Update fbdev plugin to gracefully handle old/broken symbol tables #1686
Conversation
| try: | ||
| num_registered_fb = kernel.object_from_symbol("num_registered_fb") | ||
| except exceptions.SymbolError: | ||
| vollog.error( |
There was a problem hiding this comment.
Do we know the exact lowest required version number of dwarf2json? I think we've got code that can check and warn on such things? (see here )
There was a problem hiding this comment.
hmm the thing there is that, if the fbdev driver is compiled into the kernel, then the plugin will work with the old symbols tables. The object_from_symbol call only fails when both conditions are met (compiled as module + old symbol table).
There was a problem hiding this comment.
Ok, so then the check belongs in here? The point is we should be able to tell whether their symbol table is too old or if that's not the problem?
|
Thanks for spotting this issue! Once the btf2json framework integration is implemented, I think we'll be able to obtain the required module symbols directly from memory and handle that case properly :) |
This plugin backtraced when 1) fbdev was compiled as a module and 2) an old version of dwarf2json was used to generate the symbol table.
This caused the existing check for the symbol to exist to succeed, but its only as a forward declaration. Then
object_from_symbolwould fail as the address was recorded as 0.My patch here makes it gracefully warn the user + exit when an old symbol table is passed, and then the existing check will work for modern symbol tables and samples with fbdev as a kernel module.