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rtld-audit.7: Clarify la_version handshake 

Returning its argument without further checks is almost always
wrong for la_version.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Signed-off-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Florian Weimer 2020-09-25 10:48:37 +02:00 committed by Michael Kerrisk
parent 7955742d0d
commit 3d49f95b4d
1 changed files with 25 additions and 11 deletions
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36
man7/rtld-audit.7
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@ -70,17 +70,30 @@ the auditing library.
When invoking this function, the dynamic linker passes, in
.IR version ,
the highest version of the auditing interface that the linker supports.
If necessary, the auditing library can check that this version
is sufficient for its requirements.
.PP
As its function result,
this function should return the version of the auditing interface
that this auditing library expects to use (returning
A typical implementation of this function simply returns the constant
.BR LAV_CURRENT ,
which indicates the version of
.I <link.h>
that was used to build the audit module. If the dynamic linker does
not support this version of the audit interface, it will refuse to
activate this audit module. If the function returns zero, the dynamic
linker also does not activate this audit module.
.PP
In order to enable backwards compatibility with older dynamic linkers,
an audit module can examine the
.I version
is acceptable).
If the returned value is 0,
or a version that is greater than that supported by the dynamic linker,
then the audit library is ignored.
argument and return an earlier version than
.BR LAV_CURRENT ,
assuming the module can adjust its implementation to match the
requirements of the previous version of the audit interface. The
.B la_version
function should not return the value of
.I version
without further checks because it could correspond to an interface
that does not match the
.I <link.h>
definitions used to build the audit module.
.SS la_objsearch()
\&
.nf
@ -508,9 +521,10 @@ This is reportedly fixed in glibc 2.10.
unsigned int
la_version(unsigned int version)
{
printf("la_version(): %u\en", version);
printf("la_version(): version = %u; LAV_CURRENT = %u\en",
version, LAV_CURRENT);
return version;
return LAV_CURRENT;
}
char *