target/arm: Look up ARMCPRegInfo at runtime

Do not encode the pointer as a constant in the opcode stream.
This pointer is specific to the cpu that first generated the
translation, which runs into problems with both hot-pluggable
cpus and user-only threads, as cpus are removed. It's also a
potential correctness issue in the theoretical case of a
slightly-heterogenous system, because if CPU 0 generates a
TB and then CPU 1 executes it, CPU 1 will end up using CPU 0's
hash table, which might have a wrong set of registers in it.
(All our current systems are either completely homogenous,
M-profile, or have CPUs sufficiently different that they
wouldn't be sharing TBs anyway because the differences would
show up in the TB flags, so the correctness issue is only
theoretical, not practical.)

Perform the lookup in either helper_access_check_cp_reg,
or a new helper_lookup_cp_reg.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230106194451.1213153-3-richard.henderson@linaro.org
[PMM: added note in commit message about correctness issue]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

5 files changed, 95 insertions, 49 deletions

diff --git a/target/arm/helper.h b/target/arm/helper.h
index 92f36d9dbb..018b00ea75 100644
--- a/target/arm/helper.h
+++ b/target/arm/helper.h
@@ -79,11 +79,12 @@ DEF_HELPER_2(v8m_stackcheck, void, env, i32)
 
 DEF_HELPER_FLAGS_2(check_bxj_trap, TCG_CALL_NO_WG, void, env, i32)
 
-DEF_HELPER_4(access_check_cp_reg, void, env, ptr, i32, i32)
-DEF_HELPER_3(set_cp_reg, void, env, ptr, i32)
-DEF_HELPER_2(get_cp_reg, i32, env, ptr)
-DEF_HELPER_3(set_cp_reg64, void, env, ptr, i64)
-DEF_HELPER_2(get_cp_reg64, i64, env, ptr)
+DEF_HELPER_4(access_check_cp_reg, cptr, env, i32, i32, i32)
+DEF_HELPER_FLAGS_2(lookup_cp_reg, TCG_CALL_NO_RWG_SE, cptr, env, i32)
+DEF_HELPER_3(set_cp_reg, void, env, cptr, i32)
+DEF_HELPER_2(get_cp_reg, i32, env, cptr)
+DEF_HELPER_3(set_cp_reg64, void, env, cptr, i64)
+DEF_HELPER_2(get_cp_reg64, i64, env, cptr)
 
 DEF_HELPER_2(get_r13_banked, i32, env, i32)
 DEF_HELPER_3(set_r13_banked, void, env, i32, i32)
diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
index 70672bcd9f..31f89db899 100644
--- a/target/arm/op_helper.c
+++ b/target/arm/op_helper.c
@@ -624,14 +624,16 @@ uint32_t HELPER(mrs_banked)(CPUARMState *env, uint32_t tgtmode, uint32_t regno)
     }
 }
 
-void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
-                                 uint32_t isread)
+const void *HELPER(access_check_cp_reg)(CPUARMState *env, uint32_t key,
+                                        uint32_t syndrome, uint32_t isread)
 {
     ARMCPU *cpu = env_archcpu(env);
-    const ARMCPRegInfo *ri = rip;
+    const ARMCPRegInfo *ri = get_arm_cp_reginfo(cpu->cp_regs, key);
     CPAccessResult res = CP_ACCESS_OK;
     int target_el;
 
+    assert(ri != NULL);
+
     if (arm_feature(env, ARM_FEATURE_XSCALE) && ri->cp < 14
         && extract32(env->cp15.c15_cpar, ri->cp, 1) == 0) {
         res = CP_ACCESS_TRAP;
@@ -663,7 +665,7 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
         res = ri->accessfn(env, ri, isread);
     }
     if (likely(res == CP_ACCESS_OK)) {
-        return;
+        return ri;
     }
 
  fail:
@@ -705,7 +707,16 @@ void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
     raise_exception(env, EXCP_UDEF, syndrome, target_el);
 }
 
-void HELPER(set_cp_reg)(CPUARMState *env, void *rip, uint32_t value)
+const void *HELPER(lookup_cp_reg)(CPUARMState *env, uint32_t key)
+{
+    ARMCPU *cpu = env_archcpu(env);
+    const ARMCPRegInfo *ri = get_arm_cp_reginfo(cpu->cp_regs, key);
+
+    assert(ri != NULL);
+    return ri;
+}
+
+void HELPER(set_cp_reg)(CPUARMState *env, const void *rip, uint32_t value)
 {
     const ARMCPRegInfo *ri = rip;
 
