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Message-ID: <26c34f9e-3b09-7b10-09a2-993a50790447@amd.com>
Date: Tue, 22 Nov 2022 15:49:29 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Michael Roth <michael.roth@....com>
Subject: Re: [PATCH v3 00/17] x86: head_64.S spring cleaning
On 11/22/22 15:37, Ard Biesheuvel wrote:
> On Tue, 22 Nov 2022 at 21:48, Tom Lendacky <thomas.lendacky@....com> wrote:
>>
>> On 11/22/22 10:10, Ard Biesheuvel wrote:
>>> After doing some cleanup work on the EFI code in head_64.S, the mixed
>>> mode code in particular, I noticed that the memory encryption pieces
>>> could use some attention as well, so I cleaned that up too.
>>>
>>> Changes since v2:
>>> - add some clarifying comments to the EFI mixed mode changes
>>> - include patch to make the EFI handover protocol optional that was sent
>>> out separately before
>>> - rebase onto tip/master
>>>
>>> Changes since v1:
>>> - at Boris's request, split the patches into smaller ones that are
>>> easier to review
>>>
>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>> Cc: Ingo Molnar <mingo@...hat.com>
>>> Cc: Borislav Petkov <bp@...en8.de>
>>> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>>> Cc: Michael Roth <michael.roth@....com>
>>
>> This causes an SEV guest to blow up on boot in the early boot code. It
>> looks like the stack pointer is not valid and it triple faults on a pushq
>> instruction (pushq $__KERNEL_CS in arch/x86/boot/compressed/head_64.S of
>> startup_64).
>>
>
> Thanks for the report.
>
> So the mystery here (at least to me) is that all the changes are to
> the 32-bit code, and startup_64 reloads the stack pointer from the
> symbol
I bisected it to:
99b7f4b23d9f ("x86/boot/compressed, efi: Merge multiple definitions of image_offset into one")
And doing the following fixed it:
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index cb5f0befee57..a0bfd31358ba 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -23,7 +23,7 @@
const efi_system_table_t *efi_system_table;
const efi_dxe_services_table_t *efi_dxe_table;
-u32 image_offset;
+u32 image_offset __section(".data");
static efi_loaded_image_t *image = NULL;
static efi_status_t
I assume it has to do with being in .data vs .bss and not being explicitly
cleared with the encryption bit set. With the change to put image_offset in
the .data section, it is read as zero, where as when it was in the .bss
section it was reading "ciphertext".
Thanks,
Tom
>
> Does your config have CONFIG_EFI_MIXED enabled?
>
> Can I reproduce this fully emulated with QEMU? Or do I need a SEV host?
>
>> Here is the Qemu register dump:
>> RAX=00000000029cc260 RBX=ffffffffdd98c000 RCX=0000000000000010 RDX=0000000000000002
>> RSI=000000003dec1000 RDI=0000000000000000 RBP=ffffffffdb000000 RSP=ffffffffde36e000
>> R8 =000000003dec1410 R9 =000000003dec13fc R10=000000000000006c R11=0000000000000000
>> R12=0000000000000000 R13=0000000000000001 R14=0000000000000004 R15=000000003eacdf44
>> RIP=0000000002000263 RFL=00200002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
>> ES =0000 0000000000000000 00000000 00000000
>> CS =0038 0000000000000000 ffffffff 00a09b00 DPL=0 CS64 [-RA]
>> SS =0000 0000000000000000 00000000 00000000
>> DS =0000 0000000000000000 00000000 00000000
>> FS =0000 0000000000000000 00000000 00000000
>> GS =0000 0000000000000000 00000000 00000000
>> LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
>> TR =0000 0000000000000000 0000ffff 00008b00 DPL=0 TSS64-busy
>> GDT= 00000000029cc270 0000002f
>> IDT= 000000003f55e018 00000fff
>> CR0=80010033 CR2=ffffffffde36dff8 CR3=000000003fc01000 CR4=00000668
>> DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
>> DR6=00000000ffff0ff0 DR7=0000000000000400
>> EFER=0000000000000d00
>>
>> Thanks,
>> Tom
>>
>>>
>>> Ard Biesheuvel (17):
>>> x86/compressed: efi-mixed: rename efi_thunk_64.S to efi-mixed.S
>>> x86/compressed: efi-mixed: move 32-bit entrypoint code into .text
>>> section
>>> x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup
>>> code
>>> x86/compressed: efi-mixed: move efi32_pe_entry into .text section
>>> x86/compressed: efi-mixed: move efi32_entry out of head_64.S
>>> x86/compressed: efi-mixed: move efi32_pe_entry() out of head_64.S
>>> x86/compressed: efi: merge multiple definitions of image_offset into
>>> one
>>> x86/compressed: efi-mixed: simplify IDT/GDT preserve/restore
>>> x86/compressed: avoid touching ECX in startup32_set_idt_entry()
>>> x86/compressed: pull global variable ref up into startup32_load_idt()
>>> x86/compressed: move startup32_load_idt() into .text section
>>> x86/compressed: move startup32_load_idt() out of head_64.S
>>> x86/compressed: move startup32_check_sev_cbit() into .text
>>> x86/compressed: move startup32_check_sev_cbit() out of head_64.S
>>> x86/compressed: adhere to calling convention in
>>> get_sev_encryption_bit()
>>> x86/compressed: only build mem_encrypt.S if AMD_MEM_ENCRYPT=y
>>> efi: x86: Make the deprecated EFI handover protocol optional
>>>
>>> arch/x86/Kconfig | 17 +
>>> arch/x86/boot/compressed/Makefile | 8 +-
>>> arch/x86/boot/compressed/efi_mixed.S | 351 ++++++++++++++++++++
>>> arch/x86/boot/compressed/efi_thunk_64.S | 195 -----------
>>> arch/x86/boot/compressed/head_32.S | 4 -
>>> arch/x86/boot/compressed/head_64.S | 303 +----------------
>>> arch/x86/boot/compressed/mem_encrypt.S | 152 ++++++++-
>>> arch/x86/boot/header.S | 2 +-
>>> arch/x86/boot/tools/build.c | 2 +
>>> drivers/firmware/efi/libstub/x86-stub.c | 2 +-
>>> 10 files changed, 533 insertions(+), 503 deletions(-)
>>> create mode 100644 arch/x86/boot/compressed/efi_mixed.S
>>> delete mode 100644 arch/x86/boot/compressed/efi_thunk_64.S
>>>
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