From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Subject: Re: [PATCH v3 18/21] vmcore: check if vmcore objects satify mmap()'s page-size boundary requirement Date: Wed, 20 Mar 2013 23:29:05 -0700 > HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> writes: >> >> Do you mean for each range represented by each PT_LOAD entry, say: >> >> [p_paddr, p_paddr + p_memsz] >> >> extend it as: >> >> [rounddown(p_paddr, PAGE_SIZE), roundup(p_paddr + p_memsz, PAGE_SIZE)]. >> >> not only objects in vmcore_list, but also updating p_paddr and p_memsz >> members themselves of each PT_LOAD entry? In other words, there's no >> new holes not referenced by any PT_LOAD entry since the regions >> referenced by some PT_LOAD entry, themselves are extended. > > No. p_paddr and p_memsz as exported should remain the same. > I am suggesting that we change p_offset. > > I am suggesting to include the data in the file as if we had changed > p_paddr and p_memsz. > >> Then, the vmcores seen from read and mmap methods are coincide in the >> direction of including both ranges >> >> [rounddown(p_paddr, PAGE_SIZE), p_paddr] >> >> and >> >> [p_paddr + p_memsz, roundup(p_paddr + p_memsz, PAGE_SIZE)] >> >> are included in both vmcores seen from read and mmap methods, although >> they are originally not dump target memory, which you are not >> problematic for ease of implementation. >> >> Is there difference here from you understanding? > > Preserving the actual PT_LOAD segments p_paddr and p_memsz values is > important. p_offset we can change as much as we want. Which means there > can be logical holes in the file between PT_LOAD segments, where we put > the extra data needed to keep everything page aligned. > So, I have to make the same question again. Is it OK if two vmcores are different? How do you intend the ``extra data'' to be deal with? I mean mmap() has to export part of old memory as the ``extra data''. If you think OK, I'll fill the ``extra data'' with 0 in case of read method. If not OK, I'll fill with the corresponding part of old memory. Thanks. HATAYAMA, Daisuke
