mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-06 19:08:57 +09:00
a5f1934fea
commit a001cd248ab244633c5fabe4f7c707e13fc1d1cc upstream.
Add "extern" to the glibc-defined weak rseq symbols to convert the rseq
selftest's usage from weak symbol definitions to weak symbol _references_.
Effectively re-defining the glibc symbols wreaks havoc when building with
-fno-common, e.g. generates segfaults when running multi-threaded programs,
as dynamically linked applications end up with multiple versions of the
symbols.
Building with -fcommon, which until recently has the been the default for
GCC and clang, papers over the bug by allowing the linker to resolve the
weak/tentative definition to glibc's "real" definition.
Note, the symbol itself (or rather its address), not the value of the
symbol, is set to 0/NULL for unresolved weak symbol references, as the
symbol doesn't exist and thus can't have a value. Check for a NULL rseq
size pointer to handle the scenario where the test is statically linked
against a libc that doesn't support rseq in any capacity.
Fixes: 3bcbc20942 ("selftests/rseq: Play nice with binaries statically linked against glibc 2.35+")
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: stable@vger.kernel.org
Closes: https://lore.kernel.org/all/87frdoybk4.ffs@tglx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.