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| From: | Richard Henderson |
| 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 |
| User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
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~
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