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Enhanced glibc documentation for core descriptor APIs.

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- Backport: manual: add dup3
- Backport: manual: add syscalls
- Adapt man pages version downstream

Resolves: RHEL-107861
This commit is contained in:
Frédéric Bérat 2025-08-06 16:55:22 +02:00
parent 5e0f6b30b8
commit 5a17d40420
3 changed files with 384 additions and 1 deletions
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@ -0,0 +1,27 @@
commit a07e000e82cb71238259e674529c37c12dc7d423
Author: DJ Delorie <dj@redhat.com>
Date: Fri May 10 17:34:29 2024 -0400
manual: add dup3
Reviewed-by: Florian Weimer <fweimer@redhat.com>
diff --git a/manual/llio.texi b/manual/llio.texi
index a65230d612eba7bf..513ba9e8859b8e6e 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -3443,6 +3443,14 @@ middle of calling @code{dup2} at which @var{new} is closed and not yet a
duplicate of @var{old}.
@end deftypefun
+@deftypefun int dup3 (int @var{old}, int @var{new}, int @var{flags})
+@standards{Linux, unistd.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+This function is the same as @code{dup2} but creates the new
+descriptor as if it had been opened with flags @var{flags}. The only
+allowed flag is @code{O_CLOEXEC}.
+@end deftypefun
+
@deftypevr Macro int F_DUPFD
@standards{POSIX.1, fcntl.h}
This macro is used as the @var{command} argument to @code{fcntl}, to

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commit 6c0be74305745c8f78bcfb69442c8c379459d99b
Author: DJ Delorie <dj@redhat.com>
Date: Mon Jul 8 17:52:15 2024 -0400
manual: add syscalls
The purpose of this patch is to add some system calls that (1) aren't
otherwise documented, and (2) are merely redirected to the kernel, so
can refer to their documentation; and define a standard way of doing
so in the future. A more detailed explaination of how system calls
are wrapped is added along with reference to the Linux Man-Pages
project.
Default version of man-pages is in configure.ac but can be overridden
by --with-man-pages=X.Y
Reviewed-by: Alejandro Colomar <alx@kernel.org>
Conflicts:
configure (skip unrelated configure changes, due to autoconf
call)
diff --git a/config.make.in b/config.make.in
index 55e8b7563b961dfc..36096881b7af4574 100644
--- a/config.make.in
+++ b/config.make.in
@@ -91,6 +91,7 @@ use-nscd = @use_nscd@
build-hardcoded-path-in-tests= @hardcoded_path_in_tests@
build-pt-chown = @build_pt_chown@
pthread-in-libc = @pthread_in_libc@
+man-pages-version = @man_pages_version@
# Build tools.
CC = @CC@
diff --git a/configure b/configure
index 432e40a59295cffd..c25b93dd0b317e4e 100755
--- a/configure
+++ b/configure
@@ -706,6 +706,7 @@ force_install
bindnow
hardcoded_path_in_tests
enable_timezone_tools
+man_pages_version
rtld_early_cflags
extra_nonshared_cflags
sysheaders
@@ -787,6 +788,7 @@ with_headers
with_nonshared_cflags
with_rtld_early_cflags
with_timeoutfactor
+with_man_pages
enable_sanity_checks
enable_shared
enable_profile
@@ -1509,6 +1511,8 @@ Optional Packages:
build early initialization with additional CFLAGS
--with-timeoutfactor=NUM
specify an integer to scale the timeout
+ --with-man-pages=VERSION
+ tie manual to a specific man-pages version
--with-cpu=CPU select code for CPU variant
Some influential environment variables:
@@ -4374,6 +4378,17 @@ fi
printf "%s\n" "#define TIMEOUTFACTOR $timeoutfactor" >>confdefs.h
+man_pages_version=6.9.1
+
+
+# Check whether --with-man-pages was given.
