HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> writes: > From: "Eric W. Biederman" <ebiederm at xmission.com> > Subject: Re: [PATCH v3 17/21] vmcore: check NT_VMCORE_PAD as a mark indicating the end of ELF note buffer > Date: Tue, 19 Mar 2013 14:11:51 -0700 > >> HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> writes: >> >>> Modern kernel marks the end of ELF note buffer with NT_VMCORE_PAD type >>> note in order to make the buffer satisfy mmap()'s page-size boundary >>> requirement. This patch makes finishing reading each buffer if the >>> note type now being read is NT_VMCORE_PAD type. >> >> Ick. Even with a pad header you can mark the end with an empty header, >> and my memory may be deceiving me but I believe an empty header is >> specified by the ELF ABI docs. >> >> Beyond which I don't quite see the point of any of this as all of these >> headers need to be combined into a single note section before being >> presented to user space. > > Though this patch might get unecessary later, I cannot find part > explaining necessity of marking end of ELF segmetns with an empty > header in ELF spec. For example: You are right. It appears to be our own invention and just part of the ABI of taking a crash dump. Something we should sit down and document someday. > Also, it's possible to get size of a whole part of ELF note segments > from p_memsz or p_filesz, and gdb and binutils are reading the note > segments until reaching the size. Agreed. Except in our weird case where we generate the notes on the fly, and generate the NOTE segment header much earlier. Eric