@@ -718,7 +729,7 @@ void HELPER(set_cp_reg)(CPUARMState *env, void *rip, uint32_t value)
     }
 }
 
-uint32_t HELPER(get_cp_reg)(CPUARMState *env, void *rip)
+uint32_t HELPER(get_cp_reg)(CPUARMState *env, const void *rip)
 {
     const ARMCPRegInfo *ri = rip;
     uint32_t res;
@@ -734,7 +745,7 @@ uint32_t HELPER(get_cp_reg)(CPUARMState *env, void *rip)
     return res;
 }
 
-void HELPER(set_cp_reg64)(CPUARMState *env, void *rip, uint64_t value)
+void HELPER(set_cp_reg64)(CPUARMState *env, const void *rip, uint64_t value)
 {
     const ARMCPRegInfo *ri = rip;
 
@@ -747,7 +758,7 @@ void HELPER(set_cp_reg64)(CPUARMState *env, void *rip, uint64_t value)
     }
 }
 
-uint64_t HELPER(get_cp_reg64)(CPUARMState *env, void *rip)
+uint64_t HELPER(get_cp_reg64)(CPUARMState *env, const void *rip)
 {
     const ARMCPRegInfo *ri = rip;
     uint64_t res;
diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 19cf371c4c..52b1b8a1f0 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -1939,13 +1939,12 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
                        unsigned int op0, unsigned int op1, unsigned int op2,
                        unsigned int crn, unsigned int crm, unsigned int rt)
 {
-    const ARMCPRegInfo *ri;
+    uint32_t key = ENCODE_AA64_CP_REG(CP_REG_ARM64_SYSREG_CP,
+                                      crn, crm, op0, op1, op2);
+    const ARMCPRegInfo *ri = get_arm_cp_reginfo(s->cp_regs, key);
+    TCGv_ptr tcg_ri = NULL;
     TCGv_i64 tcg_rt;
 
-    ri = get_arm_cp_reginfo(s->cp_regs,
-                            ENCODE_AA64_CP_REG(CP_REG_ARM64_SYSREG_CP,
-                                               crn, crm, op0, op1, op2));
-
     if (!ri) {
         /* Unknown register; this might be a guest error or a QEMU
          * unimplemented feature.
@@ -1971,8 +1970,9 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
 
         syndrome = syn_aa64_sysregtrap(op0, op1, op2, crn, crm, rt, isread);
         gen_a64_update_pc(s, 0);
-        gen_helper_access_check_cp_reg(cpu_env,
-                                       tcg_constant_ptr(ri),
+        tcg_ri = tcg_temp_new_ptr();
+        gen_helper_access_check_cp_reg(tcg_ri, cpu_env,
+                                       tcg_constant_i32(key),
                                        tcg_constant_i32(syndrome),
                                        tcg_constant_i32(isread));
     } else if (ri->type & ARM_CP_RAISES_EXC) {
@@ -1988,7 +1988,7 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
     case 0:
         break;
     case ARM_CP_NOP:
-        return;
+        goto exit;
     case ARM_CP_NZCV:
         tcg_rt = cpu_reg(s, rt);
         if (isread) {
@@ -1996,14 +1996,14 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
         } else {
             gen_set_nzcv(tcg_rt);
         }
-        return;
+        goto exit;
     case ARM_CP_CURRENTEL:
         /* Reads as current EL value from pstate, which is
          * guaranteed to be constant by the tb flags.
          */
         tcg_rt = cpu_reg(s, rt);
         tcg_gen_movi_i64(tcg_rt, s->current_el << 2);
-        return;
+        goto exit;
     case ARM_CP_DC_ZVA:
         /* Writes clear the aligned block of memory which rt points into. */
         if (s->mte_active[0]) {
@@ -2020,7 +2020,7 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
             tcg_rt = clean_data_tbi(s, cpu_reg(s, rt));
         }
         gen_helper_dc_zva(cpu_env, tcg_rt);
-        return;
+        goto exit;
     case ARM_CP_DC_GVA:
         {
             TCGv_i64 clean_addr, tag;
@@ -2041,7 +2041,7 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
                 tcg_temp_free_i64(tag);
             }
         }
-        return;
+        goto exit;
     case ARM_CP_DC_GZVA:
         {
             TCGv_i64 clean_addr, tag;
@@ -2059,16 +2059,16 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
                 tcg_temp_free_i64(tag);
             }
         }
-        return;
+        goto exit;
     default:
         g_assert_not_reached();
     }
     if ((ri->type & ARM_CP_FPU) && !fp_access_check_only(s)) {
-        return;
+        goto exit;
     } else if ((ri->type & ARM_CP_SVE) && !sve_access_check(s)) {
-        return;
+        goto exit;
     } else if ((ri->type & ARM_CP_SME) && !sme_access_check(s)) {
-        return;
+        goto exit;
     }
 
