
         }
     }
+
+    plugin_gen_mem_callbacks_i64(val, copy_addr, addr, orig_oi,
+                                 QEMU_PLUGIN_MEM_R);
+    maybe_free_addr(addr, addr_new);
 }
 
 void tcg_gen_qemu_ld_i64_chk(TCGv_i64 val, TCGTemp *addr, TCGArg idx,
@@ -392,10 +394,10 @@ void tcg_gen_qemu_ld_i64_chk(TCGv_i64 val, TCGTemp *addr, TCGArg idx,
     tcg_gen_qemu_ld_i64_int(val, addr, idx, memop);
 }
 
-static void tcg_gen_qemu_st_i64_int(TCGv_i64 val, TCGTemp *addr,
+static void tcg_gen_qemu_st_i64_int(TCGv_i64 orig_val, TCGTemp *addr,
                                     TCGArg idx, MemOp memop)
 {
-    TCGv_i64 swap = NULL;
+    TCGv_i64 val = orig_val;
     MemOpIdx orig_oi, oi;
     TCGTemp *addr_new;
 
@@ -404,32 +406,32 @@ static void tcg_gen_qemu_st_i64_int(TCGv_i64 val, TCGTemp *addr,
     orig_oi = oi = make_memop_idx(memop, idx);
 
     if ((memop & MO_BSWAP) && !tcg_target_has_memory_bswap(memop)) {
-        swap = tcg_temp_ebb_new_i64();
+        val = tcg_temp_ebb_new_i64();
         switch (memop & MO_SIZE) {
         case MO_16:
-            tcg_gen_bswap16_i64(swap, val, 0);
+            tcg_gen_bswap16_i64(val, orig_val, 0);
             break;
         case MO_32:
-            tcg_gen_bswap32_i64(swap, val, 0);
+            tcg_gen_bswap32_i64(val, orig_val, 0);
             break;
         case MO_64:
-            tcg_gen_bswap64_i64(swap, val);
+            tcg_gen_bswap64_i64(val, orig_val);
             break;
         default:
             g_assert_not_reached();
         }
-        val = swap;
         memop &= ~MO_BSWAP;
         oi = make_memop_idx(memop, idx);
     }
 
     addr_new = tci_extend_addr(addr);
     gen_st_i64(val, addr_new, oi);
-    plugin_gen_mem_callbacks_i64(val, NULL, addr, orig_oi, QEMU_PLUGIN_MEM_W);
+    plugin_gen_mem_callbacks_i64(orig_val, NULL, addr, orig_oi,
+                                 QEMU_PLUGIN_MEM_W);
     maybe_free_addr(addr, addr_new);
 
-    if (swap) {
-        tcg_temp_free_i64(swap);
+    if (val != orig_val) {
+        tcg_temp_free_i64(val);
     }
 }
 
-- 
2.47.3