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fork on UML has always somewhat subtle. The underlying cause has been the
need to initialize a stack for the new process. The only portable way to
initialize a new stack is to set it as the alternate signal stack and take a
signal. The signal handler does whatever initialization is needed and jumps
back to the original stack, where the fork processing is finished. The basic
context switching mechanism is a jmp_buf for each process. You switch to a
new process by longjmping to its jmp_buf.
Now that UML has its own implementation of setjmp and longjmp, and I can poke
around inside a jmp_buf without fear that libc will change the structure, a
much simpler mechanism is possible. The jmpbuf can simply be initialized by
hand.
This eliminates -
the need to set up and remove the alternate signal stack
sending and handling a signal
the signal blocking needed around the stack switching, since
there is no stack switching
setting up the jmp_buf needed to jump back to the original
stack after the new one is set up
In addition, since jmp_buf is now defined by UML, and not by libc, it can be
embedded in the thread struct. This makes it unnecessary to have it exist on
the stack, where it used to be. It also simplifies interfaces, since the
switch jmp_buf used to be a void * inside the thread struct, and functions
which took it as an argument needed to define a jmp_buf variable and assign it
from the void *.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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set_interval returns an error instead of panicing if setitimer fails. Some of
its callers now check the return.
enable_timer is largely tt-mode-specific, so it is marked as such, and the
only skas-mode caller is made to call set-interval instead.
user_time_init was a no-value-added wrapper around set_interval, so it is
gone.
Since set_interval is now called from kernel code, callers no longer pass
ITIMER_* to it. Instead, they pass a flag which is converted into ITIMER_REAL
or ITIMER_VIRTUAL.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Have most signals go through an arch-provided handler which recovers the
sigcontext and then calls a generic handler. This replaces the
ARCH_GET_SIGCONTEXT macro, which was somewhat fragile. On x86_64, recovering
%rdx (which holds the sigcontext pointer) must be the first thing that
happens. sig_handler duly invokes that first, but there is no guarantee that
I can see that instructions won't be reordered such that %rdx is used before
that. Having the arch provide the handler seems much more robust.
Some signals in some parts of UML require their own handlers - these places
don't call set_handler any more. They call sigaction or signal themselves.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch adds an implementation of setjmp and longjmp to UML, allowing
access to the inside of a jmpbuf without needing the access macros formerly
provided by libc.
The implementation is stolen from klibc. I copy the relevant files into
arch/um. I have another patch which avoids the copying, but requires klibc be
in the tree.
setjmp and longjmp users required some tweaking. Includes of <setjmp.h> were
removed and includes of the UML longjmp.h were added where necessary. There
are also replacements of siglongjmp with UML_LONGJMP which I somehow missed
earlier.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The UML_SETJMP macro was requiring its users to pass in a argument which it
could supply itself, since it wasn't used outside that invocation of the
macro.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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It turns out that init_new_thread_signals is always called with altstack == 1,
so we can eliminate the parameter.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Blairsorblade noticed some confusion between our use of a system
call's return value and errno. This patch fixes a number of related
bugs -
using errno instead of a return value
using a return value instead of errno
forgetting to negate a error return to get a positive error code
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Clean up the jmpbuf code. Since softints, we no longer use sig_setjmp, so
the UML_SIGSETJMP wrapper now has a misleading name. Also, I forgot to
change the buffers from sigjmp_buf to jmp_buf.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Now that GCC warns about format errors, fix them. Nothing able to cause a
crash, however.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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We weren't making sure that we initialized the FP registers of new processes
to sane values.
This patch also moves some defines in the affected area closer to where they
are used.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch implements soft interrupts. Interrupt enabling and disabling no
longer map to sigprocmask. Rather, a flag is set indicating whether
interrupts may be handled. If a signal comes in and interrupts are marked as
OK, then it is handled normally. If interrupts are marked as off, then the
signal handler simply returns after noting that a signal needs handling. When
interrupts are enabled later on, this pending signals flag is checked, and the
IRQ handlers are called at that point.
The point of this is to reduce the cost of local_irq_save et al, since they
are very much more common than the signals that they are enabling and
disabling. Soft interrupts produce a speed-up of ~25% on a kernel build.
Subtleties -
UML uses sigsetjmp/siglongjmp to switch contexts. sigsetjmp has been
wrapped in a save_flags-like macro which remembers the interrupt state at
setjmp time, and restores it when it is longjmp-ed back to.
The enable_signals function has to loop because the IRQ handler
disables interrupts before returning. enable_signals has to return with
signals enabled, and signals may come in between the disabling and the
return to enable_signals. So, it loops for as long as there are pending
signals, ensuring that signals are enabled when it finally returns, and
that there are no pending signals that need to be dealt with.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Stop using global variables to hold the file descriptor and offset used to map
the skas0 stubs. Instead, calculate them using the page physical addresses.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The serial UML OS-abstraction layer patch (um/kernel/skas dir).
This moves all systemcalls from skas/process.c file under os-Linux dir and
join skas/process.c and skas/process_kern.c files.
Signed-off-by: Gennady Sharapov <gennady.v.sharapov@intel.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The serial UML OS-abstraction layer patch (um/kernel/skas dir).
This moves all systemcalls from skas/mem_user.c file under os-Linux dir and
join skas/mem_user.c and skas/mem.c files.
Signed-off-by: Gennady Sharapov <gennady.v.sharapov@intel.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This fixes some mangled whitespace added by the earlier trap_user.c patch.
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The serial UML OS-abstraction layer patch (um/kernel dir).
This moves all systemcalls from trap_user.c file under os-Linux dir
Signed-off-by: Gennady Sharapov <Gennady.V.Sharapov@intel.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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