[Patch 2/6] PPC64-HWBKPT: Introduce PPC64 specific Hardware Breakpoint interfaces
K.Prasad
prasad at linux.vnet.ibm.com
Fri Sep 4 04:40:13 EST 2009
Introduce PPC64 implementation for the generic hardware breakpoint interfaces
defined in kernel/hw_breakpoint.c. Enable the HAVE_HW_BREAKPOINT flag and the
Makefile.
Signed-off-by: K.Prasad <prasad at linux.vnet.ibm.com>
---
arch/powerpc/Kconfig | 1
arch/powerpc/kernel/Makefile | 2
arch/powerpc/kernel/hw_breakpoint.c | 342 ++++++++++++++++++++++++++++++++++++
arch/powerpc/kernel/ptrace.c | 4
4 files changed, 348 insertions(+), 1 deletion(-)
Index: linux-2.6-tip.ppc64_hbkpt/arch/powerpc/Kconfig
===================================================================
--- linux-2.6-tip.ppc64_hbkpt.orig/arch/powerpc/Kconfig
+++ linux-2.6-tip.ppc64_hbkpt/arch/powerpc/Kconfig
@@ -126,6 +126,7 @@ config PPC
select HAVE_SYSCALL_WRAPPERS if PPC64
select GENERIC_ATOMIC64 if PPC32
select HAVE_PERF_COUNTERS
+ select HAVE_HW_BREAKPOINT if PPC64
config EARLY_PRINTK
bool
Index: linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/Makefile
===================================================================
--- linux-2.6-tip.ppc64_hbkpt.orig/arch/powerpc/kernel/Makefile
+++ linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/Makefile
@@ -35,7 +35,7 @@ obj-$(CONFIG_PPC64) += setup_64.o sys_p
signal_64.o ptrace32.o \
paca.o cpu_setup_ppc970.o \
cpu_setup_pa6t.o \
- firmware.o nvram_64.o
+ firmware.o nvram_64.o hw_breakpoint.o
obj64-$(CONFIG_RELOCATABLE) += reloc_64.o
obj-$(CONFIG_PPC64) += vdso64/
obj-$(CONFIG_ALTIVEC) += vecemu.o
Index: linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/hw_breakpoint.c
===================================================================
--- /dev/null
+++ linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/hw_breakpoint.c
@@ -0,0 +1,342 @@
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ *
+ * 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 2009 IBM Corporation
+ */
+
+#include <linux/notifier.h>
+#include <linux/kallsyms.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>
+
+/* Store the kernel-space breakpoint address value */
+static unsigned long kdabr;
+
+/*
+ * Temporarily stores address for DABR before it is written by the
+ * single-step handler routine
+ */
+static DEFINE_PER_CPU(unsigned long, dabr_data);
+static DEFINE_PER_CPU(struct hw_breakpoint*, last_hit_bp);
+
+/* Disable breakpoints on the physical debug register */
+void arch_disable_hw_breakpoint(void)
+{
+ set_dabr(0);
+}
+
+void arch_update_kernel_hw_breakpoint(void *unused)
+{
+ struct hw_breakpoint *bp;
+
+ /* Check if there is nothing to update */
+ if (hbp_kernel_pos == HBP_NUM)
+ return;
+
+ bp = per_cpu(this_hbp_kernel[hbp_kernel_pos], get_cpu());
+ if (bp == NULL)
+ kdabr = 0;
+ else
+ kdabr = (bp->info.address & ~HW_BREAKPOINT_ALIGN) |
+ bp->info.type | DABR_TRANSLATION;
+ set_dabr(kdabr);
+ put_cpu();
+}
+
+/*
+ * Install the thread breakpoints in their debug registers.
+ */
+void arch_install_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ set_dabr(tsk->thread.dabr);
+}
+
+/*
+ * Clear the DABR which contains the thread-specific breakpoint address
+ */
+void arch_uninstall_thread_hw_breakpoint()
+{
+ set_dabr(0);
+}
+
+/*
+ * Store a breakpoint's encoded address, length, and type.
