Date: Fri, 19 Oct 2012 14:41:35 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: TLS (thread-local storage) support On Sat, Oct 20, 2012 at 02:39:43AM +0800, orc wrote: > > 4) Compile musl with '-fsplit-stack' and add no_split_stack attribute > > to appropriate functions (at least all functions called before > > pthread_self_init because %gs or %fs register is unusable before this > > call). > > > > 5) set main thread stack limit to 0 (pthread_self_init) : the main > > thread stack grow is handled by the kernel. > > > > 6) add no-split-stack note to every asm file. > Why anything works only after putting a weak spikes that break after a > slight touch? I don't follow what you're saying here. > > 7) make split stack support optional (either by checking the > > -fsplit-stack option in CFLAGS or with a specific option : > > --enable-split-stack) : split stack adds overhead to every functions > > (except for those with the 'no_split_stack' attribute). > > > > > Do you have any concern about adding those features in musl ? > > > > > > Let me know if you see other issues I haven't noticed. > > > > > > > > > Regards, > > > > > > Boris > > After reading whole thread I agree with Rich that this one is not only > hard to implement, but completely useless. From other point of view: I think it's hard (read: probably impossible) to implement in a way that's robust and correct, but it may not be too hard to implement the minimal support code so that folks who insist on using -fsplit-stack will not get pathologically bad behavior due to the calling code being unaware that is already has a plenty pre-allocated stack space to run on. > people expect from musl an easy to read and understand code, that not > only works, but is easy to understand, modify, debug and build. Why > extend it with features not even related to libc? (It is mostly a hack > from gcc-binutils again?) I agree. I definitely don't want to compromise on correctness/robustness for the sake of this, and I'd also like to avoid adding complexity or maintenance burdens. Rich
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