From dd2b5443644505af51c95503898ab363e7d7c29d Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 24 Dec 2024 04:35:16 +0200
Subject: [PATCH] amd64: on any fault during call to EFI RT, restore execution
 and print fault details

The fault info should be useful to see what specifically BIOS tried to
do and why it faulted.  E.g. it might allow to see which EFI memory
segment needs to be mapped in addition to normal runtime segments, to
work around the fault.

Reviewed by:	kevans, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D48186
---
 sys/amd64/amd64/trap.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index 3b23a34662d55..8e9b115ef2241 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -423,6 +423,20 @@ trap(struct trapframe *frame)
 
 		KASSERT(cold || td->td_ucred != NULL,
 		    ("kernel trap doesn't have ucred"));
+
+		/*
+		 * Most likely, EFI RT faulted.  This check prevents
+		 * kdb from handling breakpoints set on the BIOS text,
+		 * if such option is ever needed.
+		 */
+		if ((td->td_pflags & TDP_EFIRT) != 0 &&
+		    curpcb->pcb_onfault != NULL && type != T_PAGEFLT) {
+			trap_diag(frame, 0);
+			printf("EFI RT fault %s\n", traptype_to_msg(type));
+			frame->tf_rip = (long)curpcb->pcb_onfault;
+			return;
+		}
+
 		switch (type) {
 		case T_PAGEFLT:			/* page fault */
 			(void)trap_pfault(frame, false, NULL, NULL);
@@ -586,18 +600,6 @@ trap(struct trapframe *frame)
 			 * FALLTHROUGH (TRCTRAP kernel mode, kernel address)
 			 */
 		case T_BPTFLT:
-			/*
-			 * Most likely, EFI RT hitting INT3.  This
-			 * check prevents kdb from handling
-			 * breakpoints set on the BIOS text, if such
-			 * option is ever needed.
-			 */
-			if ((td->td_pflags & TDP_EFIRT) != 0 &&
-			    curpcb->pcb_onfault != NULL) {
-				frame->tf_rip = (long)curpcb->pcb_onfault;
-				return;
-			}
-
 			/*
 			 * If KDB is enabled, let it handle the debugger trap.
 			 * Otherwise, debugger traps "can't happen".
@@ -857,6 +859,10 @@ trap_pfault(struct trapframe *frame, bool usermode, int *signo, int *ucode)
 after_vmfault:
 	if (td->td_intr_nesting_level == 0 &&
 	    curpcb->pcb_onfault != NULL) {
+		if ((td->td_pflags & TDP_EFIRT) != 0) {
+			trap_diag(frame, eva);
+			printf("EFI RT page fault\n");
+		}
 		frame->tf_rip = (long)curpcb->pcb_onfault;
 		return (0);
 	}