From: Dominik Brodowski <linux@dominikbrodowski.net>
To: Ingo Molnar <mingo@kernel.org>
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: Sun, 8 Apr 2018 11:15:36 +0200 [thread overview]
Message-ID: <20180408091536.GA10120@light.dominikbrodowski.net> (raw)
In-Reply-To: <20180408083550.32d65b6ra6yca5p7@gmail.com>
On Sun, Apr 08, 2018 at 10:35:50AM +0200, Ingo Molnar wrote:
> - _____sys_waitid() # ridiculous number of underscores?
> - __sys_waitid() # too generic sounding?
... and we'd need to rename internal helpers in net/
> - __inline_sys_waitid() # too long?
sounds acceptable, though a bit long (especially for the compat case, though
it doesn't really matter in the case of
__inline_compat_sys_sched_rr_get_interval)
> 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__);
2) We can add testing whether one of the arguments is longer than long.
__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));
3) This adds asmlinkage_protect() on m68k, but seems to be a no-op on other
architectures.
While reasons 1 and 3 seem irrelevant on x86, I'd like to keep the code
close to the generic one -- and reason 2 is valid in and by itself. So I'd
recommend keeping the __inline_sys / __do_sys indirection.
> Is UML unaffected by these renames?
UML is only affected by patch 3/3, but kept happy by the patch to
entry/syscalls/syscalltbl.sh.
On a somewhat related note: I'll try to prepare a patch this evening which
lets us build just the __ia32_sys and __x32_compat_sys stubs we actually
need. We have that information already in entry/syscalls/syscall_{32,64}.tbl,
it just needs to be extracted into another header file (in the form of
#define NEED_IA32_sys_xyzzz 1
) and then tested within the stubs. After some randconfig testing, this
might be worthwile to add on top of the patches already in tip-asm and the
three renaming patches currently under discussion.
Thanks,
Dominik
next prev parent reply other threads:[~2018-04-08 9:15 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 [this message]
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
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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