Date: Mon, 23 Jul 2001 13:18:19 -0400 (EDT) From: Zhihui Zhang <zzhang@cs.binghamton.edu> To: Weiguang SHI <weiguang_shi@hotmail.com> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: using syscalls in a module (stack problem ?) Message-ID: <Pine.SOL.4.21.0107231317380.16158-100000@opal> In-Reply-To: <F155Z2K4xDh9vXsFFsA00002adb@hotmail.com>
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Make sense. But there are other things in the UPAGES. -Zhihui On Mon, 23 Jul 2001, Weiguang SHI wrote: > I guess this is it (/usr/src/sys/i386/i386/locore.s): > > 348 /* now running relocated at KERNBASE where the system is linked to > run */ > 349 begin: > 350 /* set up bootstrap stack */ > 351 movl _proc0paddr,%esp /* location of in-kernel > pages */ > 352 addl $UPAGES*PAGE_SIZE,%esp /* bootstrap stack end > location */ > > where UPAGES is defined as 2 in > /usr/src/sys/compile/MYKERNEL/machine/param.h > > 101 #define UPAGES 2 /* pages of u-area */ > > Regards, > Weiguang > > >From: Zhihui Zhang <zzhang@cs.binghamton.edu> > >To: msmith@freebsd.org, "Eugene L. Vorokov" <vel@bugz.infotecs.ru> > >CC: freebsd-hackers@FreeBSD.ORG > >Subject: Re: using syscalls in a module (stack problem ?) > >Date: Mon, 23 Jul 2001 12:07:47 -0400 (EDT) > > > > > >Just out of curiosity, Linux's kernel stack is one page. Where in the > >kernel source code that says that we can have two pages instead of one > >page kernel stack? > > > >-Zhihui > > > > > >On Mon, 23 Jul 2001, Eugene L. Vorokov wrote: > > > > > > > I call this function with (curproc, PATH_MAX+1), and everything is > >fine > > > > > when I have just a few local variables defined in the caller (it all > > > > > works on MOD_LOAD only). However, if I have 2 buffers, 4096 bytes > >each, > > > > > as local variables and then try to allocate userspace memory the > >same > > > > > way, kernel crashes - sometimes inside mmap(), sometimes a bit > >later. > > > > > > > > > > Why could this happen ? Is it related to possible stack overflow ? > > > > > > > > Yes. The kernel stack is only two pages; you absolutely must not use > > > > large local variables in the kernel. > > > > > > I see. But I still can define them using "static", right ? > > > > > > Regards, > > > Eugene > > > > > > > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > > > with "unsubscribe freebsd-hackers" in the body of the message > > > > > > > > >To Unsubscribe: send mail to majordomo@FreeBSD.org > >with "unsubscribe freebsd-hackers" in the body of the message > > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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