Commit c44a14f2 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
Browse files

tracing: Enforce the persistent ring buffer to be page aligned 

Enforce that the address and the size of the memory used by the persistent
ring buffer is page aligned. Also update the documentation to reflect this
requirement.

Link: https://lore.kernel.org/all/CAHk-=whUOfVucfJRt7E0AH+GV41ELmS4wJqxHDnui6Giddfkzw@mail.gmail.com/

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: Mike Rapoport <rppt@kernel.org>
Cc: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/20250402144953.412882844@goodmis.org


Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 028a58ec

Documentation/admin-guide/kernel-parameters.txt

+2 −0
Original line number Diff line number Diff line
@@ -7241,6 +7241,8 @@ 
			This is just one of many ways that can clear memory. Make sure your system

			keeps the content of memory across reboots before relying on this option.



			NB: Both the mapped address and size must be page aligned for the architecture.



			See also Documentation/trace/debugging.rst

Documentation/trace/debugging.rst

+2 −0
Original line number Diff line number Diff line
@@ -136,6 +136,8 @@ kernel, so only the same kernel is guaranteed to work if the mapping is 
preserved. Switching to a different kernel version may find a different

layout and mark the buffer as invalid.



NB: Both the mapped address and size must be page aligned for the architecture.



Using trace_printk() in the boot instance

-----------------------------------------

By default, the content of trace_printk() goes into the top level tracing

kernel/trace/trace.c

+10 −0
Original line number Diff line number Diff line
@@ -10774,6 +10774,16 @@ __init static void enable_instances(void) 
		}



		if (start) {

			/* Start and size must be page aligned */

			if (start & ~PAGE_MASK) {

				pr_warn("Tracing: mapping start addr %pa is not page aligned\n", &start);

				continue;

			}

			if (size & ~PAGE_MASK) {

				pr_warn("Tracing: mapping size %pa is not page aligned\n", &size);

				continue;

			}



			addr = map_pages(start, size);

			if (addr) {

				pr_info("Tracing: mapped boot instance %s at physical memory %pa of size 0x%lx\n",