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  1. 19 9月, 2010 1 次提交
  3. 18 9月, 2010 1 次提交
    • A
      arm: fix really nasty sigreturn bug · 653d48b2
      由 Al Viro 提交于 
      If a signal hits us outside of a syscall and another gets delivered
when we are in sigreturn (e.g. because it had been in sa_mask for
the first one and got sent to us while we'd been in the first handler),
we have a chance of returning from the second handler to location one
insn prior to where we ought to return.  If r0 happens to contain -513
(-ERESTARTNOINTR), sigreturn will get confused into doing restart
syscall song and dance.

Incredible joy to debug, since it manifests as random, infrequent and
very hard to reproduce double execution of instructions in userland
code...

The fix is simple - mark it "don't bother with restarts" in wrapper,
i.e. set r8 to 0 in sys_sigreturn and sys_rt_sigreturn wrappers,
suppressing the syscall restart handling on return from these guys.
They can't legitimately return a restart-worthy error anyway.

Testcase:
	#include <unistd.h>
	#include <signal.h>
	#include <stdlib.h>
	#include <sys/time.h>
	#include <errno.h>

	void f(int n)
	{
		__asm__ __volatile__(
			"ldr r0, [%0]\n"
			"b 1f\n"
			"b 2f\n"
			"1:b .\n"
			"2:\n" : : "r"(&n));
	}

	void handler1(int sig) { }
	void handler2(int sig) { raise(1); }
	void handler3(int sig) { exit(0); }

	main()
	{
		struct sigaction s = {.sa_handler = handler2};
		struct itimerval t1 = { .it_value = {1} };
		struct itimerval t2 = { .it_value = {2} };

		signal(1, handler1);

		sigemptyset(&s.sa_mask);
		sigaddset(&s.sa_mask, 1);
		sigaction(SIGALRM, &s, NULL);

		signal(SIGVTALRM, handler3);

		setitimer(ITIMER_REAL, &t1, NULL);
		setitimer(ITIMER_VIRTUAL, &t2, NULL);

		f(-513); /* -ERESTARTNOINTR */

		write(1, "buggered\n", 9);
		return 1;
	}
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Acked-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Cc: stable@kernel.org
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      653d48b2
  5. 16 9月, 2010 1 次提交
  7. 15 9月, 2010 10 次提交
    • C
      arch/tile: fix formatting bug in register dumps · 7040dea4
      由 Chris Metcalf 提交于 
      This cut-and-paste bug was caused by rewriting the register dump
code to use only a single printk per line of output.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
      7040dea4
    • C
      arch/tile: fix memcpy_fromio()/memcpy_toio() signatures · 0fab59e5
      由 Chris Metcalf 提交于 
      This tripped up a driver (not yet committed to git).  Fix it now.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
      0fab59e5
    • C
      arch/tile: Save and restore extra user state for tilegx · a802fc68
      由 Chris Metcalf 提交于 
      During context switch, save and restore a couple of additional bits of
tilegx user state that can be persistently modified by userspace.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
      a802fc68
    • C
      arch/tile: Change struct sigcontext to be more useful · 74fca9da
      由 Chris Metcalf 提交于 
      Rather than just using pt_regs, it now contains the actual saved
state explicitly, similar to pt_regs.  By doing it this way, we
provide a cleaner API for userspace (or equivalently, we avoid the
need for libc to provide its own definition of sigcontext).

While we're at it, move PT_FLAGS_xxx to where they are not visible
from userspace.  And always pass siginfo and mcontext to signal
handlers, even if they claim they don't need it, since sometimes
they actually try to use it anyway in practice.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
      74fca9da
    • C
      arch/tile: finish const-ifying sys_execve() · e6e6c46d
      由 Chris Metcalf 提交于 
      The sys_execve() implementation was properly const-ified but not
the declaration, the syscall wrappers, or the compat version.
This change completes the constification process.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>
      e6e6c46d
    • D
      MN10300: Fix up the IRQ names for the on-chip serial ports · a4128b03
      由 David Howells 提交于 
      Fix up the IRQ names for the MN10300 on-chip serial ports in the driver as
request_interrupt() no longer allows names containing slashes, giving a warning
like the following if one is encountered:

