From: Denys Vlasenko <dvlasenk@redhat.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@amacapital.net>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Alexei Starovoitov <ast@plumgrid.com>,
Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] x86, acpi: Eliminate saved_eip
Date: Tue, 16 Jun 2015 14:46:20 +0200 [thread overview]
Message-ID: <55801A9C.9010207@redhat.com> (raw)
In-Reply-To: <20150616100546.GA22928@amd>
On 06/16/2015 12:05 PM, Pavel Machek wrote:
>
>> diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S
>> index 665c6b7..eef2bd3 100644
>> --- a/arch/x86/kernel/acpi/wakeup_32.S
>> +++ b/arch/x86/kernel/acpi/wakeup_32.S
>> @@ -31,17 +31,11 @@ wakeup_pmode_return:
>>
>> movl %cs:saved_magic, %eax
>> cmpl $0x12345678, %eax
>> - jne bogus_magic
>> -
>> - # jump to place where we left off
>> - movl saved_eip, %eax
>> - jmp *%eax
>> -
>> + je ret_point
>> bogus_magic:
>
> Longjump is supposed to flush the prefetch, but hopefully nothing
> depends on that detail... ...
>
> no.
>
> https://en.wikibooks.org/wiki/X86_Assembly/Protected_Mode#Entering_Protected_Mode
>
> longjump is supposed to be there. Sorry about that. I guess indirect
> jump is not neccessary, and we should add a comment there.
What "long jump"? It's not a far (segment:offset) jump, it's a near
jump (one which only changes the offset), indirect one through a register.
And we aren't switching to or from protected mode here.
next prev parent reply other threads:[~2015-06-16 12:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-14 13:23 [PATCH 1/3] x86, acpi: Eliminate saved_eip Denys Vlasenko
2015-06-14 13:23 ` [PATCH 2/3] x86, acpi: On S3 failure, just fall through Denys Vlasenko
2015-06-15 10:35 ` Borislav Petkov
2015-06-14 13:23 ` [PATCH 3/3] x86, acpi: Fold {save,restore}_registers into their single callers Denys Vlasenko
2015-06-15 8:58 ` [PATCH 1/3] x86, acpi: Eliminate saved_eip Borislav Petkov
2015-06-16 10:05 ` Pavel Machek
2015-06-16 12:46 ` Denys Vlasenko [this message]
2015-06-17 9:28 ` Pavel Machek
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