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Message-ID: <Pine.LNX.4.44L0.0703221544040.4669-100000@iolanthe.rowland.org>
Date: Thu, 22 Mar 2007 15:44:55 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Roland McGrath <roland@...hat.com>
cc: Prasanna S Panchamukhi <prasanna@...ibm.com>,
Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] hwbkpt: Hardware breakpoints (was Kwatch)
Roland:
Here's the most recent version of the hw-breakpoint patch. Unlike the
version I posted last week, this one actually works with 2.6.21-rc4.
Alan Stern
Index: usb-2.6/include/asm-i386/hw_breakpoint.h
===================================================================
--- /dev/null
+++ usb-2.6/include/asm-i386/hw_breakpoint.h
@@ -0,0 +1,17 @@
+#ifndef _I386_HW_BREAKPOINT_H
+#define _I386_HW_BREAKPOINT_H
+
+#include <asm-generic/hw_breakpoint.h>
+
+/* Available HW breakpoint lengths */
+#define HW_BREAKPOINT_LEN_1 1
+#define HW_BREAKPOINT_LEN_2 2
+#define HW_BREAKPOINT_LEN_4 4
+#define HW_BREAKPOINT_LEN_EXECUTE 1
+
+/* Available HW breakpoint types */
+#define HW_BREAKPOINT_EXECUTE 0x80 /* trigger on instruction execute */
+#define HW_BREAKPOINT_WRITE 0x81 /* trigger on memory write */
+#define HW_BREAKPOINT_RW 0x83 /* trigger on memory read or write */
+
+#endif /* _I386_HW_BREAKPOINT_H */
Index: usb-2.6/arch/i386/kernel/process.c
===================================================================
--- usb-2.6.orig/arch/i386/kernel/process.c
+++ usb-2.6/arch/i386/kernel/process.c
@@ -58,6 +58,7 @@
#include <asm/tlbflush.h>
#include <asm/cpu.h>
#include <asm/pda.h>
+#include <asm/debugreg.h>
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
@@ -359,9 +360,10 @@ EXPORT_SYMBOL(kernel_thread);
*/
void exit_thread(void)
{
+ struct task_struct *tsk = current;
+
/* The process may have allocated an io port bitmap... nuke it. */
if (unlikely(test_thread_flag(TIF_IO_BITMAP))) {
- struct task_struct *tsk = current;
struct thread_struct *t = &tsk->thread;
int cpu = get_cpu();
struct tss_struct *tss = &per_cpu(init_tss, cpu);
@@ -379,15 +381,17 @@ void exit_thread(void)
tss->io_bitmap_base = INVALID_IO_BITMAP_OFFSET;
put_cpu();
}
+ if (unlikely(tsk->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(tsk);
}
void flush_thread(void)
{
struct task_struct *tsk = current;
- memset(tsk->thread.debugreg, 0, sizeof(unsigned long)*8);
- memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
- clear_tsk_thread_flag(tsk, TIF_DEBUG);
+ memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
+ if (unlikely(tsk->thread.hw_breakpoint_info))
+ flush_thread_hw_breakpoint(tsk);
/*
* Forget coprocessor state..
*/
@@ -430,14 +434,21 @@ int copy_thread(int nr, unsigned long cl
savesegment(gs,p->thread.gs);
+ p->thread.hw_breakpoint_info = NULL;
+ p->thread.io_bitmap_ptr = NULL;
+
tsk = current;
+ err = -ENOMEM;
+ if (unlikely(tsk->thread.hw_breakpoint_info)) {
+ if (copy_thread_hw_breakpoint(tsk, p, clone_flags))
+ goto out;
+ }
+
if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
IO_BITMAP_BYTES, GFP_KERNEL);
- if (!p->thread.io_bitmap_ptr) {
- p->thread.io_bitmap_max = 0;
- return -ENOMEM;
- }
+ if (!p->thread.io_bitmap_ptr)
+ goto out;
set_tsk_thread_flag(p, TIF_IO_BITMAP);
}
@@ -467,7 +478,8 @@ int copy_thread(int nr, unsigned long cl
err = 0;
out:
- if (err && p->thread.io_bitmap_ptr) {
+ if (err) {
+ flush_thread_hw_breakpoint(p);
kfree(p->thread.io_bitmap_ptr);
p->thread.io_bitmap_max = 0;
}
@@ -479,18 +491,18 @@ int copy_thread(int nr, unsigned long cl
*/
void dump_thread(struct pt_regs * regs, struct user * dump)
{
- int i;
+ struct task_struct *tsk = current;
/* changed the size calculations - should hopefully work better. lbt */
dump->magic = CMAGIC;
dump->start_code = 0;
dump->start_stack = regs->esp & ~(PAGE_SIZE - 1);
- dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
- dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
+ dump->u_tsize = ((unsigned long) tsk->mm->end_code) >> PAGE_SHIFT;
+ dump->u_dsize = ((unsigned long) (tsk->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
dump->u_dsize -= dump->u_tsize;
dump->u_ssize = 0;
- for (i = 0; i < 8; i++)
- dump->u_debugreg[i] = current->thread.debugreg[i];
+
+ dump_thread_hw_breakpoint(tsk, dump->u_debugreg);
if (dump->start_stack < TASK_SIZE)
dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
@@ -540,16 +552,6 @@ static noinline void __switch_to_xtra(st
next = &next_p->thread;
- if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
- set_debugreg(next->debugreg[0], 0);
- set_debugreg(next->debugreg[1], 1);
- set_debugreg(next->debugreg[2], 2);
- set_debugreg(next->debugreg[3], 3);
- /* no 4 and 5 */
- set_debugreg(next->debugreg[6], 6);
- set_debugreg(next->debugreg[7], 7);
- }
-
if (!test_tsk_thread_flag(next_p, TIF_IO_BITMAP)) {
/*
* Disable the bitmap via an invalid offset. We still cache
@@ -682,7 +684,7 @@ struct task_struct fastcall * __switch_t
set_iopl_mask(next->iopl);
/*
- * Now maybe handle debug registers and/or IO bitmaps
+ * Now maybe handle IO bitmaps
*/
if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW)
|| test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)))
@@ -714,6 +716,13 @@ struct task_struct fastcall * __switch_t
write_pda(pcurrent, next_p);
+ /*
+ * Handle debug registers. This must be done _after_ current
+ * is updated.
+ */
+ if (unlikely(test_tsk_thread_flag(next_p, TIF_DEBUG)))
+ switch_to_thread_hw_breakpoint(next_p);
+
return prev_p;
}
Index: usb-2.6/arch/i386/kernel/signal.c
===================================================================
--- usb-2.6.orig/arch/i386/kernel/signal.c
+++ usb-2.6/arch/i386/kernel/signal.c
@@ -592,13 +592,6 @@ static void fastcall do_signal(struct pt
signr = get_signal_to_deliver(&info, &ka, regs, NULL);
if (signr > 0) {
- /* Reenable any watchpoints before delivering the
- * signal to user space. The processor register will
- * have been cleared if the watchpoint triggered
- * inside the kernel.
- */
- if (unlikely(current->thread.debugreg[7]))
- set_debugreg(current->thread.debugreg[7], 7);
/* Whee! Actually deliver the signal. */
if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
Index: usb-2.6/arch/i386/kernel/traps.c
===================================================================
--- usb-2.6.orig/arch/i386/kernel/traps.c
+++ usb-2.6/arch/i386/kernel/traps.c
@@ -807,62 +807,47 @@ fastcall void __kprobes do_int3(struct p
*/
fastcall void __kprobes do_debug(struct pt_regs * regs, long error_code)
{
- unsigned int condition;
struct task_struct *tsk = current;
+ struct die_args args;
- get_debugreg(condition, 6);
-
- if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
- SIGTRAP) == NOTIFY_STOP)
+ args.regs = regs;
+ args.str = "debug";
+ get_debugreg(args.err, 6);
+ set_debugreg(0, 6); /* DR6 is never cleared by the CPU */
+ args.trapnr = error_code;
+ args.signr = SIGTRAP;
+ if (atomic_notifier_call_chain(&i386die_chain, DIE_DEBUG, &args) ==
+ NOTIFY_STOP)
return;
+
/* It's safe to allow irq's after DR6 has been saved */
if (regs->eflags & X86_EFLAGS_IF)
local_irq_enable();
- /* Mask out spurious debug traps due to lazy DR7 setting */
- if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
- if (!tsk->thread.debugreg[7])
- goto clear_dr7;
+ if (regs->eflags & VM_MASK) {
+ handle_vm86_trap((struct kernel_vm86_regs *) regs,
+ error_code, 1);
+ return;
}
- if (regs->eflags & VM_MASK)
- goto debug_vm86;
-
- /* Save debug status register where ptrace can see it */
- tsk->thread.debugreg[6] = condition;
-
/*
- * Single-stepping through TF: make sure we ignore any events in
- * kernel space (but re-enable TF when returning to user mode).
