Date: Mon, 12 Dec 2016 20:48:40 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: cortex-m support? On Mon, Dec 12, 2016 at 06:29:13PM -0600, Rob Landley wrote: > > > On 12/08/2016 03:01 PM, Rich Felker wrote: > > On Thu, Dec 08, 2016 at 01:10:11PM -0600, Rob Landley wrote: > >> On 12/07/2016 07:16 PM, Rich Felker wrote: > >>> On Wed, Dec 07, 2016 at 06:55:56PM -0600, Rob Landley wrote: > >>>> Not sure where you get the relevant gcc patch... > >>> > >>> I have links to the repos somewhere; the problem is that they're > >>> forked from a fairly old gcc version (although not nearly as bad as > >>> sh-fdpic; I think it's 4.8 or so) > >> > >> https://github.com/mickael-guene/gcc has a 5.2 branch and "master" > >> updated 20 hours ago, although I'm not sure how much of master updating > >> is an automatic tracking branch and how much is the account owner > >> updating things. > > > > Excellent! That's new since I last communicated with him. > > In theory, what you do is follow the instructions in: > > https://github.com/mickael-guene/fdpic_manifest OK, I'll take a look. > Which uses repo to download the github repositories, and then has a > build.sh. In practice, I'm not sure what branches that uses to build > said toolchain. > > However, this would give you a uClibc-based cortex-m-fdpic toolchain you > could then swap musl into. Just diffing the tree and dropping the patch in musl-cross-make is going to be a much faster path to getting something reproducible and testable. > It also has a lsit of kernel patches that > theoretically work against vanilla, but you don't have a board for that. :) Can you get me (instructions for building) a kernel that boots on qemu but has the fdpic-support patches for arm? The main patch hunk that'll be needed is the part in signal handler invocation that uses the function pointer as either a code address or a function descriptor. BTW, upstreaming this patch without an old pending kernel change I still need to submit will introduce a CVE-worthy vulnerability on all ARM systems. :-) > I did poke you over the summer about running cortex-m binflt binaries > under qemu application emulation (works fine). I dunno if it supports > the fdpic loader or not, building this toolchain to find out. If not, > it's got an emulator there too but I haven't poked at it yet... It can load fdpic as normal ELF just fine, but signal handlers will crash if it doesn't treat the application-passed function pointer as a function descriptor. Fixing this should just be a several-line patch to qemu if nobody already did it. Rich
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