On 14/01/2025 1:47 pm, Jan Beulich wrote: > On 14.01.2025 14:28, Andrew Cooper wrote: >> On 14/01/2025 1:22 pm, Jan Beulich wrote: >>> On 12.12.2024 02:17, Andrew Cooper wrote: >>>> On 12/12/2024 12:13 am, Volodymyr Babchuk wrote: >>>>> Hello Jan, >>>>> >>>>> Jan Beulich <jbeul...@suse.com> writes: >>>>> >>>>>> On 11.12.2024 03:04, Volodymyr Babchuk wrote: >>>>>>> Both GCC and Clang support -fstack-protector feature, which add stack >>>>>>> canaries to functions where stack corruption is possible. This series >>>>>>> makes possible to use this feature in Xen. I tested this on ARM64 and >>>>>>> it is working as intended. Tested both with GCC and Clang. >>>>>>> >>>>>>> It is hard to enable this feature on x86, as GCC stores stack canary >>>>>>> in %fs:40 by default, but Xen can't use %fs for various reasons. It is >>>>>>> possibly to change stack canary location new newer GCC versions, but >>>>>>> this will change minimal GCC requirement, which is also hard due to >>>>>>> various reasons. So, this series focus mostly on ARM and RISCV. >>>>>> Why exactly would it not be possible to offer the feature when new enough >>>>>> gcc is in use? >>>>> It is possible to use this feature with a modern enough GCC, yes. Are >>>>> you suggesting to make HAS_STACK_PROTECTOR dependent on GCC_VERSION for >>>>> x86 platform? >>>> (With the knowledge that this is a disputed Kconfig pattern, and will >>>> need rebasing), the way I want this to work is simply: >>>> >>>> diff --git a/xen/Makefile b/xen/Makefile >>>> index 0de0101fd0bf..5d0a88fb3c3f 100644 >>>> --- a/xen/Makefile >>>> +++ b/xen/Makefile >>>> @@ -434,6 +434,9 @@ endif >>>> >>>> ifeq ($(CONFIG_STACK_PROTECTOR),y) >>>> CFLAGS += -fstack-protector >>>> +ifeq ($(CONFIG_X86),y) >>>> +CFLAGS += -mstack-protector-guard=global >>>> +endif >>>> else >>>> CFLAGS += -fno-stack-protector >>>> endif >>>> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig >>>> index 9cdd04721afa..7951ca908b36 100644 >>>> --- a/xen/arch/x86/Kconfig >>>> +++ b/xen/arch/x86/Kconfig >>>> @@ -28,6 +28,7 @@ config X86 >>>> select HAS_PCI_MSI >>>> select HAS_PIRQ >>>> select HAS_SCHED_GRANULARITY >>>> + select HAS_STACK_PROTECTOR if >>>> $(cc-option,-mstack-protector-guard=global) >>>> select HAS_UBSAN >>>> select HAS_VMAP >>>> select HAS_VPCI if HVM >>>> >>>> >>>> >>>> Sadly, it doesn't build. I get a handful of: >>>> >>>> prelink.o: in function `cmdline_parse': >>>> /home/andrew/xen.git/xen/common/kernel.c:216:(.init.text+0x20f2): failed >>>> to convert GOTPCREL relocation against '__stack_chk_guard'; relink with >>>> --no-relax >>>> /home/andrew/xen.git/xen/common/kernel.c:230:(.init.text+0x246f): failed >>>> to convert GOTPCREL relocation against '__stack_chk_guard'; relink with >>>> --no-relax >>>> >>>> which is more toolchain-whispering than I feel like doing tonight. >>> For reference: >>> https://sourceware.org/pipermail/binutils/2025-January/138631.html >>> >>> You didn't enter a gcc bug report yet, did you? >> No, not yet. I'm afraid I've not had the time. > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118473
Thankyou. ~Andrew
