Messages in this thread | | | From | "Roy Lee" <> | Subject | RE: [PATCH] give elf_check_arch() a chance for checking endian mismatch | Date | Sun, 23 Mar 2008 17:41:11 +0800 |
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> -----Original Message----- > From: Valdis.Kletnieks@vt.edu [mailto:Valdis.Kletnieks@vt.edu] > Sent: Sunday, March 23, 2008 1:06 PM > To: Roy Lee > Cc: linux-kernel@vger.kernel.org > Subject: Re: [PATCH] give elf_check_arch() a chance for checking endian > mismatch > > On Thu, 20 Mar 2008 03:03:30 +0800, Roy Lee said: > > (Sorry for late reply, catching up finally) > > > I'd like to warn for endianess mismatch, or unsupported feature( > > hardware float point support) when loading an ELF file. > > > - if (loc->elf_ex.e_type != ET_EXEC && loc->elf_ex.e_type != > ET_DYN) > > - goto out; > > if (!elf_check_arch(&loc->elf_ex)) > > goto out; > > + if (loc->elf_ex.e_type != ET_EXEC && loc->elf_ex.e_type != > ET_DYN) > > + goto out; > > It would seem to me that if it isn't an ET_EXEC or ET_DYN, the question of > whether it passes elf_check_arch() would be rather moot? In any case, you > don't get to actually *warn* for it, because you end up with a 'goto out' > in either case, and elf_check_arch is a pretty small macro on most archs. >
Endianness mismatch is not uncommon for bi-endian processors if their user didn't carefully choose their tool-chain or missing flags during compilation. It makes sense to add some logics for checking and issuing warning when this happens.
Without changing the order of elf_check_arch(), even if the loaded file is an ET_EXEC or ET_DYN, wrong endianness result in misinterpretation of 'elf_ex.e_type', and end up skipping elf_check_arch() in which we implement endianness checking as well as other ABI checking logics.
Changing the order of elf_check_arch() should not break current logics on most archs. If the loaded file isn't an ET_EXEC, ET_DYN or even not an ELF at all, it has great chance to return false in the elf_check_arch() since the loaded
file will not satisfy their checking logic. Even if that's not the case, the postponed checking of ET_EXEC and ET_DYN will still redirect the flow to 'goto out'.
> Also, if you change the order there, do you want to also change the order > in load_elf_interp(), where the equivalent test is done? >
Yes, I forgot to add them :)
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