[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v6] Avoid crash calling PrintErrMesg from efi_multiboot2
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 > <marmarek@xxxxxxxxxxxxxxxxxxxxxx> 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.ziglio@xxxxxxxxx> > > > > 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? -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab Attachment:
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