+ */
+int arch_store_info(struct hw_breakpoint *bp, struct task_struct *tsk)
+{
+ unsigned long sym_addr;
+
+ /* Symbol names from user-space are rejected */
+ if (tsk) {
+ if (bp->info.name)
+ return -EINVAL;
+ return 0;
+ }
+ /*
+ * User-space requests will always have the address field populated
+ * For kernel-addresses, either the address or symbol name can be
+ * specified.
+ */
+ if (bp->info.name) {
+ sym_addr = (unsigned long)kallsyms_lookup_name(bp->info.name);
+ if (bp->info.address) {
+ if (bp->info.address != sym_addr)
+ return -EINVAL;
+ } else
+ bp->info.address = sym_addr;
+ }
+ if (!bp->info.address)
+ return -EINVAL;
+ /*
+ * Determine the symbolsize if not already specified.
+ * Reject the breakpoint request if symbolsize is found
+ * to be greater than HW_BREAKPOINT_LEN
+ */
+ if (!bp->info.symbolsize) {
+ if(!kallsyms_lookup_size_offset(bp->info.address,
+ &(bp->info.symbolsize), NULL))
+ return -EINVAL;
+ }
+ if (bp->info.symbolsize <= HW_BREAKPOINT_LEN)
+ return 0;
+ return -EINVAL;
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp,
+ struct task_struct *tsk)
+{
+ int is_kernel, ret = -EINVAL;
+
+ /* User-space breakpoints cannot be restricted to a subset of CPUs */
+ if (tsk && bp->cpumask)
+ return ret;
+
+ if (!bp)
+ return ret;
+
+ switch (bp->info.type) {
+ case HW_BREAKPOINT_READ:
+ case HW_BREAKPOINT_WRITE:
+ case HW_BREAKPOINT_RW:
+ break;
+ default:
+ return ret;
+ }
+
+ if (!bp->triggered)
+ return -EINVAL;
+
+ ret = arch_store_info(bp, tsk);
+ is_kernel = is_kernel_addr(bp->info.address);
+ if ((tsk && is_kernel) || (!tsk && !is_kernel))
+ return -EINVAL;
+
+ /*
+ * 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 (bp->info.symbolsize >
+ (HW_BREAKPOINT_LEN - (bp->info.address & HW_BREAKPOINT_ALIGN)))
+ return -EINVAL;
+
+ return ret;
+}
+
+void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk)
+{
+ struct thread_struct *thread = &(tsk->thread);
+ struct hw_breakpoint *bp = thread->hbp[0];
+
+ if (bp)
+ thread->dabr = (bp->info.address & ~HW_BREAKPOINT_ALIGN) |
+ bp->info.type | DABR_TRANSLATION;
+ else
+ thread->dabr = 0;
+}
+
+void arch_flush_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ struct thread_struct *thread = &(tsk->thread);
+
+ thread->dabr = 0;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int __kprobes hw_breakpoint_handler(struct die_args *args)
+{
+ int rc = NOTIFY_STOP;
+ struct hw_breakpoint *bp;
+ struct pt_regs *regs = args->regs;
+ unsigned long dar = regs->dar;
+ int cpu, is_kernel, stepped = 1;
+
+ is_kernel = (hbp_kernel_pos == HBP_NUM) ? 0 : 1;
+
+ /* Disable breakpoints during exception handling */
+ set_dabr(0);
+
+ cpu = get_cpu();
+ /* Determine whether kernel- or user-space address is the trigger */
+ bp = is_kernel ?
+ per_cpu(this_hbp_kernel[0], cpu) : current->thread.hbp[0];
+ /*
+ * bp can be NULL due to lazy debug register switching
+ * or due to the delay between updates of hbp_kernel_pos
+ * and this_hbp_kernel.
