From: Ingo Molnar <mingo@kernel.org>
To: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: linux-kernel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>,
Andi Kleen <ak@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, Maninder Singh <maninder1.s@samsung.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 0/3] syscalls: clean up stub naming convention
Date: Mon, 9 Apr 2018 08:39:21 +0200 [thread overview]
Message-ID: <20180409063921.wkrqbnv4lzxb3isg@gmail.com> (raw)
In-Reply-To: <20180408091536.GA10120@light.dominikbrodowski.net>
* Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> > One more fundamental question: why do we have the __do_sys_waitid() and
> > __inline_sys_waitid() distinction - aren't the function call signatures the same
> > with no conversion done?
> >
> > I.e. couldn't we just do a single, static __do_sys_waitid(), where the compiler
> > would decide to what extent inlining is justified? This would allow the compiler
> > to inline all the intermediate code into the stubs themselves.
> >
> > Or is this a side effect of the error injection feature, which needs to add extra
> > logic at this intermediate level? That too should be able to use the
> > __do_sys_waitid() variant though.
>
> Error injection is unrelated. It seems to be for three reasons, if I read
> the code (include/linux/syscalls.h) correctly:
>
> asmlinkage long __do_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))
>
> 1) This takes arguments of type long (to protect against CVE-2009-0029);
> see https://lwn.net/Articles/604287/ : "Digging into the history of
> this, it turns out that the long version ensures that 32-bit values
> are correctly sign-extended for some 64-bit kernel platforms,
> preventing a historical vulnerability."
>
> {
> long ret = __in_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));
> __MAP(x,__SC_TEST,__VA_ARGS__);
I see - so it's _not_ the same function call signature, but a wrapper with a
sign-extended version, which is fair and useful. So on architectures where this
matters there's type conversion and active code generated.
Thanks,
Ingo
next prev parent reply other threads:[~2018-04-09 6:39 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-07 7:46 [PATCH 0/3] syscalls: clean up stub naming convention Dominik Brodowski
2018-04-07 7:46 ` [PATCH 1/3] syscalls: clean up syscall " Dominik Brodowski
2018-04-07 7:46 ` [PATCH 2/3] syscalls: clean up compat " Dominik Brodowski
2018-04-07 7:46 ` [PATCH 3/3] syscalls: rename struct pt_regs-based sys_*() to __x64_sys_*() Dominik Brodowski
2018-04-08 8:35 ` [PATCH 0/3] syscalls: clean up stub naming convention Ingo Molnar
2018-04-08 9:15 ` Dominik Brodowski
2018-04-08 19:59 ` Dominik Brodowski
2018-04-08 20:06 ` [PATCH 4/3] syscalls/x86: adapt syscall_wrapper.h to the new syscall " Dominik Brodowski
2018-04-09 6:49 ` [PATCH 0/3] syscalls: clean up " Ingo Molnar
2018-04-09 6:54 ` Dominik Brodowski
2018-04-09 6:39 ` Ingo Molnar [this message]
2018-04-09 19:13 ` Linus Torvalds
2018-04-09 6:45 ` Ingo Molnar
2018-04-09 6:53 ` Dominik Brodowski
2018-04-09 7:06 ` Ingo Molnar
2018-04-09 7:08 ` Dominik Brodowski
2018-04-09 7:34 ` Ingo Molnar
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