GDB's interrupt.exp test cases currenly fail on ARM. The problem is how do_signal
handled restarting interrupted system calls:
The entry.S assembler code determines that we come from a system call; and that
information is passed as "syscall" parameter to do_signal. That routine then
calls get_signal_to_deliver [*] and if a signal is to be delivered, calls into
handle_signal. If a system call is to be restarted either after the signal
handler returns, or if no handler is to be called in the first place, the PC
is updated after the get_signal_to_deliver call, either in handle_signal (if
we have a handler) or at the end of do_signal (otherwise).
Now the problem is that during [*], the call to get_signal_to_deliver, a ptrace
intercept may happen. During this intercept, the debugger may change registers,
including the PC. This is done by GDB if it wants to execute an "inferior call",
i.e. the execution of some code in the debugged program triggered by GDB.
To this purpose, GDB will save all registers, allocate a stack frame, set up
PC and arguments as appropriate for the call, and point the link register to
a dummy breakpoint instruction. Once the process is restarted, it will execute
the call and then trap back to the debugger, at which point GDB will restore
all registers and continue original execution.
This generally works fine. However, now consider what happens when GDB attempts
to do exactly that while the process was interrupted during execution of a to-be-
restarted system call: do_signal is called with the syscall flag set; it calls
get_signal_to_deliver, at which point the debugger takes over and changes the PC
to point to a completely different place. Now get_signal_to_deliver returns
without a signal to deliver; but now do_signal decides it should be restarting
a system call, and decrements the PC by 2 or 4 -- so it now points to 2 or 4
bytes before the function GDB wants to call -- which leads to a subsequent crash.
To fix this problem, two things need to be supported:
- do_signal must be able to recognize that get_signal_to_deliver changed the PC
to a different location, and skip the restart-syscall sequence
- once the debugger has restored all registers at the end of the inferior call
sequence, do_signal must recognize that *now* it needs to restart the pending
system call, even though it was now entered from a breakpoint instead of an
actual svc instruction
This set of issues is solved on other platforms, usually by one of two
mechanisms:
- The status information "do_signal is handling a system call that may need
restarting" is itself carried in some register that can be accessed via
ptrace. This is e.g. on Intel the "orig_eax" register; on Sparc the kernel
defines a magic extra bit in the flags register for this purpose.
This allows GDB to manage that state: reset it when doing an inferior call,
and restore it after the call is finished.
- On s390, do_signal transparently handles this problem without requiring
GDB interaction, by performing system call restarting in the following
way: first, adjust the PC as necessary for restarting the call. Then,
call get_signal_to_deliver; and finally just continue execution at the
PC. This way, if GDB does not change the PC, everything is as before.
If GDB *does* change the PC, execution will simply continue there --
and once GDB restores the PC it saved at that point, it will automatically
point to the *restarted* system call. (There is the minor twist how to
handle system calls that do *not* need restarting -- do_signal will undo
the PC change in this case, after get_signal_to_deliver has returned, and
only if ptrace did not change the PC during that call.)
Because there does not appear to be any obvious register to carry the
syscall-restart information on ARM, we'd either have to introduce a new
artificial ptrace register just for that purpose, or else handle the issue
transparently like on s390. The patch below implements the second option;
using this patch makes the interrupt.exp test cases pass on ARM, with no
regression in the GDB test suite otherwise.
Cc: patches@linaro.org
Signed-off-by: Ulrich Weigand <ulrich.weigand@linaro.org>
Signed-off-by: Arnd Bergmann <arnd.bergmann@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
PTRACE_SINGLESTEP is a ptrace request designed to offer single-stepping
support to userspace when the underlying architecture has hardware
support for this operation.
On ARM, we set arch_has_single_step() to 1 and attempt to emulate hardware
single-stepping by disassembling the current instruction to determine the
next pc and placing a software breakpoint on that location.
