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: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb8752b42ec8582b8750d7e014c4d76166fa2fc1..71861643ef1432bb427fb1186b643aa8f90e3846 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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
 
 

diff --git a/Documentation/trace/debugging.rst b/Documentation/trace/debugging.rst
index 54fb16239d703348e7cbca123180a916cd02f128..d54bc500af80ba32c7f2ee9c5c2dde0b7bc25e6e 100644 (file)
--- a/Documentation/trace/debugging.rst
+++ b/Documentation/trace/debugging.rst
@@ -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

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 14c38fcd6f9eda08c09b016ac3b255d42676ffc6..96129985e81c1793aa35420e3d189c2c1d9766ce 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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",