f3751ad011
__tracepoint_string's have their string data stored in .rodata, and an
address to that data stored in the "__tracepoint_str" section. Functions
that refer to those strings refer to the symbol of the address. Compiler
optimization can replace those address references with references
directly to the string data. If the address doesn't appear to have other
uses, then it appears dead to the compiler and is removed. This can
break the /tracing/printk_formats sysfs node which iterates the
addresses stored in the "__tracepoint_str" section.
Like other strings stored in custom sections in this header, mark these
__used to inform the compiler that there are other non-obvious users of
the address, so they should still be emitted.
Link: https://lkml.kernel.org/r/20200730224555.2142154-2-ndesaulniers@google.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 102c9323c3 ("tracing: Add __tracepoint_string() to export string pointers")
Reported-by: Tim Murray <timmurray@google.com>
Reported-by: Simon MacMullen <simonmacm@google.com>
Suggested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.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.