Merge tag 'trace-ringbuffer-v6.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull ring-buffer updates from Steven Rostedt:

- Restructure the persistent memory to have a "scratch" area

Instead of hard coding the KASLR offset in the persistent memory by
the ring buffer, push that work up to the callers of the persistent
memory as they are the ones that need this information. The offsets
and such is not important to the ring buffer logic and it should not
be part of that.

A scratch pad is now created when the caller allocates a ring buffer
from persistent memory by stating how much memory it needs to save.

- Allow where modules are loaded to be saved in the new scratch pad

Save the addresses of modules when they are loaded into the
persistent memory scratch pad.

- A new module_for_each_mod() helper function was created

With the acknowledgement of the module maintainers a new module
helper function was created to iterate over all the currently loaded
modules. This has a callback to be called for each module. This is
needed for when tracing is started in the persistent buffer and the
currently loaded modules need to be saved in the scratch area.

- Expose the last boot information where the kernel and modules were
loaded

The last_boot_info file is updated to print out the addresses of
where the kernel "_text" location was loaded from a previous boot, as
well as where the modules are loaded. If the buffer is recording the
current boot, it only prints "# Current" so that it does not expose
the KASLR offset of the currently running kernel.

- Allow the persistent ring buffer to be released (freed)

To have this in production environments, where the kernel command
line can not be changed easily, the ring buffer needs to be freed
when it is not going to be used. The memory for the buffer will
always be allocated at boot up, but if the system isn't going to
enable tracing, the memory needs to be freed. Allow it to be freed
and added back to the kernel memory pool.

- Allow stack traces to print the function names in the persistent
buffer

Now that the modules are saved in the persistent ring buffer, if the
same modules are loaded, the printing of the function names will
examine the saved modules. If the module is found in the scratch area
and is also loaded, then it will do the offset shift and use kallsyms
to display the function name. If the address is not found, it simply
displays the address from the previous boot in hex.

* tag 'trace-ringbuffer-v6.15-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Use _text and the kernel offset in last_boot_info
tracing: Show last module text symbols in the stacktrace
ring-buffer: Remove the unused variable bmeta
tracing: Skip update_last_data() if cleared and remove active check for save_mod()
tracing: Initialize scratch_size to zero to prevent UB
tracing: Fix a compilation error without CONFIG_MODULES
tracing: Freeable reserved ring buffer
mm/memblock: Add reserved memory release function
tracing: Update modules to persistent instances when loaded
tracing: Show module names and addresses of last boot
tracing: Have persistent trace instances save module addresses
module: Add module_for_each_mod() function
tracing: Have persistent trace instances save KASLR offset
ring-buffer: Add ring_buffer_meta_scratch()
ring-buffer: Add buffer meta data for persistent ring buffer
ring-buffer: Use kaslr address instead of text delta
ring-buffer: Fix bytes_dropped calculation issue