Date: Thu, 14 Jun 2018 22:00:23 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: broken __kernel_mode_t affecting some big endian archs On Wed, Jun 13, 2018 at 08:54:42PM -0400, Rich Felker wrote: > It's been semi-known for a long time (I say semi-, because nobody's > had the setup to test most of them well, or at least nobody I'm > communicating with regularly) that some archs are failing libc-test > sysvipc tests. I think I've tracked down the root cause. > > Linux defined __kernel_mode_t as short on some old archs, and used it > in place of mode_t in the ipc_perm structure. The field is padded out > to 32 bits, so on little endian archs it's no problem for us to just > (as we do) ignore the incorrect type and declare the structure with > mode_t, as POSIX requires. However on big-endian archs, the padding is > on the wrong side and this trick doesn't work. > > On MIPS we fixed a similar issue in struct stat, where dev_t was > incorrectly padded, with a fixup in syscall_arch.h. However this time > a large number of archs are affected, and patching them all up > individually seems nasty. > > My leaning is to have syscall_arch.h expose a macro indicating the > bug, and have msgctl, semctl, and shmctl each do the fixup if it's > set. > > FWIW the affected archs seem to be (only in big endian variants): > - ARM > - M68k (in-progress port) > - Microblaze > - SH > - Sparc (future port) > > Thoughts? Here's a draft of the fix, just for shmctl and not including the SHM_STAT or SHM_STAT_ALL operations. Rich View attachment "shmfix.diff" of type "text/plain" (792 bytes)
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