On Fri, Aug 20, 2021 at 09:34:29AM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> Commit 79419e13e808 ("x86/boot/compressed/64: Setup IDT in startup_32
> boot path") introduced an IDT into the 32 bit boot path of the
> decompressor stub. But the IDT is set up before ExitBootServices() is
> called and some UEFI firmwares rely on their own IDT.
>
> Save the firmware IDT on boot and restore it before calling into EFI
> functions to fix boot failures introduced by above commit.
>
> Reported-by: Fabio Aiuto <fabioaiuto83@xxxxxxxxx>
> Fixes: 79419e13e808 ("x86/boot/compressed/64: Setup IDT in startup_32 boot path")
> Cc: stable@xxxxxxxxxxxxxxx # 5.13+
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> arch/x86/boot/compressed/efi_thunk_64.S | 23 ++++++++++++++++++-----
> arch/x86/boot/compressed/head_64.S | 3 +++
> 2 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/efi_thunk_64.S b/arch/x86/boot/compressed/efi_thunk_64.S
> index 95a223b3e56a..99cfd5dea23c 100644
> --- a/arch/x86/boot/compressed/efi_thunk_64.S
> +++ b/arch/x86/boot/compressed/efi_thunk_64.S
> @@ -39,7 +39,7 @@ SYM_FUNC_START(__efi64_thunk)
> /*
> * Convert x86-64 ABI params to i386 ABI
> */
> - subq $32, %rsp
> + subq $64, %rsp
> movl %esi, 0x0(%rsp)
> movl %edx, 0x4(%rsp)
> movl %ecx, 0x8(%rsp)
> @@ -49,14 +49,19 @@ SYM_FUNC_START(__efi64_thunk)
> leaq 0x14(%rsp), %rbx
> sgdt (%rbx)
>
> + addq $16, %rbx
> + sidt (%rbx)
> +
> /*
> - * Switch to gdt with 32-bit segments. This is the firmware GDT
> - * that was installed when the kernel started executing. This
> - * pointer was saved at the EFI stub entry point in head_64.S.
> + * Switch to idt and gdt with 32-bit segments. This is the firmware GDT
IDT and GDT, both capitalized pls. Also, the comment at the top of the
file needs adjusting.
> + * and IDT that was installed when the kernel started executing. The
> + * pointers were saved at the EFI stub entry point in head_64.S.
> *
> * Pass the saved DS selector to the 32-bit code, and use far return to
> * restore the saved CS selector.
> */
> + leaq efi32_boot_idt(%rip), %rax
> + lidt (%rax)
> leaq efi32_boot_gdt(%rip), %rax
> lgdt (%rax)
>
> @@ -67,7 +72,7 @@ SYM_FUNC_START(__efi64_thunk)
> pushq %rax
> lretq
>
> -1: addq $32, %rsp
> +1: addq $64, %rsp
> movq %rdi, %rax
>
> pop %rbx
> @@ -132,6 +137,9 @@ SYM_FUNC_START_LOCAL(efi_enter32)
> */
Can you pls also extend this comment here to say "IDT" for faster
pinpointing when someone like me is looking for the place where the
kernel IDT/GDT get restored again.
In any case, those are all minor nitpicks, other than that LGTM.
Lemme go test it on whatever I can - if others wanna run this, it would
be very much appreciated!
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
