linux_dsm_epyc7002/kernel/bpf
Josh Poimboeuf 39853cc0cd bpf: Mark __bpf_prog_run() stack frame as non-standard
objtool reports the following false positive warnings:

  kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x5c: sibling call from callable instruction with changed frame pointer
  kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x60: function has unreachable instruction
  kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x64: function has unreachable instruction
  [...]

It's confused by the following dynamic jump instruction in
__bpf_prog_run()::

  jmp     *(%r12,%rax,8)

which corresponds to the following line in the C code:

  goto *jumptable[insn->code];

There's no way for objtool to deterministically find all possible
branch targets for a dynamic jump, so it can't verify this code.

In this case the jumps all stay within the function, and there's nothing
unusual going on related to the stack, so we can whitelist the function.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
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
Cc: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/b90e6bf3fdbfb5c4cc1b164b965502e53cf48935.1456719558.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-02-29 08:35:11 +01:00
..
arraymap.c perf/bpf: Convert perf_event_array to use struct file 2016-01-29 08:35:25 +01:00
core.c bpf: Mark __bpf_prog_run() stack frame as non-standard 2016-02-29 08:35:11 +01:00
hashtab.c bpf: hash: use per-bucket spinlock 2015-12-29 15:13:44 -05:00
helpers.c bpf: split state from prandom_u32() and consolidate {c, e}BPF prngs 2015-10-08 05:26:39 -07:00
inode.c bpf, inode: allow for rename and link ops 2015-12-12 18:44:23 -05:00
Makefile bpf: add support for persistent maps/progs 2015-11-02 22:48:39 -05:00
syscall.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-12-03 21:09:12 -05:00
verifier.c bpf: fix branch offset adjustment on backjumps after patching ctx expansion 2016-02-10 16:56:47 -05:00