+ * Single-stepping through system calls: ignore any exceptions in
+ * kernel space, but re-enable TF when returning to user mode.
+ *
+ * We already checked v86 mode above, so we can check for kernel mode
+ * by just checking the CPL of CS.
*/
- if (condition & DR_STEP) {
- /*
- * We already checked v86 mode above, so we can
- * check for kernel mode by just checking the CPL
- * of CS.
- */
- if (!user_mode(regs))
- goto clear_TF_reenable;
+ if ((args.err & DR_STEP) && !user_mode(regs)) {
+ args.err &= ~DR_STEP;
+ set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
+ regs->eflags &= ~TF_MASK;
}
- /* Ok, finally something we can handle */
- send_sigtrap(tsk, regs, error_code);
+ /* Store the virtualized DR6 value */
+ tsk->thread.vdr6 |= args.err;
- /* Disable additional traps. They'll be re-enabled when
- * the signal is delivered.
- */
-clear_dr7:
- set_debugreg(0, 7);
- return;
-
-debug_vm86:
- handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
- return;
-
-clear_TF_reenable:
- set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
- regs->eflags &= ~TF_MASK;
- return;
+ if (args.err & (DR_STEP|DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3))
+ send_sigtrap(tsk, regs, error_code);
}
/*
Index: usb-2.6/include/asm-i386/debugreg.h
===================================================================
--- usb-2.6.orig/include/asm-i386/debugreg.h
+++ usb-2.6/include/asm-i386/debugreg.h
@@ -48,6 +48,8 @@
#define DR_LOCAL_ENABLE_SHIFT 0 /* Extra shift to the local enable bit */
#define DR_GLOBAL_ENABLE_SHIFT 1 /* Extra shift to the global enable bit */
+#define DR_LOCAL_ENABLE (0x1) /* Local enable for reg 0 */
+#define DR_GLOBAL_ENABLE (0x2) /* Global enable for reg 0 */
#define DR_ENABLE_SIZE 2 /* 2 enable bits per register */
#define DR_LOCAL_ENABLE_MASK (0x55) /* Set local bits for all 4 regs */
@@ -58,7 +60,31 @@
gdt or the ldt if we want to. I am not sure why this is an advantage */
#define DR_CONTROL_RESERVED (0xFC00) /* Reserved by Intel */
-#define DR_LOCAL_SLOWDOWN (0x100) /* Local slow the pipeline */
-#define DR_GLOBAL_SLOWDOWN (0x200) /* Global slow the pipeline */
+#define DR_LOCAL_EXACT (0x100) /* Local slow the pipeline */
+#define DR_GLOBAL_EXACT (0x200) /* Global slow the pipeline */
+
+
+/*
+ * HW breakpoint additions
+ */
+
+#include <asm/hw_breakpoint.h>
+#include <linux/spinlock.h>
+
+#define HB_NUM 4 /* Number of hardware breakpoints */
+
+/* For process management */
+void flush_thread_hw_breakpoint(struct task_struct *tsk);
+int copy_thread_hw_breakpoint(struct task_struct *tsk,
+ struct task_struct *child, unsigned long clone_flags);
+void dump_thread_hw_breakpoint(struct task_struct *tsk, int u_debugreg[8]);
+void switch_to_thread_hw_breakpoint(struct task_struct *tsk);
+
+/* For CPU management */
+void load_debug_registers(void);
+
+/* For use by ptrace */
+unsigned long thread_get_debugreg(struct task_struct *tsk, int n);
+int thread_set_debugreg(struct task_struct *tsk, int n, unsigned long val);
#endif
Index: usb-2.6/include/asm-i386/processor.h
===================================================================
--- usb-2.6.orig/include/asm-i386/processor.h
+++ usb-2.6/include/asm-i386/processor.h
@@ -402,8 +402,9 @@ struct thread_struct {
unsigned long esp;
unsigned long fs;
unsigned long gs;
-/* Hardware debugging registers */
- unsigned long debugreg[8]; /* %%db0-7 debug registers */
+/* Hardware breakpoint info */
+ unsigned long vdr6;
+ struct thread_hw_breakpoint *hw_breakpoint_info;
/* fault info */
unsigned long cr2, trap_no, error_code;
/* floating point info */
Index: usb-2.6/arch/i386/kernel/hw_breakpoint.c
===================================================================
--- /dev/null
+++ usb-2.6/arch/i386/kernel/hw_breakpoint.c
@@ -0,0 +1,1211 @@
+/*
+ * 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) 2007 Alan Stern
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ */
+
+/* QUESTIONS
+
+ Error code in ptrace_triggered?
+
+ Set RF flag bit for execution faults?
+
+ TF flag bit for single-step exceptions in kernel space?
+
+ CPU hotplug, kexec, etc?
+*/
+
+#include <linux/init.h>
+#include <linux/irqflags.h>
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+
+#include <asm-generic/percpu.h>
+
+#include <asm/debugreg.h>
+#include <asm/kdebug.h>
+#include <asm/processor.h>
+
+
+/* Per-thread HW breakpoint and debug register info */
+struct thread_hw_breakpoint {
+
+ /* utrace support */
+ struct list_head node; /* Entry in thread list */
+ struct list_head thread_bps; /* Thread's breakpoints */
+ struct hw_breakpoint *bps[HB_NUM]; /* Highest-priority bps */
+ unsigned long tdr[HB_NUM]; /* and their addresses */
+ unsigned long tdr7; /* Thread's DR7 value */
+ int last_num_kbps; /* Value of num_kbps when
+ * the thread last ran */
+
+ /* ptrace support -- note that vdr6 is stored directly in the
+ * thread_struct so that it is always available */
+ unsigned long vdr7; /* Virtualized DR7 */
+ struct hw_breakpoint vdr_bps[HB_NUM]; /* Breakpoints
+ * representing virtualized debug registers 0 - 3 */
+};
+
+/* Per-CPU debug register info */
+struct cpu_hw_breakpoint {
+ struct hw_breakpoint *bps[HB_NUM]; /* Loaded breakpoints */
+ int num_kbps; /* Number of kernel bps */
+ unsigned long kdr7; /* Current kernel DR7 value */
+ unsigned long kdr7_mask; /* Mask for kernel part */
+ unsigned long dr7; /* Current DR7 value */
+ struct task_struct *bp_task; /* The thread whose bps
+ are currently loaded in the debug registers */
+};
+
+static DEFINE_PER_CPU(struct cpu_hw_breakpoint, cpu_info);
+
+/* Kernel-space breakpoint data */
+static LIST_HEAD(kernel_bps); /* Kernel breakpoint list */
+static int num_kbps; /* Number of kernel bps */
+static unsigned long kdr7; /* Kernel DR7 value */
+
+static u8 tprio[HB_NUM]; /* Thread bp max priorities */
+static LIST_HEAD(thread_list); /* thread_hw_breakpoint list */
+static DEFINE_MUTEX(hw_breakpoint_mutex); /* Protects everything */
+
+/* Masks for the bits in DR7 related to kernel breakpoints, for various
+ * values of num_kbps. Entry n is the mask for when there are n kernel
+ * breakpoints, in debug registers 0 - (n-1). */
+static const unsigned long kdr7_masks[HB_NUM + 1] = {
+ 0x00000000,
+ 0x000f0203, /* LEN0, R/W0, GE, G0, L0 */
+ 0x00ff020f, /* Same for 0,1 */
+ 0x0fff023f, /* Same for 0,1,2 */
+ 0xffff02ff /* Same for 0,1,2,3 */
+};
+
+
+/*
+ * Install the debug register values for a new thread.
