diff options
Diffstat (limited to 'usr/src/lib/libc')
| -rw-r--r-- | usr/src/lib/libc/README | 60 |
1 files changed, 59 insertions, 1 deletions
diff --git a/usr/src/lib/libc/README b/usr/src/lib/libc/README index 1644d534ec..cad0234210 100644 --- a/usr/src/lib/libc/README +++ b/usr/src/lib/libc/README @@ -23,6 +23,8 @@ # Use is subject to license terms. # +# Process Model Unification + The Solaris Process Model Unification project: PSARC/2002/117 Solaris Process Model Unification 4470917 Solaris Process Model Unification @@ -183,7 +185,7 @@ many of these rules are enforced by ASSERT() statements scattered about in the libc sources. This is the default mode for building libc when a DEBUG nightly build is performed. ------ +# libaio/librt Implementation In libc The putback of the project: 6416832 libaio and librt can and should be folded into libc @@ -219,3 +221,59 @@ long-term waits.) Just follow a few rules to be self-consistent: - The sig_*() interfaces are not in themselves fork-safe. You have to employ other logic to make your code fork-safe. See the tail of postfork1_child() for examples. + +# Removal Of Synonym Symbols + +The following project: + PSARC 2008/309 expunge synonyms.h + 6700179 expunge synonyms.h + +Removed the historical "synonym" symbols from the C Library. + +Historically, for every public function symbol in the C library a second, +private, symbol of the same value was defined to be used internally by libc +(generally, one or the other will be a weak symbol, precisely which is +inconsistent). + +These synonym symbols existed such that an application which provided +otherwise conflicting symbols could interpose on the version in libc without +compromising libc itself, that is if libc defines fopen() which needs open() it +would call _open() and an application defined open() would not cause fopen() +to break. This was made transparent to code within libc via a header, +synonyms.h, which would #define open _open, for all such symbols. + +Since ON now uses direct bindings extensively all symbols not explicitly +marked "NODIRECT" are directly bound within libc anyway, and none of this is +actually necessary. Thus synonyms.h was removed, and no new synonym symbols +need be added. However, unfortunately, certain of the private symbols were +inadvertently exposed to applications, and several are known to have been +used, thus these existing synonyms must continue to exist to maintain +compatibility. A preloadable library, /lib/c_synonyms.so.1 is provided which +also provides the historical names with underscore prefixes to allow any other +incorrect application to continue to function. + +It should never be necessary to add additional synonym symbols to libc nor to +add underscore prefixed aliases to c_synonyms.so.1. + +# libc Internals Scoped Protected + +The integration of the fix for: + 6689238 libc needs global protection against ld.so.1 + +Scopes all function symbols within libc protected, excepting those that need +to be accepting of interposition and to have a consistent version called both +within and without libc (basically, the malloc() family). + +This causes references by libc to itself to be permanently and unavoidably +bound, and thus to never enter ld.so (and potentially from there audit +libraries or other such support libraries). This maintains an otherwise +complicated to verify invariant: within critical sections (with any internal +lock held, etc) execution can never leave the context of libc. Previously +this was done with a selection of known-to-be-problematic functions having +weak synonyms scoped private, but this was both difficult to verify, difficult +to remember, and thus always at least somewhat incomplete. + +In summary, any new function symbol in libc must be scoped protected unless it +is one of a very small group of functions that must allow interposed versions +to be bound to from the C library itself -- it is grossly unlikely that more +of these will occur. |