From mboxrd@z Thu Jan 1 00:00:00 1970 From: miyoshi@hpc.bs1.fc.nec.co.jp Date: Fri, 16 Nov 2001 06:17:09 +0000 Subject: Re: [Linux-ia64] Pagesize is different between IA32 and IA64 Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Hi, Thank you for your patch! Hideki tested it and it seems to work fine. BTW, how about the following optimization? IA32-glibc's calloc can call sbrk with 4K boundary. When we do 4k sbrk, we do not need fully zero-ing up to 16K boundary, but just up to obrk. (Think about four sbrk(-0x1000) case) Thanks. +asmlinkage unsigned long +sys32_brk(unsigned int brk) +{ + unsigned long ret, obrk; + struct mm_struct *mm = current->mm; + + obrk = mm->brk; + ret = sys_brk(brk); + if (ret < obrk){ + unsigned long to; + to = (obrk < PAGE_ALIGN(ret) ? obrk : PAGE_ALIGN(ret)); + clear_user(ret, to-ret); + } + return(ret); +} > David- > > OK, here's the patch to fix this. I guess the only issue is that we > have to have Yet Another IA32 System call shim but other than that > the change is pretty minor. > > PS: Hideki, please note that this is a different, slightly better > patch than the one I sent you last night. You should use this one. > > On Tue, Nov 13, 2001 at 11:43:55PM -0700, Dugger's wrote: > > Never mind, I found the `calloc' code and I'm very depressed because it > > does indeed assume that `brk' zeros out newly allocated memory which is > > obviously going to create problems if `calloc' thinks the kernel has 4K > > pages when it really has bigger ones. > > > > Unfortunately, this means I'll have to make an IA32 specific `brk' call that > > zero's out the last part of the last page currently allocated to a process. > > Oh well, patch to follow later. > > -- > > Don Dugger > > n0ano@indstorage.com > > ----- Original Message ----- > > From: "Dugger's" > > To: ; > > Cc: "Hideki Yamamoto" ; > > > > Sent: Tuesday, November 13, 2001 11:16 PM > > Subject: Re: [Linux-ia64] Pagesize is different between IA32 and IA64 > > > > > > > I'm a little confused. From Hideki's test program the problem actually > > > seems > > > to be using `sbrk' to return memory and then allocating memory again. The > > > second > > > time the re-allocated memory is not zeroed, e.g.: > > > > > > p = sbrk(4096); > > > q = sbrk(-4096); > > > r = sbrk(4096); > > > > > > and the memory pointed to by `r' is not zeroed. I just got through > > reading > > > the > > > man page for `brk' and `sbrk' and neither one specifies that newly > > allocated > > > memory is zeroed and therefore I interpret this issue as undefined > > behavior. > > > Any program that depends upon the contents of newly allocated memory is > > > broken. In fact, if you compile the test program, `d.c', for IA64 and run > > > it it > > > fails. Also, if you compile the test program for IA32 and use 1K > > allocation > > > blocks > > > the program fails on an IA32 machine also. > > > > > > Someone correct me if I'm wrong about this. > > > > > > PS: I know that `calloc' is defined to zero out the allocated memory but > > > from > > > what I can tell it does this by explicitly calling `memset'. I'm trying > > to > > > verify this > > > but I haven't found the `calloc' code in the `glibc' tree yet. (The > > `glibc' > > > tree always > > > confuses me, if anyone can tell me exactly where to find the `calloc' code > > > I'd > > > appreciate it :-) > > > -- > > > Don Dugger > > > n0ano@indstorage.com > > > ----- Original Message ----- > > > From: "David Mosberger" > > > To: > > > Cc: "Hideki Yamamoto" ; > > > > > > Sent: Monday, November 12, 2001 4:58 PM > > > Subject: Re: [Linux-ia64] Pagesize is different between IA32 and IA64 > > > > > > > > > > But I think the page size problem with brk() is real and can be fixed > > > > quite easily. If I understood correctly, the problem is that doing > > > > something along the lines of: > > > > > > > > x = ALIGN_TO_4K(sbrk(8192)); > > > > memset(x, 0xff, 4096); > > > > brk(x); > > > > brk(x+4096); > > > > > > > > might preserve the contents of the page at X on under the ia32 > > > > subsystem of ia64 when in fact it should be cleared to zero. > > > > > > > > Would you be able/interested into looking into this? > > > > > > > > --david > > > > > > > > > > > > > _______________________________________________ > > Linux-IA64 mailing list > > Linux-IA64@linuxia64.org > > http://lists.linuxia64.org/lists/listinfo/linux-ia64 > > -- > Don Dugger > "Censeo Toto nos in Kansa esse decisse." - D. Gale > n0ano@indstorage.com > Ph: 303/652-0870x117 > > diff -aur kernel-bigsur-ref/arch/ia64/ia32/ia32_entry.S kernel-bigsur/arch/ia64/ia32/ia32_entry.S > --- kernel-bigsur-ref/arch/ia64/ia32/ia32_entry.S Tue Sep 25 19:40:29 2001 > +++ kernel-bigsur/arch/ia64/ia32/ia32_entry.S Wed Nov 14 21:07:28 2001 > @@ -209,7 +209,7 @@ > data8 sys32_pipe > data8 sys32_times > data8 sys32_ni_syscall /* old prof syscall holder */ > - data8 sys_brk /* 45 */ > + data8 sys32_brk /* 45 */ > data8 sys_setgid /* 16-bit version */ > data8 sys_getgid /* 16-bit version */ > data8 sys32_signal > diff -aur kernel-bigsur-ref/arch/ia64/ia32/sys_ia32.c kernel-bigsur/arch/ia64/ia32/sys_ia32.c > --- kernel-bigsur-ref/arch/ia64/ia32/sys_ia32.c Tue Sep 25 19:40:29 2001 > +++ kernel-bigsur/arch/ia64/ia32/sys_ia32.c Thu Nov 15 07:29:24 2001 > @@ -68,6 +68,7 @@ > > /* forward declaration: */ > asmlinkage long sys32_mprotect (unsigned int, unsigned int, int); > +asmlinkage unsigned long sys_brk(unsigned long); > > static int > nargs (unsigned int arg, char **ap) > @@ -2123,6 +2124,7 @@ > default: > return -EINVAL; > } > + return -EINVAL; > } > > /* > @@ -3376,6 +3378,19 @@ > ret = PER_LINUX; > return ret; > } > + > +asmlinkage unsigned long > +sys32_brk(unsigned int brk) > +{ > + unsigned long ret, obrk; > + struct mm_struct *mm = current->mm; > + > + obrk = mm->brk; > + ret = sys_brk(brk); > + if (ret < obrk) > + clear_user(ret, PAGE_ALIGN(ret) - ret); > + return(ret); > +} > > #ifdef NOTYET /* UNTESTED FOR IA64 FROM HERE DOWN */ > > > _______________________________________________ > Linux-IA64 mailing list > Linux-IA64@linuxia64.org > http://lists.linuxia64.org/lists/listinfo/linux-ia64 >