path: root/dynamic.list
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authorRich Felker <>2019-07-30 14:51:53 -0400
committerRich Felker <>2019-07-31 17:32:01 -0400
commit8b2497047010e199bb04ed45e25a03c6f1e517fa (patch)
tree3d26b3ec57fa3a4f37be2f7544a3035aa6e85905 /dynamic.list
parentfe5e72ae782238038ba4eaa3e1889e7bd16fecec (diff)
sysvipc: overhaul {sem,shm,msg}ctl for time64
being "ctl" functions that take command numbers, these will be handled like ioctl/sockopt/etc., using new command numbers for the time64 variants with an "IPC_TIME64" bit added to their values. to obtain such a reserved bit, we reuse the IPC_64 bit, 0x100, which served only as part of the libc-to-kernel interface, not as a public interface of the libc functions. using new command numbers avoids the need for compat shims (in ABIs doing time64 through symbol redirection and compat shims) and, by virtue of having a fixed time64 bit for all commands, we can ensure that libc can perform the appropriate translations, even if the application is using new commands from a newer version of the libc headers than the libc available at runtime. for the vast majority of 32-bit archs, the kernel {sem,shm,msq}id64_ds definitions left padding space intended for expanding their time_t fields to 64 bits in-place, and it would have been really nice to be able to do time64 support that way. however the padding was almost always in little-endian order (except on powerpc, and for msqid_ds only on mips, where it matched the arch's byte order), and more importantly, the alignment was overlooked. in semid_ds and msqid_ds, the time_t members were not suitably aligned to be expanded to 64-bit, due to the ipc_perm header consisting of 9 32-bit words -- except on powerpc where ipc_perm contains an extra padding word. in shmid_ds, the time_t members were suitably aligned, except that mips (accidentally?) omitted the padding for them alltogether. as a result, we're stuck with adding new time_t fields on the end of the structures, and assembling the 32-bit lo/hi parts (or 16-bit hi parts, for mips shmid_ds, which lacked sufficient reserved space for full 32-bit hi parts) to fill them in. all of the functional changes here are conditional on the IPC_TIME64 macro having a nonzero definition, which will only happen when IPC_STAT is redefined for 32-bit archs, and on time_t being larger than long, so for now the new code is all dead code.
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