D57611.diff
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	diff --git a/sys/amd64/amd64/exception.S b/sys/amd64/amd64/exception.S
	--- a/sys/amd64/amd64/exception.S
	+++ b/sys/amd64/amd64/exception.S
	@@ -1161,12 +1161,15 @@
	.globl ld_fs
	ld_fs:
	movw %ax,%fs
	+ testl $PCB_32BIT,PCB_FLAGS(%r8)
	+ jnz after_ld_fsbase
	movl $MSR_FSBASE,%ecx
	movl PCB_FSBASE(%r8),%eax
	movl PCB_FSBASE+4(%r8),%edx
	.globl ld_fsbase
	ld_fsbase:
	wrmsr
	+after_ld_fsbase:
	/* Restore %gs and gsbase */
	movw TF_GS(%rsp),%si
	pushfq
	@@ -1179,6 +1182,8 @@
	.globl ld_gs
	ld_gs:
	movw %si,%gs
	+ testl $PCB_32BIT,PCB_FLAGS(%r8)
	+ jnz ld_gsbase_32
	/* Restore kernel %gs base */
	movl %r12d,%eax
	movl %r13d,%edx
	@@ -1194,6 +1199,8 @@
	.globl ld_gsbase
	ld_gsbase:
	wrmsr /* May trap if non-canonical, but only for TLS. */
	+
	+after_ld_gsbase:
	.globl ld_es
	ld_es:
	movw TF_ES(%rsp),%es
	@@ -1241,6 +1248,30 @@
	doreti_iret:
	iretq

	+ /*
	+ * 32bit gsbase path.
	+ * The KGSBASE is not loaded from the pcb_gsbase, instead we move
	+ * the GSBASE value into KGSBASE right after loading user %gs, then
	+ * restore kernel gsbase.
	+ */
	+ld_gsbase_32:
	+ /* Read the user gsbase into %r14d:%r15d. */
	+ movl $MSR_GSBASE,%ecx
	+ rdmsr
	+ movl %eax,%r14d
	+ movl %edx,%r15d
	+ /* Restore kernel %gs base */
	+ movl %r12d,%eax
	+ movl %r13d,%edx
	+ wrmsr
	+ popfq
	+ /* Load the user gsbase into KGSBASE. */
	+ movl $MSR_KGSBASE,%ecx
	+ movl %r14d,%eax
	+ movl %r15d,%edx
	+ wrmsr
	+ jmp after_ld_gsbase
	+
	set_segs:
	movw $KUDSEL,%ax
	movw %ax,TF_DS(%rsp)