objtool: Track DRAP separately from callee-saved registers

When GCC realigns a function's stack, it sometimes uses %r13 as the DRAP
register, like:

  push	%r13
  lea	0x10(%rsp), %r13
  and	$0xfffffffffffffff0, %rsp
  pushq	-0x8(%r13)
  push	%rbp
  mov	%rsp, %rbp
  push	%r13
  ...
  mov	-0x8(%rbp),%r13
  leaveq
  lea	-0x10(%r13), %rsp
  pop	%r13
  retq

Since %r13 was pushed onto the stack twice, its two stack locations need
to be stored separately.  The first push of %r13 is its original value,
and the second push of %r13 is the caller's stack frame address.

Since %r13 is a callee-saved register, we need to track the stack
location of its original value separately from the DRAP register.

This fixes the following false positive warning:

  lib/ubsan.o: warning: objtool: val_to_string.constprop.7()+0x97: leave instruction with modified stack frame

Reported-by: Arnd Bergmann <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Fixes: baa41469a7b9 ("objtool: Implement stack validation 2.0")
Link: http://lkml.kernel.org/r/3da23a6d4c5b3c1e21fc2ccc21a73941b97ff20a.1502401017.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions