[PATCH] Add more prevent_tail_call()
authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Wed, 19 Apr 2006 21:41:39 +0000 (06:41 +0900)
committerLinus Torvalds <torvalds@g5.osdl.org>
Wed, 19 Apr 2006 23:27:18 +0000 (16:27 -0700)
commit5a7b46b369419493bab4de67b1526e9f76b22a7f
treec6c25e52dfd063db53db93d756da77ab67550ec6
parent52824b6b5fa0533e2b2adc9df396d0e9ff6fb02a
[PATCH] Add more prevent_tail_call()

Those also break userland regs like following.

   00000000 <sys_chown16>:
      0: 0f b7 44 24 0c        movzwl 0xc(%esp),%eax
      5: 83 ca ff              or     $0xffffffff,%edx
      8: 0f b7 4c 24 08        movzwl 0x8(%esp),%ecx
      d: 66 83 f8 ff           cmp    $0xffffffff,%ax
     11: 0f 44 c2              cmove  %edx,%eax
     14: 66 83 f9 ff           cmp    $0xffffffff,%cx
     18: 0f 45 d1              cmovne %ecx,%edx
     1b: 89 44 24 0c           mov    %eax,0xc(%esp)
     1f: 89 54 24 08           mov    %edx,0x8(%esp)
     23: e9 fc ff ff ff        jmp    24 <sys_chown16+0x24>

where the tailcall at the end overwrites the incoming stack-frame.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
[ I would _really_ like to have a way to tell gcc about calling
  conventions. The "prevent_tail_call()" macro is pretty ugly ]
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
kernel/uid16.c