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SubjectRe: [PATCH] x86: KPROBE_ENTRY should be paired wth KPROBE_END
[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.

- Cyrill -


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