alltraps was branching multiple times on whether the trap was from kernel

vs user, so expand INTRENTRY() and then carry the test it does through the
entire routine.  This will permit splitting of trap() later and makes it
easier to treat the from-user path with kid gloves.

ok mlarkin@, prodding deraadt@

1 files changed, 48 insertions, 17 deletions

diff --git a/sys/arch/amd64/amd64/vector.S b/sys/arch/amd64/amd64/vector.S
index cd3f63744fa..2a9ed1496ba 100644
--- a/sys/arch/amd64/amd64/vector.S
+++ b/sys/arch/amd64/amd64/vector.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: vector.S,v 1.64 2018/06/10 15:51:41 guenther Exp $	*/
+/*	$OpenBSD: vector.S,v 1.65 2018/06/13 23:39:00 guenther Exp $	*/
 /*	$NetBSD: vector.S,v 1.5 2004/06/28 09:13:11 fvdl Exp $	*/
 
 /*
@@ -187,13 +187,10 @@ INTRENTRY_LABEL(trap03):
 	sti
 	cld
 	SMAP_CLAC
-#ifdef DIAGNOSTIC
-	movl	CPUVAR(ILEVEL),%ebx
-#endif /* DIAGNOSTIC */
 	movq	%rsp, %rdi
 	call	_C_LABEL(db_prof_hook)
 	cmpl	$1, %eax
-	jne	recall_trap
+	jne	.Lreal_kern_trap
 
 	cli
 	movq	TF_RDI(%rsp),%rdi
@@ -355,29 +352,45 @@ Xexceptions:
 	.quad	_C_LABEL(Xtrap1e), _C_LABEL(Xtrap1f)
 
 /*
- * All traps go through here. Call the generic trap handler, and
- * check for ASTs afterwards.
+ * All traps go through here.  Figure out whether we're
+ * a) coming from usermode and need the Meltdown mitigation before
+ *    jumping to user trap handling followed by AST and
+ *    return-to-userspace handling, or
+ * b) coming from supervisor mode and can directly jump to kernel
+ *    trap handling before returning sans AST or other handling.
  */
 KUENTRY(alltraps)
-	INTRENTRY(alltraps)
+	testb	$SEL_RPL,24(%rsp)
+	je	alltraps_kern
+	swapgs
+	movq	%rax,CPUVAR(SCRATCH)
+	movq	CPUVAR(KERN_CR3),%rax
+	testq	%rax,%rax
+	jz	alltraps_user
+	movq	%rax,%cr3
+	jmp	alltraps_user
+END(alltraps)
+
+/*
+ * Traps from supervisor mode (kernel)
+ */
+NENTRY(alltraps_kern)
+	INTR_ENTRY_KERN
+	INTR_SAVE_MOST_GPRS_NO_ADJ
 	sti
 	cld
 	SMAP_CLAC
+.Lreal_kern_trap:
 #ifdef DIAGNOSTIC
 	movl	CPUVAR(ILEVEL),%ebx
 #endif /* DIAGNOSTIC */
-	.globl	recall_trap
-recall_trap:
 	movq	%rsp, %rdi
-	call	_C_LABEL(trap)
-2:	/* Check for ASTs on exit to user mode. */
-	cli
-	testb	$SEL_RPL,TF_CS(%rsp)
-	jnz	intr_user_exit
+	call	_C_LABEL(trap)		/* kerntrap */
+2:	cli
 #ifndef DIAGNOSTIC
-1:	INTRFASTEXIT
+	INTRFASTEXIT
 #else /* DIAGNOSTIC */
-1:	cmpl	CPUVAR(ILEVEL),%ebx
+	cmpl	CPUVAR(ILEVEL),%ebx
 	jne	3f
 	INTRFASTEXIT
 3:	sti
@@ -397,6 +410,24 @@ spl_lowered:
 	.asciz	"WARNING: SPL NOT LOWERED ON TRAP EXIT %x %x\n"
 	.text
 #endif /* DIAGNOSTIC */
+END(alltraps_kern)
+
+/*
+ * Traps from userspace
+ */
+NENTRY(alltraps_user)
+	INTR_ENTRY_USER
+	INTR_SAVE_MOST_GPRS_NO_ADJ
+	sti
+	cld
+	SMAP_CLAC
+	.globl	recall_trap
+recall_trap:
+	movq	%rsp, %rdi
+	call	_C_LABEL(trap)		/* usertrap */
+	cli
+	jmp	intr_user_exit
+END(alltraps_user)
 
 
 /*