From: Jann Horn <jannh@google.com>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: kernel list <linux-kernel@vger.kernel.org>,
sean.j.christopherson@intel.com,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
"the arch/x86 maintainers" <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [RFC][PATCH 6/8] x86/mm: add vsyscall address helper
Date: Sat, 8 Sep 2018 02:46:35 +0200 [thread overview]
Message-ID: <CAG48ez0FAizJH-4LivpMPSnZqDUeUq0XHf6K8cA4xCqkiPMNYw@mail.gmail.com> (raw)
In-Reply-To: <20180907194901.C54A0101@viggo.jf.intel.com>
On Sat, Sep 8, 2018 at 2:25 AM Dave Hansen <dave.hansen@linux.intel.com> wrote:
> We will shortly be using this check in two locations. Put it in
> a helper before we do so.
[...]
> +/*
> + * The (legacy) vsyscall page is the long page in the kernel portion
> + * of the address space that has user-accessible permissions.
> + */
> +static bool is_vsyscall_vaddr(unsigned long vaddr)
> +{
> + return (vaddr & ~0xfff) == VSYSCALL_ADDR;
> +}
<bikeshed>
Since you're touching this code anyway: Would it make sense to change
that constant to a more explicit "~0xfffUL" (or alternatively
PAGE_MASK)? I tend to end up staring at code like this forever, trying
to figure out whether the upper 32 bits of the constant end up being
set or clear. As a reader, looking at the current code, it's quite
annoying to see what actually happens - first there's a signed 32-bit
literal 0xfff, then a 32-bit negation happens, and then the number is
converted to 64 bits with sign extension.
</bikeshed>
next prev parent reply other threads:[~2018-09-08 0:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 19:48 [RFC][PATCH 0/8] x86/mm: page fault handling cleanups Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 1/8] x86/mm: clarify hardware vs. software "error_code" Dave Hansen
2018-09-07 22:48 ` Andy Lutomirski
2018-09-10 20:07 ` Dave Hansen
2018-09-10 21:17 ` Andy Lutomirski
2018-09-07 19:48 ` [RFC][PATCH 2/8] x86/mm: break out kernel address space handling Dave Hansen
2018-09-07 21:06 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen
2018-09-07 22:21 ` Andy Lutomirski
2018-09-07 22:37 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 3/8] x86/mm: break out user " Dave Hansen
2018-09-08 9:38 ` Peter Zijlstra
2018-09-10 20:20 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 4/8] x86/mm: add clarifying comments for user addr space Dave Hansen
2018-09-07 19:49 ` [RFC][PATCH 5/8] x86/mm: fix exception table comments Dave Hansen
2018-09-07 21:04 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen
2018-09-10 20:43 ` Sean Christopherson
2018-09-08 0:37 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 6/8] x86/mm: add vsyscall address helper Dave Hansen
2018-09-08 0:46 ` Jann Horn [this message]
2018-09-07 19:49 ` [RFC][PATCH 7/8] x86/mm/vsyscall: consider vsyscall page part of user address space Dave Hansen
2018-09-07 22:58 ` Andy Lutomirski
2018-09-08 1:16 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 8/8] x86/mm: remove spurious fault pkey check Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAG48ez0FAizJH-4LivpMPSnZqDUeUq0XHf6K8cA4xCqkiPMNYw@mail.gmail.com \
--to=jannh@google.com \
--cc=dave.hansen@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=peterz@infradead.org \
--cc=sean.j.christopherson@intel.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).