Unfortunately this has the following problems:
1.) Only a subset of ARMv7 instructions are supported
2.) Thumb-2 is unsupported
3.) The code is not SMP safe
We could try to fix this code, but it turns out that because of the above
issues it is rarely used in practice. GDB, for example, uses PTRACE_POKETEXT
and PTRACE_PEEKTEXT to manage breakpoints itself and does not require any
kernel assistance.
This patch removes the single-step emulation code from ptrace meaning that
the PTRACE_SINGLESTEP request will return -EIO on ARM. Portable code must
check the return value from a ptrace call and handle the failure gracefully.
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Ensure a predictable endian state when entering signal handlers. This
avoids programs which use SETEND to momentarily switch their endian
state from having their signal handlers entered with an unpredictable
endian state.
Cc: <stable@kernel.org>
Acked-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
From: Imre Deak <imre.deak@nokia.com>
Signal handlers can use floating point, so prevent them to corrupt
the main thread's VFP context. So far there were two signal stack
frame formats defined based on the VFP implementation, but the user
struct used for ptrace covers all posibilities, so use it for the
signal stack too.
Introduce also a new user struct for VFP exception registers. In
this too fields not relevant to the current VFP architecture are
ignored.
Support to save / restore the exception registers was added by
Will Deacon.
Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Using OABI, the call to put_user in do_signal can fail causing the
calling app to hang.
The solution is to check if put_user fails and force the app to
seg fault in that case.
Tested with multiple sleeping apps/threads (using the nanosleep syscall)
and suspend/resume.
Signed-off-by: janboe <janboe.ye at gmail.com>
Signed-off-by: Jean Pihet <jpihet@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The signal restarting code was placed on the user stack when OABI
compatibility is enabled. Unfortunately, with an EABI NX executable,
this results in an attempt to run code from the non-executable stack,
which segfaults the application.
Fix this by placing the code in the vectors page, along side the
signal return code, and directing the application to that code.
Reported-by: saeed bishara <saeed.bishara@gmail.com>
Tested-by: saeed bishara <saeed.bishara@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
* 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm: (257 commits)
[ARM] Update mach-types
ARM: 5636/1: Move vendor enum to AMBA include
ARM: Fix pfn_valid() for sparse memory
[ARM] orion5x: Add LaCie NAS 2Big Network support
[ARM] pxa/sharpsl_pm: zaurus c3000 aka spitz: fix resume
ARM: 5686/1: at91: Correct AC97 reset line in at91sam9263ek board
ARM: 5640/1: This patch modifies the support of AC97 on the at91sam9263 ek board
ARM: 5689/1: Update default config of HP Jornada 700-series machines
ARM: 5691/1: fix cache aliasing issues between kmap() and kmap_atomic() with highmem
ARM: 5688/1: ks8695_serial: disable_irq() lockup
ARM: 5687/1: fix an oops with highmem
ARM: 5684/1: Add nuc960 platform to w90x900
ARM: 5683/1: Add nuc950 platform to w90x900
ARM: 5682/1: Add cpu.c and dev.c and modify some files of w90p910 platform
ARM: 5626/1: add suspend/resume functions to amba-pl011 serial driver
ARM: 5625/1: fix hard coded 4K resource size in amba bus detection
MMC: MMCI: convert realview MMC to use gpiolib
ARM: 5685/1: Make MMCI driver compile without gpiolib
ARM: implement highpte
ARM: Show FIQ in /proc/interrupts on CONFIG_FIQ
...
Fix up trivial conflict in arch/arm/kernel/signal.c.
It was due to the TIF_NOTIFY_RESUME addition in commit d0420c83f ("KEYS:
Extend TIF_NOTIFY_RESUME to (almost) all architectures") and follow-ups.
Add #inclusions of linux/tracehook.h to those arch files that had the tracehook
call for TIF_NOTIFY_RESUME added when support for that flag was added to that
arch.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Add a keyctl to install a process's session keyring onto its parent. This
replaces the parent's session keyring. Because the COW credential code does
not permit one process to change another process's credentials directly, the
change is deferred until userspace next starts executing again. Normally this
will be after a wait*() syscall.
