linux-kernel - Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v6)

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: <632671842.3079.1548781059601.JavaMail.zimbra@efficios.com>
Date:   Tue, 29 Jan 2019 11:57:39 -0500 (EST)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     carlos <carlos@...hat.com>, Florian Weimer <fweimer@...hat.com>
Cc:     Joseph Myers <joseph@...esourcery.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>,
        libc-alpha <libc-alpha@...rceware.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ben Maurer <bmaurer@...com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Rich Felker <dalias@...c.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>
Subject: Re: [RFC PATCH glibc 1/4] glibc: Perform rseq(2) registration at C
 startup and thread creation (v6)

----- On Jan 21, 2019, at 4:35 PM, Mathieu Desnoyers mathieu.desnoyers@...icios.com wrote:
[...]

> diff --git a/sysdeps/unix/sysv/linux/sys/rseq.h
> b/sysdeps/unix/sysv/linux/sys/rseq.h
> new file mode 100644
> index 0000000000..61937fb193
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/sys/rseq.h
> @@ -0,0 +1,64 @@

[...]
> +
> +#ifndef _SYS_RSEQ_H
> +#define _SYS_RSEQ_H	1
> +
> +/* We use the structures declarations from the kernel headers.  */
> +#include <linux/rseq.h>
> +#include <stdint.h>
> +
> +/* Signature required before each abort handler code.  */
> +#define RSEQ_SIG 0x53053053

I recalled that aarch64 defines RSEQ_SIG to a different value which maps to
a valid trap instruction. So I plan to move the RSEQ_SIG define to per-arch
headers like this:

 sysdeps/unix/sysv/linux/aarch64/bits/rseq.h                  |   24 ++
 sysdeps/unix/sysv/linux/arm/bits/rseq.h                      |   24 ++
 sysdeps/unix/sysv/linux/bits/rseq.h                          |   23 ++
 sysdeps/unix/sysv/linux/mips/bits/rseq.h                     |   24 ++
 sysdeps/unix/sysv/linux/powerpc/bits/rseq.h                  |   24 ++
 sysdeps/unix/sysv/linux/s390/bits/rseq.h                     |   24 ++
 sysdeps/unix/sysv/linux/x86/bits/rseq.h                      |   24 ++

where "bits/rseq.h" contains a #error:

# error "Architecture does not define RSEQ_SIG.

sys/rseq.h will now include <bits/rseq.h>.


> +
> +enum rseq_register_state
> +{
> +  /* Value RSEQ_REGISTER_ALLOWED means it is allowed to update
> +     the refcount field and to register/unregister rseq.  */
> +  RSEQ_REGISTER_ALLOWED = 0,
> +  /* Value RSEQ_REGISTER_NESTED means it is temporarily forbidden
> +     to update the refcount field or to register/unregister rseq.  */
> +  RSEQ_REGISTER_NESTED = 1,

I plan to rename "RSEQ_REGISTER_NESTED" to "RSEQ_REGISTER_ONGOING" which
seems to better represent the current registration state.

Please let me know if anything is wrong with those changes.

Thanks,

Mathieu


> +  /* Value RSEQ_REGISTER_EXITING means it is forbidden to update the
> +     refcount field or to register/unregister rseq for the rest of the
> +     thread's lifetime.  */
> +  RSEQ_REGISTER_EXITING = 2,
> +};
-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com