On Fri, 20 Aug 2021 at 09:34, Joerg Roedel <joro@xxxxxxxxxx> 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>
Acked by: Ard Biesheuvel <ardb@xxxxxxxxxx>
One nit below
> ---
> 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
Any reason in particular for the increase by 32?
> 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
> + * 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)
> */
> cli
>
> + lidtl (%ebx)
> + subl $16, %ebx
> +
> lgdtl (%ebx)
>
> movl %cr4, %eax
> @@ -166,6 +174,11 @@ SYM_DATA_START(efi32_boot_gdt)
> .quad 0
> SYM_DATA_END(efi32_boot_gdt)
>
> +SYM_DATA_START(efi32_boot_idt)
> + .word 0
> + .quad 0
> +SYM_DATA_END(efi32_boot_idt)
> +
> SYM_DATA_START(efi32_boot_cs)
> .word 0
> SYM_DATA_END(efi32_boot_cs)
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index a2347ded77ea..572c535cf45b 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -319,6 +319,9 @@ SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL)
> movw %cs, rva(efi32_boot_cs)(%ebp)
> movw %ds, rva(efi32_boot_ds)(%ebp)
>
> + /* Store firmware IDT descriptor */
> + sidtl rva(efi32_boot_idt)(%ebp)
> +
> /* Disable paging */
> movl %cr0, %eax
> btrl $X86_CR0_PG_BIT, %eax
> --
> 2.32.0
>
