Date: Mon, 23 Jul 2001 16:16:00 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Weiguang SHI <weiguang_shi@hotmail.com> Cc: freebsd-hackers@FreeBSD.org Subject: RE: jmp after setting PE? Message-ID: <XFMail.010723161600.jhb@FreeBSD.org> In-Reply-To: <F94Fsxf4yp8ARf3sllN00002f3d@hotmail.com>
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On 23-Jul-01 Weiguang SHI wrote: > Thanks. > I think I've found it in btx.s: > > 213 mov %eax,%cr0 # > 214 ljmp $SEL_SCODE,$init.8 # To 32-bit code > 215 .code32 > 216 init.8: xorl %ecx,%ecx # Zero > > And there IS this "ljmp". Yes. > Well, this BTX thing is amazing: all this effort, (btxld, run-time > library crt0.o, loader, etc.) seems to just to provide a 32-bit > protected and possibly paging-enabled environment to start the > kernel/loader(and to confuse a new-comer like me.) What are the > other gains? Where can I found more info about this BTX before going > through the ultimate source code? (I've search the mailing-lists.) That's its purpose, to provide a mini-kenrel for the loader so we can write the loader in C and not assembly. (gcc doesn't do well with generating code for real mode). -- John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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