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ring-buffer: Use kaslr address instead of text delta

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Instead of saving off the text and data pointers and using them to compare
with the current boot's text and data pointers, just save off the KASLR
offset. Then that can be used to figure out how to read the previous boots
buffer.

The last_boot_info will now show this offset, but only if it is for a
previous boot:

  ~# cat instances/boot_mapped/last_boot_info
  39000000	[kernel]

  ~# echo function > instances/boot_mapped/current_tracer
  ~# cat instances/boot_mapped/last_boot_info
  # Current

If the KASLR offset saved is for the current boot, the last_boot_info will
show the value of "current".

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/20250305164608.274956504@goodmis.org
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt
2025-03-05 11:45:40 -05:00
committed by Steven Rostedt (Google)
parent c73f0b6964
commit bcba8d4dbe
4 changed files with 39 additions and 34 deletions
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include/linux/ring_buffer.h
+1 -2
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@@ -94,8 +94,7 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flag
unsigned long range_size,
struct lock_class_key *key);
bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text,
long *data);
bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long *kaslr_addr);
/*
* Because the ring buffer is generic, if other users of the ring buffer get