+ */
+void switch_to_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+ struct cpu_hw_breakpoint *chbi;
+ unsigned long flags;
+
+ /* Other CPUs might be making updates to the list of kernel
+ * breakpoints at this same time, so we can't use the global
+ * value stored in num_kbps. Instead we'll use the per-CPU
+ * value stored in cpu_info. */
+
+ /* Block kernel breakpoint updates from other CPUs */
+ local_irq_save(flags);
+ chbi = &per_cpu(cpu_info, get_cpu());
+ chbi->bp_task = tsk;
+
+ /* Normally we can keep the same debug register settings as the
+ * last time this task ran. But if the number of registers
+ * allocated to the kernel has changed or any user breakpoints
+ * have been registered or unregistered, we need to send out
+ * some notifications. */
+ if (unlikely(thbi->last_num_kbps != chbi->num_kbps)) {
+ struct hw_breakpoint *bp;
+ int i = HB_NUM;
+
+ thbi->last_num_kbps = chbi->num_kbps;
+
+ /* This code can be invoked while a debugger is actively
+ * updating the thread's breakpoint list (for example, if
+ * someone sends SIGKILL to the task). We use RCU to
+ * protect our access to the list pointers. */
+ rcu_read_lock();
+ list_for_each_entry_rcu(bp, &thbi->thread_bps, node) {
+
+ /* If this register is allocated for kernel bps,
+ * don't install. Otherwise do. */
+ if (--i < chbi->num_kbps) {
+ if (bp->status == HW_BREAKPOINT_INSTALLED) {
+ if (bp->uninstalled)
+ (bp->uninstalled)(bp);
+ bp->status = HW_BREAKPOINT_REGISTERED;
+ }
+ } else {
+ if (bp->status != HW_BREAKPOINT_INSTALLED) {
+ bp->status = HW_BREAKPOINT_INSTALLED;
+ if (bp->installed)
+ (bp->installed)(bp);
+ }
+ }
+ }
+ rcu_read_unlock();
+ }
+
+ /* Install the thread breakpoints. Kernel breakpoints are stored
+ * starting in DR0 and going up, and there are num_kbps of them.
+ * Thread breakpoints are stored starting in DR3 and going down,
+ * as many as we have room for. */
+ switch (chbi->num_kbps) {
+ case 0:
+ set_debugreg(thbi->tdr[0], 0);
+ case 1:
+ set_debugreg(thbi->tdr[1], 1);
+ case 2:
+ set_debugreg(thbi->tdr[2], 2);
+ case 3:
+ set_debugreg(thbi->tdr[3], 3);
+ }
+
+ /* Mask in the parts of DR7 that refer to the new thread */
+ chbi->dr7 = chbi->kdr7 | (~chbi->kdr7_mask & thbi->tdr7);
+ set_debugreg(chbi->dr7, 7);
+
+ put_cpu_no_resched();
+ local_irq_restore(flags);
+}
+
+/*
+ * Install the debug register values for just the kernel, no thread.
+ */
+static void switch_to_none_hw_breakpoint(void)
+{
+ struct cpu_hw_breakpoint *chbi;
+ unsigned long flags;
+
+ /* Block kernel breakpoint updates from other CPUs */
+ local_irq_save(flags);
+ chbi = &per_cpu(cpu_info, get_cpu());
+
+ chbi->bp_task = NULL;
+ chbi->dr7 = chbi->kdr7;
+ set_debugreg(chbi->dr7, 7);
+
+ put_cpu_no_resched();
+ local_irq_restore(flags);
+}
+
+/*
+ * Install the kernel breakpoints in their debug registers.
+ */
+static void switch_kernel_hw_breakpoint(struct cpu_hw_breakpoint *chbi)
+{
+ struct hw_breakpoint *bp;
+ int i;
+
+ /* Don't allow debug exceptions while we update the registers */
+ set_debugreg(0, 7);
+ chbi->num_kbps = num_kbps;
+
+ /* Kernel breakpoints are stored starting in DR0 and going up */
+ i = 0;
+ list_for_each_entry(bp, &kernel_bps, node) {
+ if (i >= chbi->num_kbps)
+ break;
+ chbi->bps[i] = bp;
+ switch (i) {
+ case 0:
+ set_debugreg(bp->address.va, 0);
+ break;
+ case 1:
+ set_debugreg(bp->address.va, 1);
+ break;
+ case 2:
+ set_debugreg(bp->address.va, 2);
+ break;
+ case 3:
+ set_debugreg(bp->address.va, 3);
+ break;
+ }
+ ++i;
+ }
+
+ chbi->kdr7_mask = kdr7_masks[chbi->num_kbps];
+ chbi->kdr7 = kdr7 & chbi->kdr7_mask;
+ set_debugreg(chbi->kdr7, 7);
+}
+
+/*
+ * Update the debug registers on this CPU.
+ */
+static void update_this_cpu(void *unused)
+{
+ struct cpu_hw_breakpoint *chbi;
+ struct task_struct *tsk = current;
+
+ /* Install both the kernel and the user breakpoints */
+ chbi = &per_cpu(cpu_info, get_cpu());
+
+ switch_kernel_hw_breakpoint(chbi);
+ if (test_tsk_thread_flag(tsk, TIF_DEBUG))
+ switch_to_thread_hw_breakpoint(tsk);
+
+ put_cpu_no_resched();
+}
+
+/*
+ * Tell all CPUs to update their debug registers.
+ *
+ * The caller must hold hw_breakpoint_mutex.
+ */
+static void update_all_cpus(void)
+{
+ on_each_cpu(update_this_cpu, NULL, 0, 0);
+}
+
+/*
+ * Load the debug registers during startup of a CPU.
+ */
+void load_debug_registers(void)
+{
+ mutex_lock(&hw_breakpoint_mutex);
+ update_this_cpu(NULL);
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+
+/*
+ * Take the 4 highest-priority breakpoints in a thread and accumulate
+ * their priorities in tprio. Highest-priority entry is in tprio[3].
+ */
+static void accum_thread_tprio(struct thread_hw_breakpoint *thbi)
+{
+ int i;
+
+ for (i = HB_NUM - 1; i >= 0 && thbi->bps[i]; --i)
+ tprio[i] = max(tprio[i], thbi->bps[i]->priority);
+}
+
+/*
+ * Recalculate the value of the tprio array, the maximum priority levels
+ * requested by user breakpoints in all threads.
+ *
+ * Each thread has a list of registered breakpoints, kept in order of
+ * decreasing priority. We'll set tprio[0] to the maximum priority of
+ * the first entries in all the lists, tprio[1] to the maximum priority
+ * of the second entries in all the lists, etc. In the end, we'll know
+ * that no thread requires breakpoints with priorities higher than the
+ * values in tprio.
+ *
+ * The caller must hold hw_breakpoint_mutex.
+ */
+static void recalc_tprio(void)
+{
+ struct thread_hw_breakpoint *thbi;
+
+ memset(tprio, 0, sizeof tprio);
+
+ /* Loop through all threads having registered breakpoints
+ * and accumulate the maximum priority levels in tprio. */
+ list_for_each_entry(thbi, &thread_list, node)
+ accum_thread_tprio(thbi);
+}
+
+/*
+ * Decide how many debug registers will be allocated to kernel breakpoints
+ * and consequently, how many remain available for user breakpoints.
+ *
+ * The priorities of the entries in the list of registered kernel bps
+ * are compared against the priorities stored in tprio[]. The 4 highest
+ * winners overall get to be installed in a debug register; num_kpbs
+ * keeps track of how many of those winners come from the kernel list.
+ *
+ * If num_kbps changes, or if a kernel bp changes its installation status,
+ * then call update_all_cpus() so that the debug registers will be set
+ * correctly on every CPU. If neither condition holds then the set of
+ * kernel bps hasn't changed, and nothing more needs to be done.
+ *
+ * The caller must hold hw_breakpoint_mutex.
+ */
+static void balance_kernel_vs_user(void)
+{
+ int k, u;
+ int changed = 0;
+ struct hw_breakpoint *bp;
+
+ /* Determine how many debug registers are available for kernel
+ * breakpoints as opposed to user breakpoints, based on the
+ * priorities. Ties are resolved in favor of user bps. */
+ k = 0; /* Next kernel bp to allocate */
+ u = HB_NUM - 1; /* Next user bp to allocate */
+ bp = list_entry(kernel_bps.next, struct hw_breakpoint, node);
+ while (k <= u) {
+ if (&bp->node == &kernel_bps || tprio[u] >= bp->priority)
+ --u; /* User bps win a slot */
+ else {
+ ++k; /* Kernel bp wins a slot */
+ if (bp->status != HW_BREAKPOINT_INSTALLED)
+ changed = 1;
+ bp = list_entry(bp->node.next, struct hw_breakpoint,
+ node);
+ }
+ }
+ if (k != num_kbps) {
+ changed = 1;
+ num_kbps = k;
+ }
+
+ /* Notify the remaining kernel breakpoints that they are about
+ * to be uninstalled. */
+ list_for_each_entry_from(bp, &kernel_bps, node) {
+ if (bp->status == HW_BREAKPOINT_INSTALLED) {
+ if (bp->uninstalled)
+ (bp->uninstalled)(bp);
+ bp->status = HW_BREAKPOINT_REGISTERED;
+ changed = 1;
+ }
+ }
+
+ if (changed) {
+
+ /* Tell all the CPUs to update their debug registers */
+ update_all_cpus();
+
+ /* Notify the breakpoints that just got installed */
+ k = 0;
+ list_for_each_entry(bp, &kernel_bps, node) {
+ if (k++ >= num_kbps)
+ break;
+ if (bp->status != HW_BREAKPOINT_INSTALLED) {
+ bp->status = HW_BREAKPOINT_INSTALLED;
+ if (bp->installed)
+ (bp->installed)(bp);
+ }
+ }
+ }
+}
+
+/*
+ * Return the pointer to a thread's hw_breakpoint info area,
+ * and try to allocate one if it doesn't exist.
