From: "H. Peter Anvin" <hpa@zytor.com>
To: Kees Cook <keescook@chromium.org>, Andy Lutomirski <luto@amacapital.net>
Cc: "Dmitry V. Levin" <ldv@altlinux.org>,
LKML <linux-kernel@vger.kernel.org>,
Will Drewry <wad@chromium.org>, Oleg Nesterov <oleg@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Linux MIPS Mailing List <linux-mips@linux-mips.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
Alexei Starovoitov <ast@plumgrid.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Michael Kerrisk-manpages <mtk.manpages@gmail.com>
Subject: Re: [PATCH v5 3/5] x86: Split syscall_trace_enter into two phases
Date: Fri, 06 Feb 2015 12:11:44 -0800 [thread overview]
Message-ID: <54D52000.40508@zytor.com> (raw)
In-Reply-To: <CAGXu5j+nopAMFukwMu=Cy0GOapziOLTb-ryJhA-aywk_uerg9A@mail.gmail.com>
On 02/06/2015 11:23 AM, Kees Cook wrote:
>
> Strictly speaking (ISO C, "man 3 errno"), errno is supposed to be a
> full int, though digging around I find this in include/linux/err.h:
>
That doesn't mean the kernel has to support them.
> /*
> * Kernel pointers have redundant information, so we can use a
> * scheme where we can return either an error code or a normal
> * pointer with the same return value.
> *
> * This should be a per-architecture thing, to allow different
> * error and pointer decisions.
> */
> #define MAX_ERRNO 4095
>
> #ifndef __ASSEMBLY__
>
> #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
>
> But no architecture overrides this.
>
We used to have a much lower value, that was per-architecture, in order
to optimize the resulting assembly (e.g. 8-bit immediates on x86). This
didn't work as the number of errnos increased. The other motivation was
probably binary compatibility with other Unices, which was an idea for a
while.
-hpa
WARNING: multiple messages have this Message-ID (diff)
From: hpa@zytor.com (H. Peter Anvin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 3/5] x86: Split syscall_trace_enter into two phases
Date: Fri, 06 Feb 2015 12:11:44 -0800 [thread overview]
Message-ID: <54D52000.40508@zytor.com> (raw)
In-Reply-To: <CAGXu5j+nopAMFukwMu=Cy0GOapziOLTb-ryJhA-aywk_uerg9A@mail.gmail.com>
On 02/06/2015 11:23 AM, Kees Cook wrote:
>
> Strictly speaking (ISO C, "man 3 errno"), errno is supposed to be a
> full int, though digging around I find this in include/linux/err.h:
>
That doesn't mean the kernel has to support them.
> /*
> * Kernel pointers have redundant information, so we can use a
> * scheme where we can return either an error code or a normal
> * pointer with the same return value.
> *
> * This should be a per-architecture thing, to allow different
> * error and pointer decisions.
> */
> #define MAX_ERRNO 4095
>
> #ifndef __ASSEMBLY__
>
> #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
>
> But no architecture overrides this.
>
We used to have a much lower value, that was per-architecture, in order
to optimize the resulting assembly (e.g. 8-bit immediates on x86). This
didn't work as the number of errnos increased. The other motivation was
probably binary compatibility with other Unices, which was an idea for a
while.
-hpa
next prev parent reply other threads:[~2015-02-06 20:11 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-05 22:13 [PATCH v5 0/5] x86: two-phase syscall tracing and seccomp fastpath Andy Lutomirski
2014-09-05 22:13 ` Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 1/5] x86,x32,audit: Fix x32's AUDIT_ARCH wrt audit Andy Lutomirski
2014-09-05 22:13 ` Andy Lutomirski
2014-09-09 2:43 ` [tip:x86/seccomp] x86, x32, audit: " tip-bot for Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 2/5] x86,entry: Only call user_exit if TIF_NOHZ Andy Lutomirski
2014-09-05 22:13 ` Andy Lutomirski
2014-09-09 2:43 ` [tip:x86/seccomp] x86, entry: " tip-bot for Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 3/5] x86: Split syscall_trace_enter into two phases Andy Lutomirski
2014-09-05 22:13 ` Andy Lutomirski
2014-09-09 2:44 ` [tip:x86/seccomp] " tip-bot for Andy Lutomirski
2015-02-05 21:19 ` [PATCH v5 3/5] " Dmitry V. Levin
2015-02-05 21:19 ` Dmitry V. Levin
2015-02-05 21:27 ` Kees Cook
2015-02-05 21:27 ` Kees Cook
2015-02-05 21:40 ` Dmitry V. Levin
2015-02-05 21:40 ` Dmitry V. Levin
2015-02-05 21:52 ` Andy Lutomirski
2015-02-05 21:52 ` Andy Lutomirski
2015-02-05 23:12 ` Kees Cook
2015-02-05 23:12 ` Kees Cook
2015-02-05 23:39 ` Dmitry V. Levin
2015-02-05 23:39 ` Dmitry V. Levin
2015-02-05 23:49 ` Kees Cook
2015-02-05 23:49 ` Kees Cook
2015-02-06 0:09 ` Andy Lutomirski
2015-02-06 0:09 ` Andy Lutomirski
2015-02-06 2:32 ` Dmitry V. Levin
2015-02-06 2:32 ` Dmitry V. Levin
2015-02-06 2:38 ` Andy Lutomirski
2015-02-06 2:38 ` Andy Lutomirski
2015-02-06 19:23 ` Kees Cook
2015-02-06 19:23 ` Kees Cook
2015-02-06 19:32 ` Andy Lutomirski
2015-02-06 19:32 ` Andy Lutomirski
2015-02-06 20:07 ` Kees Cook
2015-02-06 20:07 ` Kees Cook
2015-02-06 20:12 ` Andy Lutomirski
2015-02-06 20:12 ` Andy Lutomirski
2015-02-06 20:16 ` Kees Cook
2015-02-06 20:16 ` Kees Cook
2015-02-06 20:20 ` Andy Lutomirski
2015-02-06 20:20 ` Andy Lutomirski
2015-02-06 23:17 ` a method to distinguish between syscall-enter/exit-stop Dmitry V. Levin
2015-02-06 23:17 ` Dmitry V. Levin
2015-02-07 1:07 ` Kees Cook
2015-02-07 1:07 ` Kees Cook
2015-02-07 3:04 ` Dmitry V. Levin
2015-02-07 3:04 ` Dmitry V. Levin
2015-02-06 20:11 ` H. Peter Anvin [this message]
2015-02-06 20:11 ` [PATCH v5 3/5] x86: Split syscall_trace_enter into two phases H. Peter Anvin
2014-09-05 22:13 ` [PATCH v5 4/5] x86_64,entry: Treat regs->ax the same in fastpath and slowpath syscalls Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 4/5] x86_64, entry: " Andy Lutomirski
2014-09-09 2:44 ` [tip:x86/seccomp] x86_64, entry: Treat regs-> ax " tip-bot for Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 5/5] x86_64,entry: Use split-phase syscall_trace_enter for 64-bit syscalls Andy Lutomirski
2014-09-05 22:13 ` [PATCH v5 5/5] x86_64, entry: " Andy Lutomirski
2014-09-09 2:44 ` [tip:x86/seccomp] " tip-bot for Andy Lutomirski
2014-09-08 19:29 ` [PATCH v5 0/5] x86: two-phase syscall tracing and seccomp fastpath Kees Cook
2014-09-08 19:29 ` Kees Cook
2014-09-08 19:49 ` H. Peter Anvin
2014-09-08 19:49 ` H. Peter Anvin
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