From 3d49f95b4d9d70716173dabbc1a6cfb5c8c6a8f9 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Fri, 25 Sep 2020 10:48:37 +0200 Subject: [PATCH] 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 Signed-off-by: Florian Weimer Signed-off-by: Michael Kerrisk --- man7/rtld-audit.7 | 36 +++++++++++++++++++++++++----------- 1 file changed, 25 insertions(+), 11 deletions(-) diff --git a/man7/rtld-audit.7 b/man7/rtld-audit.7 index b1b7dfebc..21cc339d0 100644 --- a/man7/rtld-audit.7 +++ b/man7/rtld-audit.7 @@ -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 +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 +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 *