From 2c7387ef9969bb073c25ecbdcc5be30770267b16 Mon Sep 17 00:00:00 2001 From: Chris Metcalf Date: Thu, 28 Oct 2010 16:07:07 -0400 Subject: [PATCH] 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 --- arch/tile/include/asm/stat.h | 3 +++ arch/tile/include/asm/unistd.h | 1 + arch/tile/kernel/compat.c | 10 +++++----- include/asm-generic/stat.h | 14 +++++++------- 4 files changed, 16 insertions(+), 12 deletions(-) diff --git a/arch/tile/include/asm/stat.h b/arch/tile/include/asm/stat.h index 3dc90fa92c70..b16e5db8f0e7 100644 --- a/arch/tile/include/asm/stat.h +++ b/arch/tile/include/asm/stat.h @@ -1 +1,4 @@ +#ifdef CONFIG_COMPAT +#define __ARCH_WANT_STAT64 /* Used for compat_sys_stat64() etc. */ +#endif #include diff --git a/arch/tile/include/asm/unistd.h b/arch/tile/include/asm/unistd.h index f2e3ff485333..b35c2db71199 100644 --- a/arch/tile/include/asm/unistd.h +++ b/arch/tile/include/asm/unistd.h @@ -41,6 +41,7 @@ __SYSCALL(__NR_cmpxchg_badaddr, sys_cmpxchg_badaddr) #ifdef CONFIG_COMPAT #define __ARCH_WANT_SYS_LLSEEK #endif +#define __ARCH_WANT_SYS_NEWFSTATAT #endif #endif /* _ASM_TILE_UNISTD_H */ diff --git a/arch/tile/kernel/compat.c b/arch/tile/kernel/compat.c index 77739cdd9462..67617a05e602 100644 --- a/arch/tile/kernel/compat.c +++ b/arch/tile/kernel/compat.c @@ -148,11 +148,11 @@ long tile_compat_sys_msgrcv(int msqid, #define compat_sys_readahead sys32_readahead #define compat_sys_sync_file_range compat_sys_sync_file_range2 -/* The native 64-bit "struct stat" matches the 32-bit "struct stat64". */ -#define compat_sys_stat64 sys_newstat -#define compat_sys_lstat64 sys_newlstat -#define compat_sys_fstat64 sys_newfstat -#define compat_sys_fstatat64 sys_newfstatat +/* We leverage the "struct stat64" type for 32-bit time_t/nsec. */ +#define compat_sys_stat64 sys_stat64 +#define compat_sys_lstat64 sys_lstat64 +#define compat_sys_fstat64 sys_fstat64 +#define compat_sys_fstatat64 sys_fstatat64 /* The native sys_ptrace dynamically handles compat binaries. */ #define compat_sys_ptrace sys_ptrace diff --git a/include/asm-generic/stat.h b/include/asm-generic/stat.h index 47e64170305d..bd8cad21998e 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. */