+ *
+ * The caller must hold hw_breakpoint_mutex.
+ */
+static struct thread_hw_breakpoint *alloc_thread_hw_breakpoint(
+ struct task_struct *tsk)
+{
+ if (!tsk->thread.hw_breakpoint_info && !(tsk->flags & PF_EXITING)) {
+ struct thread_hw_breakpoint *thbi;
+
+ thbi = kzalloc(sizeof(struct thread_hw_breakpoint),
+ GFP_KERNEL);
+ if (thbi) {
+ INIT_LIST_HEAD(&thbi->node);
+ INIT_LIST_HEAD(&thbi->thread_bps);
+ tsk->thread.hw_breakpoint_info = thbi;
+ }
+ }
+ return tsk->thread.hw_breakpoint_info;
+}
+
+/*
+ * Erase all the hardware breakpoint info associated with a thread.
+ *
+ * If tsk != current then tsk must not be usable (for example, a
+ * child being cleaned up from a failed fork).
+ */
+void flush_thread_hw_breakpoint(struct task_struct *tsk)
+{
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+ struct hw_breakpoint *bp;
+
+ if (!thbi)
+ return;
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* Let the breakpoints know they are being uninstalled */
+ list_for_each_entry(bp, &thbi->thread_bps, node) {
+ if (bp->status == HW_BREAKPOINT_INSTALLED && bp->uninstalled)
+ (bp->uninstalled)(bp);
+ bp->status = 0;
+ }
+
+ /* Remove tsk from the list of all threads with registered bps */
+ list_del(&thbi->node);
+
+ /* The thread no longer has any breakpoints associated with it */
+ clear_tsk_thread_flag(tsk, TIF_DEBUG);
+ tsk->thread.hw_breakpoint_info = NULL;
+ kfree(thbi);
+
+ /* Recalculate and rebalance the kernel-vs-user priorities */
+ recalc_tprio();
+ balance_kernel_vs_user();
+
+ /* Actually uninstall the breakpoints if necessary */
+ if (tsk == current)
+ switch_to_none_hw_breakpoint();
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+
+/*
+ * Copy the hardware breakpoint info from a thread to its cloned child.
+ */
+int copy_thread_hw_breakpoint(struct task_struct *tsk,
+ struct task_struct *child, unsigned long clone_flags)
+{
+ /* We will assume that breakpoint settings are not inherited
+ * and the child starts out with no debug registers set.
+ * But what about CLONE_PTRACE? */
+
+ clear_tsk_thread_flag(child, TIF_DEBUG);
+ return 0;
+}
+
+/*
+ * Copy out the debug register information for a core dump.
+ *
+ * tsk must be equal to current.
+ */
+void dump_thread_hw_breakpoint(struct task_struct *tsk, int u_debugreg[8])
+{
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+ int i;
+
+ memset(u_debugreg, 0, sizeof u_debugreg);
+ if (thbi) {
+ for (i = 0; i < HB_NUM; ++i)
+ u_debugreg[i] = (unsigned long)
+ thbi->vdr_bps[i].address.va;
+ u_debugreg[7] = thbi->vdr7;
+ }
+ u_debugreg[6] = tsk->thread.vdr6;
+}
+
+/*
+ * Validate the settings in a hw_breakpoint structure.
+ */
+static int validate_settings(struct hw_breakpoint *bp, struct task_struct *tsk)
+{
+ int rc = -EINVAL;
+
+ switch (bp->type) {
+ case HW_BREAKPOINT_EXECUTE:
+ if (bp->len != HW_BREAKPOINT_LEN_EXECUTE)
+ return rc;
+ break;
+ case HW_BREAKPOINT_WRITE:
+ case HW_BREAKPOINT_RW:
+ break;
+ default:
+ return rc;
+ }
+
+ switch (bp->len) {
+ case 1: case 2: case 4: /* 8 is also valid on x86_64 */
+ break;
+ default:
+ return rc;
+ }
+
+ /* Check that the low-order bits of the address are appropriate
+ * for the alignment implied by len. */
+ if (bp->address.va & (bp->len - 1))
+ return rc;
+
+ /* Check that the address is in the proper range. Note that tsk
+ * is NULL for kernel bps and non-NULL for user bps.
+ * With x86_64, use TASK_SIZE_OF(tsk) instead of TASK_SIZE. */
+ if ((tsk != NULL) != (bp->address.va < TASK_SIZE))
+ return rc;
+
+ if (bp->triggered)
+ rc = 0;
+ return rc;
+}
+
+/*
+ * Encode the length, type, Exact, and Enable bits for a particular breakpoint
+ * as stored in debug register 7.
+ */
+static inline unsigned long encode_dr7(int drnum, u8 len, u8 type, int local)
+{
+ unsigned long temp;
+
+ /* For x86_64:
+ *
+ * if (len == 8)
+ * len = 3;
+ */
+ temp = ((len - 1) << 2) | (type & 0x7f);
+ temp <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
+ if (local)
+ temp |= (DR_LOCAL_ENABLE << (drnum * DR_ENABLE_SIZE)) |
+ DR_LOCAL_EXACT;
+ else
+ temp |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)) |
+ DR_GLOBAL_EXACT;
+ return temp;
+}
+
+/*
+ * Calculate the DR7 value for a list of kernel or user breakpoints.
+ */
+static unsigned long calculate_dr7(struct list_head *bp_list, int is_user)
+{
+ struct hw_breakpoint *bp;
+ int i;
+ int drnum;
+ unsigned long dr7;
+
+ /* Kernel bps are assigned from DR0 on up, and user bps are assigned
+ * from DR3 on down. Accumulate all 4 bps; the kernel DR7 mask will
+ * select the appropriate bits later. */
+ dr7 = 0;
+ i = 0;
+ list_for_each_entry(bp, bp_list, node) {
+
+ /* Get the debug register number and accumulate the bits */
+ drnum = (is_user ? HB_NUM - 1 - i : i);
+ dr7 |= encode_dr7(drnum, bp->len, bp->type, is_user);
+ if (++i >= HB_NUM)
+ break;
+ }
+ return dr7;
+}
+
+/*
+ * Update the DR7 value for a user thread.
+ */
+static void update_user_dr7(struct thread_hw_breakpoint *thbi)
+{
+ thbi->tdr7 = calculate_dr7(&thbi->thread_bps, 1);
+}
+
+/*
+ * Store the highest-priority thread breakpoint entries in an array.
+ */
+static void store_thread_bp_array(struct thread_hw_breakpoint *thbi)
+{
+ struct hw_breakpoint *bp;
+ int i;
+
+ i = HB_NUM - 1;
+ list_for_each_entry(bp, &thbi->thread_bps, node) {
+ thbi->bps[i] = bp;
+ thbi->tdr[i] = bp->address.va;
+ if (--i < 0)
+ break;
+ }
+ while (i >= 0)
+ thbi->bps[i--] = NULL;
+}
+
+/*
+ * Insert a new breakpoint in a priority-sorted list.
+ * Return the bp's index in the list.
+ *
+ * Thread invariants:
+ * tsk_thread_flag(tsk, TIF_DEBUG) set implies
+ * tsk->thread.hw_breakpoint_info is not NULL.
+ * tsk_thread_flag(tsk, TIF_DEBUG) set iff thbi->thread_bps is non-empty
+ * iff thbi->node is on thread_list.
