From 2c7387ef9969bb073c25ecbdcc5be30770267b16 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Thu, 28 Oct 2010 16:07:07 -0400 Subject: asm-generic/stat.h: support 64-bit file time_t for stat() 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 Acked-by: Arnd Bergmann --- include/asm-generic/stat.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'include/asm-generic') diff --git a/include/asm-generic/stat.h b/include/asm-generic/stat.h index 47e6417..bd8cad2 100644 --- a/include/asm-generic/stat.h +++ b/include/asm-generic/stat.h @@ -33,18 +33,18 @@ struct stat { int st_blksize; /* Optimal block size for I/O. */ int __pad2; long st_blocks; /* Number 512-byte blocks allocated. */ - int st_atime; /* Time of last access. */ - unsigned int st_atime_nsec; - int st_mtime; /* Time of last modification. */ - unsigned int st_mtime_nsec; - int st_ctime; /* Time of last status change. */ - unsigned int st_ctime_nsec; + long st_atime; /* Time of last access. */ + unsigned long st_atime_nsec; + long st_mtime; /* Time of last modification. */ + unsigned long st_mtime_nsec; + long st_ctime; /* Time of last status change. */ + unsigned long st_ctime_nsec; unsigned int __unused4; unsigned int __unused5; }; -#if __BITS_PER_LONG != 64 /* This matches struct stat64 in glibc2.1. Only used for 32 bit. */ +#if __BITS_PER_LONG != 64 || defined(__ARCH_WANT_STAT64) struct stat64 { unsigned long long st_dev; /* Device. */ unsigned long long st_ino; /* File serial number. */ -- cgit v1.1