Messages in this thread | | | Date | Sun, 23 Nov 2008 18:04:06 +0300 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END |
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[Ingo Molnar - Sun, Nov 23, 2008 at 03:55:54PM +0100] | | * Cyrill Gorcunov <gorcunov@gmail.com> 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) | > | > 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. | | looks good! | | Can we somehow detect a missing .cfi_endproc? That's another pattern | i've seen. | | Ingo |
As only I finish with this pattern we could add anything we need :) Will keep you in touch.
- Cyrill -
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