[v6,1/4] tracing: Enforce the persistent ring buffer to be page aligned

Commit Message

Steven Rostedt April 2, 2025, 2:49 p.m. UTC

From: Steven Rostedt <[e-mail]>

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-=[e-mail]/

Suggested-by: Linus Torvalds <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>
---
Change since v5: https://lore.kernel.org/linux-trace-kernel/[e-mail]/

- Use %pa instead of %lx for start and size sizes (Mike Rapoport)

 Documentation/admin-guide/kernel-parameters.txt |  2 ++
 Documentation/trace/debugging.rst               |  2 ++
 kernel/trace/trace.c                            | 10 ++++++++++
 3 files changed, 14 insertions(+)

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb8752b42ec8..71861643ef14 100644
--- 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 54fb16239d70..d54bc500af80 100644
--- 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 14c38fcd6f9e..96129985e81c 100644
--- 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",