From: Michael Ellerman <mpe@ellerman.id.au>
To: "Michal Suchánek" <msuchanek@suse.de>
Cc: Michael Neuling <mikey@neuling.org>,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
Andrew Donnellan <andrew.donnellan@au1.ibm.com>,
Arnd Bergmann <arnd@arndb.de>,
David Hildenbrand <david@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Diana Craciun <diana.craciun@nxp.com>,
Paul Mackerras <paulus@samba.org>, Joel Stanley <joel@jms.id.au>,
Allison Randal <allison@lohutok.net>,
Breno Leitao <leitao@debian.org>,
Firoz Khan <firoz.khan@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
linuxppc-dev@lists.ozlabs.org,
Andrew Morton <akpm@linux-foundation.org>,
Hari Bathini <hbathini@linux.ibm.com>,
Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v7 5/6] powerpc/64: Make COMPAT user-selectable disabled on littleendian by default.
Date: Wed, 18 Sep 2019 15:36:24 +1000 [thread overview]
Message-ID: <87k1a6w4h3.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20190914122202.307707c0@naga>
Michal Suchánek <msuchanek@suse.de> writes:
> On Tue, 03 Sep 2019 10:00:57 +1000
> Michael Ellerman <mpe@ellerman.id.au> wrote:
>> Michal Suchánek <msuchanek@suse.de> writes:
>> > On Mon, 02 Sep 2019 12:03:12 +1000
>> > Michael Ellerman <mpe@ellerman.id.au> wrote:
>> >
>> >> Michal Suchanek <msuchanek@suse.de> writes:
>> >> > On bigendian ppc64 it is common to have 32bit legacy binaries but much
>> >> > less so on littleendian.
>> >>
>> >> I think the toolchain people will tell you that there is no 32-bit
>> >> little endian ABI defined at all, if anything works it's by accident.
>> >
>> > I have seen a piece of software that workarounds code issues on 64bit
>> > by always compiling 32bit code. So it does work in some way.
>>
>> What software is that?
>
> The only one I have seen is stockfish (v9)
OK, not sure how many people are testing that on powerpc :)
>> > Also it has been pointed out that you can still switch to BE even with
>> > the 'fast-switch' removed.
>>
>> Yes we have a proper syscall for endian switching, sys_switch_endian(),
>> which is definitely supported.
>>
>> But that *only* switches the endian-ness of the process, it does nothing
>> to the syscall layer. So any process that switches to the other endian
>> must endian flip syscall arguments (that aren't in registers), or flip
>> back to the native endian before calling syscalls.
>
> In other words just installing a chroot of binaries built for the other
> endian won't work. You need something like qemu to do the syscall
> translation or run full VM with a kernel that has the swapped endian
> syscall ABI.
Yes that's right.
cheers
next prev parent reply other threads:[~2019-09-18 5:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 21:03 [PATCH v7 0/6] Disable compat cruft on ppc64le v7 Michal Suchanek
2019-08-30 21:03 ` [PATCH v7 1/6] powerpc: Add back __ARCH_WANT_SYS_LLSEEK macro Michal Suchanek
2019-08-30 21:03 ` [PATCH v7 2/6] powerpc: move common register copy functions from signal_32.c to signal.c Michal Suchanek
2019-08-30 21:03 ` [PATCH v7 3/6] powerpc/perf: consolidate read_user_stack_32 Michal Suchanek
2019-09-02 3:53 ` Michael Ellerman
2019-09-02 4:01 ` Michael Ellerman
2019-09-02 8:26 ` Michal Suchánek
2019-09-02 23:45 ` Michael Ellerman
2019-08-30 21:03 ` [PATCH v7 4/6] powerpc/64: make buildable without CONFIG_COMPAT Michal Suchanek
2019-08-31 6:43 ` Christophe Leroy
2019-08-31 13:02 ` Michal Suchánek
2019-08-30 21:03 ` [PATCH v7 5/6] powerpc/64: Make COMPAT user-selectable disabled on littleendian by default Michal Suchanek
2019-09-02 2:03 ` Michael Ellerman
2019-09-02 9:42 ` Michal Suchánek
2019-09-03 0:00 ` Michael Ellerman
2019-09-14 10:22 ` Michal Suchánek
2019-09-18 5:36 ` Michael Ellerman [this message]
2019-09-02 13:00 ` Segher Boessenkool
2019-09-02 23:53 ` Michael Ellerman
2019-09-03 5:21 ` Christophe Leroy
2019-08-30 21:03 ` [PATCH v7 6/6] powerpc/perf: split callchain.c by bitness Michal Suchanek
2019-08-31 18:51 ` Michal Suchánek
2019-08-31 6:41 ` [PATCH v7 0/6] Disable compat cruft on ppc64le v7 Christophe Leroy
2019-08-31 18:03 ` Michal Suchánek
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