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  1. 19 Apr, 2006 38 commits
  3. 18 Apr, 2006 2 commits
    • Linus Torvalds's avatar
      x86: be careful about tailcall breakage for sys_open[at] too · 385910f2
      Linus Torvalds authored 
      Came up through a quick grep for other cases similar to the ftruncate()
one in commit 0a489cb3.

Also, add a comment, so that people who read the code understand why we
do what looks like a no-op.

(Again, this won't actually matter to any sane user, since libc will
save and restore the register gcc stomps on, but it's still wrong to
stomp on it)
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      385910f2
    • Linus Torvalds's avatar
      x86: don't allow tail-calls in sys_ftruncate[64]() · 0a489cb3
      Linus Torvalds authored 
      Gcc thinks it owns the incoming argument stack, but that's not true for
"asmlinkage" functions, and it corrupts the caller-set-up argument stack
when it pushes the third argument onto the stack.  Which can result in
%ebx getting corrupted in user space.

Now, normally nobody sane would ever notice, since libc will save and
restore %ebx anyway over the system call, but it's still wrong.

I'd much rather have "asmlinkage" tell gcc directly that it doesn't own
the stack, but no such attribute exists, so we're stuck with our hacky
manual "prevent_tail_call()" macro once more (we've had the same issue
before with sys_waitpid() and sys_wait4()).

Thanks to Hans-Werner Hilse <hilse@sub.uni-goettingen.de> for reporting
the issue and testing the fix.
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
      0a489cb3
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