Messages in this thread | | | Date | Sun, 23 Nov 2008 17:12:37 +0300 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END |
| |
[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.
- Cyrill -
| |