	------------[ cut here ]------------
	WARNING: at fs/proc/generic.c:323 __xlate_proc_name+0x62/0x7c()
	name 'ttySM0/Rx'
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a4128b03
    • R
      x86-64, compat: Retruncate rax after ia32 syscall entry tracing · eefdca04
      由 Roland McGrath 提交于 
      In commit d4d67150, we reopened an old hole for a 64-bit ptracer touching a
32-bit tracee in system call entry.  A %rax value set via ptrace at the
entry tracing stop gets used whole as a 32-bit syscall number, while we
only check the low 32 bits for validity.

Fix it by truncating %rax back to 32 bits after syscall_trace_enter,
in addition to testing the full 64 bits as has already been added.
Reported-by: NBen Hawkes <hawkes@sota.gen.nz>
Signed-off-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
      eefdca04
    • H
      x86-64, compat: Test %rax for the syscall number, not %eax · 36d001c7
      由 H. Peter Anvin 提交于 
      On 64 bits, we always, by necessity, jump through the system call
table via %rax.  For 32-bit system calls, in theory the system call
number is stored in %eax, and the code was testing %eax for a valid
system call number.  At one point we loaded the stored value back from
the stack to enforce zero-extension, but that was removed in checkin
d4d67150.  An actual 32-bit process
will not be able to introduce a non-zero-extended number, but it can
happen via ptrace.

Instead of re-introducing the zero-extension, test what we are
actually going to use, i.e. %rax.  This only adds a handful of REX
prefixes to the code.
Reported-by: NBen Hawkes <hawkes@sota.gen.nz>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@kernel.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
      36d001c7
    • H
      compat: Make compat_alloc_user_space() incorporate the access_ok() · c41d68a5
      由 H. Peter Anvin 提交于 
      compat_alloc_user_space() expects the caller to independently call
access_ok() to verify the returned area.  A missing call could
introduce problems on some architectures.

This patch incorporates the access_ok() check into
compat_alloc_user_space() and also adds a sanity check on the length.
The existing compat_alloc_user_space() implementations are renamed
arch_compat_alloc_user_space() and are used as part of the
implementation of the new global function.

This patch assumes NULL will cause __get_user()/__put_user() to either
fail or access userspace on all architectures.  This should be
followed by checking the return value of compat_access_user_space()
for NULL in the callers, at which time the access_ok() in the callers
can also be removed.
Reported-by: NBen Hawkes <hawkes@sota.gen.nz>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: NChris Metcalf <cmetcalf@tilera.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NTony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: James Bottomley <jejb@parisc-linux.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <stable@kernel.org>
      c41d68a5
    • T
      x86: hpet: Work around hardware stupidity · 54ff7e59
      由 Thomas Gleixner 提交于 
      This more or less reverts commits 08be9796 (x86: Force HPET
readback_cmp for all ATI chipsets) and 30a564be (x86, hpet: Restrict
read back to affected ATI chipsets) to the status of commit 8da854cb
(x86, hpet: Erratum workaround for read after write of HPET
comparator).

The delta to commit 8da854cb is mostly comments and the change from
WARN_ONCE to printk_once as we know the call path of this function
already.

This needs really in depth explanation:

First of all the HPET design is a complete failure. Having a counter
compare register which generates an interrupt on matching values
forces the software to do at least one superfluous readback of the
counter register.

While it is nice in theory to program "absolute" time events it is
practically useless because the timer runs at some absurd frequency
which can never be matched to real world units. So we are forced to
calculate a relative delta and this forces a readout of the actual
counter value, adding the delta and programming the compare
register. When the delta is small enough we run into the danger that
we program a compare value which is already in the past. Due to the
compare for equal nature of HPET we need to read back the counter
value after writing the compare rehgister (btw. this is necessary for
absolute timeouts as well) to make sure that we did not miss the timer
event. We try to work around that by setting the minimum delta to a
value which is larger than the theoretical time which elapses between
the counter readout and the compare register write, but that's only
true in theory. A NMI or SMI which hits between the readout and the
write can easily push us beyond that limit. This would result in
waiting for the next HPET timer interrupt until the 32bit wraparound
of the counter happens which takes about 306 seconds.

