target/hppa: Allow, but diagnose, LDCW aligned only mod 4

The PA-RISC 1.1 specification says that LDCW must be aligned mod 16
or the operation is undefined.  However, real hardware only generates
an unaligned access trap for unaligned mod 4.

Match real hardware, but diagnose with GUEST_ERROR a violation of
the specification.

At the same time fix a bug in the initialization of mop, where the
size was specified twice, and another to free the zero temporary.

Tested-by: Helge Deller <deller@gmx.de>
Reported-by: Helge Deller <deller@gmx.de>
Suggested-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/hppa/helper.h

@@ -17,6 +17,8 @@ DEF_HELPER_FLAGS_3(stby_b_parallel, TCG_CALL_NO_WG, void, env, tl, tr)
 DEF_HELPER_FLAGS_3(stby_e, TCG_CALL_NO_WG, void, env, tl, tr)
 DEF_HELPER_FLAGS_3(stby_e_parallel, TCG_CALL_NO_WG, void, env, tl, tr)
 
+DEF_HELPER_FLAGS_1(ldc_check, TCG_CALL_NO_RWG, void, tl)
+
 DEF_HELPER_FLAGS_4(probe, TCG_CALL_NO_WG, tr, env, tl, i32, i32)
 
 DEF_HELPER_FLAGS_1(loaded_fr0, TCG_CALL_NO_RWG, void, env)

target/hppa/op_helper.c

@@ -153,6 +153,15 @@ void HELPER(stby_e_parallel)(CPUHPPAState *env, target_ulong addr,
     do_stby_e(env, addr, val, true, GETPC());
 }
 
+void HELPER(ldc_check)(target_ulong addr)
+{
+    if (unlikely(addr & 0xf)) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "Undefined ldc to unaligned address mod 16: "
+                      TARGET_FMT_lx "\n", addr);
+    }
+}
+
 target_ureg HELPER(probe)(CPUHPPAState *env, target_ulong addr,
                           uint32_t level, uint32_t want)
 {

target/hppa/translate.c

@@ -2942,7 +2942,7 @@ static bool trans_st(DisasContext *ctx, arg_ldst *a)
 
 static bool trans_ldc(DisasContext *ctx, arg_ldst *a)
 {
-    MemOp mop = MO_TEUL | MO_ALIGN_16 | a->size;
+    MemOp mop = MO_TE | MO_ALIGN | a->size;
     TCGv_reg zero, dest, ofs;
     TCGv_tl addr;
 
@@ -2958,8 +2958,21 @@ static bool trans_ldc(DisasContext *ctx, arg_ldst *a)
 
     form_gva(ctx, &addr, &ofs, a->b, a->x, a->scale ? a->size : 0,
              a->disp, a->sp, a->m, ctx->mmu_idx == MMU_PHYS_IDX);
+
+    /*
+     * For hppa1.1, LDCW is undefined unless aligned mod 16.
+     * However actual hardware succeeds with aligned mod 4.
+     * Detect this case and log a GUEST_ERROR.
+     *
+     * TODO: HPPA64 relaxes the over-alignment requirement
+     * with the ,co completer.
+     */
+    gen_helper_ldc_check(addr);
+
     zero = tcg_const_reg(0);
     tcg_gen_atomic_xchg_reg(dest, addr, zero, ctx->mmu_idx, mop);
+    tcg_temp_free(zero);
+
     if (a->m) {
         save_gpr(ctx, a->b, ofs);
     }