Message ID | 20201013131603.12557-1-lukma@denx.de |
---|---|
State | New |
Headers | show |
Series | [1/2] y2038: Adjust struct __stat64_t64 to be usable by redirected {f}stat{at} calls | expand |
On Tue, 13 Oct 2020, Lukasz Majewski wrote: > When glibc port with __WORDSIZE==32 and __TIMESIZE!=64 (e.g. armv7) will > use redirected calls to {f}stat{at}64_time64 functions, it will accept > the struct __stat64_t64 as its argument. > > To avoid errors related to proper data placement after casting from > struct __stat64_t64 to struct stat{64} it is necessary to add some missing > padding and update type of {__}st_ino member. When redirecting to those functions, the definitions of struct stat / struct stat64 should automatically change as a result of the _TIME_BITS=64 definition so that they match the definitions of the __stat64_t64 type - just as _FILE_OFFSET_BITS=64 results in changes to the content of struct stat. I believe the design is that __stat64_t64 has an architecture-independent layout that is never required to match any particular kernel layout because translation (typically from statx) will always occur in userspace. Note that struct_stat_time64.h is currently an *uninstalled* header, despite the name of the multiple-include guard in the header, and despite the testing of feature test macros within the header (which only makes sense for installed headers); it's not a bits/ header at present. Maybe there should be some indirection so that the installed version of struct_stat_time64.h defines a macro with all the contents of __stat64_t64, so that all the many architecture-specific bits/struct_stat.h headers can just use that macro to get the right contents when _TIME_BITS=64 rather than needing to duplicate the structure contents (at least twice per header, for both stat and stat64). But I don't think any change to the layout of __stat64_t64 is indicated, because there should always be explicit conversions between different layouts.
Hi Joseph, > On Tue, 13 Oct 2020, Lukasz Majewski wrote: > > > When glibc port with __WORDSIZE==32 and __TIMESIZE!=64 (e.g. armv7) > > will use redirected calls to {f}stat{at}64_time64 functions, it > > will accept the struct __stat64_t64 as its argument. > > > > To avoid errors related to proper data placement after casting from > > struct __stat64_t64 to struct stat{64} it is necessary to add some > > missing padding and update type of {__}st_ino member. > > When redirecting to those functions, the definitions of struct stat / > struct stat64 should automatically change as a result of the > _TIME_BITS=64 definition so that they match the definitions of the > __stat64_t64 type - just as _FILE_OFFSET_BITS=64 results in changes > to the content of struct stat. Thanks for the explanation. I will adjust exported struct stat{64] accordingly. > > I believe the design is that __stat64_t64 has an > architecture-independent layout that is never required to match any > particular kernel layout because translation (typically from statx) > will always occur in userspace. > > Note that struct_stat_time64.h is currently an *uninstalled* header, > despite the name of the multiple-include guard in the header, and > despite the testing of feature test macros within the header (which > only makes sense for installed headers); it's not a bits/ header at > present. The only change, that I'm going to do is to mode __ino64_t st_ino member of struct __stat64_t64 (@ sysdeps/unix/sysv/linux/struct_stat_time64.h) to the end of this structure (as it is in the exported struct stat{64} placed). This would allow less #ifndef __USE_TIME_BITS64 in the exported struct stat{64}. > > Maybe there should be some indirection so that the installed version > of struct_stat_time64.h defines a macro with all the contents of > __stat64_t64, so that all the many architecture-specific > bits/struct_stat.h headers can just use that macro to get the right > contents when _TIME_BITS=64 rather than needing to duplicate the > structure contents (at least twice per header, for both stat and > stat64). But I don't think any change to the layout of __stat64_t64 > is indicated, because there should always be explicit conversions > between different layouts. > Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
On Wed, 14 Oct 2020, Lukasz Majewski wrote: > The only change, that I'm going to do is to mode __ino64_t st_ino > member of struct __stat64_t64 > (@ sysdeps/unix/sysv/linux/struct_stat_time64.h) to the end of this > structure (as it is in the exported struct stat{64} placed). > > This would allow less #ifndef __USE_TIME_BITS64 in the exported struct > stat{64}. I don't think any reordering is needed. I expect each header defining struct stat / struct stat64 to do something like #if __GLIBC_USE (TIME_BITS64) __STAT64_T64_CONTENT #else /* existing struct contents */ #endif so just one #if in each such struct definition (given that you define __STAT64_T64_CONTENT in some installed bits/ header to avoid duplication).
diff --git a/sysdeps/unix/sysv/linux/struct_stat_time64.h b/sysdeps/unix/sysv/linux/struct_stat_time64.h index b85385b6f3..ca3f06c077 100644 --- a/sysdeps/unix/sysv/linux/struct_stat_time64.h +++ b/sysdeps/unix/sysv/linux/struct_stat_time64.h @@ -43,12 +43,14 @@ struct __stat64_t64 { __dev_t st_dev; /* Device. */ - __ino64_t st_ino; /* file serial number. */ + unsigned int __pad1; + __ino_t __st_ino; /* 32bit file serial number. */ __mode_t st_mode; /* File mode. */ __nlink_t st_nlink; /* Link count. */ __uid_t st_uid; /* User ID of the file's owner. */ __gid_t st_gid; /* Group ID of the file's group.*/ __dev_t st_rdev; /* Device number, if device. */ + unsigned int __pad2; __off64_t st_size; /* Size of file, in bytes. */ __blksize_t st_blksize; /* Optimal block size for I/O. */ __blkcnt64_t st_blocks; /* Number 512-byte blocks allocated. */ @@ -70,6 +72,7 @@ struct __stat64_t64 __fieldts64 (st_mtime); __fieldts64 (st_ctime); # endif /* __USE_XOPEN2K8 */ + __ino64_t st_ino; /* file serial number. */ }; # define _STATBUF_ST_BLKSIZE