From: Pavel Machek <pavel@ucw.cz>
To: Denys Vlasenko <dvlasenk@redhat.com>
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: Wed, 17 Jun 2015 11:28:32 +0200 [thread overview]
Message-ID: <20150617092832.GA17009@amd> (raw)
In-Reply-To: <55801A9C.9010207@redhat.com>
On Tue 2015-06-16 14:46:20, Denys Vlasenko wrote:
> 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.
Yup, you are right, the ljmp is few instructions above that.
> And we aren't switching to or from protected mode here.
wakeup_pmode_return... that's just after switching to protected mode
AFAICT.
Anyway,
Acked-by: Pavel Machek <pavel@ucw.cz>
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
prev parent reply other threads:[~2015-06-17 9:28 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
2015-06-17 9:28 ` Pavel Machek [this message]
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