To support this, three new security hooks have been provided:
cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
the blank security creds and key_session_to_parent() - which asks the LSM if
the process may replace its parent's session keyring.
The replacement may only happen if the process has the same ownership details
as its parent, and the process has LINK permission on the session keyring, and
the session keyring is owned by the process, and the LSM permits it.
Note that this requires alteration to each architecture's notify_resume path.
This has been done for all arches barring blackfin, m68k* and xtensa, all of
which need assembly alteration to support TIF_NOTIFY_RESUME. This allows the
replacement to be performed at the point the parent process resumes userspace
execution.
This allows the userspace AFS pioctl emulation to fully emulate newpag() and
the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
alter the parent process's PAG membership. However, since kAFS doesn't use
PAGs per se, but rather dumps the keys into the session keyring, the session
keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
the newpag flag.
This can be tested with the following program:
#include <stdio.h>
#include <stdlib.h>
#include <keyutils.h>
#define KEYCTL_SESSION_TO_PARENT 18
#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)
int main(int argc, char **argv)
{
key_serial_t keyring, key;
long ret;
keyring = keyctl_join_session_keyring(argv[1]);
OSERROR(keyring, "keyctl_join_session_keyring");
key = add_key("user", "a", "b", 1, keyring);
OSERROR(key, "add_key");
ret = keyctl(KEYCTL_SESSION_TO_PARENT);
OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");
return 0;
}
Compiled and linked with -lkeyutils, you should see something like:
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
355907932 --alswrv 4043 -1 \_ keyring: _uid.4043
[dhowells@andromeda ~]$ /tmp/newpag
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: _ses
1055658746 --alswrv 4043 4043 \_ user: a
[dhowells@andromeda ~]$ /tmp/newpag hello
[dhowells@andromeda ~]$ keyctl show
Session Keyring
-3 --alswrv 4043 4043 keyring: hello
340417692 --alswrv 4043 4043 \_ user: a
Where the test program creates a new session keyring, sticks a user key named
'a' into it and then installs it on its parent.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Implement TIF_NOTIFY_RESUME for most of those architectures in which isn't yet
available, and, whilst we're at it, have it call the appropriate tracehook.
After this patch, blackfin, m68k* and xtensa still lack support and need
alteration of assembly code to make it work.
Resume notification can then be used (by a later patch) to install a new
session keyring on the parent of a process.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
cc: linux-arch@vger.kernel.org
Signed-off-by: James Morris <jmorris@namei.org>
This patch adds support for TIF_RESTORE_SIGMASK to ARM's
signal handling, which allows to hook up the pselect6, ppoll,
and epoll_pwait syscalls on ARM.
Tested here with eabi userspace and a test program with a
deliberate race between a child's exit and the parent's
sigprocmask/select sequence. Using sys_pselect6() instead
of sigprocmask/select reliably prevents the race.
The other arch's support for TIF_RESTORE_SIGMASK has evolved
over time:
In 2.6.16:
- add TIF_RESTORE_SIGMASK which parallels TIF_SIGPENDING
- test both when checking for pending signal [changed later]
- reimplement sys_sigsuspend() to use current->saved_sigmask,
TIF_RESTORE_SIGMASK [changed later], and -ERESTARTNOHAND;
ditto for sys_rt_sigsuspend(), but drop private code and
use common code via __ARCH_WANT_SYS_RT_SIGSUSPEND;
- there are now no "extra" calls to do_signal() so its oldset
parameter is always ¤t->blocked so need not be passed,
also its return value is changed to void
- change handle_signal() to return 0/-errno
- change do_signal() to honor TIF_RESTORE_SIGMASK:
+ get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
is set
+ if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
+ if no signal was delivered and TIF_RESTORE_SIGMASK is set then
clear it and restore the sigmask
- hook up sys_pselect6() and sys_ppoll()
In 2.6.19:
- hook up sys_epoll_pwait()
In 2.6.26:
- allow archs to override how TIF_RESTORE_SIGMASK is implemented;
default set_restore_sigmask() sets both TIF_RESTORE_SIGMASK and
TIF_SIGPENDING; archs need now just test TIF_SIGPENDING again
when checking for pending signal work; some archs now implement
TIF_RESTORE_SIGMASK as a secondary/non-atomic thread flag bit
- call set_restore_sigmask() in sys_sigsuspend() instead of setting
TIF_RESTORE_SIGMASK
In 2.6.29-rc:
- kill sys_pselect7() which no arch wanted
So for 2.6.31-rc6/ARM this patch does the following:
- Add TIF_RESTORE_SIGMASK. Use the generic set_restore_sigmask()
which sets both TIF_SIGPENDING and TIF_RESTORE_SIGMASK, so
TIF_RESTORE_SIGMASK need not claim one of the scarce low thread
flags, and existing TIF_SIGPENDING and _TIF_WORK_MASK tests need
not be extended for TIF_RESTORE_SIGMASK.
