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objtool reports the following warnings for __schedule(): kernel/sched/core.o: warning: objtool:__schedule()+0x3c0: duplicate frame pointer save kernel/sched/core.o: warning: objtool:__schedule()+0x3fd: sibling call from callable instruction with changed frame pointer kernel/sched/core.o: warning: objtool:__schedule()+0x40a: call without frame pointer save/setup kernel/sched/core.o: warning: objtool:__schedule()+0x7fd: frame pointer state mismatch kernel/sched/core.o: warning: objtool:__schedule()+0x421: frame pointer state mismatch Basically it's confused by two unusual attributes of the switch_to() macro: 1. It saves prev's frame pointer to the old stack and restores next's frame pointer from the new stack. 2. For new tasks it jumps directly to ret_from_fork. Eventually it would probably be a good idea to clean up the ret_from_fork hack so that new tasks are created with a valid initial stack, as suggested by Andy: https://lkml.kernel.org/r/CALCETrWsqCw4L1qKO9j9L5F+4ED4viuLQTFc=n1pKBZfFPQUFg@mail.gmail.com Then __schedule() could return normally into the new code and objtool hopefully wouldn't have a problem anymore. In the meantime, mark its stack frame as non-standard so we can have a baseline with no objtool warnings. The marker also serves as a reminder that this code could be improved a bit. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> 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: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> 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/91190e324ebd7fcd01748d508d0dfd4693e84d91.1456719558.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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| .. | ||
| auto_group.c | ||
| auto_group.h | ||
| clock.c | ||
| completion.c | ||
| core.c | ||
| cpuacct.c | ||
| cpuacct.h | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle_task.c | ||
| idle.c | ||
| loadavg.c | ||
| Makefile | ||
| rt.c | ||
| sched.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| wait.c | ||