+ */
+static int insert_bp_in_list(struct hw_breakpoint *bp,
+ struct thread_hw_breakpoint *thbi, struct task_struct *tsk)
+{
+ struct list_head *head;
+ int pos;
+ struct hw_breakpoint *temp_bp;
+
+ /* tsk and thbi are NULL for kernel bps, non-NULL for user bps */
+ if (tsk)
+ head = &thbi->thread_bps;
+ else
+ head = &kernel_bps;
+
+ /* Equal-priority breakpoints get listed first-come-first-served */
+ pos = 0;
+ list_for_each_entry(temp_bp, head, node) {
+ if (bp->priority > temp_bp->priority)
+ break;
+ ++pos;
+ }
+ list_add_tail_rcu(&bp->node, &temp_bp->node);
+ bp->status = HW_BREAKPOINT_REGISTERED;
+
+ if (tsk) {
+ store_thread_bp_array(thbi);
+
+ /* Is this the thread's first registered breakpoint? */
+ if (list_empty(&thbi->node)) {
+ set_tsk_thread_flag(tsk, TIF_DEBUG);
+ list_add(&thbi->node, &thread_list);
+ }
+ if (tsk != current)
+ synchronize_rcu();
+ }
+ return pos;
+}
+
+/*
+ * Remove a breakpoint from its priority-sorted list.
+ *
+ * See the invariants mentioned above.
+ */
+static void remove_bp_from_list(struct hw_breakpoint *bp,
+ struct thread_hw_breakpoint *thbi, struct task_struct *tsk)
+{
+ /* Remove bp from the thread's/kernel's list. If the list is now
+ * empty we must clear the TIF_DEBUG flag. But keep the
+ * thread_hw_breakpoint structure, so that the virtualized debug
+ * register values will remain valid. */
+ list_del_rcu(&bp->node);
+ if (tsk) {
+ store_thread_bp_array(thbi);
+
+ if (list_empty(&thbi->thread_bps)) {
+ list_del_init(&thbi->node);
+ clear_tsk_thread_flag(tsk, TIF_DEBUG);
+ }
+ if (tsk != current)
+ synchronize_rcu();
+ }
+
+ /* Tell the breakpoint it is being uninstalled */
+ if (bp->status == HW_BREAKPOINT_INSTALLED && bp->uninstalled)
+ (bp->uninstalled)(bp);
+ bp->status = 0;
+}
+
+/*
+ * Actual implementation of register_user_hw_breakpoint.
+ */
+int __register_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ int rc;
+ struct thread_hw_breakpoint *thbi;
+ int pos;
+
+ bp->status = 0;
+ rc = validate_settings(bp, tsk);
+ if (rc)
+ return rc;
+
+ thbi = alloc_thread_hw_breakpoint(tsk);
+ if (!thbi)
+ return -ENOMEM;
+
+ /* Insert bp in the thread's list and update the DR7 value */
+ pos = insert_bp_in_list(bp, thbi, tsk);
+ update_user_dr7(thbi);
+
+ /* Force an update notification */
+ thbi->last_num_kbps = -1;
+
+ /* Update and rebalance the priorities. We don't need to go through
+ * the list of all threads; adding a breakpoint can only cause the
+ * priorities for this thread to increase. */
+ accum_thread_tprio(thbi);
+ balance_kernel_vs_user();
+
+ /* Did bp get allocated to a debug register? We can tell from its
+ * position in the list. The number of registers allocated to
+ * kernel breakpoints is num_kbps; all the others are available for
+ * user breakpoints. If bp's position in the priority-ordered list
+ * is low enough, it will get a register. */
+ if (pos < HB_NUM - num_kbps) {
+ rc = 1;
+
+ /* Does it need to be installed right now? */
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+ /* Otherwise it will get installed the next time tsk runs */
+ }
+ return rc;
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @tsk: the task in whose memory space the breakpoint will be set
+ * @bp: the breakpoint structure to register
+ *
+ * This routine registers a breakpoint to be associated with @tsk's
+ * memory space and active only while @tsk is running. It does not
+ * guarantee that the breakpoint will be allocated to a debug register
+ * immediately; there may be other higher-priority breakpoints registered
+ * which require the use of all the debug registers.
+ *
+ * @tsk will normally be a process being debugged by the current process,
+ * but it may also be the current process.
+ *
+ * The fields in @bp are checked for validity. @bp->len, @bp->type,
+ * @bp->address, @bp->triggered, and @bp->priority must be set properly.
+ *
+ * Returns 1 if @bp is allocated to a debug register, 0 if @bp is
+ * registered but not allowed to be installed, otherwise a negative error
+ * code.
+ */
+int register_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ int rc;
+
+ mutex_lock(&hw_breakpoint_mutex);
+ rc = __register_user_hw_breakpoint(tsk, bp);
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+
+/*
+ * Actual implementation of unregister_user_hw_breakpoint.
+ */
+void __unregister_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+
+ if (!bp->status)
+ return; /* Not registered */
+
+ /* Remove bp from the thread's list and update the DR7 value */
+ remove_bp_from_list(bp, thbi, tsk);
+ update_user_dr7(thbi);
+
+ /* Force an update notification */
+ thbi->last_num_kbps = -1;
+
+ /* Recalculate and rebalance the kernel-vs-user priorities,
+ * and actually uninstall bp if necessary. */
+ recalc_tprio();
+ balance_kernel_vs_user();
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+}
+
+/**
+ * unregister_user_hw_breakpoint - unregister a hardware breakpoint for user space
+ * @tsk: the task in whose memory space the breakpoint is registered
+ * @bp: the breakpoint structure to unregister
+ *
+ * Uninstalls and unregisters @bp.
+ */
+void unregister_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp)
+{
+ mutex_lock(&hw_breakpoint_mutex);
+ __unregister_user_hw_breakpoint(tsk, bp);
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+
+/*
+ * Actual implementation of modify_user_hw_breakpoint.
+ */
+int __modify_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp, const void __user *address,
+ u8 len, u8 type)
+{
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+ int i;
+
+ if (!bp->status) { /* Not registered, just store the values */
+ bp->address.user = address;
+ bp->len = len;
+ bp->type = type;
+ return 0;
+ }
+
+ /* Check the new values */
+ {
+ struct hw_breakpoint temp_bp = *bp;
+ int rc;
+
+ temp_bp.address.user = address;
+ temp_bp.len = len;
+ temp_bp.type = type;
+ rc = validate_settings(&temp_bp, tsk);
+ if (rc)
+ return rc;
+ }
+
+ /* Okay, update the breakpoint */
+ bp->address.user = address;
+ bp->len = len;
+ bp->type = type;
+ update_user_dr7(thbi);
+
+ for (i = 0; i < HB_NUM; ++i) {
+ if (thbi->bps[i] == bp)
+ thbi->tdr[i] = bp->address.va;
+ }
+
+ /* The priority hasn't changed so we don't need to rebalance
+ * anything. Just install the new breakpoint, if necessary. */
+ if (tsk == current)
+ switch_to_thread_hw_breakpoint(tsk);
+ return 0;
+}
+
+/**
+ * modify_user_hw_breakpoint - modify a hardware breakpoint for user space
+ * @tsk: the task in whose memory space the breakpoint is registered
+ * @bp: the breakpoint structure to modify
+ * @address: the new value for @bp->address
+ * @len: the new value for @bp->len
+ * @type: the new value for @bp->type
+ *
+ * @bp need not currently be registered. If it isn't, the new values
+ * are simply stored in it and @tsk is ignored. Otherwise the new values
+ * are validated first and then stored. If @tsk is the current process
+ * and @bp is installed in a debug register, the register is updated.
+ *
+ * Returns 0 if the new values are acceptable, otherwise a negative error
+ * number.
+ */
+int modify_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp, const void __user *address,
+ u8 len, u8 type)
+{
+ int rc;
+
+ mutex_lock(&hw_breakpoint_mutex);
+ rc = __modify_user_hw_breakpoint(tsk, bp, address, len, type);
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+
+/*
+ * Update the DR7 value for the kernel.
+ */
+static void update_kernel_dr7(void)
+{
+ kdr7 = calculate_dr7(&kernel_bps, 0);
+}
+
+/**
+ * register_kernel_hw_breakpoint - register a hardware breakpoint for kernel space
+ * @bp: the breakpoint structure to register
+ *
+ * This routine registers a breakpoint to be active at all times. It
+ * does not guarantee that the breakpoint will be allocated to a debug
+ * register immediately; there may be other higher-priority breakpoints
+ * registered which require the use of all the debug registers.
+ *
+ * The fields in @bp are checked for validity. @bp->len, @bp->type,
+ * @bp->address, @bp->triggered, and @bp->priority must be set properly.
