linux/arch/sh/kernel/hw_breakpoint.c
Christoph Lameter c473b2c6f6 sh: Replace __get_cpu_var uses
__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>
2014-06-04 16:53:52 -07:00

422 lines
8.6 KiB
C

/*
* arch/sh/kernel/hw_breakpoint.c
*
* Unified kernel/user-space hardware breakpoint facility for the on-chip UBC.
*
* Copyright (C) 2009 - 2010 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/init.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/percpu.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <asm/hw_breakpoint.h>
#include <asm/mmu_context.h>
#include <asm/ptrace.h>
#include <asm/traps.h>
/*
* Stores the breakpoints currently in use on each breakpoint address
* register for each cpus
*/
static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
/*
* A dummy placeholder for early accesses until the CPUs get a chance to
* register their UBCs later in the boot process.
*/
static struct sh_ubc ubc_dummy = { .num_events = 0 };
static struct sh_ubc *sh_ubc __read_mostly = &ubc_dummy;
/*
* Install a perf counter breakpoint.
*
* We seek a free UBC channel and use it for this breakpoint.
*
* Atomic: we hold the counter->ctx->lock and we only handle variables
* and registers local to this cpu.
*/
int arch_install_hw_breakpoint(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
int i;
for (i = 0; i < sh_ubc->num_events; i++) {
struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
if (!*slot) {
*slot = bp;
break;
}
}
if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
return -EBUSY;
clk_enable(sh_ubc->clk);
sh_ubc->enable(info, i);
return 0;
}
/*
* Uninstall the breakpoint contained in the given counter.
*
* First we search the debug address register it uses and then we disable
* it.
*
* Atomic: we hold the counter->ctx->lock and we only handle variables
* and registers local to this cpu.
*/
void arch_uninstall_hw_breakpoint(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
int i;
for (i = 0; i < sh_ubc->num_events; i++) {
struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
if (*slot == bp) {
*slot = NULL;
break;
}
}
if (WARN_ONCE(i == sh_ubc->num_events, "Can't find any breakpoint slot"))
return;
sh_ubc->disable(info, i);
clk_disable(sh_ubc->clk);
}
static int get_hbp_len(u16 hbp_len)
{
unsigned int len_in_bytes = 0;
switch (hbp_len) {
case SH_BREAKPOINT_LEN_1:
len_in_bytes = 1;
break;
case SH_BREAKPOINT_LEN_2:
len_in_bytes = 2;
break;
case SH_BREAKPOINT_LEN_4:
len_in_bytes = 4;
break;
case SH_BREAKPOINT_LEN_8:
len_in_bytes = 8;
break;
}
return len_in_bytes;
}
/*
* Check for virtual address in kernel space.
*/
int arch_check_bp_in_kernelspace(struct perf_event *bp)
{
unsigned int len;
unsigned long va;
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
va = info->address;
len = get_hbp_len(info->len);
return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
}
int arch_bp_generic_fields(int sh_len, int sh_type,
int *gen_len, int *gen_type)
{
/* Len */
switch (sh_len) {
case SH_BREAKPOINT_LEN_1:
*gen_len = HW_BREAKPOINT_LEN_1;
break;
case SH_BREAKPOINT_LEN_2:
*gen_len = HW_BREAKPOINT_LEN_2;
break;
case SH_BREAKPOINT_LEN_4:
*gen_len = HW_BREAKPOINT_LEN_4;
break;
case SH_BREAKPOINT_LEN_8:
*gen_len = HW_BREAKPOINT_LEN_8;
break;
default:
return -EINVAL;
}
/* Type */
switch (sh_type) {
case SH_BREAKPOINT_READ:
*gen_type = HW_BREAKPOINT_R;
case SH_BREAKPOINT_WRITE:
*gen_type = HW_BREAKPOINT_W;
break;
case SH_BREAKPOINT_RW:
*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
break;
default:
return -EINVAL;
}
return 0;
}
static int arch_build_bp_info(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
info->address = bp->attr.bp_addr;
/* Len */
switch (bp->attr.bp_len) {
case HW_BREAKPOINT_LEN_1:
info->len = SH_BREAKPOINT_LEN_1;
break;
case HW_BREAKPOINT_LEN_2:
info->len = SH_BREAKPOINT_LEN_2;
break;
case HW_BREAKPOINT_LEN_4:
info->len = SH_BREAKPOINT_LEN_4;
break;
case HW_BREAKPOINT_LEN_8:
info->len = SH_BREAKPOINT_LEN_8;
break;
default:
return -EINVAL;
}
/* Type */
switch (bp->attr.bp_type) {
case HW_BREAKPOINT_R:
info->type = SH_BREAKPOINT_READ;
break;
case HW_BREAKPOINT_W:
info->type = SH_BREAKPOINT_WRITE;
break;
case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
info->type = SH_BREAKPOINT_RW;
break;
default:
return -EINVAL;
}
return 0;
}
/*
* Validate the arch-specific HW Breakpoint register settings
*/
int arch_validate_hwbkpt_settings(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
unsigned int align;
int ret;
ret = arch_build_bp_info(bp);
if (ret)
return ret;
ret = -EINVAL;
switch (info->len) {
case SH_BREAKPOINT_LEN_1:
align = 0;
break;
case SH_BREAKPOINT_LEN_2:
align = 1;
break;
case SH_BREAKPOINT_LEN_4:
align = 3;
break;
case SH_BREAKPOINT_LEN_8:
align = 7;
break;
default:
return ret;
}
/*
* For kernel-addresses, either the address or symbol name can be
* specified.
