target/arm: Merge allocation of the cpreg and its name

Simplify freeing cp_regs hash table entries by using a single
allocation for the entire value.

This fixes a theoretical bug if we were to ever free the entire
hash table, because we've been installing string literal constants
into the cpreg structure in define_arm_vh_e2h_redirects_aliases.
However, at present we only free entries created for AArch32
wildcard cpregs which get overwritten by more specific cpregs,
so this bug is never exposed.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20220501055028.646596-13-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu.c

@@ -1071,27 +1071,13 @@ uint64_t arm_cpu_mp_affinity(int idx, uint8_t clustersz)
     return (Aff1 << ARM_AFF1_SHIFT) | Aff0;
 }
 
-static void cpreg_hashtable_data_destroy(gpointer data)
-{
-    /*
-     * Destroy function for cpu->cp_regs hashtable data entries.
-     * We must free the name string because it was g_strdup()ed in
-     * add_cpreg_to_hashtable(). It's OK to cast away the 'const'
-     * from r->name because we know we definitely allocated it.
-     */
-    ARMCPRegInfo *r = data;
-
-    g_free((void *)r->name);
-    g_free(r);
-}
-
 static void arm_cpu_initfn(Object *obj)
 {
     ARMCPU *cpu = ARM_CPU(obj);
 
     cpu_set_cpustate_pointers(cpu);
     cpu->cp_regs = g_hash_table_new_full(g_direct_hash, g_direct_equal,
-                                         NULL, cpreg_hashtable_data_destroy);
+                                         NULL, g_free);
 
     QLIST_INIT(&cpu->pre_el_change_hooks);
     QLIST_INIT(&cpu->el_change_hooks);

target/arm/helper.c

@@ -8506,11 +8506,17 @@ static void add_cpreg_to_hashtable(ARMCPU *cpu, const ARMCPRegInfo *r,
      * add a single reginfo struct to the hash table.
      */
     uint32_t key;
-    ARMCPRegInfo *r2 = g_memdup(r, sizeof(ARMCPRegInfo));
+    ARMCPRegInfo *r2;
     int is64 = (r->type & ARM_CP_64BIT) ? 1 : 0;
     int ns = (secstate & ARM_CP_SECSTATE_NS) ? 1 : 0;
+    size_t name_len;
+
+    /* Combine cpreg and name into one allocation. */
+    name_len = strlen(name) + 1;
+    r2 = g_malloc(sizeof(*r2) + name_len);
+    *r2 = *r;
+    r2->name = memcpy(r2 + 1, name, name_len);
 
-    r2->name = g_strdup(name);
     /* Reset the secure state to the specific incoming state.  This is
      * necessary as the register may have been defined with both states.
      */