Introduce s390 specific implementation for the perf-events based hardware
breakpoint interfaces defined in kernel/hw_breakpoint.c. Enable the
HAVE_HW_BREAKPOINT flag and the Makefile.
Signed-off-by: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
---
arch/s390/Kconfig | 1
arch/s390/include/asm/Kbuild | 1
arch/s390/kernel/Makefile | 2
arch/s390/kernel/hw_breakpoint.c | 340 ++++++++++++++++++++++++++++++++
kernel/hw_breakpoint.c | 13 +
samples/hw_breakpoint/data_breakpoint.c | 4
6 files changed, 360 insertions(+), 1 deletion(-)
Index: linux-2.6-tip/arch/s390/kernel/hw_breakpoint.c
===================================================================
--- /dev/null
+++ linux-2.6-tip/arch/s390/kernel/hw_breakpoint.c
@@ -0,0 +1,340 @@
+/*
+ * 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 (C) 2009 IBM Corporation
+ * Author: Mahesh Salgaonkar <mahesh@xxxxxxxxxxxxxxxxxx>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's PER control registers.
+ */
+
+#include <asm/bitsperlong.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/irqflags.h>
+#include <linux/notifier.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>
+#include <linux/percpu.h>
+#include <linux/kdebug.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/sections.h>
+#include <asm/uaccess.h>
+
+/* Per cpu PER control register values */
+DEFINE_PER_CPU(per_cr_bits, cpu_per_regs[1]);
+
+/*
+ * 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]);
+
+/*
+ * Install a perf counter breakpoint.
+ *
+ * S390 provides only one hardware breakpoint register. Use it for this
+ * breakpoint if free.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables,
+ * lowcore area and control 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;
+ struct task_struct *tsk = bp->ctx->task;
+ per_cr_bits per_regs[1];
+
+ memset(per_regs, 0, sizeof(per_cr_bits));
+
+ slot = &__get_cpu_var(bp_per_reg[0]);
+ if (!*slot) {
+ *slot = bp;
+ } else {
+ WARN_ONCE(1 , "Can't find any breakpoint slot");
+ return -EBUSY;
+ }
+
+ per_regs[0].em_storage_alteration =
+ (info->type == S390_BREAKPOINT_WRITE) ? 1 : 0;
+ per_regs[0].em_instruction_fetch =
+ (info->type == S390_BREAKPOINT_EXECUTE) ? 1 : 0;
+ per_regs[0].starting_addr = (unsigned long) info->address;
+ per_regs[0].ending_addr =
+ (unsigned long) info->address + info->len - 1;
+
+ /* Load the control register 9, 10 and 11 with per info */
+ __ctl_load(per_regs, 9, 11);
+ __get_cpu_var(cpu_per_regs[0]) = per_regs[0];
+
+ if (((per_cr_words *)per_regs)->cr[0] & PER_EM_MASK) {
+ if (!tsk) {
+ /* wide breakpoint in the kernel */
+ /* Disable lowcore protection */
+ __ctl_clear_bit(0, 28);
+
+ S390_lowcore.svc_new_psw.mask |= PSW_MASK_PER;
+
+ /* Enable lowcore protection */
+ __ctl_set_bit(0, 28);
+ } else {
+ /* user-space hardware breakpoint */
+ struct pt_regs *regs = task_pt_regs(tsk);
+
+ regs->psw.mask |= PSW_MASK_PER;
+ }
+ }
+ return 0;
+}
+
+/*
+ * Uninstall the breakpoint contained in the given counter.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables,
+ * lowcore area and control registers local to this cpu.
+ */
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+ struct perf_event **slot;
+ per_cr_bits per_regs[1];
+ struct task_struct *tsk = bp->ctx->task;
+
+ slot = &__get_cpu_var(bp_per_reg[0]);
+ if (*slot == bp) {
+ *slot = NULL;
+ } else {
+ WARN_ONCE(1, "Can't find any breakpoint slot");
+ return;
+ }
+ memset(per_regs, 0, sizeof(per_cr_bits));
+ __ctl_load(per_regs, 9, 11);
+
+ if (!tsk) {
+ /* wide breakpoint in the kernel */
+ /* Disable lowcore protection */
+ __ctl_clear_bit(0, 28);
+ S390_lowcore.svc_new_psw.mask &= ~PSW_MASK_PER;
+ /* Enable lowcore protection */
+ __ctl_set_bit(0, 28);
+ } else {
+ /* user-space hardware breakpoint */
+ struct pt_regs *regs = task_pt_regs(tsk);
+
+ regs->psw.mask &= ~PSW_MASK_PER;
+ }
+ return;
+}
+
+/*
+ * Check for virtual address in user space.