+ *
+ * Returns 1 if @bp is allocated to a debug register, 0 if @bp is
+ * registered but not allowed to be installed, otherwise a negative error
+ * code.
+ */
+int register_kernel_hw_breakpoint(struct hw_breakpoint *bp)
+{
+ int rc;
+ int pos;
+
+ bp->status = 0;
+ rc = validate_settings(bp, NULL);
+ if (rc)
+ return rc;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* Insert bp in the kernel's list and update the DR7 value */
+ pos = insert_bp_in_list(bp, NULL, NULL);
+ update_kernel_dr7();
+
+ /* Rebalance the priorities. This will install bp if it
+ * was allocated a debug register. */
+ balance_kernel_vs_user();
+
+ /* Did bp get allocated to a debug register? We can tell from its
+ * position in the list. The number of registers allocated to
+ * kernel breakpoints is num_kbps; all the others are available for
+ * user breakpoints. If bp's position in the priority-ordered list
+ * is low enough, it will get a register. */
+ if (pos < num_kbps)
+ rc = 1;
+
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+EXPORT_SYMBOL_GPL(register_kernel_hw_breakpoint);
+
+/**
+ * unregister_kernel_hw_breakpoint - unregister a hardware breakpoint for kernel space
+ * @bp: the breakpoint structure to unregister
+ *
+ * Uninstalls and unregisters @bp.
+ */
+void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp)
+{
+ if (!bp->status)
+ return; /* Not registered */
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* Remove bp from the kernel's list and update the DR7 value */
+ remove_bp_from_list(bp, NULL, NULL);
+ update_kernel_dr7();
+
+ /* Rebalance the priorities. This will uninstall bp if it
+ * was allocated a debug register. */
+ balance_kernel_vs_user();
+
+ mutex_unlock(&hw_breakpoint_mutex);
+}
+EXPORT_SYMBOL_GPL(unregister_kernel_hw_breakpoint);
+
+/*
+ * Ptrace support: breakpoint trigger routine.
+ */
+static void ptrace_triggered(struct hw_breakpoint *bp, struct pt_regs *regs)
+{
+ struct task_struct *tsk = current;
+ struct thread_hw_breakpoint *thbi = tsk->thread.hw_breakpoint_info;
+ int i;
+
+ /* Store in the virtual DR6 register the fact that breakpoint i
+ * was hit, so the thread's debugger will see it, and send the
+ * debugging signal. */
+ if (thbi) {
+ i = bp - thbi->vdr_bps;
+ tsk->thread.vdr6 |= (DR_TRAP0 << i);
+ send_sigtrap(tsk, regs, 0);
+ }
+}
+
+/*
+ * Handle PTRACE_PEEKUSR calls for the debug register area.
+ */
+unsigned long thread_get_debugreg(struct task_struct *tsk, int n)
+{
+ struct thread_hw_breakpoint *thbi;
+ unsigned long val = 0;
+
+ mutex_lock(&hw_breakpoint_mutex);
+ thbi = tsk->thread.hw_breakpoint_info;
+ if (n < HB_NUM) {
+ if (thbi)
+ val = (unsigned long) thbi->vdr_bps[n].address.va;
+ } else if (n == 6)
+ val = tsk->thread.vdr6;
+ else if (n == 7) {
+ if (thbi)
+ val = thbi->vdr7;
+ }
+ mutex_unlock(&hw_breakpoint_mutex);
+ return val;
+}
+
+/*
+ * Decode the length and type bits for a particular breakpoint as
+ * stored in debug register 7. Return the "enabled" status.
+ */
+static inline int decode_dr7(unsigned long dr7, int bpnum, u8 *len, u8 *type)
+{
+ int temp = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
+ int tlen = 1 + ((temp >> 2) & 0x3);
+
+ /* For x86_64:
+ *
+ * if (tlen == 3)
+ * tlen = 8;
+ */
+ *len = tlen;
+ *type = (temp & 0x3) | 0x80;
+ return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
+}
+
+/*
+ * Handle ptrace writes to debug register 7.
+ */
+static int ptrace_write_dr7(struct task_struct *tsk,
+ struct thread_hw_breakpoint *thbi, unsigned long data)
+{
+ struct hw_breakpoint *bp;
+ int i;
+ int rc = 0;
+ unsigned long old_dr7 = thbi->vdr7;
+
+ data &= ~DR_CONTROL_RESERVED;
+
+ /* Loop through all the hardware breakpoints,
+ * making the appropriate changes to each. */
+restore_settings:
+ thbi->vdr7 = data;
+ bp = &thbi->vdr_bps[0];
+ for (i = 0; i < HB_NUM; (++i, ++bp)) {
+ int enabled;
+ u8 len, type;
+
+ enabled = decode_dr7(data, i, &len, &type);
+
+ /* Unregister the breakpoint if it should now be disabled.
+ * Do this first so that setting invalid values for len
+ * or type won't cause an error. */
+ if (!enabled && bp->status)
+ __unregister_user_hw_breakpoint(tsk, bp);
+
+ /* Insert the breakpoint's settings. If the bp is enabled,
+ * an invalid entry will cause an error. */
+ if (__modify_user_hw_breakpoint(tsk, bp,
+ bp->address.user, len, type) < 0 && rc == 0)
+ break;
+
+ /* Now register the breakpoint if it should be enabled.
+ * New invalid entries will cause an error here. */
+ if (enabled && !bp->status) {
+ bp->triggered = ptrace_triggered;
+ bp->priority = HW_BREAKPOINT_PRIO_PTRACE;
+ if (__register_user_hw_breakpoint(tsk, bp) < 0 &&
+ rc == 0)
+ break;
+ }
+ }
+
+ /* If anything above failed, restore the original settings */
+ if (i < HB_NUM) {
+ rc = -EIO;
+ data = old_dr7;
+ goto restore_settings;
+ }
+ return rc;
+}
+
+/*
+ * Handle PTRACE_POKEUSR calls for the debug register area.