- sys_sigsuspend() is reimplemented to use current->saved_sigmask
and set_restore_sigmask(), making it identical to most other archs
- The private code for sys_rt_sigsuspend() is removed, instead
generic code supplies it via __ARCH_WANT_SYS_RT_SIGSUSPEND.
- sys_sigsuspend() and sys_rt_sigsuspend() no longer need a pt_regs
parameter, so their assembly code wrappers are removed.
- handle_signal() is changed to return 0 on success or -errno.
- The oldset parameter to do_signal() is now redundant and removed,
and the return value is now also redundant and changed to void.
- do_signal() is changed to honor TIF_RESTORE_SIGMASK:
+ get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
is set
+ if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
+ if no signal was delivered and TIF_RESTORE_SIGMASK is set then
clear it and restore the sigmask
- Hook up sys_pselect6, sys_ppoll, and sys_epoll_pwait.
Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
preserve_crunch_context() calls __copy_to_user() which expects the
destination address to be in __user space. setup_sigframe() properly
passes the destination address.
restore_crunch_context() calls __copy_from_user() which expects the
source address to be in __user space. restore_sigframe() properly
passes the source address.
This fixes {preserve/restore}_crunch_context() to accept the
address as __user space and resolves the following sparse warnings:
arch/arm/kernel/signal.c:146:31:
warning: incorrect type in argument 1 (different address spaces)
expected void [noderef] <asn:1>*to
got struct crunch_sigframe *frame
arch/arm/kernel/signal.c:156:38:
warning: incorrect type in argument 2 (different address spaces)
expected void const [noderef] <asn:1>*from
got struct crunch_sigframe *frame
arch/arm/kernel/signal.c:250:48:
warning: incorrect type in argument 1 (different address spaces)
expected struct crunch_sigframe *frame
got struct crunch_sigframe [noderef] <asn:1>*<noident>
arch/arm/kernel/signal.c:365:49:
warning: incorrect type in argument 1 (different address spaces)
expected struct crunch_sigframe *frame
got struct crunch_sigframe [noderef] <asn:1>*<noident>
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
If a process is interrupted during an If-Then block and a signal is
invoked, the ITSTATE bits must be cleared otherwise the handler would
not run correctly.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Joseph S. Myers <joseph@codesourcery.com>
Stephen Rothwell <sfr@canb.auug.org.au> writes:
> Today's linux-next build of at least some av32 and arm configs failed like this:
>
> arch/avr32/kernel/signal.c:216: error: conflicting types for 'restart_syscall'
> include/linux/sched.h:2184: error: previous definition of 'restart_syscall' was here
>
> Caused by commit 690cc3ffe3 ("syscall:
> Implement a convinience function restart_syscall") from the net tree.
Grrr. Some days it feels like all of the good names are already taken.
Let's just rename the two static users in arm and avr32 to get this
sorted out.