*/
if (info->name)
info->address = (unsigned long)kallsyms_lookup_name(info->name);
/*
* Check that the low-order bits of the address are appropriate
* for the alignment implied by len.
*/
if (info->address & align)
return -EINVAL;
return 0;
}
/*
* Release the user breakpoints used by ptrace
*/
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
int i;
struct thread_struct *t = &tsk->thread;
for (i = 0; i < sh_ubc->num_events; i++) {
unregister_hw_breakpoint(t->ptrace_bps[i]);
t->ptrace_bps[i] = NULL;
}
}
static int __kprobes hw_breakpoint_handler(struct die_args *args)
{
int cpu, i, rc = NOTIFY_STOP;
struct perf_event *bp;
unsigned int cmf, resume_mask;
/*
* Do an early return if none of the channels triggered.
*/
cmf = sh_ubc->triggered_mask();
if (unlikely(!cmf))
return NOTIFY_DONE;
/*
* By default, resume all of the active channels.
*/
resume_mask = sh_ubc->active_mask();
/*
* Disable breakpoints during exception handling.
*/
sh_ubc->disable_all();
cpu = get_cpu();
for (i = 0; i < sh_ubc->num_events; i++) {
unsigned long event_mask = (1 << i);
if (likely(!(cmf & event_mask)))
continue;
/*
* The counter may be concurrently released but that can only
* occur from a call_rcu() path. We can then safely fetch
* the breakpoint, use its callback, touch its counter
* while we are in an rcu_read_lock() path.
*/
rcu_read_lock();
bp = per_cpu(bp_per_reg[i], cpu);
if (bp)
rc = NOTIFY_DONE;
/*
* Reset the condition match flag to denote completion of
* exception handling.
*/
sh_ubc->clear_triggered_mask(event_mask);
/*
* bp can be NULL due to concurrent perf counter
* removing.
*/
if (!bp) {
rcu_read_unlock();
break;
}
/*
* Don't restore the channel if the breakpoint is from
* ptrace, as it always operates in one-shot mode.
*/
if (bp->overflow_handler == ptrace_triggered)
resume_mask &= ~(1 << i);
perf_bp_event(bp, args->regs);
/* Deliver the signal to userspace */
if (!arch_check_bp_in_kernelspace(bp)) {
siginfo_t info;
info.si_signo = args->signr;
info.si_errno = notifier_to_errno(rc);
info.si_code = TRAP_HWBKPT;
force_sig_info(args->signr, &info, current);
}
rcu_read_unlock();
}
if (cmf == 0)
rc = NOTIFY_DONE;
sh_ubc->enable_all(resume_mask);
put_cpu();
return rc;
}
BUILD_TRAP_HANDLER(breakpoint)
{
unsigned long ex = lookup_exception_vector();
TRAP_HANDLER_DECL;
notify_die(DIE_BREAKPOINT, "breakpoint", regs, 0, ex, SIGTRAP);
}
/*
* Handle debug exception notifications.
*/
int __kprobes hw_breakpoint_exceptions_notify(struct notifier_block *unused,
unsigned long val, void *data)
{
struct die_args *args = data;
if (val != DIE_BREAKPOINT)
return NOTIFY_DONE;
/*
* If the breakpoint hasn't been triggered by the UBC, it's
* probably from a debugger, so don't do anything more here.
*
* This also permits the UBC interface clock to remain off for
* non-UBC breakpoints, as we don't need to check the triggered
* or active channel masks.
*/
if (args->trapnr != sh_ubc->trap_nr)
return NOTIFY_DONE;
return hw_breakpoint_handler(data);
}
void hw_breakpoint_pmu_read(struct perf_event *bp)
{
/* TODO */
}
int register_sh_ubc(struct sh_ubc *ubc)
{
/* Bail if it's already assigned */
if (sh_ubc != &ubc_dummy)
return -EBUSY;
sh_ubc = ubc;
pr_info("HW Breakpoints: %s UBC support registered\n", ubc->name);
WARN_ON(ubc->num_events > HBP_NUM);
return 0;
}