Date: Thu, 11 Jan 2018 12:07:24 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r327816 - in head/sys: amd64/amd64 i386/i386 Message-ID: <201801111207.w0BC7O9p094919@repo.freebsd.org>
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Author: kib Date: Thu Jan 11 12:07:24 2018 New Revision: 327816 URL: https://svnweb.freebsd.org/changeset/base/327816 Log: Update comment explaining the check, to reality. Discussed with: jhb Sponsored by: The FreeBSD Foundation MFC after: 3 days Modified: head/sys/amd64/amd64/support.S head/sys/i386/i386/support.s Modified: head/sys/amd64/amd64/support.S ============================================================================== --- head/sys/amd64/amd64/support.S Thu Jan 11 09:42:24 2018 (r327815) +++ head/sys/amd64/amd64/support.S Thu Jan 11 12:07:24 2018 (r327816) @@ -249,12 +249,10 @@ ENTRY(copyout) jz done_copyout /* - * Check explicitly for non-user addresses. If 486 write protection - * is being used, this check is essential because we are in kernel - * mode so the h/w does not provide any protection against writing - * kernel addresses. + * Check explicitly for non-user addresses. This check is essential + * because it prevents usermode from writing into kernel. We do not + * verify that user did not specified a rogue address anywhere else. */ - /* * First, prevent address wrapping. */ Modified: head/sys/i386/i386/support.s ============================================================================== --- head/sys/i386/i386/support.s Thu Jan 11 09:42:24 2018 (r327815) +++ head/sys/i386/i386/support.s Thu Jan 11 12:07:24 2018 (r327816) @@ -291,12 +291,10 @@ ENTRY(copyout) jz done_copyout /* - * Check explicitly for non-user addresses. If 486 write protection - * is being used, this check is essential because we are in kernel - * mode so the h/w does not provide any protection against writing - * kernel addresses. + * Check explicitly for non-user addresses. This check is essential + * because it prevents usermode from writing into kernel. We do not + * verify that user did not specified a rogue address anywhere else. */ - /* * First, prevent address wrapping. */
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