Date: Thu, 20 Feb 2014 22:50:35 -0500 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: How can I assess compatibility of a statically linked binary? On Thu, Feb 20, 2014 at 06:20:51PM +0000, Oliver Schneider wrote: > > Musl is built on the Linux syscall layer. Linux kernel >=2.6.39 is > > necessary for POSIX conformant behaviour, older kernels will work > > with varying degrees of non-conformance, 2.4 kernels will only work > > for simple single-threaded applications. > > > I had mistakenly expected it under > > <http://wiki.musl-libc.org/wiki/Compatibility> > > when it was of course to be found under: > > <http://wiki.musl-libc.org/wiki/Supported_Platforms> This will also be documented more formally in the official manual to be released in conjunction with musl 1.0. For this we should clarify what version is really needed. I don't think 2.6.39 is necessary; something like 2.6.32 should be sufficient for POSIX 2008, barring any arch-specific bugs (or just general bugs that need to be patched to avoid having an unstable/insecure kernel). I know glibc is planning on requiring at least 2.6.32 in the next release, so it would be nice if we could just state the same requirement. As for older kernels, somewhere down to 2.6.22 works if you don't care about atomic close-on-exec working atomically (musl has fallback for kernels that lack it, but the fallback is of course non-atomic). Then there are also ranges going all the way back to 2.6.0 or even 2.5.x that work if you don't care about certain POSIX signal semantics (mainly, wrongly-generated EINTR where a syscall should have restarted) and don't need *at() functions (note that musl presently does not emulate these, even though it could do so using /proc). And if in addition you don't need threads, even 2.4.x will work. It would also be nice to get these version ranges documented in detail, in case anyone has need to use musl binaries with such old kernels (some users adding new software to existing embedded systems may care; otherwise it's probably a non-issue). Rich
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