     if ((tb_cflags(s->base.tb) & CF_USE_ICOUNT) && (ri->type & ARM_CP_IO)) {
@@ -2081,16 +2081,22 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
         if (ri->type & ARM_CP_CONST) {
             tcg_gen_movi_i64(tcg_rt, ri->resetvalue);
         } else if (ri->readfn) {
-            gen_helper_get_cp_reg64(tcg_rt, cpu_env, tcg_constant_ptr(ri));
+            if (!tcg_ri) {
+                tcg_ri = gen_lookup_cp_reg(key);
+            }
+            gen_helper_get_cp_reg64(tcg_rt, cpu_env, tcg_ri);
         } else {
             tcg_gen_ld_i64(tcg_rt, cpu_env, ri->fieldoffset);
         }
     } else {
         if (ri->type & ARM_CP_CONST) {
             /* If not forbidden by access permissions, treat as WI */
-            return;
+            goto exit;
         } else if (ri->writefn) {
-            gen_helper_set_cp_reg64(cpu_env, tcg_constant_ptr(ri), tcg_rt);
+            if (!tcg_ri) {
+                tcg_ri = gen_lookup_cp_reg(key);
+            }
+            gen_helper_set_cp_reg64(cpu_env, tcg_ri, tcg_rt);
         } else {
             tcg_gen_st_i64(tcg_rt, cpu_env, ri->fieldoffset);
         }
@@ -2113,6 +2119,11 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
          */
         s->base.is_jmp = DISAS_UPDATE_EXIT;
     }
+
+ exit:
+    if (tcg_ri) {
+        tcg_temp_free_ptr(tcg_ri);
+    }
 }
 
 /* System
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 40f9f07ea3..365e02fb0b 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -4714,12 +4714,11 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
                            int opc1, int crn, int crm, int opc2,
                            bool isread, int rt, int rt2)
 {
-    const ARMCPRegInfo *ri;
+    uint32_t key = ENCODE_CP_REG(cpnum, is64, s->ns, crn, crm, opc1, opc2);
+    const ARMCPRegInfo *ri = get_arm_cp_reginfo(s->cp_regs, key);
+    TCGv_ptr tcg_ri = NULL;
     bool need_exit_tb;
 
-    ri = get_arm_cp_reginfo(s->cp_regs,
-            ENCODE_CP_REG(cpnum, is64, s->ns, crn, crm, opc1, opc2));
-
     if (!ri) {
         /*
          * Unknown register; this might be a guest error or a QEMU
@@ -4800,8 +4799,9 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
 
