On Thu, Mar 20, 2025 at 3:15 PM Jan Beulich <jbeul...@suse.com> wrote:
>
> On 20.03.2025 15:33, Frediano Ziglio wrote:
> > On Thu, Mar 6, 2025 at 3:02 PM Frediano Ziglio
> > <frediano.zig...@cloud.com> wrote:
> >>
> >> On Thu, Mar 6, 2025 at 2:26 PM Jan Beulich <jbeul...@suse.com> wrote:
> >>>
> >>> On 26.02.2025 19:54, Marek Marczykowski-Górecki wrote:
> >>>> On Mon, Feb 24, 2025 at 02:31:00PM +0000, Frediano Ziglio wrote:
> >>>>> On Mon, Feb 24, 2025 at 1:16 PM Marek Marczykowski-Górecki
> >>>>> <marma...@invisiblethingslab.com> wrote:
> >>>>>>
> >>>>>> On Mon, Feb 24, 2025 at 12:57:13PM +0000, Frediano Ziglio wrote:
> >>>>>>> On Fri, Feb 21, 2025 at 8:20 PM Marek Marczykowski-Górecki
> >>>>>>> <marma...@invisiblethingslab.com> wrote:
> >>>>>>>>
> >>>>>>>> On Mon, Feb 17, 2025 at 04:26:59PM +0000, Frediano Ziglio wrote:
> >>>>>>>>> Although code is compiled with -fpic option data is not position
> >>>>>>>>> independent. This causes data pointer to become invalid if
> >>>>>>>>> code is not relocated properly which is what happens for
> >>>>>>>>> efi_multiboot2 which is called by multiboot entry code.
> >>>>>>>>>
> >>>>>>>>> Code tested adding
> >>>>>>>>> PrintErrMesg(L"Test message", EFI_BUFFER_TOO_SMALL);
> >>>>>>>>> in efi_multiboot2 before calling efi_arch_edd (this function
> >>>>>>>>> can potentially call PrintErrMesg).
> >>>>>>>>>
> >>>>>>>>> Before the patch (XenServer installation on Qemu, xen replaced
> >>>>>>>>> with vanilla xen.gz):
> >>>>>>>>> Booting `XenServer (Serial)'Booting `XenServer (Serial)'
> >>>>>>>>> Test message: !!!! X64 Exception Type - 0E(#PF - Page-Fault) CPU
> >>>>>>>>> Apic ID - 00000000 !!!!
> >>>>>>>>> ExceptionData - 0000000000000000 I:0 R:0 U:0 W:0 P:0 PK:0 SS:0
> >>>>>>>>> SGX:0
> >>>>>>>>> RIP - 000000007EE21E9A, CS - 0000000000000038, RFLAGS -
> >>>>>>>>> 0000000000210246
> >>>>>>>>> RAX - 000000007FF0C1B5, RCX - 0000000000000050, RDX -
> >>>>>>>>> 0000000000000010
> >>>>>>>>> RBX - 0000000000000000, RSP - 000000007FF0C180, RBP -
> >>>>>>>>> 000000007FF0C210
> >>>>>>>>> RSI - FFFF82D040467CE8, RDI - 0000000000000000
> >>>>>>>>> R8 - 000000007FF0C1C8, R9 - 000000007FF0C1C0, R10 -
> >>>>>>>>> 0000000000000000
> >>>>>>>>> R11 - 0000000000001020, R12 - FFFF82D040467CE8, R13 -
> >>>>>>>>> 000000007FF0C1B8
> >>>>>>>>> R14 - 000000007EA33328, R15 - 000000007EA332D8
> >>>>>>>>> DS - 0000000000000030, ES - 0000000000000030, FS -
> >>>>>>>>> 0000000000000030
> >>>>>>>>> GS - 0000000000000030, SS - 0000000000000030
> >>>>>>>>> CR0 - 0000000080010033, CR2 - FFFF82D040467CE8, CR3 -
> >>>>>>>>> 000000007FC01000
> >>>>>>>>> CR4 - 0000000000000668, CR8 - 0000000000000000
> >>>>>>>>> DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 -
> >>>>>>>>> 0000000000000000
> >>>>>>>>> DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 -
> >>>>>>>>> 0000000000000400
> >>>>>>>>> GDTR - 000000007F9DB000 0000000000000047, LDTR - 0000000000000000
> >>>>>>>>> IDTR - 000000007F48E018 0000000000000FFF, TR - 0000000000000000
> >>>>>>>>> FXSAVE_STATE - 000000007FF0BDE0
> >>>>>>>>> !!!! Find image based on IP(0x7EE21E9A) (No PDB)
> >>>>>>>>> (ImageBase=000000007EE20000, EntryPoint=000000007EE23935) !!!!
