From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Paul Burton <paul.burton@mips.com>
Cc: Carlos O'Donell <codonell@redhat.com>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
heiko carstens <heiko.carstens@de.ibm.com>,
gor <gor@linux.ibm.com>, schwidefsky <schwidefsky@de.ibm.com>,
"Russell King, ARM Linux" <linux@armlinux.org.uk>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>, carlos <carlos@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
Joseph Myers <joseph@codesourcery.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
libc-alpha <libc-alpha@sourceware.org>,
Thomas Gleixner <tglx@linutronix.de>, Ben Maurer <bmaurer@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Rich Felker <dalias@libc.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: Re: [PATCH 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v7)
Date: Wed, 24 Apr 2019 11:05:42 -0400 (EDT) [thread overview]
Message-ID: <1103046939.521.1556118342613.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <1031613720.1496.1555613900993.JavaMail.zimbra@efficios.com>
----- On Apr 18, 2019, at 2:58 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> ----- On Apr 4, 2019, at 5:41 PM, Paul Burton paul.burton@mips.com wrote:
> [...]
>
>>> 2a. A uncommon TRAP hopefully with some immediate data encoded (maybe uncommon)
>>
>> Our break instruction has a 19b immediate in nanoMIPS (20b for microMIPS
>> & classic MIPS) so that could be something like:
>>
>> break 0x7273 # ASCII 'rs'
>>
>
> Hi Paul,
>
> I like this uncommon break instruction as signature choice.
>
> However, if I try to compile assembler with a break 0x7273 instruction
> with mips64 and mips32 toolchains (gcc version 8.2.0 (Ubuntu
> 8.2.0-1ubuntu2~18.04))
> I get:
>
> /tmp/ccVh9F7T.s: Assembler messages:
> /tmp/ccVh9F7T.s:24: Error: operand 1 out of range `break 0x7273'
>
> It works up to the value 0x3FF, which seems to use the top 10
> code bits:
>
> a: 03ff 0007 break 0x3ff
>
> Would a "break 0x350" be a good choice as well ?
>
> Any idea why 0x7273 is not accepted by my assembler ?
>
> I also tried crafting the assembler with values between 0x3FF and 0x7273
> in the 20 code bits. It seems fine from an objdump perspective:
>
> ".long 0x03FFFC7\n\t"
>
> generates:
>
> 10: 003f ffc7 break 0x3f,0x3ff
>
> What I don't understand is why the instruction generated by my
> toolchain ends with the last 6 bits "000111", whereas the mips32
> instruction set specifies break as ending with "001101" [1].
> What am I missing ?
>
> Also, the nanomips break code [2] has a completely different
> instruction layout. Should we use a different signature when
> compiling for nanomips ? What #ifdef should we use ? Do I
> need a special toolchain to generate nanomips binaries ?
Hi Paul, I'm still waiting for feedback on the MIPS front.
Meanwhile, I plan to use #define RSEQ_SIG 0x0350000d which maps to:
0350000d break 0x350
and use RSEQ_SIG in assembly with:
".word " __rseq_str(RSEQ_SIG) "\n\t"
on big and little endian MIPS, for MIPS32 and MIPS64, based on
code generated with gcc version 8.2.0 (Ubuntu 8.2.0-1ubuntu2~18.04).
Let me know if it needs to be tweaked.
Thanks,
Mathieu
>
> Thanks,
>
> Mathieu
>
> [1]
> http://hades.mech.northwestern.edu/images/1/16/MIPS32_Architecture_Volume_II-A_Instruction_Set.pdf
> [2]
> https://s3-eu-west-1.amazonaws.com/downloads-mips/I7200/I7200+product+launch/MIPS_nanomips32_ISA_TRM_01_01_MD01247.pdf
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2019-04-24 15:05 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190212194253.1951-1-mathieu.desnoyers@efficios.com>
2019-02-12 19:42 ` [PATCH 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v7) Mathieu Desnoyers
2019-03-22 20:09 ` Carlos O'Donell
2019-03-25 15:54 ` Mathieu Desnoyers
2019-03-27 9:16 ` Martin Schwidefsky
2019-03-27 20:01 ` Mathieu Desnoyers
2019-03-27 20:38 ` Carlos O'Donell
2019-03-28 7:49 ` Martin Schwidefsky
2019-03-28 15:42 ` Mathieu Desnoyers
2019-04-02 6:02 ` Michael Ellerman
2019-04-02 7:08 ` Florian Weimer
2019-04-04 20:32 ` Carlos O'Donell
2019-04-05 9:16 ` Florian Weimer
2019-04-05 15:40 ` Carlos O'Donell
2019-04-08 19:20 ` Tulio Magno Quites Machado Filho
2019-04-08 21:45 ` Carlos O'Donell
2019-04-09 4:23 ` Michael Ellerman
2019-04-09 9:29 ` Alan Modra
[not found] ` <871s2bp9f9.fsf@linux.ibm.com>
2019-04-09 14:13 ` Carlos O'Donell
2019-04-09 15:45 ` Mathieu Desnoyers
2019-04-18 15:31 ` Mathieu Desnoyers
2019-04-09 16:33 ` Mathieu Desnoyers
2019-04-04 20:15 ` Carlos O'Donell
2019-04-04 20:50 ` Carlos O'Donell
2019-04-04 21:41 ` Paul Burton
2019-04-09 16:40 ` Mathieu Desnoyers
2019-04-18 18:58 ` Mathieu Desnoyers
2019-04-24 15:05 ` Mathieu Desnoyers [this message]
2019-04-24 23:13 ` Paul Burton
2019-04-25 0:41 ` Maciej W. Rozycki
2019-02-12 19:42 ` [PATCH 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Mathieu Desnoyers
2019-03-22 20:13 ` Carlos O'Donell
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