On Tue, Jan 12, 2016 at 09:01:22AM -0500, Brian Foster wrote:
> On Mon, Jan 11, 2016 at 03:46:44PM -0800, Darrick J. Wong wrote:
> > Check on-disk structure sizes against known values.
> > Use this to catch inadvertent changes in structure size due to padding
> > and alignment issues, etc.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > ---
>
> What's the need for this in userspace? Not a big deal really, but it
> seems like it serves the fundamental purpose sufficiently in the kernel.
The primary point is to make sure that we didn't make any errors with the
on-disk structures when porting libxfs changes. The kernel build is the first
line of defense since it tends to big get changes first, but I figure a
defensive build check for xfsprogs won't harm anyone...
> That aside, this does fail if I tweak a structure size, though I don't
> think I get the intended error. I end up with a linker error instead:
...except for that. Should I dig deeper into figuring out why this doesn't
work in userland, or is a filename and line number sufficient to figure out
which structure is misbehaving?
--D
>
> ...
> [LD] xfs_db
> ondisk.o: In function `xfs_check_ondisk_structs':
> /home/bfoster/repos/xfsprogs-dev/db/ondisk.c:26: undefined reference to `__compiletime_assert_26'
> collect2: error: ld returned 1 exit status
> ../include/buildrules:45: recipe for target 'xfs_db' failed
> gmake[3]: *** [xfs_db] Error 1
> include/buildrules:35: recipe for target 'db' failed
> gmake[2]: *** [db] Error 2
> Makefile:70: recipe for target 'default' failed
> make[1]: *** [default] Error 2
> Makefile:68: recipe for target 'default' failed
> make: *** [default] Error 2
>
> This is with gcc 5.3.1. It works fine with the kernel patch so I don't
> _think_ it's my environment, but I could be wrong...
>
> Brian
>
> > db/Makefile | 2 -
> > db/init.c | 3 +
> > db/ondisk.c | 63 +++++++++++++++++++++++
> > db/ondisk.h | 139 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > libxfs/xfs_format.h | 4 +
> > 5 files changed, 210 insertions(+), 1 deletion(-)
> > create mode 100644 db/ondisk.c
> > create mode 100644 db/ondisk.h
> >
> > diff --git a/db/Makefile b/db/Makefile
> > index 8260da3..ba3e942 100644
> > --- a/db/Makefile
> > +++ b/db/Makefile
> > @@ -12,7 +12,7 @@ HFILES = addr.h agf.h agfl.h agi.h attr.h attrshort.h bit.h block.h bmap.h \
> > dir2.h dir2sf.h dquot.h echo.h faddr.h field.h \
> > flist.h fprint.h frag.h freesp.h hash.h help.h init.h inode.h input.h \
> > io.h logformat.h malloc.h metadump.h output.h print.h quit.h sb.h \
> > - sig.h strvec.h text.h type.h write.h attrset.h symlink.h
> > + sig.h strvec.h text.h type.h write.h attrset.h symlink.h ondisk.h
> > CFILES = $(HFILES:.h=.c)
> > LSRCFILES = xfs_admin.sh xfs_ncheck.sh xfs_metadump.sh
> >
> > diff --git a/db/init.c b/db/init.c
> > index c0472c8..d6df093 100644
> > --- a/db/init.c
> > +++ b/db/init.c
> > @@ -28,6 +28,7 @@
> > #include "output.h"
> > #include "malloc.h"
> > #include "type.h"
> > +#include "ondisk.h"
> >
> > static char **cmdline;
> > static int ncmdline;
> > @@ -60,6 +61,8 @@ init(
> > struct xfs_buf *bp;
> > int c;
> >
> > + xfs_check_ondisk_structs();
> > +
> > setlocale(LC_ALL, "");
> > bindtextdomain(PACKAGE, LOCALEDIR);
> > textdomain(PACKAGE);
> > diff --git a/db/ondisk.c b/db/ondisk.c
> > new file mode 100644
> > index 0000000..532333d
> > --- /dev/null
> > +++ b/db/ondisk.c
> > @@ -0,0 +1,63 @@
> > +/*
> > + * Copyright (c) 2016 Oracle.