+ */
+int arch_check_va_in_userspace(unsigned long va, unsigned long hbp_len)
+{
+ return access_ok(VERIFY_WRITE, (void __user *)va, hbp_len);
+}
+
+static inline int is_kernel(unsigned long addr)
+{
+ if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
+ return 1;
+ return in_gate_area_no_task(addr);
+}
+
+/*
+ * Check for virtual address in kernel space.
+ */
+static int arch_check_va_in_kernelspace(unsigned long va, unsigned long hbp_len)
+{
+ if (is_kernel(va))
+ return is_kernel(va + hbp_len);
+
+ if (is_module_address(va))
+ return is_module_address(va + hbp_len);
+
+ return 0;
+}
+
+/*
+ * Store a breakpoint's encoded address, length, and type.
+ */
+static int arch_store_info(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ /*
+ * For kernel-addresses, either the address or symbol name can be
+ * specified.
+ */
+ if (info->name)
+ info->address = (unsigned long)
+ kallsyms_lookup_name(info->name);
+
+ if (info->len == 0)
+ 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;
+ info->len = bp->attr.bp_len;
+
+ /*
+ * For now, we'll allow only data modification breakpoint.
+ */
+ switch (bp->attr.bp_type) {
+ case HW_BREAKPOINT_W:
+ info->type = S390_BREAKPOINT_WRITE;
+ break;
+ case HW_BREAKPOINT_X:
+ info->type = S390_BREAKPOINT_EXECUTE;
+ if (info->len == 0)
+ info->len = 1;
+ break;
+ case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int arch_validate_hwbkpt_settings(struct perf_event *bp,
+ struct task_struct *tsk)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ int ret;
+
+ ret = arch_build_bp_info(bp);
+ if (ret)
+ return ret;
+
+ ret = arch_store_info(bp);
+
+ if (ret < 0)
+ return ret;
+
+ /* Check that the virtual address is in the proper range */
+ if (tsk) {
+ if (!arch_check_va_in_userspace(info->address, info->len))
+ return -EFAULT;
+ } else {
+ if (!arch_check_va_in_kernelspace(info->address, info->len))
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+/*
+ * 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;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+static int __kprobes hw_breakpoint_handler(struct die_args *args)
+{
+ struct perf_event *bp;
+ per_cr_bits saved_cregs[1];
+ per_cr_bits per_regs[1];
+ per_lowcore_bits *per_code;
+ int cpu, rc = NOTIFY_STOP;
+
+ /* Do an early return if this is not a storage-alteration/instruction
+ * fetch event */
+ per_code = (per_lowcore_bits *)&S390_lowcore.per_perc_atmid;
+ if ((!per_code->perc_storage_alteration &&
+ !per_code->perc_instruction_fetch) ||
+ (per_code->perc_storage_alteration &&
+ per_code->perc_store_real_address))
+ return NOTIFY_DONE;
+
+ /* Disable breakpoints during exception handling */
+ __ctl_store(saved_cregs, 9, 11);
+ memset(per_regs, 0, sizeof(per_cr_bits));
+ __ctl_load(per_regs, 9, 11);
+
+ cpu = get_cpu();
+
+ /*
+ * 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[0], cpu);
+ /*
+ * bp can be NULL due to lazy debug register switching
+ * or due to concurrent perf counter removing.
