Date: Sun, 27 Apr 2014 14:00:32 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Bare metal progress and an oddity. On Sun, Apr 27, 2014 at 12:37:13PM -0500, Richard Pennington wrote: > As part of my quixotic quest to run musl on ARM bare metal I've > started to handle interrupts and an ARM timer to implement the > clock_* functions to prepare for pre-emptive scheduling of > pthread_create'd threads. The current sources are here: > http://ellcc.org/viewvc/svn/ellcc/trunk/baremetal/arm/ > > An oddity: If I use printf() to print out values in an interrupt > handler it sort of works. The format string prints perfectly, but it > seems that the va_arg values are getting messed up. The stack is > large enough, fp and sp are sane. Am I missing something in > pop_arg() that is causing this? Come to think of it, do I have to > insure a certain stack alignment, for example? Most of the messed up > values are "long long". > > Any thoughts appreciated. Yes, ARM EABI requires the stack to be aligned to at least an 8-byte boundary (maybe 16 but I think 8 is all that's required). If your stack is only aligned to 4 bytes, this will mess things up badly. Rich
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