x86/kprobes: Mark kretprobe_trampoline() stack frame as non-standard
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>
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@ -49,6 +49,7 @@
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#include <linux/kdebug.h>
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#include <linux/kallsyms.h>
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#include <linux/ftrace.h>
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#include <linux/frame.h>
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#include <asm/cacheflush.h>
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#include <asm/desc.h>
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@ -703,6 +704,7 @@ asm(
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".size kretprobe_trampoline, .-kretprobe_trampoline\n"
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);
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NOKPROBE_SYMBOL(kretprobe_trampoline);
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STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
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/*
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* Called from kretprobe_trampoline
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