linux-kernel - Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag

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 for Android: free password hash cracker in your pocket

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

Date:   Tue, 11 Oct 2022 11:00:15 +1100
From:   Andrew Donnellan <ajd@...ux.ibm.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Michael Ellerman <mpe@...erman.id.au>, rmclure@...ux.ibm.com
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        aneesh.kumar@...ux.ibm.com, atrajeev@...ux.vnet.ibm.com,
        christophe.leroy@...roup.eu, cuigaosheng1@...wei.com,
        david@...hat.com, farosas@...ux.ibm.com, geoff@...radead.org,
        gustavoars@...nel.org, haren@...ux.ibm.com, hbathini@...ux.ibm.com,
        joel@....id.au, lihuafei1@...wei.com, linux-kernel@...r.kernel.org,
        linux@...ck-us.net, linuxppc-dev@...ts.ozlabs.org,
        lukas.bulwahn@...il.com, mikey@...ling.org, nathan@...nel.org,
        nathanl@...ux.ibm.com, nicholas@...ux.ibm.com, npiggin@...il.com,
        pali@...nel.org, paul@...l-moore.com, ruscur@...sell.cc,
        windhl@....com, wsa+renesas@...g-engineering.com,
        ye.xingchen@....com.cn, yuanjilin@...rlc.com,
        zhengyongjun3@...wei.com
Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag

On Mon, 2022-10-10 at 16:26 -0600, Jason A. Donenfeld wrote:
> 
> Bisected:
> 
> 7e92e01b724526b98cbc7f03dd4afa0295780d56 is the first bad commit
> commit 7e92e01b724526b98cbc7f03dd4afa0295780d56
> Author: Rohan McLure <rmclure@...ux.ibm.com>
> Date:   Wed Sep 21 16:56:01 2022 +1000
> 
>     powerpc: Provide syscall wrapper
> 
>     Implement syscall wrapper as per s390, x86, arm64. When enabled
>     cause handlers to accept parameters from a stack frame rather
> than
>     from user scratch register state. This allows for user registers
> to be
>     safely cleared in order to reduce caller influence on speculation
>     within syscall routine. The wrapper is a macro that emits syscall
>     handler symbols that call into the target handler, obtaining its
>     parameters from a struct pt_regs on the stack.
> 
>     As registers are already saved to the stack prior to calling
>     system_call_exception, it appears that this function is executed
> more
>     efficiently with the new stack-pointer convention than with
> parameters
>     passed by registers, avoiding the allocation of a stack frame for
> this
>     method. On a 32-bit system, we see >20% performance increases on
> the
>     null_syscall microbenchmark, and on a Power 8 the performance
> gains
>     amortise the cost of clearing and restoring registers which is
>     implemented at the end of this series, seeing final result of
> ~5.6%
>     performance improvement on null_syscall.
> 
>     Syscalls are wrapped in this fashion on all platforms except for
> the
>     Cell processor as this commit does not provide SPU support. This
> can be
>     quickly fixed in a successive patch, but requires
> spu_sys_callback to
>     allocate a pt_regs structure to satisfy the wrapped calling
> convention.
> 
>     Co-developed-by: Andrew Donnellan <ajd@...ux.ibm.com>
>     Signed-off-by: Andrew Donnellan <ajd@...ux.ibm.com>
>     Signed-off-by: Rohan McLure <rmclure@...ux.ibm.com>
>     Reviewed-by: Nicholas Piggin <npiggin@...i.com>
>     [mpe: Make incompatible with COMPAT to retain clearing of high
> bits of args]
>     Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
>     Link:
> https://lore.kernel.org/r/20220921065605.1051927-22-rmclure@linux.ibm.com

Thanks for bisecting, this is interesting! Could you provide your
.config and the environment you're running in? Your reproducer doesn't
seem to trigger it on my baremetal POWER8 pseries_le_defconfig.

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@...ux.ibm.com   IBM Australia Limited