amd64: Add MD bits for KASAN

- Initialize KASAN before executing SYSINITs.
- Add a GENERIC-KASAN kernel config, akin to GENERIC-KCSAN.
- Increase the kernel stack size if KASAN is enabled.  Some of the
  ASAN instrumentation increases stack usage and it's enough to
  trigger stack overflows in ZFS.
- Mark the trapframe as valid in interrupt handlers if it is
  assigned to td_intr_frame.  Otherwise, an interrupt in a function
  which creates a poisoned alloca region can trigger false positives.

MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D29455

sys/amd64/amd64/machdep.c

@@ -58,6 +58,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/proc.h>
 #include <sys/systm.h>
+#include <sys/asan.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/bus.h>
@@ -1916,6 +1917,8 @@ hammer_time(u_int64_t modulep, u_int64_t physfree)
 #endif
 	thread0.td_critnest = 0;
 
+	kasan_init();
+
 	TSEXIT();
 
 	/* Location of kernel stack for locore */

sys/amd64/conf/GENERIC-KASAN

@@ -0,0 +1,7 @@
+# $FreeBSD$
+
+include GENERIC
+
+ident   GENERIC-KASAN
+
+options 	KASAN

sys/amd64/include/param.h

@@ -134,8 +134,12 @@
 #define	IOPERM_BITMAP_SIZE	(IOPAGES * PAGE_SIZE + 1)
 
 #ifndef	KSTACK_PAGES
+#ifdef KASAN
+#define	KSTACK_PAGES	6
+#else
 #define	KSTACK_PAGES	4	/* pages of kstack (with pcb) */
 #endif
+#endif
 #define	KSTACK_GUARD_PAGES 1	/* pages of kstack guard; 0 disables */
 
 /*

sys/x86/isa/atpic.c

@@ -37,6 +37,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/asan.h>
 #include <sys/bus.h>
 #include <sys/interrupt.h>
 #include <sys/kernel.h>
@@ -522,6 +523,9 @@ atpic_handle_intr(u_int vector, struct trapframe *frame)
 {
 	struct intsrc *isrc;
 
+	/* The frame may have been written into a poisoned region. */
+	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
+
 	KASSERT(vector < NUM_ISA_IRQS, ("unknown int %u\n", vector));
 	isrc = &atintrs[vector].at_intsrc;
 

sys/x86/x86/local_apic.c

@@ -43,6 +43,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/asan.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
@@ -1299,6 +1300,9 @@ lapic_handle_intr(int vector, struct trapframe *frame)
 {
 	struct intsrc *isrc;
 
+	/* The frame may have been written into a poisoned region. */
+	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
+
 	isrc = intr_lookup_source(apic_idt_to_irq(PCPU_GET(apic_id),
 	    vector));
 	intr_execute_handlers(isrc, frame);
@@ -1314,6 +1318,9 @@ lapic_handle_timer(struct trapframe *frame)
 	/* Send EOI first thing. */
 	lapic_eoi();
 
+	/* The frame may have been written into a poisoned region. */
+	kasan_mark(frame, sizeof(*frame), sizeof(*frame), 0);
+
 #if defined(SMP) && !defined(SCHED_ULE)
 	/*
 	 * Don't do any accounting for the disabled HTT cores, since it