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x86/kprobes: Mark kretprobe_trampoline() stack frame as non-standard

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objtool reports the following warning for kretprobe_trampoline():

  arch/x86/kernel/kprobes/core.o: warning: objtool: kretprobe_trampoline()+0x20: call without frame pointer save/setup

kretprobes are a special case where the stack is intentionally wrong.
The return address isn't known at the beginning of the trampoline, so
the stack frame can't be set up properly before it calls
trampoline_handler().

Because kretprobe handlers don't sleep, the frame pointer doesn't *have*
to be accurate in the trampoline.  So it's ok to tell objtool to ignore
it.  This results in no actual changes to the generated code.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/7eaf37de52456ff822ffc86b928edb5d48a40ef1.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2016-02-28 22:22:40 -06:00 committed by Ingo Molnar
parent 049369487e
commit 87aaff2ae0
1 changed files with 2 additions and 0 deletions
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2
arch/x86/kernel/kprobes/core.c
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@ -49,6 +49,7 @@
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>
#include <linux/frame.h>
#include <asm/cacheflush.h>
#include <asm/desc.h>
@ -703,6 +704,7 @@ asm(
".size kretprobe_trampoline, .-kretprobe_trampoline\n"
);
NOKPROBE_SYMBOL(kretprobe_trampoline);
STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
/*
* Called from kretprobe_trampoline