On Tue, Apr 01, 2025 at 06:58:12PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rost...@goodmis.org>
>
> 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+gv41elms4wjqxhdnui6giddf...@mail.gmail.com/
>
> Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 2 ++
> Documentation/trace/debugging.rst | 2 ++
> kernel/trace/trace.c | 12 ++++++++++++
> 3 files changed, 16 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt
> b/Documentation/admin-guide/kernel-parameters.txt
> index 3435a062a208..f904fd8481bd 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -7266,6 +7266,8 @@
> 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 de6d7f0e6206..de9c237e5826 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -10788,6 +10788,18 @@ __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 %lx is not
> page aligned\n",
> + (unsigned long)start);
> + continue;
> + }
> + if (size & ~PAGE_MASK) {
> + pr_warn("Tracing: mapping size %lx is not page
> aligned\n",
> + (unsigned long)size);
> + continue;
> + }
Better use %pa for printing physical address as on 32-bit systems
phys_addr_t may be unsigned long long:
pr_warn("Tracing: mapping size %pa is not page aligned\n", &size);
> +
> addr = map_pages(start, size);
> if (addr) {
> pr_info("Tracing: mapped boot instance %s at
> physical memory %pa of size 0x%lx\n",
> --
> 2.47.2
>
>
--
Sincerely yours,
Mike.