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
fix signal return code when enable CONFIG_OABI_COMPAT
Signed-off-by: Janboe Ye <janboe.ye@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
* 'for-linus' of master.kernel.org:/home/rmk/linux-2.6-arm: (76 commits)
[ARM] 4002/1: S3C24XX: leave parent IRQs unmasked
[ARM] 4001/1: S3C24XX: shorten reboot time
[ARM] 3983/2: remove unused argument to __bug()
[ARM] 4000/1: Osiris: add third serial port in
[ARM] 3999/1: RX3715: suspend to RAM support
[ARM] 3998/1: VR1000: LED platform devices
[ARM] 3995/1: iop13xx: add iop13xx support
[ARM] 3968/1: iop13xx: add iop13xx_defconfig
[ARM] Update mach-types
[ARM] Allow gcc to optimise arm_add_memory a little more
[ARM] 3991/1: i.MX/MX1 high resolution time source
[ARM] 3990/1: i.MX/MX1 more precise PLL decode
[ARM] 3986/1: H1940: suspend to RAM support
[ARM] 3985/1: ixp4xx clocksource cleanup
[ARM] 3984/1: ixp4xx/nslu2: Fix disk LED numbering (take 2)
[ARM] 3994/1: ixp23xx: fix handling of pci master aborts
[ARM] 3981/1: sched_clock for PXA2xx
[ARM] 3980/1: extend the ARM Versatile sched_clock implementation from 32 to 63 bit
[ARM] 3979/1: extend the SA11x0 sched_clock implementation from 32 to 63 bit period
[ARM] 3978/1: macro to provide a 63-bit value from a 32-bit hardware counter
...
Move process freezing functions from include/linux/sched.h to freezer.h, so
that modifications to the freezer or the kernel configuration don't require
recompiling just about everything.
[akpm@osdl.org: fix ueagle driver]
Signed-off-by: Nigel Cunningham <nigel@suspend2.net>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
These files want to provide/access ELF hwcap information, so should
be including asm/elf.h rather than asm/procinfo.h
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Lennert Buytenhek
This patch makes the kernel save Crunch state in userland signal frames,
so that any userland signal handler can safely use the Crunch coprocessor
without corrupting the Crunch state of the code it preempted.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Daniel Jacobowitz
In order for userspace to find saved coprocessor registers, move them from
struct rt_sigframe into struct ucontext. Also allow space for glibc's
sigset_t, so that userspace and kernelspace can use the same ucontext
layout. Define the magic numbers for iWMMXt in the header file for easier
reference. Include the size of the coprocessor data in the magic numbers.
Also define magic numbers and layout for VFP, not yet saved.
Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
GDB couldn't reliably tell the difference between the old and new
non-rt sigframes, so provide it with a number at the beginning which
will never appear in the old sigframe, and hence provide gdb with a
reliable way to tell the two apart.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Nicolas Pitre
The RESTARTBLOCK case currently store some code on the stack to invoke
sys_restart_syscall. However this is ABI dependent and there is a
mismatch with the way __NR_restart_syscall gets defined when the kernel
is compiled for EABI.
There is also a long standing bug in the thumb case since with OABI the
__NR_restart_syscall value includes __NR_SYSCALL_BASE which should not
be the case for Thumb syscalls.
Credits to Yauheni Kaliuta <yauheni.kaliuta@gmail.com> for finding the
EABI bug.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Gather the common sigmask savbing code inside setup_sigcontext(), and
rename the function setup_sigframe(). Pass it a sigframe structure.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Gather the sigmask restoration code inside restore_sigcontext(), and
rename the function restore_sigframe(). Pass it a sigframe structure.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
sigframe is now a contained subset of rt_sigframe, so we can start
to re-use code which accesses sigframe data for both rt and non-rt
signals.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
ucontext contains both the sigcontext and sigmask structures, and
is also used for rt signal contexts. Re-use this structure for
non-rt signals.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
There's not much point in splitting the sigmask between two different
locations, so copy it entirely into a proper sigset_t. This will
eventually allow rt_sigframe and sigframe to share more code.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
These two members appear to be surplus to requirements. Discussing
this issue with glibc folk:
| > Additionally, do you see any need for these weird "puc" and "pinfo"
| > pointers in the kernels rt_sigframe structure? Can we kill them?