+ */
+int thread_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
+{
+ struct thread_hw_breakpoint *thbi;
+ int rc = -EIO;
+
+ mutex_lock(&hw_breakpoint_mutex);
+
+ /* There are no DR4 or DR5 registers */
+ if (n == 4 || n == 5)
+ ;
+
+ /* Writes to DR6 modify the virtualized value */
+ else if (n == 6) {
+ tsk->thread.vdr6 = val;
+ rc = 0;
+ }
+
+ else if (!tsk->thread.hw_breakpoint_info && val == 0)
+ rc = 0; /* Minor optimization */
+
+ else if ((thbi = alloc_thread_hw_breakpoint(tsk)) == NULL)
+ rc = -ENOMEM;
+
+ /* Writes to DR0 - DR3 change a breakpoint address */
+ else if (n < HB_NUM) {
+ struct hw_breakpoint *bp = &thbi->vdr_bps[n];
+
+ if (__modify_user_hw_breakpoint(tsk, bp, (void *) val,
+ bp->len, bp->type) >= 0)
+ rc = 0;
+ }
+
+ /* All that's left is DR7 */
+ else
+ rc = ptrace_write_dr7(tsk, thbi, val);
+
+ mutex_unlock(&hw_breakpoint_mutex);
+ return rc;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+static int __kprobes hw_breakpoint_handler(struct die_args *data)
+{
+ struct cpu_hw_breakpoint *chbi;
+ int i;
+ struct hw_breakpoint *bp;
+ struct thread_hw_breakpoint *thbi;
+
+ /* The value of DR6 is stored in data->err */
+#define DR6 (data->err)
+
+ if (!(DR6 & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)))
+ return NOTIFY_DONE;
+
+ /* Assert that local interrupts are disabled */
+
+ /* Are we a victim of lazy debug-register switching? */
+ chbi = &per_cpu(cpu_info, get_cpu());
+ if (!chbi->bp_task)
+ thbi = NULL;
+ else if (chbi->bp_task != current) {
+
+ /* No user breakpoints are valid. Perform the belated
+ * debug-register switch. */
+ switch_to_none_hw_breakpoint();
+ thbi = NULL;
+ } else
+ thbi = chbi->bp_task->thread.hw_breakpoint_info;
+
+ /* Disable all breakpoints so that the callbacks can run without
+ * triggering recursive debug exceptions. */
+ set_debugreg(0, 7);
+
+ /* Handle all the breakpoints that were triggered */
+ for (i = 0; i < HB_NUM; ++i) {
+ if (!(DR6 & (DR_TRAP0 << i)))
+ continue;
+
+ /* Find the corresponding hw_breakpoint structure and
+ * invoke its triggered callback. */
+ if (i < chbi->num_kbps)
+ bp = chbi->bps[i];
+ else if (thbi)
+ bp = thbi->bps[i];
+ else /* False alarm due to lazy DR switching */
+ continue;
+ if (bp) /* Should always be non-NULL */
+ (bp->triggered)(bp, data->regs);
+ }
+
+ /* Re-enable the breakpoints */
+ set_debugreg(chbi->dr7, 7);
+ put_cpu_no_resched();
+
+ /* Mask away the bits we have handled */
+ DR6 &= ~(DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3);
+
+ /* Early exit from the notifier chain if everything has been handled */
+ if (data->err == 0)
+ return NOTIFY_STOP;
+ return NOTIFY_DONE;
+#undef DR6
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+static int __kprobes hw_breakpoint_exceptions_notify(
+ struct notifier_block *unused, unsigned long val, void *data)
+{
+ if (val != DIE_DEBUG)
+ return NOTIFY_DONE;
+ return hw_breakpoint_handler(data);
+}
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+ .notifier_call = hw_breakpoint_exceptions_notify
+};
+
+static int __init init_hw_breakpoint(void)
+{
+ return register_die_notifier(&hw_breakpoint_exceptions_nb);
+}
+
+core_initcall(init_hw_breakpoint);
Index: usb-2.6/arch/i386/kernel/ptrace.c
===================================================================
--- usb-2.6.orig/arch/i386/kernel/ptrace.c
+++ usb-2.6/arch/i386/kernel/ptrace.c
@@ -383,11 +383,11 @@ long arch_ptrace(struct task_struct *chi
tmp = 0; /* Default return condition */
if(addr < FRAME_SIZE*sizeof(long))
tmp = getreg(child, addr);
- if(addr >= (long) &dummy->u_debugreg[0] &&
- addr <= (long) &dummy->u_debugreg[7]){
+ else if (addr >= (long) &dummy->u_debugreg[0] &&
+ addr <= (long) &dummy->u_debugreg[7]) {
addr -= (long) &dummy->u_debugreg[0];
addr = addr >> 2;
- tmp = child->thread.debugreg[addr];
+ tmp = thread_get_debugreg(child, addr);
}
ret = put_user(tmp, datap);
break;
@@ -417,59 +417,11 @@ long arch_ptrace(struct task_struct *chi
have to be selective about what portions we allow someone
to modify. */
- ret = -EIO;
- if(addr >= (long) &dummy->u_debugreg[0] &&
- addr <= (long) &dummy->u_debugreg[7]){
-
- if(addr == (long) &dummy->u_debugreg[4]) break;
- if(addr == (long) &dummy->u_debugreg[5]) break;
- if(addr < (long) &dummy->u_debugreg[4] &&
- ((unsigned long) data) >= TASK_SIZE-3) break;
-
- /* Sanity-check data. Take one half-byte at once with
- * check = (val >> (16 + 4*i)) & 0xf. It contains the
- * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
- * 2 and 3 are LENi. Given a list of invalid values,
- * we do mask |= 1 << invalid_value, so that
- * (mask >> check) & 1 is a correct test for invalid
- * values.
- *
- * R/Wi contains the type of the breakpoint /
- * watchpoint, LENi contains the length of the watched
- * data in the watchpoint case.
- *
- * The invalid values are:
- * - LENi == 0x10 (undefined), so mask |= 0x0f00.
- * - R/Wi == 0x10 (break on I/O reads or writes), so
- * mask |= 0x4444.
- * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
- * 0x1110.
- *
- * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
- *
- * See the Intel Manual "System Programming Guide",
- * 15.2.4
- *
- * Note that LENi == 0x10 is defined on x86_64 in long
- * mode (i.e. even for 32-bit userspace software, but
- * 64-bit kernel), so the x86_64 mask value is 0x5454.
- * See the AMD manual no. 24593 (AMD64 System
- * Programming)*/
-
- if(addr == (long) &dummy->u_debugreg[7]) {
- data &= ~DR_CONTROL_RESERVED;
- for(i=0; i<4; i++)
- if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
- goto out_tsk;
- if (data)
- set_tsk_thread_flag(child, TIF_DEBUG);
- else
- clear_tsk_thread_flag(child, TIF_DEBUG);
- }
- addr -= (long) &dummy->u_debugreg;
- addr = addr >> 2;
- child->thread.debugreg[addr] = data;
- ret = 0;
+ if (addr >= (long) &dummy->u_debugreg[0] &&
+ addr <= (long) &dummy->u_debugreg[7]) {
+ addr -= (long) &dummy->u_debugreg;
+ addr = addr >> 2;
+ ret = thread_set_debugreg(child, addr, data);
}
break;
@@ -625,7 +577,6 @@ long arch_ptrace(struct task_struct *chi
ret = ptrace_request(child, request, addr, data);
break;
}
- out_tsk:
return ret;
}
Index: usb-2.6/arch/i386/kernel/Makefile
===================================================================
--- usb-2.6.orig/arch/i386/kernel/Makefile
+++ usb-2.6/arch/i386/kernel/Makefile
@@ -7,7 +7,8 @@ extra-y := head.o init_task.o vmlinux.ld
obj-y := process.o signal.o entry.o traps.o irq.o \
ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_i386.o \
pci-dma.o i386_ksyms.o i387.o bootflag.o e820.o\
- quirks.o i8237.o topology.o alternative.o i8253.o tsc.o
+ quirks.o i8237.o topology.o alternative.o i8253.o tsc.o \
+ hw_breakpoint.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-y += cpu/
Index: usb-2.6/arch/i386/power/cpu.c
===================================================================
--- usb-2.6.orig/arch/i386/power/cpu.c
+++ usb-2.6/arch/i386/power/cpu.c
@@ -11,6 +11,7 @@
#include <linux/suspend.h>
#include <asm/mtrr.h>
#include <asm/mce.h>
+#include <asm/debugreg.h>
static struct saved_context saved_context;
@@ -45,6 +46,11 @@ void __save_processor_state(struct saved
ctxt->cr2 = read_cr2();
ctxt->cr3 = read_cr3();
ctxt->cr4 = read_cr4();
+
+ /*
+ * disable the debug registers
+ */
+ set_debugreg(0, 7);
}
void save_processor_state(void)
@@ -69,20 +75,7 @@ static void fix_processor_context(void)
load_TR_desc(); /* This does ltr */
load_LDT(¤t->active_mm->context); /* This does lldt */
-
- /*
- * Now maybe reload the debug registers
- */
- if (current->thread.debugreg[7]){
- set_debugreg(current->thread.debugreg[0], 0);
- set_debugreg(current->thread.debugreg[1], 1);
- set_debugreg(current->thread.debugreg[2], 2);
- set_debugreg(current->thread.debugreg[3], 3);
- /* no 4 and 5 */
- set_debugreg(current->thread.debugreg[6], 6);
- set_debugreg(current->thread.debugreg[7], 7);
- }
-
+ load_debug_registers();
}
void __restore_processor_state(struct saved_context *ctxt)
Index: usb-2.6/arch/i386/kernel/kprobes.c
===================================================================
--- usb-2.6.orig/arch/i386/kernel/kprobes.c
+++ usb-2.6/arch/i386/kernel/kprobes.c
@@ -670,8 +670,11 @@ int __kprobes kprobe_exceptions_notify(s
ret = NOTIFY_STOP;
break;
case DIE_DEBUG:
- if (post_kprobe_handler(args->regs))
- ret = NOTIFY_STOP;
+ if ((args->err & DR_STEP) && post_kprobe_handler(args->regs)) {
+ args->err &= ~DR_STEP;
+ if (args->err == 0)
+ ret = NOTIFY_STOP;
+ }
break;
case DIE_GPF:
case DIE_PAGE_FAULT:
Index: usb-2.6/include/asm-generic/hw_breakpoint.h
===================================================================
--- /dev/null
+++ usb-2.6/include/asm-generic/hw_breakpoint.h
@@ -0,0 +1,200 @@
+#ifndef _ASM_GENERIC_HW_BREAKPOINT_H
+#define _ASM_GENERIC_HW_BREAKPOINT_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+
+/**
+ *
+ * struct hw_breakpoint - unified kernel/user-space hardware breakpoint
+ * @node: internal linked-list management
+ * @triggered: callback invoked when the breakpoint is hit
+ * @installed: callback invoked when the breakpoint is installed
+ * @uninstalled: callback invoked when the breakpoint is uninstalled
+ * @address: location (virtual address) of the breakpoint
+ * @len: extent of the breakpoint address (1, 2, 4, or 8 bytes)
+ * @type: breakpoint type (read-only, write-only, read/write, or execute)
+ * @priority: requested priority level
+ * @status: current registration/installation status
+ *
+ * %hw_breakpoint structures are the kernel's way of representing
+ * hardware breakpoints. These can be either execute breakpoints
+ * (triggered on instruction execution) or data breakpoints (also known
+ * as "watchpoints", triggered on data access), and the breakpoint's
+ * target address can be located in either kernel space or user space.