+if test ${with_man_pages+y}
+then :
+ withval=$with_man_pages; man_pages_version=$withval
+fi
+
+
+
# Check whether --enable-sanity-checks was given.
if test ${enable_sanity_checks+y}
then :
diff --git a/configure.ac b/configure.ac
index bdc385d03c3dc7f5..f00fc36f387af09d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -168,6 +168,15 @@ AC_ARG_WITH([timeoutfactor],
[timeoutfactor=1])
AC_DEFINE_UNQUOTED(TIMEOUTFACTOR, $timeoutfactor)
+man_pages_version=6.9.1
+
+AC_ARG_WITH([man-pages],
+ AS_HELP_STRING([--with-man-pages=VERSION],
+ [tie manual to a specific man-pages version]),
+ [man_pages_version=$withval],
+ [])
+AC_SUBST(man_pages_version)
+
AC_ARG_ENABLE([sanity-checks],
AS_HELP_STRING([--disable-sanity-checks],
[really do not use threads (should not be used except in special situations) @<:@default=yes@:>@]),
diff --git a/manual/Makefile b/manual/Makefile
index b5fda4a7ae07a785..a6c05db540d6c1da 100644
--- a/manual/Makefile
+++ b/manual/Makefile
@@ -117,6 +117,7 @@ $(objpfx)stamp-pkgvers: $(common-objpfx)config.make
echo "@set PKGVERSION_DEFAULT" >> $(objpfx)pkgvers-tmp; \
fi
echo "@set REPORT_BUGS_TO $(REPORT_BUGS_TEXI)" >> $(objpfx)pkgvers-tmp
+ echo "@set man_pages_version $(man-pages-version)" >> $(objpfx)pkgvers-tmp; \
echo "@end ifclear" >> $(objpfx)pkgvers-tmp
$(move-if-change) $(objpfx)pkgvers-tmp $(objpfx)pkgvers.texi
touch $@
diff --git a/manual/intro.texi b/manual/intro.texi
index ff43c5a7fbb969a0..879c1b38d9b73a46 100644
--- a/manual/intro.texi
+++ b/manual/intro.texi
@@ -85,6 +85,7 @@ standards each function or symbol comes from.
* Berkeley Unix:: BSD and SunOS.
* SVID:: The System V Interface Description.
* XPG:: The X/Open Portability Guide.
+* Linux Kernel:: The Linux kernel.
@end menu
@node ISO C, POSIX, , Standards and Portability
@@ -941,7 +942,7 @@ inter-process communication and shared memory, the @code{hsearch} and
@code{drand48} families of functions, @code{fmtmsg} and several of the
mathematical functions.
-@node XPG, , SVID, Standards and Portability
+@node XPG, Linux Kernel, SVID, Standards and Portability
@subsection XPG (The X/Open Portability Guide)
The X/Open Portability Guide, published by the X/Open Company, Ltd., is
@@ -960,6 +961,20 @@ fulfilling the XPG standard with the Unix extensions is a
precondition for getting the Unix brand chances are good that the
functionality is available on commercial systems.
+@node Linux Kernel, , XPG, Standards and Portability
+@subsection Linux (The Linux Kernel)
+
+@Theglibc{} includes by reference the Linux man-pages
+@value{man_pages_version} documentation to document the listed
+syscalls for the Linux kernel. For reference purposes only the latest
+@uref{https://www.kernel.org/doc/man-pages/,Linux man-pages Project}
+documentation can be accessed from the
+@uref{https://www.kernel.org,Linux kernel} website. Where the syscall
+has more specific documentation in this manual that more specific
+documentation is considered authoritative.
+
+Additional details on the Linux system call interface can be found in
+@xref{System Calls}.
@node Using the Library, Roadmap to the Manual, Standards and Portability, Introduction
@section Using the Library
diff --git a/manual/llio.texi b/manual/llio.texi
index 513ba9e8859b8e6e..17fe1181d5cc2cef 100644
--- a/manual/llio.texi
+++ b/manual/llio.texi
@@ -65,6 +65,7 @@ directly.)
* Interrupt Input:: Getting an asynchronous signal when
input arrives.
* IOCTLs:: Generic I/O Control operations.
+* Other Low-Level I/O APIs:: Other low-level-I/O-related functions.
@end menu
@@ -2242,6 +2243,8 @@ file descriptor, or until the timeout period expires.
There is another example showing the use of @code{select} to multiplex
input from multiple sockets in @ref{Server Example}.
+For an alternate interface to this functionality, see @code{poll}
+(@pxref{Other Low-Level I/O APIs}).
@node Synchronizing I/O
@section Synchronizing I/O operations
@@ -3325,7 +3328,9 @@ require additional arguments to be supplied. These additional arguments
and the return value and error conditions are given in the detailed
descriptions of the individual commands.
