From ed4c884f2e7774bf4f2c86e2af644be8365c8029 Mon Sep 17 00:00:00 2001
From: Andrew Turner <andrew@FreeBSD.org>
Date: Tue, 20 Mar 2018 13:35:20 +0000
Subject: [PATCH] Check if the gettime runtime service is valid.

The U-Boot efi runtime service expects us to set the address map before
calling any runtime services. It will then remap a few functions to their
runtime version. One of these is the gettime function. If we call into
this without having set a runtime map we get a page fault.

Add a check to see if this is valid in efi_init() so we don't try to use
the possibly invalid pointer.

Reviewed by:	imp, kevans (both previous version)
X-MFC-With:	r330868
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D14759
---
 sys/dev/efidev/efirt.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/sys/dev/efidev/efirt.c b/sys/dev/efidev/efirt.c
index 6fd6d0066e35..f1c543b116de 100644
--- a/sys/dev/efidev/efirt.c
+++ b/sys/dev/efidev/efirt.c
@@ -99,6 +99,25 @@ efi_status_to_errno(efi_status status)
 
 static struct mtx efi_lock;
 
+static bool
+efi_is_in_map(struct efi_md *map, int ndesc, int descsz, vm_offset_t addr)
+{
+	struct efi_md *p;
+	int i;
+
+	for (i = 0, p = map; i < ndesc; i++, p = efi_next_descriptor(p,
+	    descsz)) {
+		if ((p->md_attr & EFI_MD_ATTR_RT) == 0)
+			continue;
+
+		if (addr >= (uintptr_t)p->md_virt &&
+		    addr < (uintptr_t)p->md_virt + p->md_pages * PAGE_SIZE)
+			return (true);
+	}
+
+	return (false);
+}
+
 static int
 efi_init(void)
 {
@@ -164,6 +183,24 @@ efi_init(void)
 		return (ENXIO);
 	}
 
+	/*
+	 * Some UEFI implementations have multiple implementations of the
+	 * RS->GetTime function. They switch from one we can only use early
+	 * in the boot process to one valid as a RunTime service only when we
+	 * call RS->SetVirtualAddressMap. As this is not always the case, e.g.
+	 * with an old loader.efi, check if the RS->GetTime function is within
+	 * the EFI map, and fail to attach if not.
+	 */
+	if (!efi_is_in_map(map, efihdr->memory_size / efihdr->descriptor_size,
+	    efihdr->descriptor_size, (vm_offset_t)efi_runtime->rt_gettime)) {
+		if (bootverbose)
+			printf(
+			 "EFI runtime services table has an invalid pointer\n");
+		efi_runtime = NULL;
+		efi_destroy_1t1_map();
+		return (ENXIO);
+	}
+
 	return (0);
 }