From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Date: Wed, 19 Apr 2006 21:41:39 +0000 (+0900)
Subject: [PATCH] Add more prevent_tail_call()
X-Git-Tag: v2.6.17-rc3~78
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5a7b46b369419493bab4de67b1526e9f76b22a7f;p=pandora-kernel.git

[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>
---

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