Date: Sun, 28 May 2023 14:07:48 GMT From: Dmitry Chagin <dchagin@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 037b60fb0fbc - main - linux(4): Preserve %rcx (return address) like a Linux do Message-ID: <202305281407.34SE7mSc067238@gitrepo.freebsd.org>
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The branch main has been updated by dchagin: URL: https://cgit.FreeBSD.org/src/commit/?id=037b60fb0fbcb2dd6b6cbb632b05a2939ff4ff29 commit 037b60fb0fbcb2dd6b6cbb632b05a2939ff4ff29 Author: Dmitry Chagin <dchagin@FreeBSD.org> AuthorDate: 2023-05-28 14:06:47 +0000 Commit: Dmitry Chagin <dchagin@FreeBSD.org> CommitDate: 2023-05-28 14:06:47 +0000 linux(4): Preserve %rcx (return address) like a Linux do Perhaps, this does not makes much sense as destroyng %rcx declared by the x86_64 Linux syscall ABI. However,: a) if we get a signal while we are in the kernel, we should restore tf_rcx when preparing machine context for signal handlers. b) the Linux world is strange, someone can depend on %rcx value after syscall, something like go. Differential Revision: https://reviews.freebsd.org/D40155 MFC after: 1 month --- sys/amd64/linux/linux_sysvec.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sys/amd64/linux/linux_sysvec.c b/sys/amd64/linux/linux_sysvec.c index 422cfbe7c5ba..05afcdfcd045 100644 --- a/sys/amd64/linux/linux_sysvec.c +++ b/sys/amd64/linux/linux_sysvec.c @@ -169,6 +169,8 @@ linux_fetch_syscall_args(struct thread *td) /* Restore r10 earlier to avoid doing this multiply times. */ frame->tf_r10 = frame->tf_rcx; + /* Restore %rcx for machine context. */ + frame->tf_rcx = frame->tf_rip; td->td_retval[0] = 0; return (0);
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