[TLS] Kept x86 TCB self consistent with pthread_self() (#4112)

src/emu/x64tls.c

@@ -2,6 +2,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <errno.h>
+#include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -51,11 +52,11 @@ uint32_t my_set_thread_area_32(x64emu_t* emu, thread_area_32_t* td)
     int isempty = 0;
     // first, check if the "user_desc", here td, is "empty"
     if(td->read_exec_only==1 && td->seg_not_present==1)
-        if( !td->base_addr 
+        if( !td->base_addr
          && !td->limit
-         && !td->seg_32bit 
-         && !td->contents 
-         && !td->limit_in_pages 
+         && !td->seg_32bit
+         && !td->contents
+         && !td->limit_in_pages
          && !td->useable)
             isempty = 1;
     int idx = td->entry_number;
@@ -297,7 +298,9 @@ static tlsdatasize_t* setupTLSData(box64context_t* context)
         memcpy((void*)((uintptr_t)ptr+0x28), context->canary, sizeof(void*));      // put canary in place
         uintptr_t tlsptr = (uintptr_t)ptr;
         memcpy((void*)((uintptr_t)ptr+0x0), &tlsptr, sizeof(void*));
-        memcpy((void*)((uintptr_t)ptr+0x10), &tlsptr, sizeof(void*));  // set tcb and self same address
+        // Wrapped pthread symbols expose native pthread_t handles, so keep the fast self slot consistent.
+        uintptr_t pthread_self_value = (uintptr_t)pthread_self();
+        memcpy((void*)((uintptr_t)ptr+0x10), &pthread_self_value, sizeof(void*));
         uintptr_t dtp = (uintptr_t)ptr+POS_TLS;
         memcpy((void*)(tlsptr+sizeof(void*)), &dtp, sizeof(void*));
         if(dtssize) {

tests/test11.c

@@ -1,5 +1,6 @@
 #define _MULTI_THREADED
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <pthread.h>
@@ -40,11 +41,23 @@ typedef struct {
 	int   data2;
 } threadparm_t; 
 
+static uintptr_t fast_pthread_self(void)
+{
+	uintptr_t self;
+	__asm__ volatile("movq %%fs:0x10, %0" : "=r"(self));
+	return self;
+}
+
 void *thread_run(void *parm)
 {
 	int               rc;
 	threadparm_t     *gData;
 
+	if (fast_pthread_self() != (uintptr_t)pthread_self()) {
+		fprintf(stderr, "TLS self pointer does not match pthread_self()\n");
+		exit(1);
+	}
+
 	pthread_mutex_lock(mutex_ptr);
 	if (pthread_self()==thread[0]) {
 		printf("Thread 1: Entered (%d/%d)\n", TLS_data1, TLS_data2);