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171 lines
6.1 KiB
171 lines
6.1 KiB
2 years ago
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commit e4a2fb76efb45210c541ee3f8ef32f317783c3a8
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Wed May 11 20:30:49 2022 +0200
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manual: Document the dlinfo function
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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Tested-by: Carlos O'Donell <carlos@rehdat.com>
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(cherry picked from commit 93804a1ee084d4bdc620b2b9f91615c7da0fabe1)
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Also includes partial backport of commit 5d28a8962dcb6ec056b81d730e
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(the addition of manual/dynlink.texi).
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diff --git a/manual/Makefile b/manual/Makefile
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index e83444341e282916..31678681ef059e0f 100644
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--- a/manual/Makefile
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+++ b/manual/Makefile
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@@ -39,7 +39,7 @@ chapters = $(addsuffix .texi, \
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pipe socket terminal syslog math arith time \
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resource setjmp signal startup process ipc job \
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nss users sysinfo conf crypt debug threads \
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- probes tunables)
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+ dynlink probes tunables)
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appendices = lang.texi header.texi install.texi maint.texi platform.texi \
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contrib.texi
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licenses = freemanuals.texi lgpl-2.1.texi fdl-1.3.texi
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diff --git a/manual/dynlink.texi b/manual/dynlink.texi
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new file mode 100644
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index 0000000000000000..dbf3de11769d8e57
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--- /dev/null
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+++ b/manual/dynlink.texi
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@@ -0,0 +1,100 @@
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+@node Dynamic Linker
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+@c @node Dynamic Linker, Internal Probes, Threads, Top
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+@c %MENU% Loading programs and shared objects.
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+@chapter Dynamic Linker
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+@cindex dynamic linker
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+@cindex dynamic loader
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+
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+The @dfn{dynamic linker} is responsible for loading dynamically linked
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+programs and their dependencies (in the form of shared objects). The
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+dynamic linker in @theglibc{} also supports loading shared objects (such
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+as plugins) later at run time.
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+
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+Dynamic linkers are sometimes called @dfn{dynamic loaders}.
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+
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+@menu
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+* Dynamic Linker Introspection:: Interfaces for querying mapping information.
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+@end menu
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+
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+@node Dynamic Linker Introspection
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+@section Dynamic Linker Introspection
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+
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+@Theglibc{} provides various functions for querying information from the
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+dynamic linker.
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+
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+@deftypefun {int} dlinfo (void *@var{handle}, int @var{request}, void *@var{arg})
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+@safety{@mtsafe{}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
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+@standards{GNU, dlfcn.h}
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+This function returns information about @var{handle} in the memory
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+location @var{arg}, based on @var{request}. The @var{handle} argument
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+must be a pointer returned by @code{dlopen} or @code{dlmopen}; it must
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+not have been closed by @code{dlclose}.
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+
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+On success, @code{dlinfo} returns 0. If there is an error, the function
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+returns @math{-1}, and @code{dlerror} can be used to obtain a
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+corresponding error message.
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+
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+The following operations are defined for use with @var{request}:
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+
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+@vtable @code
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+@item RTLD_DI_LINKMAP
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+The corresponding @code{struct link_map} pointer for @var{handle} is
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+written to @code{*@var{arg}}. The @var{arg} argument must be the
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+address of an object of type @code{struct link_map *}.
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+
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+@item RTLD_DI_LMID
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+The namespace identifier of @var{handle} is written to
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+@code{*@var{arg}}. The @var{arg} argument must be the address of an
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+object of type @code{Lmid_t}.
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+
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+@item RTLD_DI_ORIGIN
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+The value of the @code{$ORIGIN} dynamic string token for @var{handle} is
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+written to the character array starting at @var{arg} as a
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+null-terminated string.
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+
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+This request type should not be used because it is prone to buffer
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+overflows.
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+
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+@item RTLD_DI_SERINFO
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+@itemx RTLD_DI_SERINFOSIZE
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+These requests can be used to obtain search path information for
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+@var{handle}. For both requests, @var{arg} must point to a
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+@code{Dl_serinfo} object. The @code{RTLD_DI_SERINFOSIZE} request must
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+be made first; it updates the @code{dls_size} and @code{dls_cnt} members
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+of the @code{Dl_serinfo} object. The caller should then allocate memory
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+to store at least @code{dls_size} bytes and pass that buffer to a
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+@code{RTLD_DI_SERINFO} request. This second request fills the
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+@code{dls_serpath} array. The number of array elements was returned in
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+the @code{dls_cnt} member in the initial @code{RTLD_DI_SERINFOSIZE}
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+request. The caller is responsible for freeing the allocated buffer.
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+
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+This interface is prone to buffer overflows in multi-threaded processes
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+because the required size can change between the
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+@code{RTLD_DI_SERINFOSIZE} and @code{RTLD_DI_SERINFO} requests.
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+
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+@item RTLD_DI_TLS_DATA
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+This request writes the address of the TLS block (in the current thread)
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+for the shared object identified by @var{handle} to @code{*@var{arg}}.
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+The argument @var{arg} must be the address of an object of type
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+@code{void *}. A null pointer is written if the object does not have
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+any associated TLS block.
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+
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+@item RTLD_DI_TLS_MODID
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+This request writes the TLS module ID for the shared object @var{handle}
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+to @code{*@var{arg}}. The argument @var{arg} must be the address of an
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+object of type @code{size_t}. The module ID is zero if the object
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+does not have an associated TLS block.
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+@end vtable
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+
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+The @code{dlinfo} function is a GNU extension.
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+@end deftypefun
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+
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+@c FIXME these are undocumented:
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+@c dladdr
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+@c dladdr1
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+@c dlclose
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+@c dlerror
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+@c dlmopen
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+@c dlopen
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+@c dlsym
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+@c dlvsym
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diff --git a/manual/libdl.texi b/manual/libdl.texi
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deleted file mode 100644
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index e3fe0452d9f41d47..0000000000000000
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--- a/manual/libdl.texi
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+++ /dev/null
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@@ -1,10 +0,0 @@
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-@c FIXME these are undocumented:
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-@c dladdr
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-@c dladdr1
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-@c dlclose
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-@c dlerror
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-@c dlinfo
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-@c dlmopen
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-@c dlopen
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-@c dlsym
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-@c dlvsym
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diff --git a/manual/probes.texi b/manual/probes.texi
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index 4aae76b81921f347..ee019e651706f492 100644
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--- a/manual/probes.texi
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+++ b/manual/probes.texi
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@@ -1,5 +1,5 @@
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@node Internal Probes
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-@c @node Internal Probes, Tunables, Threads, Top
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+@c @node Internal Probes, Tunables, Dynamic Linker, Top
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@c %MENU% Probes to monitor libc internal behavior
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@chapter Internal probes
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diff --git a/manual/threads.texi b/manual/threads.texi
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index 06b6b277a1228af1..7f166bfa87e88c36 100644
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--- a/manual/threads.texi
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+++ b/manual/threads.texi
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@@ -1,5 +1,5 @@
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@node Threads
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-@c @node Threads, Internal Probes, Debugging Support, Top
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+@c @node Threads, Dynamic Linker, Debugging Support, Top
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@c %MENU% Functions, constants, and data types for working with threads
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@chapter Threads
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@cindex threads
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