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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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2c7387ef99
The existing asm-generic/stat.h specifies st_mtime, etc., as a 32-value, and works well for 32-bit architectures (currently microblaze, score, and 32-bit tile). However, for 64-bit architectures it isn't sufficient to return 32 bits of time_t; this isn't good insurance against the 2037 rollover. (It also makes glibc support less convenient, since we can't use glibc's handy STAT_IS_KERNEL_STAT mode.) This change extends the two "timespec" fields for each of the three atime, mtime, and ctime fields from "int" to "long". As a result, on 32-bit platforms nothing changes, and 64-bit platforms will now work as expected. The only wrinkle is 32-bit userspace under 64-bit kernels taking advantage of COMPAT mode. For these, we leave the "struct stat64" definitions with the "int" versions of the time_t and nsec fields, so that architectures can implement compat_sys_stat64() and friends with sys_stat64(), etc., and get the expected 32-bit structure layout. This requires a field-by-field copy in the kernel, implemented by the code guarded under __ARCH_WANT_STAT64. This does mean that the shape of the "struct stat" and "struct stat64" structures is different on a 64-bit kernel, but only one of the two structures should ever be used by any given process: "struct stat" is meant for 64-bit userspace only, and "struct stat64" for 32-bit userspace only. (On a 32-bit kernel the two structures continue to have the same shape, since "long" is 32 bits.) The alternative is keeping the two structures the same shape on 64-bit kernels, which means a 64-bit time_t in "struct stat64" for 32-bit processes. This is a little unnatural since 32-bit userspace can't do anything with 64 bits of time_t information, since time_t is just "long", not "int64_t"; and in any case 32-bit userspace might expect to be running under a 32-bit kernel, which can't provide the high 32 bits anyway. In the case of a 32-bit kernel we'd then be extending the kernel's 32-bit time_t to 64 bits, then truncating it back to 32 bits again in userspace, for no particular reason. And, as mentioned above, if we have 64-bit time_t for 32-bit processes we can't easily use glibc's STAT_IS_KERNEL_STAT, since glibc's stat structure requires an embedded "struct timespec", which is a pair of "long" (32-bit) values in a 32-bit userspace. "Inventive" solutions are possible, but are pretty hacky. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> Acked-by: Arnd Bergmann <arnd@arndb.de>
48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/*
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* Copyright 2010 Tilera Corporation. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation, version 2.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for
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* more details.
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*/
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#if !defined(_ASM_TILE_UNISTD_H) || defined(__SYSCALL)
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#define _ASM_TILE_UNISTD_H
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#ifndef __LP64__
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/* Use the flavor of this syscall that matches the 32-bit API better. */
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#define __ARCH_WANT_SYNC_FILE_RANGE2
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#endif
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/* Use the standard ABI for syscalls. */
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#include <asm-generic/unistd.h>
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/* Additional Tilera-specific syscalls. */
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#define __NR_flush_cache (__NR_arch_specific_syscall + 1)
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__SYSCALL(__NR_flush_cache, sys_flush_cache)
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#ifndef __tilegx__
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/* "Fast" syscalls provide atomic support for 32-bit chips. */
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#define __NR_FAST_cmpxchg -1
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#define __NR_FAST_atomic_update -2
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#define __NR_FAST_cmpxchg64 -3
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#define __NR_cmpxchg_badaddr (__NR_arch_specific_syscall + 0)
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__SYSCALL(__NR_cmpxchg_badaddr, sys_cmpxchg_badaddr)
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#endif
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#ifdef __KERNEL__
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/* In compat mode, we use sys_llseek() for compat_sys_llseek(). */
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#ifdef CONFIG_COMPAT
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#define __ARCH_WANT_SYS_LLSEEK
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#endif
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#define __ARCH_WANT_SYS_NEWFSTATAT
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#endif
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#endif /* _ASM_TILE_UNISTD_H */
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