Messages in this thread | | | Date | Mon, 26 Sep 2022 18:18:33 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH printk 18/18] printk: Handle dropped message smarter |
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On (22/09/26 10:00), John Ogness wrote: > > Oh, hmm. This does not look to me as a simplification. Quite > > the opposite, moving cons_text_buf::text pointer to point to > > cons_text_buf::text - strlen("... dropped messages...") looks > > somewhat fragile. > > It relies on @ext_text and @text being packed together, which yes, may > be fragile.
Right, and this assumption can be broken by both internal and external sources: new gcc/clang plugins, config options, etc.
> As an alternative we could memcpy the message text (@text) > to the end of the dropped message text. There would be enough room. > > Generally speaking, the dropped text will be less text to copy. But > since dropped messages are rare anyway, it might be worth copying more > data so that the code is not fragile. It would also allow us to remove > the __no_randomize_layout in "struct cons_text_buf".
Agreed.
> If the end of cons_print_dropped was changed to: > > memcpy(txtbuf->ext_text + len, txtbuf->text, desc->len); > desc->len += len; > desc->outbuf = txtbuf->ext_text; > > Would that be OK for you?
Yes, this looks solid (nothing should be able to break it and cause mem corruptions).
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