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powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors

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Implement perf-events based hw-breakpoint interfaces for PowerPC
64-bit server (Book III S) processors.  This allows access to a
given location to be used as an event that can be counted or
profiled by the perf_events subsystem.

This is done using the DABR (data breakpoint register), which can
also be used for process debugging via ptrace.  When perf_event
hw_breakpoint support is configured in, the perf_event subsystem
manages the DABR and arbitrates access to it, and ptrace then
creates a perf_event when it is requested to set a data breakpoint.

[Adopted suggestions from Paul Mackerras <paulus@samba.org> to
- emulate_step() all system-wide breakpoints and single-step only the
  per-task breakpoints
- perform arch-specific cleanup before unregistration through
  arch_unregister_hw_breakpoint()
]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
K.Prasad 2010-06-15 11:35:19 +05:30 committed by Paul Mackerras
parent f7136c5150
commit 5aae8a5370
11 changed files with 495 additions and 0 deletions
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1
arch/powerpc/Kconfig
View File

@ -141,6 +141,7 @@ config PPC
select GENERIC_ATOMIC64 if PPC32
select HAVE_PERF_EVENTS
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_HW_BREAKPOINT if PERF_EVENTS && PPC_BOOK3S_64
config EARLY_PRINTK
bool

4
arch/powerpc/include/asm/cputable.h
View File

@ -517,6 +517,10 @@ static inline int cpu_has_feature(unsigned long feature)
& feature);
}
#ifdef CONFIG_HAVE_HW_BREAKPOINT
#define HBP_NUM 1
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */

73
arch/powerpc/include/asm/hw_breakpoint.h Normal file
View File

@ -0,0 +1,73 @@
/*
* PowerPC BookIII S hardware breakpoint definitions
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright 2010, IBM Corporation.
* Author: K.Prasad <prasad@linux.vnet.ibm.com>
*
*/
#ifndef _PPC_BOOK3S_64_HW_BREAKPOINT_H
#define _PPC_BOOK3S_64_HW_BREAKPOINT_H
#ifdef __KERNEL__
#ifdef CONFIG_HAVE_HW_BREAKPOINT
struct arch_hw_breakpoint {
u8 len; /* length of the target data symbol */
int type;
unsigned long address;
};
#include <linux/kdebug.h>
#include <asm/reg.h>
#include <asm/system.h>
static inline int hw_breakpoint_slots(int type)
{
return HBP_NUM;
}
struct perf_event;
struct pmu;
struct perf_sample_data;
#define HW_BREAKPOINT_ALIGN 0x7
/* Maximum permissible length of any HW Breakpoint */
#define HW_BREAKPOINT_LEN 0x8
extern int arch_bp_generic_fields(int type, int *gen_bp_type);
extern int arch_check_bp_in_kernelspace(struct perf_event *bp);
extern int arch_validate_hwbkpt_settings(struct perf_event *bp);
extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
unsigned long val, void *data);
int arch_install_hw_breakpoint(struct perf_event *bp);
void arch_uninstall_hw_breakpoint(struct perf_event *bp);
void hw_breakpoint_pmu_read(struct perf_event *bp);
extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
extern struct pmu perf_ops_bp;
extern void ptrace_triggered(struct perf_event *bp, int nmi,
struct perf_sample_data *data, struct pt_regs *regs);
static inline void hw_breakpoint_disable(void)
{
set_dabr(0);
}
#else /* CONFIG_HAVE_HW_BREAKPOINT */
static inline void hw_breakpoint_disable(void) { }
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif /* __KERNEL__ */
#endif /* _PPC_BOOK3S_64_HW_BREAKPOINT_H */

8
arch/powerpc/include/asm/processor.h
View File

@ -209,6 +209,14 @@ struct thread_struct {
#ifdef CONFIG_PPC64
unsigned long start_tb; /* Start purr when proc switched in */
unsigned long accum_tb; /* Total accumilated purr for process */
#ifdef CONFIG_HAVE_HW_BREAKPOINT
struct perf_event *ptrace_bps[HBP_NUM];
/*
* Helps identify source of single-step exception and subsequent
* hw-breakpoint enablement
*/
struct perf_event *last_hit_ubp;
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif
unsigned long dabr; /* Data address breakpoint register */
#ifdef CONFIG_ALTIVEC

