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[libvirt PATCH] tests: fix stat mocking with Fedora rawhide

Daniel P. Berrangé posted 1 patch 3 years, 5 months ago
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git fetch https://github.com/patchew-project/libvirt tags/patchew/20201029172507.96634-1-berrange@redhat.com
meson.build                | 28 ++++++++++++-----
tests/virmockstathelpers.c | 62 ++++++++++++++++++++++----------------
2 files changed, 56 insertions(+), 34 deletions(-)
[libvirt PATCH] tests: fix stat mocking with Fedora rawhide
Posted by Daniel P. Berrangé 3 years, 5 months ago 
GLibC has a really complicated way of dealing with the 'stat' function
historically, which means our mocks in turn have to look at four
different possible functions to replace, stat, stat64, __xstat,
__xstat64.

In Fedora 33 and earlier:

 - libvirt.so links to __xstat64
 - libc.so library exports stat, stat64, __xstat, __xstat64
 - sys/stat.h header exposes stat and __xstat

In Fedora 34 rawhide:

 - libvirt.so links to stat64
 - libc.so library exports stat, stat64, __xstat, __xstat64
 - sys/stat.h header exposes stat

Historically we only looked at the exported symbols from libc.so to
decide which to mock.

In F34 though we must not consider __xstat / __xstat64 though because
they only existance for binary compatibility. Newly built binaries
won't reference them.

Thus we must introduce a header file check into our logic for deciding
which symbol to mock. We must ignore the __xstat / __xstat64 symbols
if they don't appear in the sys/stat.h header, even if they appear
in libc.so

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---

Validated with this pipeline:

  https://gitlab.com/berrange/libvirt/-/pipelines/209361200

 meson.build                | 28 ++++++++++++-----
 tests/virmockstathelpers.c | 62 ++++++++++++++++++++++----------------
 2 files changed, 56 insertions(+), 34 deletions(-)

diff --git a/meson.build b/meson.build
index c3ba34bbe0..365c16d167 100644
--- a/meson.build
+++ b/meson.build
@@ -636,10 +636,6 @@ libvirt_export_dynamic = cc.first_supported_link_argument([
 # check availability of various common functions (non-fatal if missing)
 
 functions = [
-  '__lxstat',
-  '__lxstat64',
-  '__xstat',
-  '__xstat64',
   'elf_aux_info',
   'fallocate',
   'getauxval',
@@ -653,8 +649,6 @@ functions = [
   'getuid',
   'getutxid',
   'if_indextoname',
-  'lstat',
-  'lstat64',
   'mmap',
   'newlocale',
   'pipe2',
@@ -666,12 +660,23 @@ functions = [
   'setgroups',
   'setns',
   'setrlimit',
-  'stat',
-  'stat64',
   'symlink',
   'sysctlbyname',
 ]
 
+stat_functions = [
+  '__lxstat',
+  '__lxstat64',
+  '__xstat',
+  '__xstat64',
+  'lstat',
+  'lstat64',
+  'stat',
+  'stat64',
+]
+
+functions += stat_functions
+
 foreach function : functions
   if cc.has_function(function)
     conf.set('WITH_@0@'.format(function.to_upper()), 1)
@@ -679,6 +684,13 @@ foreach function : functions
 endforeach
 
 
+foreach function : stat_functions
+  if cc.has_header_symbol('sys/stat.h', function)
+    conf.set('WITH_@0@_DECL'.format(function.to_upper()), 1)
+  endif
+endforeach
+
+
 # various header checks
 
 headers = [
diff --git a/tests/virmockstathelpers.c b/tests/virmockstathelpers.c
index 5c9759551d..3bd2437ffe 100644
--- a/tests/virmockstathelpers.c
+++ b/tests/virmockstathelpers.c
@@ -67,39 +67,49 @@
  *  - If __xstat & __xstat64 exist, then stat & stat64 will not exist
  *    as symbols in the library, so the latter should not be mocked.
  *
+ *  - If __xstat exists in the library, but not the header than it
+ *    it is just there for binary back compat and should not be
+ *    mocked
+ *
  * The same all applies to lstat()
  */
 
