From 6cbccc4071ef49a8c591ecaddfdcb1cc26d28411 Mon Sep 17 00:00:00 2001 From: Michal Orzel 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 Reviewed-by: Luca Fancellu Tested-by: Luca Fancellu Acked-by: Julien Grall (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