tracing: Have reserve_mem use phys_to_virt() and separate from memmap buffer

The reserve_mem kernel command line option may pass back a physical
address, but the memory is still part of the normal memory just like
using memblock_alloc() would be. This means that the physical memory
returned by the reserve_mem command line option can be converted directly
to virtual memory by simply using phys_to_virt().

When freeing the buffer there's no need to call vunmap() anymore as the
memory allocated by reserve_mem is freed by the call to
reserve_mem_release_by_name().

Because the persistent ring buffer can also be allocated via the memmap
option, which *is* different than normal memory as it cannot be added back
to the buddy system, it must be treated differently. It still needs to be
virtually mapped to have access to it. It also can not be freed nor can it
ever be memory mapped to user space.

Create a new trace_array flag called TRACE_ARRAY_FL_MEMMAP which gets set
if the buffer is created by the memmap option, and this will prevent the
buffer from being memory mapped by user space.

Also increment the ref count for memmap'ed buffers so that they can never
be freed.

Link: https://lore.kernel.org/all/Z-wFszhJ_9o4dc8O@kernel.org/

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/20250402144953.583750106@goodmis.org
Suggested-by: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

0 files changed, 0 insertions, 0 deletions