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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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f991f01571
Most architectures now use the asm-generic copy of the sysvipc data
structures (msqid64_ds, semid64_ds, shmid64_ds), which use 32-bit
__kernel_time_t on 32-bit architectures but have padding behind them to
allow extending the type to 64-bit.
Unfortunately, that fails on all big-endian architectures, which have the
padding on the wrong side. As so many of them get it wrong, we decided to
not bother even trying to fix it up when we introduced the asm-generic
copy. Instead we always use the padding word now to provide the upper
32 bits of the seconds value, regardless of the endianess.
A libc implementation on a typical big-endian system can deal with
this by providing its own copy of the structure definition to user
space, and swapping the two 32-bit words before returning from the
semctl/shmctl/msgctl system calls.
Note that msqid64_ds and shmid64_ds were broken on x32 since commit
f4b4aae182 ("x86/headers/uapi: Fix __BITS_PER_LONG value for x32
builds"). I have sent a separate fix for that, but as we no longer
have to worry about x32 here, I no longer worry about x32 here and
use 'unsigned long' instead of __kernel_ulong_t.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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#ifndef __ASM_GENERIC_SHMBUF_H
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#define __ASM_GENERIC_SHMBUF_H
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#include <asm/bitsperlong.h>
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/*
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* The shmid64_ds structure for x86 architecture.
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* Note extra padding because this structure is passed back and forth
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* between kernel and user space.
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*
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* shmid64_ds was originally meant to be architecture specific, but
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* everyone just ended up making identical copies without specific
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* optimizations, so we may just as well all use the same one.
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*
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* 64 bit architectures typically define a 64 bit __kernel_time_t,
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* so they do not need the first two padding words.
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* On big-endian systems, the padding is in the wrong place.
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*
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*
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* Pad space is left for:
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* - 2 miscellaneous 32-bit values
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*/
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struct shmid64_ds {
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struct ipc64_perm shm_perm; /* operation perms */
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size_t shm_segsz; /* size of segment (bytes) */
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#if __BITS_PER_LONG == 64
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__kernel_time_t shm_atime; /* last attach time */
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__kernel_time_t shm_dtime; /* last detach time */
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__kernel_time_t shm_ctime; /* last change time */
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#else
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unsigned long shm_atime; /* last attach time */
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unsigned long shm_atime_high;
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unsigned long shm_dtime; /* last detach time */
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unsigned long shm_dtime_high;
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unsigned long shm_ctime; /* last change time */
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unsigned long shm_ctime_high;
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#endif
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__kernel_pid_t shm_cpid; /* pid of creator */
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__kernel_pid_t shm_lpid; /* pid of last operator */
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unsigned long shm_nattch; /* no. of current attaches */
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unsigned long __unused4;
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unsigned long __unused5;
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};
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struct shminfo64 {
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unsigned long shmmax;
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unsigned long shmmin;
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unsigned long shmmni;
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unsigned long shmseg;
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unsigned long shmall;
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unsigned long __unused1;
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unsigned long __unused2;
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unsigned long __unused3;
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unsigned long __unused4;
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};
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#endif /* __ASM_GENERIC_SHMBUF_H */
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