+ */
+ if (bp)
+ rc = NOTIFY_DONE;
+
+ perf_bp_event(bp, args->regs);
+ rcu_read_unlock();
+
+ /* Enable breakpoints */
+ __ctl_load(saved_cregs, 9, 11);
+ put_cpu();
+
+ return rc;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int __kprobes hw_breakpoint_exceptions_notify(
+ struct notifier_block *unused, unsigned long val, void *data)
+{
+ if (val != DIE_SSTEP)
+ return NOTIFY_DONE;
+
+ return hw_breakpoint_handler(data);
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+ /* TODO */
+}
+
+void hw_breakpoint_pmu_unthrottle(struct perf_event *bp)
+{
+ /* TODO */
+}
Index: linux-2.6-tip/arch/s390/kernel/Makefile
===================================================================
--- linux-2.6-tip.orig/arch/s390/kernel/Makefile
+++ linux-2.6-tip/arch/s390/kernel/Makefile
@@ -23,7 +23,7 @@ CFLAGS_sysinfo.o += -Iinclude/math-emu -
obj-y := bitmap.o traps.o time.o process.o base.o early.o setup.o \
processor.o sys_s390.o ptrace.o signal.o cpcmd.o ebcdic.o \
s390_ext.o debug.o irq.o ipl.o dis.o diag.o mem_detect.o \
- vdso.o vtime.o sysinfo.o nmi.o sclp.o
+ vdso.o vtime.o sysinfo.o nmi.o sclp.o hw_breakpoint.o
obj-y += $(if $(CONFIG_64BIT),entry64.o,entry.o)
obj-y += $(if $(CONFIG_64BIT),reipl64.o,reipl.o)
Index: linux-2.6-tip/arch/s390/Kconfig
===================================================================
--- linux-2.6-tip.orig/arch/s390/Kconfig
+++ linux-2.6-tip/arch/s390/Kconfig
@@ -123,6 +123,7 @@ config S390
select ARCH_INLINE_WRITE_UNLOCK_BH
select ARCH_INLINE_WRITE_UNLOCK_IRQ
select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
+ select HAVE_HW_BREAKPOINT
config SCHED_OMIT_FRAME_POINTER
bool
Index: linux-2.6-tip/arch/s390/include/asm/Kbuild
===================================================================
--- linux-2.6-tip.orig/arch/s390/include/asm/Kbuild
+++ linux-2.6-tip/arch/s390/include/asm/Kbuild
@@ -8,6 +8,7 @@ header-y += ucontext.h
header-y += vtoc.h
header-y += zcrypt.h
header-y += chsc.h
+header-y += hw_breakpoint.h
unifdef-y += cmb.h
unifdef-y += debug.h
Index: linux-2.6-tip/samples/hw_breakpoint/data_breakpoint.c
===================================================================
--- linux-2.6-tip.orig/samples/hw_breakpoint/data_breakpoint.c
+++ linux-2.6-tip/samples/hw_breakpoint/data_breakpoint.c
@@ -58,7 +58,11 @@ static int __init hw_break_module_init(v
hw_breakpoint_init(&attr);
attr.bp_addr = kallsyms_lookup_name(ksym_name);
attr.bp_len = HW_BREAKPOINT_LEN_4;
+#ifdef CONFIG_S390
+ attr.bp_type = HW_BREAKPOINT_W;
+#else
attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+#endif
sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler);
if (IS_ERR(sample_hbp)) {
Index: linux-2.6-tip/kernel/hw_breakpoint.c
===================================================================
--- linux-2.6-tip.orig/kernel/hw_breakpoint.c
+++ linux-2.6-tip/kernel/hw_breakpoint.c
@@ -298,6 +298,10 @@ int register_perf_hw_breakpoint(struct p
if (!bp->attr.disabled || !bp->overflow_handler)
ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+ /* if arch_validate_hwbkpt_settings() fails then release bp slot */
+ if (ret)
+ release_bp_slot(bp);
+
return ret;
}
@@ -391,7 +395,16 @@ register_wide_hw_breakpoint(struct perf_
if (!cpu_events)
return ERR_PTR(-ENOMEM);
+#ifdef CONFIG_S390
+ /* In s390, possible_cpu > online_cpu and the perf event framework does
+ * not yet handle this situation and returns error -ENODEV.
+ * We will use for_each_possible_cpu() once the perf event framework
+ * handles this situation.
+ */
+ for_each_online_cpu(cpu) {
+#else
for_each_possible_cpu(cpu) {
+#endif
pevent = per_cpu_ptr(cpu_events, cpu);
bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
--
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