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From: Florian Weimer <fw@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/release/2.35/master] manual: Document the dlinfo function Date: Wed, 11 May 2022 18:24:48 +0000 (GMT) [thread overview] Message-ID: <20220511182448.6F8EF3857425@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=78f82ab4ef839b52df022234aff63e2d4d7f264f commit 78f82ab4ef839b52df022234aff63e2d4d7f264f Author: Florian Weimer <fweimer@redhat.com> Date: Fri Apr 29 17:00:48 2022 +0200 manual: Document the dlinfo function Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@rehdat.com> (cherry picked from commit 93804a1ee084d4bdc620b2b9f91615c7da0fabe1) Diff: --- manual/dynlink.texi | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 70 insertions(+), 1 deletion(-) diff --git a/manual/dynlink.texi b/manual/dynlink.texi index 54091be18e..bc3b779b69 100644 --- a/manual/dynlink.texi +++ b/manual/dynlink.texi @@ -22,6 +22,76 @@ Dynamic linkers are sometimes called @dfn{dynamic loaders}. @Theglibc{} provides various functions for querying information from the dynamic linker. +@deftypefun {int} dlinfo (void *@var{handle}, int @var{request}, void *@var{arg}) +@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}} +@standards{GNU, dlfcn.h} +This function returns information about @var{handle} in the memory +location @var{arg}, based on @var{request}. The @var{handle} argument +must be a pointer returned by @code{dlopen} or @code{dlmopen}; it must +not have been closed by @code{dlclose}. + +On success, @code{dlinfo} returns 0. If there is an error, the function +returns @math{-1}, and @code{dlerror} can be used to obtain a +corresponding error message. + +The following operations are defined for use with @var{request}: + +@vtable @code +@item RTLD_DI_LINKMAP +The corresponding @code{struct link_map} pointer for @var{handle} is +written to @code{*@var{arg}}. The @var{arg} argument must be the +address of an object of type @code{struct link_map *}. + +@item RTLD_DI_LMID +The namespace identifier of @var{handle} is written to +@code{*@var{arg}}. The @var{arg} argument must be the address of an +object of type @code{Lmid_t}. + +@item RTLD_DI_ORIGIN +The value of the @code{$ORIGIN} dynamic string token for @var{handle} is +written to the character array starting at @var{arg} as a +null-terminated string. + +This request type should not be used because it is prone to buffer +overflows. + +@item RTLD_DI_SERINFO +@itemx RTLD_DI_SERINFOSIZE +These requests can be used to obtain search path information for +@var{handle}. For both requests, @var{arg} must point to a +@code{Dl_serinfo} object. The @code{RTLD_DI_SERINFOSIZE} request must +be made first; it updates the @code{dls_size} and @code{dls_cnt} members +of the @code{Dl_serinfo} object. The caller should then allocate memory +to store at least @code{dls_size} bytes and pass that buffer to a +@code{RTLD_DI_SERINFO} request. This second request fills the +@code{dls_serpath} array. The number of array elements was returned in +the @code{dls_cnt} member in the initial @code{RTLD_DI_SERINFOSIZE} +request. The caller is responsible for freeing the allocated buffer. + +This interface is prone to buffer overflows in multi-threaded processes +because the required size can change between the +@code{RTLD_DI_SERINFOSIZE} and @code{RTLD_DI_SERINFO} requests. + +@item RTLD_DI_TLS_DATA +This request writes the address of the TLS block (in the current thread) +for the shared object identified by @var{handle} to @code{*@var{arg}}. +The argument @var{arg} must be the address of an object of type +@code{void *}. A null pointer is written if the object does not have +any associated TLS block. + +@item RTLD_DI_TLS_MODID +This request writes the TLS module ID for the shared object @var{handle} +to @code{*@var{arg}}. The argument @var{arg} must be the address of an +object of type @code{size_t}. The module ID is zero if the object +does not have an associated TLS block. +@end vtable + +The @code{dlinfo} function is a GNU extension. +@end deftypefun + +The remainder of this section documents the @code{_dl_find_object} +function and supporting types and constants. + @deftp {Data Type} {struct dl_find_object} @standards{GNU, dlfcn.h} This structure contains information about a main program or loaded @@ -130,7 +200,6 @@ This function is a GNU extension. @c dladdr1 @c dlclose @c dlerror -@c dlinfo @c dlmopen @c dlopen @c dlsym
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