|
| We can kill them. I checked with Phil B. about them last week, and he
| didn't remember any reason they still needed to be there. And nothing
| should know where they are on the stack. Unfortunately, doing this
| will upset GDB, which knows that the saved registers are 0x88 bytes
| above the stack pointer on entrance to an rt signal trampoline; but,
| since puc and pinfo are quite recognizable, I can adapt GDB to support
| the new layout if you want to remove them.
So remove them.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Nicolas Pitre
The signal return path consists of user code provided by the kernel.
Since a syscall is used, it has to be updated to work with EABI.
Noticed by Daniel Jacobowitz.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Patch from Daniel Jacobowitz
After delivering a signal (creating its stack frame) we must check for
additional pending unblocked signals before returning to userspace.
Otherwise signals may be delayed past the next syscall or reschedule.
Once that was fixed it became obvious that the ARM signal mask manipulation
was broken. It was a little bit broken before the recent SA_NODEFER
changes, and then very broken after them. We must block the requested
signals before starting the handler or the same signal can be delivered
again before the handler even gets a chance to run.
Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Prepare arm for the split page_table_lock: three issues.
Signal handling's preserve and restore of iwmmxt context currently involves
reading and writing that context to and from user space, while holding
page_table_lock to secure the user page(s) against kswapd. If we split the
lock, then the structure might span two pages, secured by to read into and
write from a kernel stack buffer, copying that out and in without locking (the
structure is 160 bytes in size, and here we're near the top of the kernel
stack). Or would the overhead be noticeable?
arm_syscall's cmpxchg emulation use pte_offset_map_lock, instead of
pte_offset_map and mm-wide page_table_lock; and strictly, it should now also
take mmap_sem before descending to pmd, to guard against another thread
munmapping, and the page table pulled out beneath this thread.
Updated two comments in fault-armv.c. adjust_pte is interesting, since its
modification of a pte in one part of the mm depends on the lock held when
calling update_mmu_cache for a pte in some other part of that mm. This can't
be done with a split page_table_lock (and we've already taken the lowest lock
in the hierarchy here): so we'll have to disable split on arm, unless
CONFIG_CPU_CACHE_VIPT to ensures adjust_pte never used.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
It has been reported that the way Linux handles NODEFER for signals is
not consistent with the way other Unix boxes handle it. I've written a
program to test the behavior of how this flag affects signals and had
several reports from people who ran this on various Unix boxes,
confirming that Linux seems to be unique on the way this is handled.
The way NODEFER affects signals on other Unix boxes is as follows:
1) If NODEFER is set, other signals in sa_mask are still blocked.
2) If NODEFER is set and the signal is in sa_mask, then the signal is
still blocked. (Note: this is the behavior of all tested but Linux _and_
NetBSD 2.0 *).
The way NODEFER affects signals on Linux:
1) If NODEFER is set, other signals are _not_ blocked regardless of
sa_mask (Even NetBSD doesn't do this).
2) If NODEFER is set and the signal is in sa_mask, then the signal being
handled is not blocked.
The patch converts signal handling in all current Linux architectures to
the way most Unix boxes work.
Unix boxes that were tested: DU4, AIX 5.2, Irix 6.5, NetBSD 2.0, SFU
3.5 on WinXP, AIX 5.3, Mac OSX, and of course Linux 2.6.13-rcX.
* NetBSD was the only other Unix to behave like Linux on point #2. The
main concern was brought up by point #1 which even NetBSD isn't like
Linux. So with this patch, we leave NetBSD as the lonely one that
behaves differently here with #2.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Another swsusp fixup.
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Move the signal return code into the vector page instead of placing
it on the user mode stack, which will allow us to avoid flushing
the instruction cache on signals, as well as eventually allowing
non-exec stack.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Arnd Bergmann