releases/5.0.18/objtool-fix-function-fallthrough-detection.patch

   1 From e6f393bc939d566ce3def71232d8013de9aaadde Mon Sep 17 00:00:00 2001
   2 From: Josh Poimboeuf <jpoimboe@redhat.com>
   3 Date: Mon, 13 May 2019 12:01:32 -0500
   4 Subject: objtool: Fix function fallthrough detection
   5
   6 From: Josh Poimboeuf <jpoimboe@redhat.com>
   7
   8 commit e6f393bc939d566ce3def71232d8013de9aaadde upstream.
   9
  10 When a function falls through to the next function due to a compiler
  11 bug, objtool prints some obscure warnings.  For example:
  12
  13   drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x95: return with modified stack frame
  14   drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x0: stack state mismatch: cfa1=7+32 cfa2=7+8
  15
  16 Instead it should be printing:
  17
  18   drivers/regulator/core.o: warning: objtool: regulator_supply_is_couple() falls through to next function regulator_count_voltages()
  19
  20 This used to work, but was broken by the following commit:
  21
  22   13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
  23
  24 The padding nops at the end of a function aren't actually part of the
  25 function, as defined by the symbol table.  So the 'func' variable in
  26 validate_branch() is getting cleared to NULL when a padding nop is
  27 encountered, breaking the fallthrough detection.
  28
  29 If the current instruction doesn't have a function associated with it,
  30 just consider it to be part of the previously detected function by not
  31 overwriting the previous value of 'func'.
  32
  33 Reported-by: kbuild test robot <lkp@intel.com>
  34 Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
  35 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  36 Cc: Peter Zijlstra <peterz@infradead.org>
  37 Cc: Thomas Gleixner <tglx@linutronix.de>
  38 Cc: <stable@vger.kernel.org>
  39 Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
  40 Link: http://lkml.kernel.org/r/546d143820cd08a46624ae8440d093dd6c902cae.1557766718.git.jpoimboe@redhat.com
  41 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  42 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  43
  44 ---
  45  tools/objtool/check.c |    3 ++-
  46  1 file changed, 2 insertions(+), 1 deletion(-)
  47
  48 --- a/tools/objtool/check.c
  49 +++ b/tools/objtool/check.c
  50 @@ -1832,7 +1832,8 @@ static int validate_branch(struct objtoo
  51                         return 1;
  52                 }
  53
  54 -               func = insn->func ? insn->func->pfunc : NULL;
  55 +               if (insn->func)
  56 +                       func = insn->func->pfunc;
  57
  58                 if (func && insn->ignore) {
  59                         WARN_FUNC("BUG: why am I validating an ignored function?",