1
arch/powerpc/kernel/Makefile
View File

@ -34,6 +34,7 @@ obj-y += vdso32/
obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
signal_64.o ptrace32.o \
paca.o nvram_64.o firmware.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_PPC_BOOK3S_64) += cpu_setup_ppc970.o cpu_setup_pa6t.o
obj64-$(CONFIG_RELOCATABLE) += reloc_64.o
obj-$(CONFIG_PPC_BOOK3E_64) += exceptions-64e.o

1
arch/powerpc/kernel/exceptions-64s.S
View File

@ -828,6 +828,7 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
/* We have a data breakpoint exception - handle it */
handle_dabr_fault:
bl .save_nvgprs
ld r4,_DAR(r1)
ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD

325
arch/powerpc/kernel/hw_breakpoint.c Normal file
View File

@ -0,0 +1,325 @@
/*
* HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
* using the CPU's debug registers. Derived from
* "arch/x86/kernel/hw_breakpoint.c"
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright 2010 IBM Corporation
* Author: K.Prasad <prasad@linux.vnet.ibm.com>
*
*/
#include <linux/hw_breakpoint.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/percpu.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <asm/hw_breakpoint.h>
#include <asm/processor.h>
#include <asm/sstep.h>
#include <asm/uaccess.h>
/*
* Stores the breakpoints currently in use on each breakpoint address
* register for every cpu
*/
static DEFINE_PER_CPU(struct perf_event *, bp_per_reg);
/*
* Install a perf counter breakpoint.
*
* We seek a free debug address register 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);
struct perf_event **slot = &__get_cpu_var(bp_per_reg);
*slot = bp;
/*
* Do not install DABR values if the instruction must be single-stepped.
* If so, DABR will be populated in single_step_dabr_instruction().
*/
if (current->thread.last_hit_ubp != bp)
set_dabr(info->address | info->type | DABR_TRANSLATION);
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 perf_event **slot = &__get_cpu_var(bp_per_reg);
if (*slot != bp) {
WARN_ONCE(1, "Can't find the breakpoint");
return;
}
*slot = NULL;
set_dabr(0);
}
/*
* Perform cleanup of arch-specific counters during unregistration
* of the perf-event
*/
void arch_unregister_hw_breakpoint(struct perf_event *bp)
{
/*
* If the breakpoint is unregistered between a hw_breakpoint_handler()
* and the single_step_dabr_instruction(), then cleanup the breakpoint
* restoration variables to prevent dangling pointers.
*/
if (bp->ctx->task)
bp->ctx->task->thread.last_hit_ubp = NULL;
}
/*
* Check for virtual address in kernel space.
*/
int arch_check_bp_in_kernelspace(struct perf_event *bp)
{
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
return is_kernel_addr(info->address);
}
int arch_bp_generic_fields(int type, int *gen_bp_type)
{
switch (type) {
case DABR_DATA_READ:
*gen_bp_type = HW_BREAKPOINT_R;
break;
case DABR_DATA_WRITE:
*gen_bp_type = HW_BREAKPOINT_W;
break;
case (DABR_DATA_WRITE | DABR_DATA_READ):
*gen_bp_type = (HW_BREAKPOINT_W | HW_BREAKPOINT_R);
break;
default:
return -EINVAL;
}
return 0;
}
/*
* Validate the arch-specific HW Breakpoint register settings
*/
int arch_validate_hwbkpt_settings(struct perf_event *bp)
{
int ret = -EINVAL;
struct arch_hw_breakpoint *info = counter_arch_bp(bp);
if (!bp)
return ret;
switch (bp->attr.bp_type) {
case HW_BREAKPOINT_R:
info->type = DABR_DATA_READ;
break;
case HW_BREAKPOINT_W:
info->type = DABR_DATA_WRITE;
break;
case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
info->type = (DABR_DATA_READ | DABR_DATA_WRITE);
break;
default:
return ret;
}
info->address = bp->attr.bp_addr;
