[PATCH] linux-user: fix bug about incorrect base addresss of gdt on i386 and x86_64

[fanwj]

On linux user mode, CPUX86State::gdt::base from Different CPUX86State Objects 
have same value, It is incorrect! Every CPUX86State::gdt::base Must points to 
independent memory space. 

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1405
Signed-off-by: fanwenjie <fanwj@mail.ustc.edu.cn>
---
 linux-user/i386/cpu_loop.c | 9 +++++++++
 linux-user/main.c          | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/linux-user/i386/cpu_loop.c b/linux-user/i386/cpu_loop.c
index 865413c..48511cd 100644
--- a/linux-user/i386/cpu_loop.c
+++ b/linux-user/i386/cpu_loop.c
@@ -314,8 +314,17 @@ void cpu_loop(CPUX86State *env)
     }
 }
 
+static void target_cpu_free(void *obj)
+{
+    CPUArchState* env = ((CPUState*)obj)->env_ptr;
+    target_munmap(env->gdt.base, sizeof(uint64_t) * TARGET_GDT_ENTRIES);
+    g_free(obj);
+}
+
 void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
 {
+    CPUState* cpu = env_cpu(env);
+    OBJECT(cpu)->free = target_cpu_free;
     env->cr[0] = CR0_PG_MASK | CR0_WP_MASK | CR0_PE_MASK;
     env->hflags |= HF_PE_MASK | HF_CPL_MASK;
     if (env->features[FEAT_1_EDX] & CPUID_SSE) {
diff --git a/linux-user/main.c b/linux-user/main.c
index a17fed0..3acd9b4 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -234,6 +234,13 @@ CPUArchState *cpu_copy(CPUArchState *env)
 
     new_cpu->tcg_cflags = cpu->tcg_cflags;
     memcpy(new_env, env, sizeof(CPUArchState));
+#if defined(TARGET_I386) || defined(TARGET_X86_64)
+    new_env->gdt.base = target_mmap(0, sizeof(uint64_t) * TARGET_GDT_ENTRIES,
+                                    PROT_READ|PROT_WRITE,
+                                    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+    memcpy((void*)g2h_untagged(new_env->gdt.base), 
(void*)g2h_untagged(env->gdt.base), sizeof(uint64_t) * TARGET_GDT_ENTRIES);
+    OBJECT(new_cpu)->free = OBJECT(cpu)->free;
+#endif
 
     /* Clone all break/watchpoints.
        Note: Once we support ptrace with hw-debug register access, make sure
-- 
2.34.1