-Briefly, here is a list of what the various commands are.
+Briefly, here is a list of what the various commands are. For an
+exhaustive list of kernel-specific options, please see @xref{System
+Calls}.
@vtable @code
@item F_DUPFD
@@ -4661,5 +4666,28 @@ Most IOCTLs are OS-specific and/or only used in special system utilities,
and are thus beyond the scope of this document. For an example of the use
of an IOCTL, see @ref{Out-of-Band Data}.
-@c FIXME this is undocumented:
-@c dup3
+@node Other Low-Level I/O APIs
+@section Other low-level-I/O-related functions
+
+@deftp {Data Type} {struct pollfd}
+@standards{POSIX.1,poll.h}
+@end deftp
+
+@deftp {Data Type} {struct epoll_event}
+@standards{Linux,sys/epoll.h}
+@end deftp
+
+@deftypefun int poll (struct pollfd *@var{fds}, nfds_t @var{nfds}, int @var{timeout})
+
+@manpagefunctionstub{poll,2}
+@end deftypefun
+
+@deftypefun int epoll_create(int @var{size})
+
+@manpagefunctionstub{epoll_create,2}
+@end deftypefun
+
+@deftypefun int epoll_wait(int @var{epfd}, struct epoll_event *@var{events}, int @var{maxevents}, int @var{timeout})
+
+@manpagefunctionstub{epoll_wait,2}
+@end deftypefun
diff --git a/manual/macros.texi b/manual/macros.texi
index 4a2e22f4730d2390..579da3fb81e59da0 100644
--- a/manual/macros.texi
+++ b/manual/macros.texi
@@ -282,4 +282,11 @@ cwd\comments\
@macro standardsx {element, standard, header}
@end macro
+@macro manpagefunctionstub {func,sec}
+This documentation is a stub. For additional information on this
+function, consult the manual page
+@url{https://man7.org/linux/man-pages/man\sec\/\func\.\sec\.html}.
+@xref{Linux Kernel}.
+@end macro
+
@end ifclear
diff --git a/manual/socket.texi b/manual/socket.texi
index f0e35d9e13175212..8708cbb07ca02b5c 100644
--- a/manual/socket.texi
+++ b/manual/socket.texi
@@ -41,6 +41,7 @@ aren't documented either so far.
is to make it work with Inetd.
* Socket Options:: Miscellaneous low-level socket options.
* Networks Database:: Accessing the database of network names.
+* Other Socket APIs:: Other socket-related functions.
@end menu
@node Socket Concepts
@@ -3134,38 +3135,8 @@ You can use plain @code{recv} (@pxref{Receiving Data}) instead of
treat all possible senders alike). Even @code{read} can be used if
you don't want to specify @var{flags} (@pxref{I/O Primitives}).
-@ignore
-@c sendmsg and recvmsg are like readv and writev in that they
-@c use a series of buffers. It's not clear this is worth
-@c supporting or that we support them.
-@c !!! they can do more; it is hairy
-
-@deftp {Data Type} {struct msghdr}
-@standards{BSD, sys/socket.h}
-@end deftp
-
-@deftypefun ssize_t sendmsg (int @var{socket}, const struct msghdr *@var{message}, int @var{flags})
-@standards{BSD, sys/socket.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-
-This function is defined as a cancellation point in multi-threaded
-programs, so one has to be prepared for this and make sure that
-allocated resources (like memory, files descriptors, semaphores or
-whatever) are freed even if the thread is cancel.
-@c @xref{pthread_cleanup_push}, for a method how to do this.
-@end deftypefun
-
-@deftypefun ssize_t recvmsg (int @var{socket}, struct msghdr *@var{message}, int @var{flags})
-@standards{BSD, sys/socket.h}
-@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
-
-This function is defined as a cancellation point in multi-threaded
-programs, so one has to be prepared for this and make sure that
-allocated resources (like memory, files descriptors, semaphores or
-whatever) are freed even if the thread is canceled.
-@c @xref{pthread_cleanup_push}, for a method how to do this.
-@end deftypefun
-@end ignore
+If you need more flexibility and/or control over sending and receiving
+packets, see @code{sendmsg} and @code{recvmsg} (@pxref{Other Socket APIs}).
