Messages in this thread | | | Date | Sun, 23 Nov 2008 16:04:18 +0100 | From | Alexander van Heukelum <> | Subject | Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END |
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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
> will fail like > > cyrill@lenovo linux-2.6.git $ make arch/x86/kernel/entry_64.o > CHK include/linux/version.h > CHK include/linux/utsrelease.h > SYMLINK include/asm -> include/asm-x86 > CALL scripts/checksyscalls.sh > AS arch/x86/kernel/entry_64.o > arch/x86/kernel/entry_64.S: Assembler messages: > arch/x86/kernel/entry_64.S:84: Error: END should be used > arch/x86/kernel/entry_64.S:84: Fatal error: .abort detected. Abandoning ship. > make[1]: *** [arch/x86/kernel/entry_64.o] Error 1 > make: *** [arch/x86/kernel/entry_64.o] Error 2 > cyrill@lenovo linux-2.6.git $ > > So if such an approach is acceptable (in general) -- I could take a more > deeper look. So every ENTRY would check if other ENTRY/KPROBE is active > and report that. > > - Cyrill -
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