+ *
+ * The @address field contains the breakpoint's address, as either a
+ * regular kernel pointer or an %__user pointer. @len is the
+ * breakpoint's extent in bytes, which is subject to certain limitations.
+ * include/asm/hw_breakpoint.h contains macros defining the available
+ * lengths for a specific architecture. Note that @len must be a power
+ * of 2, and @address must have the alignment specified by @len. The
+ * breakpoint will catch accesses to any byte in the range from @address
+ * to @address + (@len - 1).
+ *
+ * @type indicates the type of access that will trigger the breakpoint.
+ * Possible values may include:
+ *
+ * %HW_BREAKPOINT_EXECUTE (triggered on instruction execution),
+ * %HW_BREAKPOINT_IO (triggered on I/O space access),
+ * %HW_BREAKPOINT_RW (triggered on read or write access),
+ * %HW_BREAKPOINT_WRITE (triggered on write access), and
+ * %HW_BREAKPOINT_READ (triggered on read access).
+ *
+ * Appropriate macros are defined in include/asm/hw_breakpoint.h.
+ * Execute breakpoints must have @len equal to the special value
+ * %HW_BREAKPOINT_LEN_EXECUTE.
+ *
+ * In register_user_hw_breakpoint() and modify_user_hw_breakpoint(),
+ * @address must refer to a location in user space (use @address.user).
+ * The breakpoint will be active only while the requested task is running.
+ * Conversely, in register_kernel_hw_breakpoint() @address must refer to a
+ * location in kernel space (use @address.kernel), and the breakpoint will
+ * be active on all CPUs regardless of the current task.
+ *
+ * When a breakpoint gets hit, the @triggered callback is invoked
+ * in_interrupt with a pointer to the %hw_breakpoint structure and the
+ * processor registers. Execute-breakpoint traps occur before the
+ * breakpointed instruction runs; all other types of trap occur after the
+ * memory access has taken place. All breakpoints are disabled while
+ * @triggered runs, to avoid recursive traps and allow unhindered access
+ * to breakpointed memory.
+ *
+ * Hardware breakpoints are implemented using the CPU's debug registers,
+ * which are a limited hardware resource. Requests to register a
+ * breakpoint will always succeed (provided the parameters are valid),
+ * but the breakpoint may not be installed in a debug register right
+ * away. Physical debug registers are allocated based on the priority
+ * level stored in @priority (higher values indicate higher priority).
+ * User-space breakpoints within a single thread compete with one
+ * another, and all user-space breakpoints compete with all kernel-space
+ * breakpoints; however user-space breakpoints in different threads do
+ * not compete. %HW_BREAKPOINT_PRIO_PTRACE is the level used for ptrace
+ * requests; an unobtrusive kernel-space breakpoint will use
+ * %HW_BREAKPOINT_PRIO_NORMAL to avoid disturbing user programs. A
+ * kernel-space breakpoint that always wants to be installed and doesn't
+ * care about disrupting user debugging sessions can specify
+ * %HW_BREAKPOINT_PRIO_HIGH.
+ *
+ * A particular breakpoint may be allocated (installed in) a debug
+ * register or deallocated (uninstalled) from its debug register at any
+ * time, as other breakpoints are registered and unregistered. The
+ * @installed and @uninstalled callbacks are invoked in_atomic when these
+ * events occur. It is legal for @installed or @uninstalled to be %NULL,
+ * however @triggered must not be. Note that it is not possible to
+ * register or unregister a breakpoint from within a callback routine,
+ * since doing so requires a process context. Note also that for user
+ * breakpoints, @installed and @uninstalled may be called during the
+ * middle of a context switch, at a time when it is not safe to call
+ * printk().
+ *
+ * For kernel-space breakpoints, @installed is invoked after the
+ * breakpoint is actually installed and @uninstalled is invoked before
+ * the breakpoint is actually uninstalled. As a result @triggered can
+ * be called when you may not expect it, but this way you will know that
+ * during the time interval from @installed to @uninstalled, all events
+ * are faithfully reported. (It is not possible to do any better than
+ * this in general, because on SMP systems there is no way to set a debug
+ * register simultaneously on all CPUs.) The same isn't always true with
+ * user-space breakpoints, but the differences should not be visible to a
+ * user process.
+ *
+ * The @address, @len, and @type fields in a user-space breakpoint can be
+ * changed by calling modify_user_hw_breakpoint(). Kernel-space
+ * breakpoints cannot be modified, nor can the @priority value in
+ * user-space breakpoints, after the breakpoint has been registered. And
+ * of course all the fields in a %hw_breakpoint structure should be
+ * treated as read-only while the breakpoint is registered.
+ *
+ * @node and @status are intended for internal use. However @status
+ * may be read to determine whether or not the breakpoint is currently
+ * installed.
+ *
+ * This sample code sets a breakpoint on pid_max and registers a callback
+ * function for writes to that variable.
+ *
+ * ----------------------------------------------------------------------
+ *
+ * #include <asm/hw_breakpoint.h>
+ *
+ * static void triggered(struct hw_breakpoint *bp, struct pt_regs *regs)
+ * {
+ * printk(KERN_DEBUG "Breakpoint triggered\n");
+ * dump_stack();
+ * .......<more debugging output>........
+ * }
+ *
+ * static struct hw_breakpoint my_bp;
+ *
+ * static int init_module(void)
+ * {
+ * ..........<do anything>............
+ * my_bp.address.kernel = &pid_max;
+ * my_bp.type = HW_BREAKPOINT_WRITE;
+ * my_bp.len = HW_BREAKPOINT_LEN_4;
+ * my_bp.triggered = triggered;
+ * my_bp.priority = HW_BREAKPOINT_PRIO_NORMAL;
+ * rc = register_kernel_hw_breakpoint(&my_bp);
+ * ..........<do anything>............
+ * }
+ *
+ * static void cleanup_module(void)
+ * {
+ * ..........<do anything>............
+ * unregister_kernel_hw_breakpoint(&my_bp);
+ * ..........<do anything>............
+ * }
+ *
+ * ----------------------------------------------------------------------
+ *
+ */
+struct hw_breakpoint {
+ struct list_head node;
+ void (*triggered)(struct hw_breakpoint *, struct pt_regs *);
+ void (*installed)(struct hw_breakpoint *);
+ void (*uninstalled)(struct hw_breakpoint *);
+ union {
+ const void *kernel;
+ const void __user *user;
+ unsigned long va;
+ } address;
+ u8 len;
+ u8 type;
+ u8 priority;
+ u8 status;
+};
+
+/* len and type values are defined in include/asm/hw_breakpoint.h */
+
+/* Standard HW breakpoint priority levels (higher value = higher priority) */
+#define HW_BREAKPOINT_PRIO_NORMAL 25
+#define HW_BREAKPOINT_PRIO_PTRACE 50
+#define HW_BREAKPOINT_PRIO_HIGH 75
+
+/* HW breakpoint status values */
+#define HW_BREAKPOINT_REGISTERED 1
+#define HW_BREAKPOINT_INSTALLED 2
+
+/*
+ * The following three routines are meant to be called only from within
+ * the ptrace or utrace subsystems. The tsk argument will usually be a
+ * process being debugged by the current task, although it is also legal
+ * for tsk to be the current task. In any case it must be guaranteed
+ * that tsk will not start running in user mode while its breakpoints are
+ * being modified.
+ */
+int register_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp);
+void unregister_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp);
+int modify_user_hw_breakpoint(struct task_struct *tsk,
+ struct hw_breakpoint *bp, const void __user *address,
+ u8 len, u8 type);
+
+/*
+ * Kernel breakpoints are not associated with any particular thread.
+ */
+int register_kernel_hw_breakpoint(struct hw_breakpoint *bp);
+void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp);
+
+#endif /* _ASM_GENERIC_HW_BREAKPOINT_H */
-
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