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From 6cbccc4071ef49a8c591ecaddfdcb1cc26d28411 Mon Sep 17 00:00:00 2001
From: Michal Orzel <michal.orzel@amd.com>
Date: Thu, 8 Feb 2024 11:43:39 +0100
Subject: [PATCH 24/67] xen/arm: Fix UBSAN failure in start_xen()
When running Xen on arm32, in scenario where Xen is loaded at an address
such as boot_phys_offset >= 2GB, UBSAN reports the following:
(XEN) UBSAN: Undefined behaviour in arch/arm/setup.c:739:58
(XEN) pointer operation underflowed 00200000 to 86800000
(XEN) Xen WARN at common/ubsan/ubsan.c:172
(XEN) ----[ Xen-4.19-unstable arm32 debug=y ubsan=y Not tainted ]----
...
(XEN) Xen call trace:
(XEN) [<0031b4c0>] ubsan.c#ubsan_epilogue+0x18/0xf0 (PC)
(XEN) [<0031d134>] __ubsan_handle_pointer_overflow+0xb8/0xd4 (LR)
(XEN) [<0031d134>] __ubsan_handle_pointer_overflow+0xb8/0xd4
(XEN) [<004d15a8>] start_xen+0xe0/0xbe0
(XEN) [<0020007c>] head.o#primary_switched+0x4/0x30
The failure is reported for the following line:
(paddr_t)(uintptr_t)(_start + boot_phys_offset)
This occurs because the compiler treats (ptr + size) with size bigger than
PTRDIFF_MAX as undefined behavior. To address this, switch to macro
virt_to_maddr(), given the future plans to eliminate boot_phys_offset.
Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Tested-by: Luca Fancellu <luca.fancellu@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>
(cherry picked from commit e11f5766503c0ff074b4e0f888bbfc931518a169)
---
xen/arch/arm/setup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 4395640019..9ee19c2bc1 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -1025,7 +1025,7 @@ void __init start_xen(unsigned long boot_phys_offset,
/* Register Xen's load address as a boot module. */
xen_bootmodule = add_boot_module(BOOTMOD_XEN,
- (paddr_t)(uintptr_t)(_start + boot_phys_offset),
+ virt_to_maddr(_start),
(paddr_t)(uintptr_t)(_end - _start), false);
BUG_ON(!xen_bootmodule);
--
2.44.0
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