From mboxrd@z Thu Jan 1 00:00:00 1970 From: n0ano@indstorage.com Date: Thu, 15 Nov 2001 15:33:29 +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 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 */