x86/idt: Switch early trap init to IDT tables

Add the initialization table for the early trap setup and replace the early
trap init code.

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/20170828064958.929139008@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/idt.c

@@ -48,6 +48,28 @@ struct idt_data {
 #define TSKG(_vector, _gdt)				\
 	G(_vector, NULL, DEFAULT_STACK, GATE_TASK, DPL0, _gdt << 3)
 
+/*
+ * Early traps running on the DEFAULT_STACK because the other interrupt
+ * stacks work only after cpu_init().
+ */
+static const __initdata struct idt_data early_idts[] = {
+	INTG(X86_TRAP_DB,		debug),
+	SYSG(X86_TRAP_BP,		int3),
+#ifdef CONFIG_X86_32
+	INTG(X86_TRAP_PF,		page_fault),
+#endif
+};
+
+#ifdef CONFIG_X86_64
+/*
+ * Early traps running on the DEFAULT_STACK because the other interrupt
+ * stacks work only after cpu_init().
+ */
+static const __initdata struct idt_data early_pf_idts[] = {
+	INTG(X86_TRAP_PF,		page_fault),
+};
+#endif
+
 /* Must be page-aligned because the real IDT is used in a fixmap. */
 gate_desc idt_table[IDT_ENTRIES] __page_aligned_bss;
 
@@ -92,6 +114,37 @@ idt_setup_from_table(gate_desc *idt, const struct idt_data *t, int size)
 	}
 }
 
+/**
+ * idt_setup_early_traps - Initialize the idt table with early traps
+ *
+ * On X8664 these traps do not use interrupt stacks as they can't work
+ * before cpu_init() is invoked and sets up TSS. The IST variants are
+ * installed after that.
+ */
+void __init idt_setup_early_traps(void)
+{
+	idt_setup_from_table(idt_table, early_idts, ARRAY_SIZE(early_idts));
+	load_idt(&idt_descr);
+}
+
+#ifdef CONFIG_X86_64
+/**
+ * idt_setup_early_pf - Initialize the idt table with early pagefault handler
+ *
+ * On X8664 this does not use interrupt stacks as they can't work before
+ * cpu_init() is invoked and sets up TSS. The IST variant is installed
+ * after that.
+ *
+ * FIXME: Why is 32bit and 64bit installing the PF handler at different
+ * places in the early setup code?
+ */
+void __init idt_setup_early_pf(void)
+{
+	idt_setup_from_table(idt_table, early_pf_idts,
+			     ARRAY_SIZE(early_pf_idts));
+}
+#endif
+
 /**
  * idt_setup_early_handler - Initializes the idt table with early handlers
  */

arch/x86/kernel/setup.c

@@ -891,7 +891,7 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	olpc_ofw_detect();
 
-	early_trap_init();
+	idt_setup_early_traps();
 	early_cpu_init();
 	early_ioremap_init();
 
@@ -1162,7 +1162,7 @@ void __init setup_arch(char **cmdline_p)
 
 	init_mem_mapping();
 
-	early_trap_pf_init();
+	idt_setup_early_pf();
 
 	/*
 	 * Update mmu_cr4_features (and, indirectly, trampoline_cr4_features)

arch/x86/kernel/traps.c

@@ -923,33 +923,6 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 }
 #endif
 
-/* Set of traps needed for early debugging. */
-void __init early_trap_init(void)
-{
-	/*
-	 * Don't use IST to set DEBUG_STACK as it doesn't work until TSS
-	 * is ready in cpu_init() <-- trap_init(). Before trap_init(),
-	 * CPU runs at ring 0 so it is impossible to hit an invalid
-	 * stack.  Using the original stack works well enough at this
-	 * early stage. DEBUG_STACK will be equipped after cpu_init() in
-	 * trap_init().
-	 */
-	set_intr_gate(X86_TRAP_DB, debug);
-	/* int3 can be called from all */
-	set_system_intr_gate(X86_TRAP_BP, &int3);
-#ifdef CONFIG_X86_32
-	set_intr_gate(X86_TRAP_PF, page_fault);
-#endif
-	load_idt(&idt_descr);
-}
-
-void __init early_trap_pf_init(void)
-{
-#ifdef CONFIG_X86_64
-	set_intr_gate(X86_TRAP_PF, page_fault);
-#endif
-}
-
 void __init trap_init(void)
 {
 	int i;