@node Datagram Example
@subsection Datagram Socket Example
@@ -3664,3 +3635,20 @@ returns a null pointer if there are no more entries.
@c libc_lock_unlock @aculock
This function closes the networks database.
@end deftypefun
+
+@node Other Socket APIs
+@section Other Socket APIs
+
+@deftp {Data Type} {struct msghdr}
+@standards{BSD, sys/socket.h}
+@end deftp
+
+@deftypefun ssize_t sendmsg (int @var{socket}, const struct msghdr *@var{message}, int @var{flags})
+
+@manpagefunctionstub{sendmsg,2}
+@end deftypefun
+
+@deftypefun ssize_t recvmsg (int @var{socket}, struct msghdr *@var{message}, int @var{flags})
+
+@manpagefunctionstub{recvmsg,2}
+@end deftypefun
diff --git a/manual/startup.texi b/manual/startup.texi
index 9bf24123f562f75b..1426f5e1abfb2f51 100644
--- a/manual/startup.texi
+++ b/manual/startup.texi
@@ -690,7 +690,25 @@ you don't need to know about it because you can just use @theglibc{}'s
@code{chmod} function.
@cindex kernel call
-System calls are sometimes called kernel calls.
+System calls are sometimes called syscalls or kernel calls, and this
+interface is mostly a purely mechanical translation from the kernel's
+ABI to the C ABI. For the set of syscalls where we do not guarantee
+POSIX Thread cancellation the wrappers only organize the incoming
+arguments from the C calling convention to the calling convention of
+the target kernel. For the set of syscalls where we provided POSIX
+Thread cancellation the wrappers set some internal state in the
+library to support cancellation, but this does not impact the
+behaviour of the syscall provided by the kernel.
+
+In some cases, if @theglibc{} detects that a system call has been
+superseded by a more capable one, the wrapper may map the old call to
+the new one. For example, @code{dup2} is implemented via @code{dup3}
+by passing an additional empty flags argument, and @code{open} calls
+@code{openat} passing the additional @code{AT_FDCWD}. Sometimes even
+more is done, such as converting between 32-bit and 64-bit time
+values. In general, though, such processing is only to make the
+system call better match the C ABI, rather than change its
+functionality.
However, there are times when you want to make a system call explicitly,
and for that, @theglibc{} provides the @code{syscall} function.
@@ -712,6 +730,8 @@ we won't describe it here either because anyone who is coding
library source code as a specification of the interface between them
anyway.
+@code{syscall} does not provide cancellation logic, even if the system
+call you're calling is listed as cancellable above.
@code{syscall} is declared in @file{unistd.h}.

10
glibc.spec
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@ -80,6 +80,8 @@
# glibc_shell_* below.
%undefine _auto_set_build_flags
%define man_pages_version 6.06-3.el10
##############################################################################
# Utility functions for pre/post scripts. Stick them at the beginning of
# any lua %pre, %post, %postun, etc. sections to have them expand into
@ -145,7 +147,7 @@ Version: %{glibcversion}
# - It allows using the Release number without the %%dist tag in the dependency
# generator to make the generated requires interchangeable between Rawhide
# and ELN (.elnYY < .fcXX).
%global baserelease 50
%global baserelease 51
Release: %{baserelease}%{?dist}
# Licenses:
@ -615,6 +617,8 @@ Patch291: glibc-RHEL-106562-21.patch
Patch292: glibc-RHEL-106562-22.patch
Patch293: glibc-RHEL-106562-23.patch
Patch294: glibc-RHEL-106562-24.patch
Patch295: glibc-RHEL-107861-1.patch
Patch296: glibc-RHEL-107861-2.patch
##############################################################################
# Continued list of core "glibc" package information:
@ -1630,6 +1634,7 @@ build()
%ifarch aarch64
--enable-memory-tagging \
%endif
--with-man-pages=%{man_pages_version} \
--disable-crypt \
--disable-build-nscd \
--disable-nscd \
@ -2627,6 +2632,9 @@ update_gconv_modules_cache ()
%endif
%changelog
* Wed Aug 06 2025 Frédéric Bérat <fberat@redhat.com> - 2.39-51
- Enhanced glibc documentation for core descriptor APIs. (RHEL-107861)
* Wed Aug 06 2025 Arjun Shankar <arjun@redhat.com> - 2.39-50
- Improve test coverage (RHEL-106562)