From: Richard Henderson <richard.henderson@linaro.org>
To: Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com>,
dgibson@redhat.com, riku.voipio@iki.fi, laurent@vivier.eu
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] linux-user: ppc64: don't use volatile register during safe_syscall
Date: Thu, 26 Jul 2018 10:26:53 -0700 [thread overview]
Message-ID: <b707ccc3-47bb-569f-3df0-aeb91e90b820@linaro.org> (raw)
In-Reply-To: <153258768962.6738.11319866502689416568.stgit@dhcp-9-109-246-16>
On 07/25/2018 11:48 PM, Shivaprasad G Bhat wrote:
> Reference:
> https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG
This document is for _CALL_ELF < 2. For ppc64le, the document is at
https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf
In both cases, it appears that we can (ab)use SP+16 to save
the value of r14 across the syscall. This slot would normally
be used for saving our own return address (LR), but we have no
need to save that value because it *is* preserved across the syscall.
r~
next prev parent reply other threads:[~2018-07-26 17:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-26 6:48 [Qemu-devel] [PATCH] linux-user: ppc64: don't use volatile register during safe_syscall Shivaprasad G Bhat
2018-07-26 7:48 ` Laurent Vivier
2018-07-26 17:15 ` Richard Henderson
2018-07-26 17:39 ` Laurent Vivier
2018-07-27 4:47 ` Richard Henderson
2018-07-27 8:01 ` Laurent Vivier
2018-07-26 17:26 ` Richard Henderson [this message]
2018-07-27 6:42 ` Shivaprasad G Bhat
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