Date: Wed, 24 Apr 2002 17:01:00 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Kenneth Culver <culverk@alpha.yumyumyum.org> Cc: FreeBSD-CURRENT List <freebsd-current@FreeBSD.ORG>, freebsd-hackers@FreeBSD.ORG, Brandon S Allbery KF8NH <allbery@ece.cmu.edu>, Andrew Gallatin <gallatin@cs.duke.edu> Subject: Re: implementing linux mmap2 syscall Message-ID: <XFMail.20020424170100.jhb@FreeBSD.org> In-Reply-To: <20020424161828.R38664-100000@alpha.yumyumyum.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On 24-Apr-2002 Kenneth Culver wrote: >> >> Brandon S Allbery KF8NH writes: >> > On Wed, 2002-04-24 at 10:41, Andrew Gallatin wrote: >> > > Maybe the argument isn't where you expect it to be, but is there. >> > > Can you make a test program which calls mmap2 with its 6th arg as >> > > something unique like 0xdeadbeef? Then print out (in hex :) the >> > > trapframe >> > > from the linux prepsyscall routine & see if you can find the deadbeef. >> > >> > My recollection is that beyond 5 arguments, a pointer to the remaining >> > ones is passed. (But my recollection may be wrong and I don't wish to >> > subject myself to the source cesspool at the moment....) >> > >> >> I think that's how it used to work. Apparently, they've changed it >> recently and they now pass 6 args in registers. Eg, in the linux >> kernel sources, old_mmap() fetches its args via copy_from_user(), >> whereas the newer sys_mmap2() doesn't. >> >> Drew >> > Yep, according to the docs and source code I looked at in the linux > kernel, the sixth arg is in the ebp register. I've looked all over the > FreeBSD kernel and the linux emulator for the place that actually sets > these, and unfortunately, due to my lack of asm coding knowledge, I can't > find anything. libc sets it before it enters the kernel. Then on kernel entry we save ebp in the trapframe. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?XFMail.20020424170100.jhb>