Messages in this thread | | | Date | Wed, 31 Dec 2014 20:42:22 +0100 | From | Mark Wielaard <> | Subject | Re: perf-probe crash in dwarf_getcfi_elf |
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On Tue, Dec 30, 2014 at 06:05:33PM +0900, Namhyung Kim wrote: > And I found a related commit (5704c8c4fa71 "getcfi_scn_eh_frame: Don't > crash and burn when .eh_frame bits aren't there.") in elfutils that > can lead to a unexpected crash like this. To safely use the function, > it needs to check the .eh_frame section is a PROGBITS type.
Sorry about that bug. It was fixed in elfutils 0.156, released July 2013. Latest elfutils release is 0.161.
Checking .eh_frame is SHT_PROGBITS (and not SHT_NOBITS) looks like the correct workaround if you have to deal with older elfutils releases.
Note that dwarf_getcfi_elf gets the CFI information from the .eh_frame section associated with the ELF file underlying the Dwarf dbg and needs to be released with a call to dwarf_cfi_end (). dwarf_getcfi () gets the CFI information from the .debug_frame section data of the Dwarf dbg and gets automatically releassed when dwarf_end () is called (you should not call dwarf_cfi_end () on the result).
If the Dwarf dbg handle is associated with a separate debuginfo file, then the .eh_frame section data will not be available (has SHT_NOBITS) and you can get the .eh_frame section (and call dwarf_getcfi_elf ()) on the original ELF file from which the Dwarf debuginfo file was split off.
In your patch you call dwarf_getcfi () as backup to get some CFI information when you cannot call dwarf_getcfi_elf (). In general it might make sense to also do this when dwarf_getcfi_elf fails. Or try to get the CFI through both .eh_frame (from the executable ELF file) with dwarf_getcfi_elf () and .debug_frame (from the Dwarf dbg file) with dwarf_getcfi () and try to match an address in both tables if one or the other fails.
Cheers,
Mark
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