linux-kernel - Re: [PATCH v5 3/5] x86: Split syscall_trace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54D52000.40508@zytor.com>
Date:	Fri, 06 Feb 2015 12:11:44 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	"Dmitry V. Levin" <ldv@...linux.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Will Drewry <wad@...omium.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>
Subject: Re: [PATCH v5 3/5] x86: Split syscall_trace_enter into two phases

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/