path: root/arch/generic/bits
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authorRich Felker <>2019-07-30 13:07:55 -0400
committerRich Felker <>2019-07-30 14:23:56 -0400
commitf56d57f8a7aa536d40014933841a8b22f9c10328 (patch)
treef34e16245f19c8b1fcf739c9a8e9526d44bbba5d /arch/generic/bits
parent722a1ae3351a03ab25010dbebd492eced664853b (diff)
move IPC_64 from public bits/ipc.h to syscall_arch.h
the definition of the IPC_64 macro controls the interface between libc and the kernel through syscalls; it's not a public API. the meaning is rather obscure. long ago, Linux's sysvipc *id_ds structures used 16-bit uids/gids and wrong types for a few other fields. this was in the libc5 era, before glibc. the IPC_64 flag (64 is a misnomer; it's more like 32) tells the kernel to use the modern[-ish] versions of the structures. the definition of IPC_64 has nothing to do with whether the arch is 32- or 64-bit. rather, due to either historical accident or intentional obnoxiousness, the kernel only accepts and masks off the 0x100 IPC_64 flag conditional on CONFIG_ARCH_WANT_IPC_PARSE_VERSION, i.e. for archs that want to provide, or that accidentally provided, both. for archs which don't define this option, no masking is performed and commands with the 0x100 bit set will fail as invalid. so ultimately, the definition is just a matter of matching an arbitrary switch defined per-arch in the kernel.
Diffstat (limited to 'arch/generic/bits')
1 files changed, 0 insertions, 2 deletions
diff --git a/arch/generic/bits/ipc.h b/arch/generic/bits/ipc.h
index 779c42fd..40d6f3a2 100644
--- a/arch/generic/bits/ipc.h
+++ b/arch/generic/bits/ipc.h
@@ -9,5 +9,3 @@ struct ipc_perm {
long __pad1;
long __pad2;
-#define IPC_64 0x100