> > + * All Rights Reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation,
> > + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> > + */
> > +
> > +#include "libxfs.h"
> > +#include "ondisk.h"
> > +
> > +void
> > +xfs_check_ondisk_structs(void)
> > +{
> > + /* on-disk structures */
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_dsb, 264);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_agf, 224);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_agi, 336);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_agfl, 36);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_timestamp, 8);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_dinode, 176);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_disk_dquot, 104);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_dqblk, 136);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_dsymlink_hdr, 56);
> > + XFS_CHECK_STRUCT_SIZE(xfs_alloc_rec_t, 8);
> > + XFS_CHECK_STRUCT_SIZE(xfs_alloc_key_t, 8);
> > + XFS_CHECK_STRUCT_SIZE(xfs_alloc_ptr_t, 4);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_inobt_rec, 16);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_inobt_key, 4);
> > + XFS_CHECK_STRUCT_SIZE(xfs_inobt_ptr_t, 4);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_bmdr_block, 4);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_bmbt_rec, 16);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_bmbt_key, 8);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_btree_block, 72);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_acl_entry, 12);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_acl, 4);
> > +
> > + /* log structures */
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_trans_header, 16);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_inode_log_format_32, 52);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_inode_log_format_64, 56);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_ictimestamp, 8);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_icdinode, 176);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_extent_32, 12);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_extent_64, 16);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_efi_log_format_32, 28);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_efi_log_format_64, 32);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_efd_log_format_32, 28);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_efd_log_format_64, 32);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_dq_logformat, 24);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_qoff_logformat, 20);
> > + XFS_CHECK_STRUCT_SIZE(struct xfs_icreate_log, 28);
> > +}
> > diff --git a/db/ondisk.h b/db/ondisk.h
> > new file mode 100644
> > index 0000000..b5784d1
> > --- /dev/null
> > +++ b/db/ondisk.h
> > @@ -0,0 +1,139 @@
> > +/*
> > + * Copyright (c) 2016 Oracle.
> > + * All Rights Reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it would be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write the Free Software Foundation,
> > + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> > + */
> > +
> > +#ifndef __XFS_DB_ONDISK_H
> > +#define __XFS_DB_ONDISK_H
> > +
> > +/* Compile time object size, -1 for unknown */
> > +#ifndef __compiletime_error
> > +# define __compiletime_error(message)
> > +/*
> > + * Sparse complains of variable sized arrays due to the temporary variable in
> > + * __compiletime_assert. Unfortunately we can't just expand it out to make
> > + * sparse see a constant array size without breaking compiletime_assert on old
> > + * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
> > + */
> > +# ifndef __CHECKER__
> > +# define __compiletime_error_fallback(condition) \
> > + do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
> > +# endif
> > +#endif
> > +#ifndef __compiletime_error_fallback
> > +# define __compiletime_error_fallback(condition) do { } while (0)
> > +#endif
> > +
> > +#define __compiletime_assert(condition, msg, prefix, suffix) \
> > + do { \
> > + bool __cond = !(condition); \
> > + extern void prefix ## suffix(void) __compiletime_error(msg); \
> > + if (__cond) \
> > + prefix ## suffix(); \
> > + __compiletime_error_fallback(__cond); \
> > + } while (0)
> > +
> > +#define _compiletime_assert(condition, msg, prefix, suffix) \
> > + __compiletime_assert(condition, msg, prefix, suffix)
> > +
> > +/**
> > + * compiletime_assert - break build and emit msg if condition is false
> > + * @condition: a compile-time constant condition to check
> > + * @msg: a message to emit if condition is false
> > + *
> > + * In tradition of POSIX assert, this macro will break the build if the
> > + * supplied condition is *false*, emitting the supplied error message if the
> > + * compiler has support to do so.