 
+#if !defined(WITH___XSTAT_DECL)
+# if defined(WITH_STAT)
+#  if !defined(WITH___XSTAT) && !defined(WITH_STAT64) || defined(__APPLE__)
+#   define MOCK_STAT
+#  endif
+# endif
+# if defined(WITH_STAT64)
+#  define MOCK_STAT64
+# endif
+#else /* WITH___XSTAT_DECL */
+# if defined(WITH___XSTAT) && !defined(WITH___XSTAT64)
+#  define MOCK___XSTAT
+# endif
+# if defined(WITH___XSTAT64)
+#  define MOCK___XSTAT64
+# endif
+#endif /* WITH___XSTAT_DECL */
 
-#if defined(WITH_STAT)
-# if !defined(WITH___XSTAT) && !defined(WITH_STAT64) || defined(__APPLE__)
-#  define MOCK_STAT
+#if !defined(WITH___LXSTAT_DECL)
+# if defined(WITH_LSTAT)
+#  if !defined(WITH___LXSTAT) && !defined(WITH_LSTAT64) || defined(__APPLE__)
+#   define MOCK_LSTAT
+#  endif
 # endif
-#endif
-#if defined(WITH_STAT64) && !defined(WITH___XSTAT64)
-# define MOCK_STAT64
-#endif
-#if defined(WITH___XSTAT) && !defined(WITH___XSTAT64)
-# define MOCK___XSTAT
-#endif
-#if defined(WITH___XSTAT64)
-# define MOCK___XSTAT64
-#endif
-#if defined(WITH_LSTAT)
-# if !defined(WITH___LXSTAT) && !defined(WITH_LSTAT64) || defined(__APPLE__)
-#  define MOCK_LSTAT
+# if defined(WITH_LSTAT64)
+#  define MOCK_LSTAT64
 # endif
-#endif
-#if defined(WITH_LSTAT64) && !defined(WITH___LXSTAT64)
-# define MOCK_LSTAT64
-#endif
-#if defined(WITH___LXSTAT) && !defined(WITH___LXSTAT64)
-# define MOCK___LXSTAT
-#endif
-#if defined(WITH___LXSTAT64)
-# define MOCK___LXSTAT64
-#endif
+#else /* WITH___LXSTAT_DECL */
+# if defined(WITH___LXSTAT) && !defined(WITH___LXSTAT64)
+#  define MOCK___LXSTAT
+# endif
+# if defined(WITH___LXSTAT64)
+#  define MOCK___LXSTAT64
+# endif
+#endif /* WITH___LXSTAT_DECL */
 
 #ifdef MOCK_STAT
 static int (*real_stat)(const char *path, struct stat *sb);
-- 
2.28.0
Re: [libvirt PATCH] tests: fix stat mocking with Fedora rawhide
Posted by Michal Privoznik 3 years, 5 months ago 
On 10/29/20 6:25 PM, Daniel P. Berrangé wrote:
> GLibC has a really complicated way of dealing with the 'stat' function
> historically, which means our mocks in turn have to look at four
> different possible functions to replace, stat, stat64, __xstat,
> __xstat64.
> 
> In Fedora 33 and earlier:
> 
>   - libvirt.so links to __xstat64
>   - libc.so library exports stat, stat64, __xstat, __xstat64
>   - sys/stat.h header exposes stat and __xstat
> 
> In Fedora 34 rawhide:
> 
>   - libvirt.so links to stat64
>   - libc.so library exports stat, stat64, __xstat, __xstat64
>   - sys/stat.h header exposes stat
> 
> Historically we only looked at the exported symbols from libc.so to
> decide which to mock.
> 
> In F34 though we must not consider __xstat / __xstat64 though because
> they only existance for binary compatibility. Newly built binaries
> won't reference them.
> 
> Thus we must introduce a header file check into our logic for deciding
> which symbol to mock. We must ignore the __xstat / __xstat64 symbols
> if they don't appear in the sys/stat.h header, even if they appear
> in libc.so
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
> 
> Validated with this pipeline:
> 
>    https://gitlab.com/berrange/libvirt/-/pipelines/209361200
> 
>   meson.build                | 28 ++++++++++++-----
>   tests/virmockstathelpers.c | 62 ++++++++++++++++++++++----------------
>   2 files changed, 56 insertions(+), 34 deletions(-)

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

Thanks for taking care of this. You know I tried but my brain was too 
small for this :-)

Michal
Re: [libvirt PATCH] tests: fix stat mocking with Fedora rawhide
Posted by Michal Privoznik 3 years, 5 months ago 
On 10/29/20 6:25 PM, Daniel P. Berrangé wrote:
> 

BTW: I've pushed this so that Jirka can cook -rc2 overnight.

Michal

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