info->len = bp->attr.bp_len;
/*
* Since breakpoint length can be a maximum of HW_BREAKPOINT_LEN(8)
* and breakpoint addresses are aligned to nearest double-word
* HW_BREAKPOINT_ALIGN by rounding off to the lower address, the
* 'symbolsize' should satisfy the check below.
*/
if (info->len >
(HW_BREAKPOINT_LEN - (info->address & HW_BREAKPOINT_ALIGN)))
return -EINVAL;
return 0;
}
/*
* Handle debug exception notifications.
*/
int __kprobes hw_breakpoint_handler(struct die_args *args)
{
bool is_ptrace_bp = false;
int rc = NOTIFY_STOP;
struct perf_event *bp;
struct pt_regs *regs = args->regs;
int stepped = 1;
struct arch_hw_breakpoint *info;
unsigned int instr;
/* Disable breakpoints during exception handling */
set_dabr(0);
/*
* 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 = __get_cpu_var(bp_per_reg);
if (!bp)
goto out;
info = counter_arch_bp(bp);
is_ptrace_bp = (bp->overflow_handler == ptrace_triggered) ?
true : false;
/*
* Return early after invoking user-callback function without restoring
* DABR if the breakpoint is from ptrace which always operates in
* one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
* generated in do_dabr().
*/
if (is_ptrace_bp) {
perf_bp_event(bp, regs);
rc = NOTIFY_DONE;
goto out;
}
/* Do not emulate user-space instructions, instead single-step them */
if (user_mode(regs)) {
bp->ctx->task->thread.last_hit_ubp = bp;
regs->msr |= MSR_SE;
goto out;
}
stepped = 0;
instr = 0;
if (!__get_user_inatomic(instr, (unsigned int *) regs->nip))
stepped = emulate_step(regs, instr);
/*
* emulate_step() could not execute it. We've failed in reliably
* handling the hw-breakpoint. Unregister it and throw a warning
* message to let the user know about it.
*/
if (!stepped) {
WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
"0x%lx will be disabled.", info->address);
perf_event_disable(bp);
goto out;
}
/*
* As a policy, the callback is invoked in a 'trigger-after-execute'
* fashion
*/
perf_bp_event(bp, regs);
set_dabr(info->address | info->type | DABR_TRANSLATION);
out:
rcu_read_unlock();
return rc;
}
/*
* Handle single-step exceptions following a DABR hit.
*/
int __kprobes single_step_dabr_instruction(struct die_args *args)
{
struct pt_regs *regs = args->regs;
struct perf_event *bp = NULL;
struct arch_hw_breakpoint *bp_info;
bp = current->thread.last_hit_ubp;
/*
* Check if we are single-stepping as a result of a
* previous HW Breakpoint exception
*/
if (!bp)
return NOTIFY_DONE;
bp_info = counter_arch_bp(bp);
/*
* We shall invoke the user-defined callback function in the single
* stepping handler to confirm to 'trigger-after-execute' semantics
*/
perf_bp_event(bp, regs);
/*
* Do not disable MSR_SE if the process was already in
* single-stepping mode.
*/
if (!test_thread_flag(TIF_SINGLESTEP))
regs->msr &= ~MSR_SE;
set_dabr(bp_info->address | bp_info->type | DABR_TRANSLATION);
current->thread.last_hit_ubp = NULL;
return NOTIFY_STOP;
}
/*
* Handle debug exception notifications.
*/
int __kprobes hw_breakpoint_exceptions_notify(
struct notifier_block *unused, unsigned long val, void *data)
{
int ret = NOTIFY_DONE;
switch (val) {
case DIE_DABR_MATCH:
ret = hw_breakpoint_handler(data);
break;
case DIE_SSTEP:
ret = single_step_dabr_instruction(data);
break;
}
return ret;
}
/*
* Release the user breakpoints used by ptrace
*/
void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
struct thread_struct *t = &tsk->thread;
unregister_hw_breakpoint(t->ptrace_bps[0]);
t->ptrace_bps[0] = NULL;
}
void hw_breakpoint_pmu_read(struct perf_event *bp)
{
/* TODO */
}

