From 0a30908b9149b2b332ccf817261125a634765566 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 28 Aug 2017 08:47:51 +0200
Subject: [PATCH] x86/idt: Move debug stack init to table based

Add the debug_idt init table and make use of it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064959.006502252@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/desc.h |  2 ++
 arch/x86/kernel/idt.c       | 23 +++++++++++++++++++++++
 arch/x86/kernel/traps.c     |  6 +-----
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 5a3cdeb7cb03..930acd5d85f6 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -509,8 +509,10 @@ extern void idt_setup_early_traps(void);
 
 #ifdef CONFIG_X86_64
 extern void idt_setup_early_pf(void);
+extern void idt_setup_debugidt_traps(void);
 #else
 static inline void idt_setup_early_pf(void) { }
+static inline void idt_setup_debugidt_traps(void) { }
 #endif
 
 extern void idt_invalidate(void *addr);
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 64e221172a17..f5281b8f1131 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -68,6 +68,15 @@ static const __initdata struct idt_data early_idts[] = {
 static const __initdata struct idt_data early_pf_idts[] = {
 	INTG(X86_TRAP_PF,		page_fault),
 };
+
+/*
+ * Override for the debug_idt. Same as the default, but with interrupt
+ * stack set to DEFAULT_STACK (0). Required for NMI trap handling.
+ */
+static const __initdata struct idt_data dbg_idts[] = {
+	INTG(X86_TRAP_DB,	debug),
+	INTG(X86_TRAP_BP,	int3),
+};
 #endif
 
 /* Must be page-aligned because the real IDT is used in a fixmap. */
@@ -82,6 +91,10 @@ struct desc_ptr idt_descr __ro_after_init = {
 /* No need to be aligned, but done to keep all IDTs defined the same way. */
 gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
 
+/*
+ * Override for the debug_idt. Same as the default, but with interrupt
+ * stack set to DEFAULT_STACK (0). Required for NMI trap handling.
+ */
 const struct desc_ptr debug_idt_descr = {
 	.size		= IDT_ENTRIES * 16 - 1,
 	.address	= (unsigned long) debug_idt_table,
@@ -143,6 +156,16 @@ void __init idt_setup_early_pf(void)
 	idt_setup_from_table(idt_table, early_pf_idts,
 			     ARRAY_SIZE(early_pf_idts));
 }
+
+/**
+ * idt_setup_debugidt_traps - Initialize the debug idt table with debug traps
+ */
+void __init idt_setup_debugidt_traps(void)
+{
+	memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);
+
+	idt_setup_from_table(debug_idt_table, dbg_idts, ARRAY_SIZE(dbg_idts));
+}
 #endif
 
 /**
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 835c7e8a0eb1..1492bf5eb549 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -990,9 +990,5 @@ void __init trap_init(void)
 
 	x86_init.irqs.trap_init();
 
-#ifdef CONFIG_X86_64
-	memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);
-	set_nmi_gate(X86_TRAP_DB, &debug);
-	set_nmi_gate(X86_TRAP_BP, &int3);
-#endif
+	idt_setup_debugidt_traps();
 }
-- 
2.20.1