Date: Fri, 13 Dec 1996 23:31:06 +1100 From: Bruce Evans <bde@zeta.org.au> To: gena@NetVision.net.il, hackers@FreeBSD.ORG Subject: Re: mmap() with offset Message-ID: <199612131231.XAA32237@godzilla.zeta.org.au>
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>For some reason mmap(...) call with offset other then 0 fails with invalid >argument error. > >The code looks like: > msg->msg_body = (char *)mmap(NULL, (size_t)mlen, PROT_READ, 0,mfd, > (off_t)mofft)) == (char *)-1); > >You can reproduce it by running cmp with skip arguments (cmp file1 file2 10 10). >Any ideas? mmap() currently requires the offset to be a multiple of PAGE_SIZE (4096). This is a bug according to the man page. Similar restrictions on other mmap args were removed in February 1996. The args get rounded up or down to a multiple of PAGE_SIZE as appropriate. Bruce
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