3
arch/powerpc/kernel/machine_kexec_64.c
View File

@ -25,6 +25,7 @@
#include <asm/sections.h> /* _end */
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/hw_breakpoint.h>
int default_machine_kexec_prepare(struct kimage *image)
{
@ -165,6 +166,7 @@ static void kexec_smp_down(void *arg)
while(kexec_all_irq_disabled == 0)
cpu_relax();
mb(); /* make sure all irqs are disabled before this */
hw_breakpoint_disable();
/*
* Now every CPU has IRQs off, we can clear out any pending
* IPIs and be sure that no more will come in after this.
@ -180,6 +182,7 @@ static void kexec_prepare_cpus_wait(int wait_state)
{
int my_cpu, i, notified=-1;
hw_breakpoint_disable();
my_cpu = get_cpu();
/* Make sure each CPU has atleast made it to the state we need */
for (i=0; i < NR_CPUS; i++) {

14
arch/powerpc/kernel/process.c
View File

@ -37,6 +37,7 @@
#include <linux/kernel_stat.h>
#include <linux/personality.h>
#include <linux/random.h>
#include <linux/hw_breakpoint.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
@ -462,8 +463,14 @@ struct task_struct *__switch_to(struct task_struct *prev,
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
switch_booke_debug_regs(&new->thread);
#else
/*
* For PPC_BOOK3S_64, we use the hw-breakpoint interfaces that would
* schedule DABR
*/
#ifndef CONFIG_HAVE_HW_BREAKPOINT
if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
set_dabr(new->thread.dabr);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif
@ -642,7 +649,11 @@ void flush_thread(void)
{
discard_lazy_cpu_state();
#ifdef CONFIG_HAVE_HW_BREAKPOINTS
flush_ptrace_hw_breakpoint(current);
#else /* CONFIG_HAVE_HW_BREAKPOINTS */
set_debug_reg_defaults(&current->thread);
#endif /* CONFIG_HAVE_HW_BREAKPOINTS */
}
void
@ -660,6 +671,9 @@ void prepare_to_copy(struct task_struct *tsk)
flush_altivec_to_thread(current);
flush_vsx_to_thread(current);
flush_spe_to_thread(current);
#ifdef CONFIG_HAVE_HW_BREAKPOINT
flush_ptrace_hw_breakpoint(tsk);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
}
/*

64
arch/powerpc/kernel/ptrace.c
View File

@ -32,6 +32,8 @@
#ifdef CONFIG_PPC32
#include <linux/module.h>
#endif
#include <linux/hw_breakpoint.h>
#include <linux/perf_event.h>
#include <asm/uaccess.h>
#include <asm/page.h>
@ -866,9 +868,34 @@ void user_disable_single_step(struct task_struct *task)
clear_tsk_thread_flag(task, TIF_SINGLESTEP);
}
#ifdef CONFIG_HAVE_HW_BREAKPOINT
void ptrace_triggered(struct perf_event *bp, int nmi,
struct perf_sample_data *data, struct pt_regs *regs)
{
struct perf_event_attr attr;
/*
* Disable the breakpoint request here since ptrace has defined a
* one-shot behaviour for breakpoint exceptions in PPC64.
* The SIGTRAP signal is generated automatically for us in do_dabr().
* We don't have to do anything about that here
*/
attr = bp->attr;
attr.disabled = true;
modify_user_hw_breakpoint(bp, &attr);
}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
unsigned long data)
{
#ifdef CONFIG_HAVE_HW_BREAKPOINT
int ret;
struct thread_struct *thread = &(task->thread);
struct perf_event *bp;
struct perf_event_attr attr;
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
/* For ppc64 we support one DABR and no IABR's at the moment (ppc64).
* For embedded processors we support one DAC and no IAC's at the
* moment.
@ -896,6 +923,43 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
/* Ensure breakpoint translation bit is set */
if (data && !(data & DABR_TRANSLATION))
return -EIO;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
bp = thread->ptrace_bps[0];
if ((!data) || !(data & (DABR_DATA_WRITE | DABR_DATA_READ))) {
if (bp) {
unregister_hw_breakpoint(bp);
thread->ptrace_bps[0] = NULL;
}
return 0;
}
if (bp) {
attr = bp->attr;
attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
arch_bp_generic_fields(data &
(DABR_DATA_WRITE | DABR_DATA_READ),
&attr.bp_type);
ret = modify_user_hw_breakpoint(bp, &attr);
if (ret)
return ret;
thread->ptrace_bps[0] = bp;
thread->dabr = data;
return 0;
}
/* Create a new breakpoint request if one doesn't exist already */
hw_breakpoint_init(&attr);
attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
arch_bp_generic_fields(data & (DABR_DATA_WRITE | DABR_DATA_READ),
&attr.bp_type);
thread->ptrace_bps[0] = bp = register_user_hw_breakpoint(&attr,
ptrace_triggered, task);
if (IS_ERR(bp)) {
thread->ptrace_bps[0] = NULL;
return PTR_ERR(bp);
}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
/* Move contents to the DABR register */
task->thread.dabr = data;

1
arch/powerpc/lib/Makefile
View File

@ -20,6 +20,7 @@ obj-$(CONFIG_PPC64) += copypage_64.o copyuser_64.o \
memcpy_64.o usercopy_64.o mem_64.o string.o
obj-$(CONFIG_XMON) += sstep.o ldstfp.o
obj-$(CONFIG_KPROBES) += sstep.o ldstfp.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += sstep.o ldstfp.o
ifeq ($(CONFIG_PPC64),y)
obj-$(CONFIG_SMP) += locks.o