On 11/22/22 15:37, Ard Biesheuvel wrote:
On Tue, 22 Nov 2022 at 21:48, Tom Lendacky <thomas.lendacky@xxxxxxx> 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@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Michael Roth <michael.roth@xxxxxxx>
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
