[edk2-devel] [PATCH] UefiCpuPkg/CpuDxe: Fix boot error
Laszlo Ersek
lersek at redhat.com
Thu Dec 3 10:21:36 UTC 2020
On 12/02/20 22:38, Guo Dong wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3084
>
> When DXE drivers are dispatched above 4GB memory and
> the system is already in 64bit mode, the address
> setCodeSelectorLongJump in stack will be override
> by parameter. so change to use 64bit address and
> jump to qword address.
>
> Signed-off-by: Guo Dong <guo.dong at intel.com>
> ---
> UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm b/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> index c3489bcc3e..6ad32b49f4 100644
> --- a/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> +++ b/UefiCpuPkg/CpuDxe/X64/CpuAsm.nasm
> @@ -23,8 +23,8 @@ ASM_PFX(SetCodeSelector):
> sub rsp, 0x10
> lea rax, [setCodeSelectorLongJump]
> mov [rsp], rax
I'll let Ray and Eric review this patch, just one question for my
understanding:
for clarity, shouldn't the above MOV have referred to "eax" in the first
place? Because (before this patch) it seems to store 8 bytes (from rax),
and then to overwrite the high-address DWORD of those 8 bytes, with the
next operation (which stores 2 bytes from CX).
IMO, for clarity's sake, the original code should have used EAX. Why
write 8 bytes when only the low-address 4 bytes matter anyway?
Anyhow, this is no longer relevant, because of the present patch; I just
wanted to ask about it so I understand better.
Thanks
Laszlo
> - mov [rsp+4], cx
> - jmp dword far [rsp]
> + mov [rsp+8], cx
> + jmp qword far [rsp]
> setCodeSelectorLongJump:
> add rsp, 0x10
> ret
>
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#68235): https://edk2.groups.io/g/devel/message/68235
Mute This Topic: https://groups.io/mt/78671060/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-
More information about the edk2-devel-archive
mailing list