So we designed the next event function to look like:

   match = read_cnt() + delta;
   write_compare_ref(match);
   return read_cnt() < match ? 0 : -ETIME;

At some point we got into trouble with certain ATI chipsets. Even the
above "safe" procedure failed. The reason was that the write to the
compare register was delayed probably for performance reasons. The
theory was that they wanted to avoid the synchronization of the write
with the HPET clock, which is understandable. So the write does not
hit the compare register directly instead it goes to some intermediate
register which is copied to the real compare register in sync with the
HPET clock. That opens another window for hitting the dreaded "wait
for a wraparound" problem.

To work around that "optimization" we added a read back of the compare
register which either enforced the update of the just written value or
just delayed the readout of the counter enough to avoid the issue. We
unfortunately never got any affirmative info from ATI/AMD about this.

One thing is sure, that we nuked the performance "optimization" that
way completely and I'm pretty sure that the result is worse than
before some HW folks came up with those.

Just for paranoia reasons I added a check whether the read back
compare register value was the same as the value we wrote right
before. That paranoia check triggered a couple of years after it was
added on an Intel ICH9 chipset. Venki added a workaround (commit
8da854cb) which was reading the compare register twice when the first
check failed. We considered this to be a penalty in general and
restricted the readback (thus the wasted CPU cycles) to the known to
be affected ATI chipsets.

This turned out to be a utterly wrong decision. 2.6.35 testers
experienced massive problems and finally one of them bisected it down
to commit 30a564be which spured some further investigation.

Finally we got confirmation that the write to the compare register can
be delayed by up to two HPET clock cycles which explains the problems
nicely. All we can do about this is to go back to Venki's initial
workaround in a slightly modified version.

Just for the record I need to say, that all of this could have been
avoided if hardware designers and of course the HPET committee would
have thought about the consequences for a split second. It's out of my
comprehension why designing a working timer is so hard. There are two
ways to achieve it:

 1) Use a counter wrap around aware compare_reg <= counter_reg
    implementation instead of the easy compare_reg == counter_reg

    Downsides:

	- It needs more silicon.

	- It needs a readout of the counter to apply a relative
	  timeout. This is necessary as the counter does not run in
	  any useful (and adjustable) frequency and there is no
	  guarantee that the counter which is used for timer events is
	  the same which is used for reading the actual time (and
	  therefor for calculating the delta)

    Upsides:

	- None

  2) Use a simple down counter for relative timer events

    Downsides:

	- Absolute timeouts are not possible, which is not a problem
	  at all in the context of an OS and the expected
	  max. latencies/jitter (also see Downsides of #1)

   Upsides:

	- It needs less or equal silicon.

	- It works ALWAYS

	- It is way faster than a compare register based solution (One
	  write versus one write plus at least one and up to four
	  reads)

I would not be so grumpy about all of this, if I would not have been
ignored for many years when pointing out these flaws to various
hardware folks. I really hate timers (at least those which seem to be
designed by janitors).

Though finally we got a reasonable explanation plus a solution and I
want to thank all the folks involved in chasing it down and providing
valuable input to this.
Bisected-by: NNix <nix@esperi.org.uk>
Reported-by: NArtur Skawina <art.08.09@gmail.com>
Reported-by: NDamien Wyart <damien.wyart@free.fr>
Reported-by: NJohn Drescher <drescherjm@gmail.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: stable@kernel.org
Acked-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      54ff7e59
  9. 14 9月, 2010 3 次提交
  11. 11 9月, 2010 2 次提交
  13. 10 9月, 2010 10 次提交
  15. 09 9月, 2010 4 次提交
  17. 08 9月, 2010 8 次提交