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tracing: Enforce the persistent ring buffer to be page aligned

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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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2025-04-02 10:49:04 -04:00 committed by Steven Rostedt (Google)
parent 028a58ec15
commit c44a14f216
3 changed files with 14 additions and 0 deletions
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2
Documentation/admin-guide/kernel-parameters.txt
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@ -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

2
Documentation/trace/debugging.rst
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@ -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

10
kernel/trace/trace.c
View File

@ -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",