Hi, In addition to the below Link discussion
Date: 16 Jul 2009 http://www.mail-archive.com/[email protected]/msg07506.html patch is not yet committed to LTP CVs. as per test case Description /*****************************************************/ * Implementation performs mapping operations over whole pages. * Thus, while the argument len * need not meet a size or alignment constraint, * the implementation shall include, in any mapping * operation, any partial page specified by the range [pa,pa+len). * The system shall always zero-fill any partial page at the end of an object. * Further, the system shall never write out any modified portions of * the last page of an object which are beyond its end. * * Test step: * 1. Create a process, in this process: a. map a file with size of 1/2 * page_size, * set len = 1/2 * page_size * b. Read the partial page beyond the object size. * Make sure the partial page is zero-filled; * c. Modify a byte in the partial page, then un-map the and close the * file descriptor. * 2. Wait for the child proces to exit, then * Map the file again, * read the byte from the position modified at step 1-c and check. */ /****************************************************/ please note the below discussion http://bugs.gentoo.org/197191 Ref: http://www.opengroup.org/onlinepubs/009695399/functions/mmap.html fan he, please make sure who is going to do this is it coming from kernel or glibc? Best regards Naresh Kamboju >On Mon, 2009-07-20 at 00:46 -0700, Garrett Cooper wrote: > On Sun, Jul 19, 2009 at 10:54 PM, Michal > Simek<[email protected]> wrote: > > Hi, > >> On Sat, 2009-07-18 at 12:28 -0700, Garrett Cooper wrote: > >> > >>> On Thu, Jul 16, 2009 at 11:37 PM, hefan<[email protected]> wrote: > >>> > >>>> hi, > >>>> > >>>> *[Patch 1/1] Patch for fixing the failed testcase openposix_mmap_11_4 > >>>> > >>>> -modified the file > >>>> *testcases/open_posix_testsuite/conformance/interfaces/mmap/11-4.c > > > > First of all - this is really small explanation why you are fixing this > > issue. After some month > > none will know why you did this change. > > > > > >>>> > >>>> Signed-off-by: fredrick he <[email protected]> > >>>> > >>>> --- > >>>> ltp.orig/testcases/open_posix_testsuite/conformance/interfaces/mmap/11-4.c > >>>> 2009-07-17 11:53:36.000000000 +0800 > >>>> +++ > >>>> ltp/testcases/open_posix_testsuite/conformance/interfaces/mmap/11-4.c > >>>> 2009-07-17 11:57:09.000000000 +0800 > >>>> @@ -130,7 +130,9 @@ int main() > >>>> flag = MAP_SHARED; > >>>> off = 0; > >>>> pa = mmap(addr, len, prot, flag, fd_2, off); > >>>> - pa_2 = mmap(addr, len, prot, flag, fd_2, off); > >>>> + addr = pa; > >>>> + memset(addr,0,len*2); > >>>> + pa_2 = mmap(addr, len, prot, flag|MAP_FIXED, fd_2, off); > >>>> if (pa_2 == MAP_FAILED) > >>>> { > >>>> printf("Test FAIL: " TNAME " Error at 2nd mmap(): %s\n", > >>>> > >>> Hi Fan, > >>> Some questions / observations: > >>> > >>> 1. Yes, the testcases does fail on my machine today. > >>> 2. Yes, doing what you say above does work (at least the testcase passes). > >>> 3. Are you positive that your set of steps above in fact don't > >>> invalidate the purpose of the testcase, by accident, in particular the > >>> memset call? I ask because of the following statement in the mmap > >>> manpage: > >>> > >>> If addr is NULL, then the kernel chooses the address at which to > >>> create > >>> the mapping; this is the most portable method of creating a new > >>> map- > >>> ping. If addr is not NULL, then the kernel takes it as a hint > >>> about > >>> where to place the mapping; on Linux, the mapping will be created > >>> at a > >>> nearby page boundary. The address of the new mapping is > >>> returned as > >>> the result of the call. > >>> > >>> What you're in effect doing is changing the 2nd mmap call from an > >>> arbitrary address to a set virtual address at 0x0. Is that indeed > >>> correct? > >>> > >> in this case, the situation is like this, we create a new file about 512 > >> bytes and mmap it into the mem, then we modify one byte besides the 512 > >> bytes address, and munmap it. and in the father process remmap it back > >> to check whether the one more byte is write back to the files. > > Ok. > > >> i have checked that when finished munmap and close the file in the child > >> process, the file didn't contain the 513th byte, the size of this file > >> is right 512 bytes.but in this case after the second mmap finished, the > >> 513th byte does appear again. it's a conflict. > >> > >> in my opinion this is because of the compiler or some optimizations. so > >> i think the memory should to be memset before mmap and it does work. > > No, according to the manpage it'll map to the boundary of the closest > page size, in my opinion what might be occurring is the system is > either overallocating or underallocating, depending on the system page > size and what's being passed in for a length. What the page size is, > I'd surely like to know... here in my environment the page size is 1024 got by using sysconf(_SC_PAGE_SIZE) in this testcase > > > If is the problem with compiler/optimization means that tests is ok - > > the problem is with your > > compiler not with code. > > This need more investigations to find out where the problem is. > > I wouldn't necessarily say that. Based on Frederick's explanation, it > sounds like someone fed in an inappropriate bound, or didn't NUL > terminate the boundary and just went off into uncharted territory > without first checking where they were `on the map'. > > Based on my experience and recollection, this is legitimate in C > behavior as long as you're within the applications memory limits -- > you've just entered the twilight zone between realities, where you're > beyond your address space, but not beyond the point of no return > (EACCES), where the kernel *should* terminate your userland app. >yeah, that's the keypoint. but it doesn't terminate our userland app. >i mean that here is a mistake on the way this testcase check the result. >ideally, the mmap should only use half a page and it has no >resposibility on the rest of the page, so we shouldn't judge the mmap by >the rest of the page which is none of business with mmap. >so if we suppose that the mmap does affect the rest of the page( is it >the purpose to design this testcase ? ), we should make sure that this >area has been clear before we mmap the file into this area. that's why i >use memset and flag MAP_FIXED. > > Whether or not that was the intention of the POSIX folks, is another > question indeed, as the documentation states (in the header of the .c > file): > > * Implementation performs mapping operations over whole pages. > * Thus, while the argument len > * need not meet a size or alignment constraint, > * the implementation shall include, in any mapping > * operation, any partial page specified by the range [pa,pa+len). > * The system shall always zero-fill any partial page at the end of an object. > * Further, the system shall never write out any modified portions of > * the last page of an object which are beyond its end. > > So unless they're completely misinterpreting the meaning of mmap, it > sounds like there's a bug in a number of `POSIX-compliant' operating > systems that needs to be resolved (FreeBSD and Linux included). > > However, before jumping to conclusions, I think that it's prudent to > narrow down where and why this is occurring... > > >>> 4. Have you talked to the openposix test suite folks about this yet? > >>> > >> no,i have no idea on how to talk to the openposix and i do want to talk > >> to them :) can you give me some suggestions about this? thx~ > > The project administrators are available, as noted, here: > > https://sourceforge.net/project/memberlist.php?group_id=64592 > > Thanks, > -Garrett ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Ltp-list mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/ltp-list
