diff options
author | Darrick J. Wong <djwong@kernel.org> | 2022-08-04 21:26:43 -0500 |
---|---|---|
committer | Eric Sandeen <sandeen@sandeen.net> | 2022-08-04 21:26:43 -0500 |
commit | 28965957f4ea5c79fc0b91b997168c656a4426c5 (patch) | |
tree | 2d65b48bb174c1884d6694cd15981247236f135b | |
parent | 50dba8189b1f628073eb61d824ae8a8a1b43cefb (diff) | |
download | xfsprogs-dev-28965957f4ea5c79fc0b91b997168c656a4426c5.tar.gz |
libxfs: stop overriding MAP_SYNC in publicly exported header files
Florian Fainelli most recently reported that xfsprogs doesn't build with
musl on mips:
"MIPS platforms building with recent kernel headers and the musl-libc
toolchain will expose the following build failure:
mmap.c: In function 'mmap_f':
mmap.c:196:12: error: 'MAP_SYNC' undeclared (first use in this function); did you mean 'MS_SYNC'?
196 | flags = MAP_SYNC | MAP_SHARED_VALIDATE;
| ^~~~~~~~
| MS_SYNC
mmap.c:196:12: note: each undeclared identifier is reported only once for each function it appears in
make[4]: *** [../include/buildrules:81: mmap.o] Error 1"
At first glance, the build failure here is caused by the fact that:
1. The configure script doesn't detect MAP_SYNC support
2. The build system doesn't set HAVE_MAP_SYNC
2. io/mmap.c includes input.h -> projects.h -> xfs.h and later sys/mman.h
3. include/linux.h #define's MAP_SYNC to 0 if HAVE_MAP_SYNC is not set
4. musl's sys/mman.h #undef MAP_SYNC on platforms that don't support it
5. io/mmap.c tries to use MAP_SYNC, not realizing that libc undefined it
Normally, xfs_io only exports functionality that is defined by the libc
and/or kernel headers on the build system. We often make exceptions for
new functionality so that we have a way to test them before the header
file packages catch up, hence this '#ifndef HAVE_FOO #define FOO'
paradigm.
MAP_SYNC is a gross and horribly broken example of this. These support
crutches are supposed to be *private* to xfsprogs for benefit of early
testing, but they were instead added to include/linux.h, which we
provide to user programs in the xfslibs-dev package. IOWs, we've been
#defining MAP_SYNC to zero for unsuspecting programs.
Worst yet, gcc 11.3 doesn't even warn about overriding a #define to 0:
#include <stdio.h>
#include <sys/mman.h>
#ifdef STUPID
# include <xfs/xfs.h>
#endif
int main(int argc, char *argv[]) {
printf("MAP_SYNC 0x%x\n", MAP_SYNC);
}
$ gcc -o a a.c -Wall
$ ./a
MAP_SYNC 0x80000
$ gcc -DSTUPID -o a a.c -Wall
$ ./a
MAP_SYNC 0x0
Four years have gone by since the introduction of MAP_SYNC, so let's get
rid of the override code entirely -- any platform that supports MAP_SYNC
has had plenty of chances to ensure their header files have the right
bits. While we're at it, fix AC_HAVE_MAP_SYNC to look for MAP_SYNC in
the same header file that the one user (io/mmap.c) uses -- sys/mman.h.
Annoyingly, I had to test this by hand because the sole fstest that
exercises MAP_SYNC (generic/470) requires dm-logwrites and dm-thinp,
neither of which support fsdax on current kernels.
Reported-by: info@mobile-stream.com
Reported-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
-rw-r--r-- | include/linux.h | 8 | ||||
-rw-r--r-- | io/io.h | 2 | ||||
-rw-r--r-- | io/mmap.c | 25 | ||||
-rw-r--r-- | m4/package_libcdev.m4 | 3 |
4 files changed, 15 insertions, 23 deletions
diff --git a/include/linux.h b/include/linux.h index 3d9f4e3dca..eddc4ad9c8 100644 --- a/include/linux.h +++ b/include/linux.h @@ -251,14 +251,6 @@ struct fsxattr { #define FS_XFLAG_COWEXTSIZE 0x00010000 /* CoW extent size allocator hint */ #endif -#ifndef HAVE_MAP_SYNC -#define MAP_SYNC 0 -#define MAP_SHARED_VALIDATE 0 -#else -#include <asm-generic/mman.h> -#include <asm-generic/mman-common.h> -#endif /* HAVE_MAP_SYNC */ - /* * Reminder: anything added to this file will be compiled into downstream * userspace projects! @@ -55,7 +55,7 @@ typedef struct mmap_region { size_t length; /* length of mapping */ off64_t offset; /* start offset into backing file */ int prot; /* protection mode of the mapping */ - bool map_sync; /* is this a MAP_SYNC mapping? */ + int flags; /* MAP_* flags passed to mmap() */ char *name; /* name of backing file */ } mmap_region_t; @@ -46,8 +46,11 @@ print_mapping( for (i = 0, p = pflags; p->prot != PROT_NONE; i++, p++) buffer[i] = (map->prot & p->prot) ? p->mode : '-'; - if (map->map_sync) +#ifdef HAVE_MAP_SYNC + if ((map->flags & (MAP_SYNC | MAP_SHARED_VALIDATE)) == + (MAP_SYNC | MAP_SHARED_VALIDATE)) sprintf(&buffer[i], " S"); +#endif printf("%c%03d%c 0x%lx - 0x%lx %s %14s (%lld : %ld)\n", braces? '[' : ' ', index, braces? ']' : ' ', @@ -139,7 +142,9 @@ mmap_help(void) " -r -- map with PROT_READ protection\n" " -w -- map with PROT_WRITE protection\n" " -x -- map with PROT_EXEC protection\n" +#ifdef HAVE_MAP_SYNC " -S -- map with MAP_SYNC and MAP_SHARED_VALIDATE flags\n" +#endif " -s <size> -- first do mmap(size)/munmap(size), try to reserve some free space\n" " If no protection mode is specified, all are used by default.\n" "\n")); @@ -193,18 +198,14 @@ mmap_f( prot |= PROT_EXEC; break; case 'S': +#ifdef HAVE_MAP_SYNC flags = MAP_SYNC | MAP_SHARED_VALIDATE; - - /* - * If MAP_SYNC and MAP_SHARED_VALIDATE aren't defined - * in the system headers we will have defined them - * both as 0. - */ - if (!flags) { - printf("MAP_SYNC not supported\n"); - return 0; - } break; +#else + printf("MAP_SYNC not supported\n"); + exitcode = 1; + return command_usage(&mmap_cmd); +#endif case 's': length2 = cvtnum(blocksize, sectsize, optarg); break; @@ -281,7 +282,7 @@ mmap_f( mapping->offset = offset; mapping->name = filename; mapping->prot = prot; - mapping->map_sync = (flags == (MAP_SYNC | MAP_SHARED_VALIDATE)); + mapping->flags = flags; return 0; } diff --git a/m4/package_libcdev.m4 b/m4/package_libcdev.m4 index 70badac357..bb1ab49c11 100644 --- a/m4/package_libcdev.m4 +++ b/m4/package_libcdev.m4 @@ -368,8 +368,7 @@ AC_DEFUN([AC_HAVE_MAP_SYNC], [ AC_MSG_CHECKING([for MAP_SYNC]) AC_COMPILE_IFELSE( [ AC_LANG_PROGRAM([[ -#include <asm-generic/mman.h> -#include <asm-generic/mman-common.h> +#include <sys/mman.h> ]], [[ int flags = MAP_SYNC | MAP_SHARED_VALIDATE; ]]) |