On Thu, Jun 5, 2014 at 8:53 AM, Borislav Petkov <bp@xxxxxxxxx> wrote: > On Thu, Jun 05, 2014 at 08:44:20AM -0700, Andy Lutomirski wrote: >> Are there weird contexts from which EFI calls can happen? It looks >> like the current code isn't necessarily safe in things that aren't >> normal process context but aren't interrupts either (e.g. debug traps, >> #GP, etc). > > The efi-pstore thing registers as a kmsg dumper which can be run in NMI > context and efi can be called there. NMI might be okay. I haven't checked. > >> I wonder if it would make sense at some point to maintain an explicit >> stack of kernel entries. There doesn't seem to be a reliable way to >> answer the question of "what context am I in" from C code right now. > > So that you can ask int ctxt = what_context_Im_in() and then that > context can go and change right underneath you. :-) > It has to change back, though. Completely unrealistic and useless example: int ctxt = what_context_im_in(); set_up_the_fpu(ctxt); // kprobe fires and changes the context // kprobe does something // kprobe changes the context back use the FPU. Life is good. put_back_the_fpu(ctxt); --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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