[Qemu-devel] [PULL 20/30] target-mips: Correct 32-bit address space wrapping

[Leon Alrae]

From: "Maciej W. Rozycki" <address@hidden>

Make sure the address space is unconditionally wrapped on 32-bit
processors, that is ones that do not implement at least the MIPS III
ISA.

Also make MIPS16 SAVE and RESTORE instructions use address calculation
rather than plain arithmetic operations for stack pointer manipulation
so that their semantics for stack accesses follows the architecture
specification.  That in particular applies to user software run on
64-bit processors with the CP0.Status.UX bit clear where the address
space is wrapped to 32 bits.

Signed-off-by: Maciej W. Rozycki <address@hidden>
Reviewed-by: Leon Alrae <address@hidden>
Signed-off-by: Leon Alrae <address@hidden>
---
 target-mips/cpu.h       |  8 +++++---
 target-mips/translate.c | 19 ++++++++++++++-----
 2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index e59cb4c..f8cf143 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -838,10 +838,12 @@ static inline void compute_hflags(CPUMIPSState *env)
         env->hflags |= MIPS_HFLAG_64;
     }
 
-    if (((env->hflags & MIPS_HFLAG_KSU) == MIPS_HFLAG_UM) &&
-        !(env->CP0_Status & (1 << CP0St_UX))) {
+    if (!(env->insn_flags & ISA_MIPS3)) {
         env->hflags |= MIPS_HFLAG_AWRAP;
-    } else if (env->insn_flags & ISA_MIPS32R6) {
+    } else if (((env->hflags & MIPS_HFLAG_KSU) == MIPS_HFLAG_UM) &&
+               !(env->CP0_Status & (1 << CP0St_UX))) {
+        env->hflags |= MIPS_HFLAG_AWRAP;
+    } else if (env->insn_flags & ISA_MIPS64R6) {
         /* Address wrapping for Supervisor and Kernel is specified in R6 */
         if ((((env->hflags & MIPS_HFLAG_KSU) == MIPS_HFLAG_SM) &&
              !(env->CP0_Status & (1 << CP0St_SX))) ||
diff --git a/target-mips/translate.c b/target-mips/translate.c
index 2173ea5..9d90da0 100644
--- a/target-mips/translate.c
+++ b/target-mips/translate.c
@@ -10728,6 +10728,7 @@ static void gen_mips16_save (DisasContext *ctx,
 {
     TCGv t0 = tcg_temp_new();
     TCGv t1 = tcg_temp_new();
+    TCGv t2 = tcg_temp_new();
     int args, astatic;
 
     switch (aregs) {
@@ -10786,7 +10787,8 @@ static void gen_mips16_save (DisasContext *ctx,
     gen_load_gpr(t0, 29);
 
 #define DECR_AND_STORE(reg) do {                                 \
-        tcg_gen_subi_tl(t0, t0, 4);                              \
+        tcg_gen_movi_tl(t2, -4);                                 \
+        gen_op_addr_add(ctx, t0, t0, t2);                        \
         gen_load_gpr(t1, reg);                                   \
         tcg_gen_qemu_st_tl(t1, t0, ctx->mem_idx, MO_TEUL); \
     } while (0)
@@ -10870,9 +10872,11 @@ static void gen_mips16_save (DisasContext *ctx,
     }
 #undef DECR_AND_STORE
 
-    tcg_gen_subi_tl(cpu_gpr[29], cpu_gpr[29], framesize);
+    tcg_gen_movi_tl(t2, -framesize);
+    gen_op_addr_add(ctx, cpu_gpr[29], cpu_gpr[29], t2);
     tcg_temp_free(t0);
     tcg_temp_free(t1);
+    tcg_temp_free(t2);
 }
 
 static void gen_mips16_restore (DisasContext *ctx,
@@ -10883,11 +10887,14 @@ static void gen_mips16_restore (DisasContext *ctx,
     int astatic;
     TCGv t0 = tcg_temp_new();
     TCGv t1 = tcg_temp_new();
+    TCGv t2 = tcg_temp_new();
 
-    tcg_gen_addi_tl(t0, cpu_gpr[29], framesize);
+    tcg_gen_movi_tl(t2, framesize);
+    gen_op_addr_add(ctx, t0, cpu_gpr[29], t2);
 
 #define DECR_AND_LOAD(reg) do {                            \
-        tcg_gen_subi_tl(t0, t0, 4);                        \
+        tcg_gen_movi_tl(t2, -4);                           \
+        gen_op_addr_add(ctx, t0, t0, t2);                  \
         tcg_gen_qemu_ld_tl(t1, t0, ctx->mem_idx, MO_TESL); \
         gen_store_gpr(t1, reg);                            \
     } while (0)
@@ -10971,9 +10978,11 @@ static void gen_mips16_restore (DisasContext *ctx,
     }
 #undef DECR_AND_LOAD
 
-    tcg_gen_addi_tl(cpu_gpr[29], cpu_gpr[29], framesize);
+    tcg_gen_movi_tl(t2, framesize);
+    gen_op_addr_add(ctx, cpu_gpr[29], cpu_gpr[29], t2);
     tcg_temp_free(t0);
     tcg_temp_free(t1);
+    tcg_temp_free(t2);
 }
 
 static void gen_addiupc (DisasContext *ctx, int rx, int imm,
-- 
2.1.0