__get_cpu_var() is used for multiple purposes in the kernel source. One
of them is address calculation via the form &__get_cpu_var(x). This
calculates the address for the instance of the percpu variable of the
current processor based on an offset.
Other use cases are for storing and retrieving data from the current
processors percpu area. __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.
__get_cpu_var() is defined as :
#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))
__get_cpu_var() always only does an address determination. However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.
this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.
This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset. Thereby address calculations are avoided and less
registers are used when code is generated.
At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.
The patch set includes passes over all arches as well. Once these
operations are used throughout then specialized macros can be defined in
non -x86 arches as well in order to optimize per cpu access by f.e. using
a global register that may be set to the per cpu base.
Transformations done to __get_cpu_var()
1. Determine the address of the percpu instance of the current processor.
DEFINE_PER_CPU(int, y);
int *x = &__get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(&y);
2. Same as #1 but this time an array structure is involved.
DEFINE_PER_CPU(int, y[20]);
int *x = __get_cpu_var(y);
Converts to
int *x = this_cpu_ptr(y);
3. Retrieve the content of the current processors instance of a per cpu
variable.
DEFINE_PER_CPU(int, y);
int x = __get_cpu_var(y)
Converts to
int x = __this_cpu_read(y);
4. Retrieve the content of a percpu struct
DEFINE_PER_CPU(struct mystruct, y);
struct mystruct x = __get_cpu_var(y);
Converts to
memcpy(&x, this_cpu_ptr(&y), sizeof(x));
5. Assignment to a per cpu variable
DEFINE_PER_CPU(int, y)
__get_cpu_var(y) = x;
Converts to
__this_cpu_write(y, x);
6. Increment/Decrement etc of a per cpu variable
DEFINE_PER_CPU(int, y);
__get_cpu_var(y)++
Converts to
__this_cpu_inc(y)
Signed-off-by: Christoph Lameter <cl@linux.com>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org> [compilation only]
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6: (127 commits)
sh: update defconfigs.
sh: Fix up the NUMA build for recent LMB changes.
sh64: provide a stub per_cpu_trap_init() definition.
sh: fix up CONFIG_KEXEC=n build.
sh: fixup the docbook paths for clock framework shuffling.
driver core: Early dev_name() depends on slab_is_available().
sh: simplify WARN usage in SH clock driver
sh: Check return value of clk_get on ms7724
sh: Check return value of clk_get on ecovec24
sh: move sh clock-cpg.c contents to drivers/sh/clk-cpg.c
sh: move sh clock.c contents to drivers/sh/clk.
sh: move sh asm/clock.h contents to linux/sh_clk.h V2
sh: remove unused clock lookup
sh: switch boards to clkdev
sh: switch sh4-202 to clkdev
sh: switch shx3 to clkdev
sh: switch sh7757 to clkdev
sh: switch sh7763 to clkdev
sh: switch sh7780 to clkdev
sh: switch sh7786 to clkdev
...
The current policies of breakpoints in x86 and SH are the following:
- task bound breakpoints can only break on userspace addresses
- cpu wide breakpoints can only break on kernel addresses
The former rule prevents ptrace breakpoints to be set to trigger on
kernel addresses, which is good. But as a side effect, we can't
breakpoint on kernel addresses for task bound breakpoints.
The latter rule simply makes no sense, there is no reason why we
can't set breakpoints on userspace while performing cpu bound
profiles.
We want the following new policies:
- task bound breakpoint can set userspace address breakpoints, with
no particular privilege required.
- task bound breakpoints can set kernelspace address breakpoints but
must be privileged to do that.
- cpu bound breakpoints can do what they want as they are privileged
already.
To implement these new policies, this patch checks if we are dealing
with a kernel address breakpoint, if so and if the exclude_kernel
parameter is set, we tell the user that the breakpoint is invalid,
which makes a good generic ptrace protection.
If we don't have exclude_kernel, ensure the user has the right
privileges as kernel breakpoints are quite sensitive (risk of
trap recursion attacks and global performance impacts).
[ Paul Mundt: keep addr space check for sh signal delivery and fix
double function declaration]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: K. Prasad <prasad@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This follows the x86 change and kills off the unthrottle stub. As the x86
change killed off the generic callback it isn't used anymore anyways.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This follows the x86 change 84d7109267
("hw-breakpoints: Accept breakpoints on NULL address") and restores the
previous expected ptrace behaviour.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This is the next big chunk of hw_breakpoint support. This decouples
the SH-4A support from the core and moves it out in to its own stub,
following many of the conventions established with the perf events
layering.
In addition to extending SH-4A support to encapsulate the remainder
of the UBC channels, clock framework support for handling the UBC
interface clock is added as well, allowing for dynamic clock gating.
This also fixes up a regression introduced by the SIGTRAP handling that
broke the ksym_tracer, to the extent that the current support works well
with all of the ksym_tracer/ptrace/kgdb. The kprobes singlestep code will
follow in turn.
With this in place, the remaining UBC variants (SH-2A and SH-4) can now
be trivially plugged in.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Presently the hw_breakpoint code is the primary notifier dispatch for
breakpoint traps, although it's only UBC traps that are of particular
interest there. This patches in a check to allow non-UBC generated
breakpoints to pass through down the remainder of the notifier chain,
giving things like kgdb a chance at getting notified.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
The event callback handling has been removed in favour of going through a
generic event handler to handle overflows. Follows the x86 change.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This adds preliminary support for the SH-4A UBC to the hw-breakpoints API.
Presently only a single channel is implemented, and the ptrace interface
still needs to be converted. This is the first step to cleaning up the
long-standing UBC mess, making the UBC more generally accessible, and
finally making it SMP safe.
An additional abstraction will be layered on top of this as with the perf
events code to permit the various CPU families to wire up support for
their own specific UBCs, as many variations exist.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Christoph Lameter