> >>>>>>>>>
> >>>>>>>>> After the patch:
> >>>>>>>>> Booting `XenServer (Serial)'Booting `XenServer (Serial)'
> >>>>>>>>> Test message: Buffer too small
> >>>>>>>>> BdsDxe: loading Boot0000 "UiApp" from
> >>>>>>>>> Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)
> >>>>>>>>> BdsDxe: starting Boot0000 "UiApp" from
> >>>>>>>>> Fv(7CB8BDC9-F8EB-4F34-AAEA-3EE4AF6516A1)/FvFile(462CAA21-7614-4503-836E-8AB6F4662331)
> >>>>>>>>>
> >>>>>>>>> This partially rollback commit 00d5d5ce23e6.
> >>>>>>>>>
> >>>>>>>>> Fixes: 9180f5365524 ("x86: add multiboot2 protocol support for EFI
> >>>>>>>>> platforms")
> >>>>>>>>> Signed-off-by: Frediano Ziglio <frediano.zig...@cloud.com>
> >>>>>>>>
> >>>>>>>> I tried testing this patch, but it seems I cannot reproduce the
> >>>>>>>> original
> >>>>>>>> failure...
> >>>>>>>>
> >>>>>>>> I did as the commit message suggests here:
> >>>>>>>> https://gitlab.com/xen-project/people/marmarek/xen/-/commit/ca3d6911c448eb886990f33d4380b5646617a982
> >>>>>>>>
> >>>>>>>> With blexit() in PrintErrMesg(), it went back to the bootloader, so
> >>>>>>>> I'm
> >>>>>>>> sure this code path was reached. But with blexit() commented out, Xen
> >>>>>>>> started correctly both with and without this patch... The branch I
> >>>>>>>> used
> >>>>>>>> is here:
> >>>>>>>> https://gitlab.com/xen-project/people/marmarek/xen/-/commits/automation-tests?ref_type=heads
> >>>>>>>>
> >>>>>>>> Are there some extra condition to reproduce the issue? Maybe it
> >>>>>>>> depends
> >>>>>>>> on the compiler version? I guess I can try also on QEMU, but based on
> >>>>>>>> the description, I would expect it to crash in any case.
> >>>>>>>>
> >>>>>>>
> >>>>>>> Did you see the correct message in both cases?
> >>>>>>> Did you use Grub or direct EFI?
> >>>>>>>
> >>>>>>> With Grub and without this patch you won't see the message, with grub
> >>>>>>> with the patch you see the correct message.
> >>>>>>
> >>>>>> I did use grub, and I didn't see the message indeed.
> >>>>>> But in the case it was supposed to crash (with added PrintErrMesg(),
> >>>>>> commented out blexit and without your patch) it did _not_ crashed and
> >>>>>> continued to normal boot. Is that #PF non-fatal here?
> >>>>>>
> >>>>>
> >>>>> Hi,
> >>>>> I tried again with my test environment.
> >>>>> Added the PrintErrMesg line before efi_arch_edd call, I got a #PF, in
> >>>>> my case the system hangs. With the fix patch machine is rebooting and
> >>>>> I can see the message in the logs.
> >>>>> I'm trying with Xen starting inside Qemu, EFI firmware, xen.gz
> >>>>> compiled as ELF file. Host system is an Ubuntu 22.04.5 LTS. Gcc is
> >>>>> version 11.4.
> >>>>
> >>>> My test was wrong, commenting out blexit made "mesg" variable unused.
> >>>> After fixing that, I can reproduce it on both QEMU and real hardware:
> >>>> without your patch it crashes and with your patch it works just fine.
> >>>> While there may be more places with similar issue, this patch clearly
> >>>> improves the situation, so:
> >>>>
> >>>> Acked-by: Marek Marczykowski-Górecki <marma...@invisiblethingslab.com>
> >>>
> >>> This had to be reverted, for breaking the build with old Clang. See the
> >>> respective Matrix conversation.
> >>
> >> To sum up the failure is:
> >>
> >> clang: error: unknown argument: '-fno-jump-tables'
> >
> > Now that the minimum clang version supports this option, can this
> > change be applied?
>
> Not sure. I for one would expect that we actively reject building with
> too old tool chains then, which is yet to be carried out. Plus I think
> you'd want to re-submit, with all tags dropped. The change was wrong to
> go in at that earlier point, and hence any such tags weren't quite
> accurate.
>
> Jan
Hi,
not sure what you intend with "tags" in the above sentence. Git tags ?
Not sure we need to carry on using old tool chains if we decide to
bump the minimal versions.
Frediano
