tree 9f15eff00dca5066fa64117f5ef9dc190ad52ebd
parent 9f3ee94e705a5b2fe352befb37e499163f98b9b6
parent 6e31b759b076eebb4184117234f0c4eb9e4bc460
author Linus Torvalds <torvalds@linux-foundation.org> 1737501114 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1737501114 -0800
mergetag object 6e31b759b076eebb4184117234f0c4eb9e4bc460
 type commit
 tag trace-ringbuffer-v6.14
 tagger Steven Rostedt (Google) <rostedt@goodmis.org> 1737332655 -0500
 
 ring-buffer changes for v6.14
 
 - Clean up the __rb_map_vma() logic
 
   The logic of __rb_map_vma() has a error check with WARN_ON() that makes
   sure that the index does not go past the end of the array of buffers. The
   test in the loop pretty much guarantees that it will never happen, but
   since the relation of the variables used is a little complex, the
   WARN_ON() check was added. It was noticed that the array was dereferenced
   before this check and if the logic does break and for some reason the
   logic goes past the array, there will be an out of bounds access here.
   Move the access to after the WARN_ON().
 
 - Consolidate how the ring buffer is determined to be empty
 
   Currently there's two ways that are used to determine if the ring buffer
   is empty. One relies on the status of the commit and reader pages and what
   was read, and the other is on what was written vs what was read. By using
   the number of entries (written) method, it can be used for reading events
   that are out of the kernel's control (what pKVM will use). Move to this
   method to make it easier to implement a pKVM ring buffer that the kernel
   can read.
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Merge tag 'trace-ringbuffer-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull trace ring-buffer updates from Steven Rostedt:

 - Clean up the __rb_map_vma() logic

   The logic of __rb_map_vma() has a error check with WARN_ON() that
   makes sure that the index does not go past the end of the array of
   buffers. The test in the loop pretty much guarantees that it will
   never happen, but since the relation of the variables used is a
   little complex, the WARN_ON() check was added. It was noticed that
   the array was dereferenced before this check and if the logic does
   break and for some reason the logic goes past the array, there will
   be an out of bounds access here. Move the access to after the
   WARN_ON().

 - Consolidate how the ring buffer is determined to be empty

   Currently there's two ways that are used to determine if the ring
   buffer is empty. One relies on the status of the commit and reader
   pages and what was read, and the other is on what was written vs what
   was read. By using the number of entries (written) method, it can be
   used for reading events that are out of the kernel's control (what
   pKVM will use). Move to this method to make it easier to implement a
   pKVM ring buffer that the kernel can read.

* tag 'trace-ringbuffer-v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Make reading page consistent with the code logic
  ring-buffer: Check for empty ring-buffer with rb_num_of_entries()