+ */
+ if (!bp)
+ goto out;
+
+ per_cpu(dabr_data, cpu) = is_kernel ? kdabr : current->thread.dabr;
+
+ /* Verify if dar lies within the address range occupied by the symbol
+ * being watched. Since we cannot get the symbol size for
+ * user-space requests we skip this check in that case
+ */
+ if (is_kernel &&
+ !((bp->info.address <= dar) &&
+ (dar <= (bp->info.address + bp->info.symbolsize))))
+ /*
+ * This exception is triggered not because of a memory access on
+ * the monitored variable but in the double-word address range
+ * in which it is contained. We will consume this exception,
+ * considering it as 'noise'.
+ */
+ goto out;
+
+ /*
+ * Return early after invoking user-callback function without restoring
+ * DABR if the breakpoint is from ptrace which always operates in
+ * one-shot mode
+ */
+ if (bp->triggered == ptrace_triggered) {
+ (bp->triggered)(bp, regs);
+ rc = NOTIFY_DONE;
+ goto out;
+ }
+
+ stepped = emulate_step(regs, regs->nip);
+ /*
+ * Single-step the causative instruction manually if
+ * emulate_step() could not execute it
+ */
+ if (stepped == 0) {
+ regs->msr |= MSR_SE;
+ per_cpu(last_hit_bp, cpu) = bp;
+ goto out;
+ }
+ (bp->triggered)(bp, regs);
+ set_dabr(per_cpu(dabr_data, cpu));
+
+out:
+ /* Enable pre-emption only if single-stepping is finished */
+ if (stepped) {
+ per_cpu(dabr_data, cpu) = 0;
+ put_cpu();
+ }
+ 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;
+ int cpu = get_cpu();
+ int ret = NOTIFY_DONE;
+ siginfo_t info;
+ unsigned long this_dabr_data = per_cpu(dabr_data, cpu);
+ struct hw_breakpoint *bp = per_cpu(last_hit_bp, cpu);
+
+ /*
+ * Check if we are single-stepping as a result of a
+ * previous HW Breakpoint exception
+ */
+ if (this_dabr_data == 0)
+ goto out;
+
+ regs->msr &= ~MSR_SE;
+ /*
+ * We shall invoke the user-defined callback function in the single
+ * stepping handler to confirm to 'trigger-after-execute' semantics
+ */
+ (bp->triggered)(bp, regs);
+
+ /* Deliver signal to user-space */
+ if (this_dabr_data < TASK_SIZE) {
+ info.si_signo = SIGTRAP;
+ info.si_errno = 0;
+ info.si_code = TRAP_HWBKPT;
+ info.si_addr = (void __user *)(per_cpu(dabr_data, cpu));
+ force_sig_info(SIGTRAP, &info, current);
+ }
+
+ set_dabr(this_dabr_data);
+ per_cpu(dabr_data, cpu) = 0;
+ ret = NOTIFY_STOP;
+ /*
+ * If single-stepped after hw_breakpoint_handler(), pre-emption is
+ * already disabled.
+ */
+ put_cpu();
+
+out:
+ /*
+ * A put_cpu() call is required to complement the get_cpu()
+ * call used initially
+ */
+ put_cpu();
+ return ret;
+}
+
+/*
+ * 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;
+}
Index: linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/ptrace.c
===================================================================
--- linux-2.6-tip.ppc64_hbkpt.orig/arch/powerpc/kernel/ptrace.c
+++ linux-2.6-tip.ppc64_hbkpt/arch/powerpc/kernel/ptrace.c
@@ -755,6 +755,10 @@ void user_disable_single_step(struct tas
clear_tsk_thread_flag(task, TIF_SINGLESTEP);
}
+void ptrace_triggered(struct hw_breakpoint *bp, struct pt_regs *regs)
+{
+}
+
int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
unsigned long data)
{
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