Messages in this thread | | | Date | Sun, 23 Nov 2008 16:31:40 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END |
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* Cyrill Gorcunov <gorcunov@gmail.com> wrote:
> [Alexander van Heukelum - Sun, Nov 23, 2008 at 04:04:18PM +0100] > | On Sun, Nov 23, 2008 at 05:12:37PM +0300, Cyrill Gorcunov wrote: > | > [Cyrill Gorcunov - Sun, Nov 23, 2008 at 04:51:34PM +0300] > | > | [Ingo Molnar - Sun, Nov 23, 2008 at 02:27:52PM +0100] > | > | | > | > | | * Alexander van Heukelum <heukelum@mailshack.com> wrote: > | > | | > | > | | > Impact: moves some code out of .kprobes.text > | > | | > > | > | | > KPROBE_ENTRY switches code generation to .kprobes.text, and KPROBE_END > | > | | > uses .popsection to get back to the previous section (.text, normally). > | > | | > Also replace ENDPROC by END, for consistency. > | > | | > > | > | | > Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm> > | > | | > | > | | applied to tip/x86/irq, thanks Alexander! > | > | | > | > | | > One more small change for today. The xen-related functions > | > | | > xen_do_hypervisor_callback and xen_failsafe_callback are put > | > | | > in the .kprobes.text even in the current kernel: ignore_sysret > | > | | > is enclosed in KPROBE_ENTRY / ENDPROC, instead of KPROBE_ENTRY / > | > | | > KPROBE_END, but I guess the situation is harmless. > | > | | > | > | | yeah. It narrows no-kprobes protection for that code, but it should > | > | | indeed be fine (and that's the intention as well). > | > | | > | > | | Note that this is a reoccuring bug type, and rather long-lived. Can > | > | | you think of any way to get automated nesting protection of both the > | > | | .cfi_startproc/endproc macros and kprobes start/end? A poor man's > | > | | solution would be to grep the number of start and end methods and > | > | | enforce that they are equal. > | > | | > | > | | Ingo > | > | | > | > | > | > | I think we could play with preprocessor and check if ENTRY/END matches. > | > | Looking now. > | > | > | > | - Cyrill - > | > > | > Here is what I've done > | > > | > 1) Add some macros like: > | > > | > .macro __set_entry > | > .set _ENTRY_IN, 1 > | > .endm > | > > | > .macro __unset_entry > | > .set _ENTRY_IN, 0 > | > .endm > | > > | > .macro __check_entry > | > .ifeq _ENTRY_IN > | > .error "END should be used" > | > .abort > | > .endif > | > .endm > | > > | > So the code > | > > | > ENTRY(mcount) > | > __unset_entry > | > retq > | > __check_entry > | > END(mcount) > | > | Looks like a good approach to me. But I assume the ENTRY cppmacro > | will include magic? > | > | Greetings, > | Alexander > | > > yes, but now I'm in doubts since we have this definition in common > linkage.h I dont know if such approach would be usable on other > platforms.
i'd suggest to introduce another entry macro name for that, for the time being. If other architectures want to pick up the method, they can generalize and test it.
( but this is assembly magic so i'm doubtful - while the features used are generic GAS features that should work everywhere, binutils variants tend to be rather fragile. So lets go with some other name like X86_ENTRY()/X86_END() or so - or maybe ENTRY_CFI()/END_CFI(). )
Ingo
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