diff options
| author | Vincent Donnefort <vdonnefort@google.com> | 2026-09-11 20:39:35 +0100 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2026-09-13 13:06:29 -0400 |
| commit | 442ffa742daa65a0e8fe003abe9fbe472366e4de (patch) | |
| tree | 1f72c21dd26526d26b19bee8d453a6b8387755a0 /include/linux | |
| parent | bcfe2816e6ec46c3f4c58aa4264476665ddb3f69 (diff) | |
tracing/remotes: Account for ring buffer page header in size calculation
trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount the
required pages because every ring buffer page contains a header
(BUF_PAGE_HDR_SIZE). Account for that header to ensure allocated remote
ring buffers aren't smaller than requested by the user.
The newly introduced helper __calc_nr_pages_ring_buffer_desc() can
return a value that overflows the descriptor nr_pages field (32 bits).
Link: https://patch.msgid.link/20260911193937.602202-2-vdonnefort@google.com
Fixes: 2e67fabd8b77 ("ring-buffer: Introduce ring-buffer remotes")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/ring_buffer.h | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index afc7daa6ee7d..11bffb6a142d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -3,8 +3,9 @@ #define _LINUX_RING_BUFFER_H #include <linux/mm.h> -#include <linux/seq_file.h> #include <linux/poll.h> +#include <linux/ring_buffer_types.h> +#include <linux/seq_file.h> #include <uapi/linux/trace_mmap.h> @@ -279,9 +280,19 @@ static inline struct ring_buffer_desc *__first_ring_buffer_desc(struct trace_buf return (struct ring_buffer_desc *)(&desc->__data[0]); } +/* + * Returns the number of pages for a ring_buffer_desc. The caller must ensure it + * does not overflow ring_buffer_desc::nr_page_va. + */ +static inline unsigned long __calc_nr_pages_ring_buffer_desc(size_t size) +{ + /* Takes into account the reader page */ + return max(DIV_ROUND_UP(size, PAGE_SIZE - BUF_PAGE_HDR_SIZE), 2UL) + 1; +} + static inline size_t trace_buffer_desc_size(size_t buffer_size, unsigned int nr_cpus) { - unsigned int nr_pages = max(DIV_ROUND_UP(buffer_size, PAGE_SIZE), 2UL) + 1; + unsigned long nr_pages = __calc_nr_pages_ring_buffer_desc(buffer_size); struct ring_buffer_desc *rbdesc; return size_add(offsetof(struct trace_buffer_desc, __data), |