X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/d1ecb069dfe24481e4a83f44cb5217a2b06746d7..0b4c1975fb5e4eccf1012a35081f7e7799b81046:/osfmk/i386/bsd_i386.c

diff --git a/osfmk/i386/bsd_i386.c b/osfmk/i386/bsd_i386.c
index 66939fac9..4b933d763 100644
--- a/osfmk/i386/bsd_i386.c
+++ b/osfmk/i386/bsd_i386.c
@@ -498,6 +498,7 @@ kern_return_t
 thread_fast_set_cthread_self64(uint64_t self)
 {
 	pcb_t pcb = current_thread()->machine.pcb;
+	cpu_data_t              *cdp;
 
 	/* check for canonical address, set 0 otherwise  */
 	if (!IS_USERADDR64_CANONICAL(self))
@@ -505,11 +506,13 @@ thread_fast_set_cthread_self64(uint64_t self)
 
 	pcb->cthread_self = self;
 	mp_disable_preemption();
+	cdp = current_cpu_datap();
 #if defined(__x86_64__)
-	if (current_cpu_datap()->cpu_uber.cu_user_gs_base != self)
+	if ((cdp->cpu_uber.cu_user_gs_base != pcb->cthread_self) ||
+	    (pcb->cthread_self != rdmsr64(MSR_IA32_KERNEL_GS_BASE)))
 		wrmsr64(MSR_IA32_KERNEL_GS_BASE, self);
 #endif
-	current_cpu_datap()->cpu_uber.cu_user_gs_base = self;
+	cdp->cpu_uber.cu_user_gs_base = self;
 	mp_enable_preemption();
 	return (USER_CTHREAD);
 }