1. 25 May, 2004 2 commits
  2. 24 May, 2004 2 commits
    • Paul Mackerras's avatar
      [PATCH] ppc64: better stack traces · 14bc28ad
      Paul Mackerras authored
      This improves the stack traces we get on PPC64 by putting a marker in
      those stack frames that are created as a result of an interrupt or
      exception.  The marker is "regshere" (0x7265677368657265).
      
      With this, stack traces show where exceptions have occurred, which can
      be very useful.  This also improves the accuracy of the trace because
      the relevant return address can be in the link register at the time of
      the exception rather than on the stack.  We now print the PC and
      exception type for each exception frame, and then the link register if
      appropriate as the next item in the trace.
      14bc28ad
    • Linus Torvalds's avatar
      Merge bk://bk.arm.linux.org.uk/linux-2.6-rmk · e1ff5fe0
      Linus Torvalds authored
      into ppc970.osdl.org:/home/torvalds/v2.6/linux
      e1ff5fe0
  3. 25 May, 2004 1 commit
  4. 24 May, 2004 15 commits
  5. 23 May, 2004 18 commits
  6. 22 May, 2004 2 commits
    • Linus Torvalds's avatar
      Linux 2.6.7-rc1 · 86042707
      Linus Torvalds authored
      86042707
    • Roland McGrath's avatar
      [PATCH] bogus sigaltstack calls by rt_sigreturn · ce34221e
      Roland McGrath authored
      There is a longstanding bug in the rt_sigreturn system call.
      This exists in both 2.4 and 2.6, and for almost every platform.
      
      I am referring to this code in sys_rt_sigreturn (arch/i386/kernel/signal.c):
      
      	if (__copy_from_user(&st, &frame->uc.uc_stack, sizeof(st)))
      		goto badframe;
      	/* It is more difficult to avoid calling this function than to
      	   call it and ignore errors.  */
      	/*
      	 * THIS CANNOT WORK! "&st" is a kernel address, and "do_sigaltstack()"
      	 * takes a user address (and verifies that it is a user address). End
      	 * result: it does exactly _nothing_.
      	 */
      	do_sigaltstack(&st, NULL, regs->esp);
      
      As the comment says, this is bogus.  On vanilla i386 kernels, this is just
      harmlessly stupid--do_sigaltstack always does nothing and returns -EFAULT.
      
      However this code actually bites users on kernels using Ingo Molnar's 4G/4G
      address space layout changes.  There some kernel stack address might very
      well be a lovely and readable user address as well.  When that happens, we
      make a sigaltstack call with some random buffer, and then the fun begins.
      
      To my knowledge, this has produced trouble in the real world only for 4G
      i386 kernels (RHEL and Fedora "hugemem" kernels) on machines that actually
      have several GB of physical memory (and in programs that are actually using
      sigaltstack and handling a lot of signals).  However, the same clearly
      broken code has been blindly copied to most other architecture ports, and
      off hand I don't know the address space details of any other well enough to
      know if real kernel stack addresses and real user addresses are in fact
      disjoint as they are on i386 when not using the nonstandard 4GB address
      space layout.
      
      The obvious intent of the call being there in the first place is to permit
      a signal handler to diddle its ucontext_t.uc_stack before returning, and
      have this effect a sigaltstack call on the signal handler return.  This is
      not only an optimization vs doing the extra system call, but makes it
      possible to make a sigaltstack change when that handler itself was running
      on the signal stack.  AFAICT this has never actually worked before, so
      certainly noone depends on it.  But the code certainly suggests that
      someone intended at one time for that to be the behavior.  Thus I am
      inclined to fix it so it works in that way, though it has not done so before.
      It would also be reasonable enough to simply rip out the bogus call and not
      have this functionality.
      
      From the current state of code in both 2.4 and 2.6, there is no fathoming
      how this broken code came about.  It's actually much simpler to just make
      it work!  I can only presume that at some point in the past the sigaltstack
      implementation functions were different such that this made sense.  Of the
      few ports I've looked at briefly, only the ppc/pc64 porters (go paulus!)
      actually tried to understand what the i386 code was doing and implemented
      it correctly rather than just carefully transliterating the bug.
      
      The patch below fixes only the i386 and x86_64 versions.  The x86_64
      patches I have not actually tested.  I think each and every arch (except
      ppc and ppc64) need to make the corresponding fixes as well.  Note that
      there is a function to fix for each native arch, and then one for each
      emulation flavor.  The details differ minutely for getting the calls right
      in each emulation flavor, but I think that most or all of the arch's with
      biarch/emulation support have similar enough code that each emulation
      flavor's fix will look very much like the arch/x86_64/ia32/ia32_signal.c
      patch here.
      ce34221e