> > + */
> > +#define compiletime_assert(condition, msg) \
> > + _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
> > +
> > +#ifdef __CHECKER__
> > +#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0)
> > +#define BUILD_BUG_ON_ZERO(e) (0)
> > +#define BUILD_BUG_ON_NULL(e) ((void*)0)
> > +#define BUILD_BUG_ON_INVALID(e) (0)
> > +#define BUILD_BUG_ON_MSG(cond, msg) (0)
> > +#define BUILD_BUG_ON(condition) (0)
> > +#define BUILD_BUG() (0)
> > +#else /* __CHECKER__ */
> > +
> > +/* Force a compilation error if a constant expression is not a power of 2 */
> > +#define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
> > + BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
> > +
> > +/* Force a compilation error if condition is true, but also produce a
> > + result (of value 0 and type size_t), so the expression can be used
> > + e.g. in a structure initializer (or where-ever else comma expressions
> > + aren't permitted). */
> > +#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
> > +#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
> > +
> > +/*
> > + * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
> > + * expression but avoids the generation of any code, even if that expression
> > + * has side-effects.
> > + */
> > +#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
> > +
> > +/**
> > + * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
> > + * error message.
> > + * @condition: the condition which the compiler should know is false.
> > + *
> > + * See BUILD_BUG_ON for description.
> > + */
> > +#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > +
> > +/**
> > + * BUILD_BUG_ON - break compile if a condition is true.
> > + * @condition: the condition which the compiler should know is false.
> > + *
> > + * If you have some code which relies on certain constants being equal, or
> > + * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
> > + * detect if someone changes it.
> > + *
> > + * The implementation uses gcc's reluctance to create a negative array, but gcc
> > + * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
> > + * inline functions). Luckily, in 4.3 they added the "error" function
> > + * attribute just for this type of case. Thus, we use a negative sized array
> > + * (should always create an error on gcc versions older than 4.4) and then call
> > + * an undefined function with the error attribute (should always create an
> > + * error on gcc 4.3 and later). If for some reason, neither creates a
> > + * compile-time error, we'll still have a link-time error, which is harder to
> > + * track down.
> > + */
> > +#ifndef __OPTIMIZE__
> > +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
> > +#else
> > +#define BUILD_BUG_ON(condition) \
> > + BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> > +#endif
> > +
> > +/**
> > + * BUILD_BUG - break compile if used.
> > + *
> > + * If you have some code that you expect the compiler to eliminate at
> > + * build time, you should use BUILD_BUG to detect if it is
> > + * unexpectedly used.
> > + */
> > +#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
> > +
> > +#endif /* __CHECKER__ */
> > +
> > +void xfs_check_ondisk_structs(void);
> > +
> > +#endif /* __XFS_DB_ONDISK_H */
> > diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
> > index a35009a..c4c0c1c 100644
> > --- a/libxfs/xfs_format.h
> > +++ b/libxfs/xfs_format.h
> > @@ -1505,4 +1505,8 @@ struct xfs_acl {
> > #define SGI_ACL_FILE_SIZE (sizeof(SGI_ACL_FILE)-1)
> > #define SGI_ACL_DEFAULT_SIZE (sizeof(SGI_ACL_DEFAULT)-1)
> >
> > +#define XFS_CHECK_STRUCT_SIZE(structname, size) \
> > + BUILD_BUG_ON_MSG(sizeof(structname) != (size), "XFS: sizeof(struct " \
> > + #structname ") is wrong, expected " #size)
> > +
> > #endif /* __XFS_FORMAT_H__ */
> >
> > _______________________________________________
> > xfs mailing list
> > xfs@xxxxxxxxxxx
> > http://oss.sgi.com/mailman/listinfo/xfs
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