         gen_set_condexec(s);
         gen_update_pc(s, 0);
-        gen_helper_access_check_cp_reg(cpu_env,
-                                       tcg_constant_ptr(ri),
+        tcg_ri = tcg_temp_new_ptr();
+        gen_helper_access_check_cp_reg(tcg_ri, cpu_env,
+                                       tcg_constant_i32(key),
                                        tcg_constant_i32(syndrome),
                                        tcg_constant_i32(isread));
     } else if (ri->type & ARM_CP_RAISES_EXC) {
@@ -4818,15 +4818,15 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
     case 0:
         break;
     case ARM_CP_NOP:
-        return;
+        goto exit;
     case ARM_CP_WFI:
         if (isread) {
             unallocated_encoding(s);
-            return;
+        } else {
+            gen_update_pc(s, curr_insn_len(s));
+            s->base.is_jmp = DISAS_WFI;
         }
-        gen_update_pc(s, curr_insn_len(s));
-        s->base.is_jmp = DISAS_WFI;
-        return;
+        goto exit;
     default:
         g_assert_not_reached();
     }
@@ -4843,9 +4843,11 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
             if (ri->type & ARM_CP_CONST) {
                 tmp64 = tcg_constant_i64(ri->resetvalue);
             } else if (ri->readfn) {
+                if (!tcg_ri) {
+                    tcg_ri = gen_lookup_cp_reg(key);
+                }
                 tmp64 = tcg_temp_new_i64();
-                gen_helper_get_cp_reg64(tmp64, cpu_env,
-                                        tcg_constant_ptr(ri));
+                gen_helper_get_cp_reg64(tmp64, cpu_env, tcg_ri);
             } else {
                 tmp64 = tcg_temp_new_i64();
                 tcg_gen_ld_i64(tmp64, cpu_env, ri->fieldoffset);
@@ -4862,8 +4864,11 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
             if (ri->type & ARM_CP_CONST) {
                 tmp = tcg_constant_i32(ri->resetvalue);
             } else if (ri->readfn) {
+                if (!tcg_ri) {
+                    tcg_ri = gen_lookup_cp_reg(key);
+                }
                 tmp = tcg_temp_new_i32();
-                gen_helper_get_cp_reg(tmp, cpu_env, tcg_constant_ptr(ri));
+                gen_helper_get_cp_reg(tmp, cpu_env, tcg_ri);
             } else {
                 tmp = load_cpu_offset(ri->fieldoffset);
             }
@@ -4881,7 +4886,7 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
         /* Write */
         if (ri->type & ARM_CP_CONST) {
             /* If not forbidden by access permissions, treat as WI */
-            return;
+            goto exit;
         }
 
         if (is64) {
@@ -4893,7 +4898,10 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
             tcg_temp_free_i32(tmplo);
             tcg_temp_free_i32(tmphi);
             if (ri->writefn) {
-                gen_helper_set_cp_reg64(cpu_env, tcg_constant_ptr(ri), tmp64);
+                if (!tcg_ri) {
+                    tcg_ri = gen_lookup_cp_reg(key);
+                }
+                gen_helper_set_cp_reg64(cpu_env, tcg_ri, tmp64);
             } else {
                 tcg_gen_st_i64(tmp64, cpu_env, ri->fieldoffset);
             }
@@ -4901,7 +4909,10 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
         } else {
             TCGv_i32 tmp = load_reg(s, rt);
             if (ri->writefn) {
-                gen_helper_set_cp_reg(cpu_env, tcg_constant_ptr(ri), tmp);
+                if (!tcg_ri) {
+                    tcg_ri = gen_lookup_cp_reg(key);
+                }
+                gen_helper_set_cp_reg(cpu_env, tcg_ri, tmp);
                 tcg_temp_free_i32(tmp);
             } else {
                 store_cpu_offset(tmp, ri->fieldoffset, 4);
@@ -4929,6 +4940,11 @@ static void do_coproc_insn(DisasContext *s, int cpnum, int is64,
     if (need_exit_tb) {
         gen_lookup_tb(s);
     }
+
+ exit:
+    if (tcg_ri) {
+        tcg_temp_free_ptr(tcg_ri);
+    }
 }
 
 /* Decode XScale DSP or iWMMXt insn (in the copro space, cp=0 or 1) */
diff --git a/target/arm/translate.h b/target/arm/translate.h
index 3cdc7dbc2f..f17f095cbe 100644
--- a/target/arm/translate.h
+++ b/target/arm/translate.h
@@ -610,6 +610,13 @@ static inline void set_disas_label(DisasContext *s, DisasLabel l)
     s->pc_save = l.pc_save;
 }
 
+static inline TCGv_ptr gen_lookup_cp_reg(uint32_t key)
+{
+    TCGv_ptr ret = tcg_temp_new_ptr();
+    gen_helper_lookup_cp_reg(ret, cpu_env, tcg_constant_i32(key));
+    return ret;
+}
+
 /*
  * Helpers for implementing sets of trans_* functions.
  * Defer the implementation of NAME to FUNC, with optional extra arguments.