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Diffstat (limited to 'arch/x86/kernel/hw_breakpoint.c')
-rw-r--r--arch/x86/kernel/hw_breakpoint.c391
1 files changed, 255 insertions, 136 deletions
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 9316a9de4de3..e622620790bd 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -15,6 +15,7 @@
*
* Copyright (C) 2007 Alan Stern
* Copyright (C) 2009 IBM Corporation
+ * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
*/
/*
@@ -22,6 +23,8 @@
* using the CPU's debug registers.
*/
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
#include <linux/irqflags.h>
#include <linux/notifier.h>
#include <linux/kallsyms.h>
@@ -38,26 +41,24 @@
#include <asm/processor.h>
#include <asm/debugreg.h>
-/* Unmasked kernel DR7 value */
-static unsigned long kdr7;
+/* Per cpu debug control register value */
+DEFINE_PER_CPU(unsigned long, dr7);
+
+/* Per cpu debug address registers values */
+static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
/*
- * Masks for the bits corresponding to registers DR0 - DR3 in DR7 register.
- * Used to clear and verify the status of bits corresponding to DR0 - DR3
+ * Stores the breakpoints currently in use on each breakpoint address
+ * register for each cpus
*/
-static const unsigned long dr7_masks[HBP_NUM] = {
- 0x000f0003, /* LEN0, R/W0, G0, L0 */
- 0x00f0000c, /* LEN1, R/W1, G1, L1 */
- 0x0f000030, /* LEN2, R/W2, G2, L2 */
- 0xf00000c0 /* LEN3, R/W3, G3, L3 */
-};
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
/*
* Encode the length, type, Exact, and Enable bits for a particular breakpoint
* as stored in debug register 7.
*/
-static unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
+unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
{
unsigned long bp_info;
@@ -68,64 +69,89 @@ static unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
return bp_info;
}
-void arch_update_kernel_hw_breakpoint(void *unused)
+/*
+ * Decode the length and type bits for a particular breakpoint as
+ * stored in debug register 7. Return the "enabled" status.
+ */
+int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
{
- struct hw_breakpoint *bp;
- int i, cpu = get_cpu();
- unsigned long temp_kdr7 = 0;
-
- /* Don't allow debug exceptions while we update the registers */
- set_debugreg(0UL, 7);
+ int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
- for (i = hbp_kernel_pos; i < HBP_NUM; i++) {
- per_cpu(this_hbp_kernel[i], cpu) = bp = hbp_kernel[i];
- if (bp) {
- temp_kdr7 |= encode_dr7(i, bp->info.len, bp->info.type);
- set_debugreg(bp->info.address, i);
- }
- }
+ *len = (bp_info & 0xc) | 0x40;
+ *type = (bp_info & 0x3) | 0x80;
- /* No need to set DR6. Update the debug registers with kernel-space
- * breakpoint values from kdr7 and user-space requests from the
- * current process
- */
- kdr7 = temp_kdr7;
- set_debugreg(kdr7 | current->thread.debugreg7, 7);
- put_cpu();
+ return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
}
/*
- * Install the thread breakpoints in their debug registers.
+ * Install a perf counter breakpoint.
+ *
+ * We seek a free debug address register and use it for this
+ * breakpoint. Eventually we enable it in the debug control register.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
*/
-void arch_install_thread_hw_breakpoint(struct task_struct *tsk)
+int arch_install_hw_breakpoint(struct perf_event *bp)
{
- struct thread_struct *thread = &(tsk->thread);
-
- switch (hbp_kernel_pos) {
- case 4:
- set_debugreg(thread->debugreg[3], 3);
- case 3:
- set_debugreg(thread->debugreg[2], 2);
- case 2:
- set_debugreg(thread->debugreg[1], 1);
- case 1:
- set_debugreg(thread->debugreg[0], 0);
- default:
- break;
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long *dr7;
+ int i;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
+
+ if (!*slot) {
+ *slot = bp;
+ break;
+ }
}
- /* No need to set DR6 */
- set_debugreg((kdr7 | thread->debugreg7), 7);
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return -EBUSY;
+
+ set_debugreg(info->address, i);
+ __get_cpu_var(cpu_debugreg[i]) = info->address;
+
+ dr7 = &__get_cpu_var(dr7);
+ *dr7 |= encode_dr7(i, info->len, info->type);
+
+ set_debugreg(*dr7, 7);
+
+ return 0;
}
/*
- * Install the debug register values for just the kernel, no thread.
+ * 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_thread_hw_breakpoint(void)
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
{
- /* Clear the user-space portion of debugreg7 by setting only kdr7 */
- set_debugreg(kdr7, 7);
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+ unsigned long *dr7;
+ int i;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
+
+ if (*slot == bp) {
+ *slot = NULL;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+ return;
+ dr7 = &__get_cpu_var(dr7);
+ *dr7 &= ~encode_dr7(i, info->len, info->type);
+
+ set_debugreg(*dr7, 7);
}
static int get_hbp_len(u8 hbp_len)
@@ -133,17 +159,17 @@ static int get_hbp_len(u8 hbp_len)
unsigned int len_in_bytes = 0;
switch (hbp_len) {
- case HW_BREAKPOINT_LEN_1:
+ case X86_BREAKPOINT_LEN_1:
len_in_bytes = 1;
break;
- case HW_BREAKPOINT_LEN_2:
+ case X86_BREAKPOINT_LEN_2:
len_in_bytes = 2;
break;
- case HW_BREAKPOINT_LEN_4:
+ case X86_BREAKPOINT_LEN_4:
len_in_bytes = 4;
break;
#ifdef CONFIG_X86_64
- case HW_BREAKPOINT_LEN_8:
+ case X86_BREAKPOINT_LEN_8:
len_in_bytes = 8;
break;
#endif
@@ -178,67 +204,146 @@ static int arch_check_va_in_kernelspace(unsigned long va, u8 hbp_len)
/*
* Store a breakpoint's encoded address, length, and type.
*/
-static int arch_store_info(struct hw_breakpoint *bp, struct task_struct *tsk)
+static int arch_store_info(struct perf_event *bp)
{
- /*
- * User-space requests will always have the address field populated
- * Symbol names from user-space are rejected
- */
- if (tsk && bp->info.name)
- return -EINVAL;
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
/*
* For kernel-addresses, either the address or symbol name can be
* specified.
*/
- if (bp->info.name)
- bp->info.address = (unsigned long)
- kallsyms_lookup_name(bp->info.name);
- if (bp->info.address)
+ if (info->name)
+ info->address = (unsigned long)
+ kallsyms_lookup_name(info->name);
+ if (info->address)
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 arch_bp_generic_fields(int x86_len, int x86_type,
+ int *gen_len, int *gen_type)
{
- unsigned int align;
- int ret = -EINVAL;
+ /* Len */
+ switch (x86_len) {
+ case X86_BREAKPOINT_LEN_1:
+ *gen_len = HW_BREAKPOINT_LEN_1;
+ break;
+ case X86_BREAKPOINT_LEN_2:
+ *gen_len = HW_BREAKPOINT_LEN_2;
+ break;
+ case X86_BREAKPOINT_LEN_4:
+ *gen_len = HW_BREAKPOINT_LEN_4;
+ break;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
+ *gen_len = HW_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ return -EINVAL;
+ }
- switch (bp->info.type) {
- /*
- * Ptrace-refactoring code
- * For now, we'll allow instruction breakpoint only for user-space
- * addresses
- */
- case HW_BREAKPOINT_EXECUTE:
- if ((!arch_check_va_in_userspace(bp->info.address,
- bp->info.len)) &&
- bp->info.len != HW_BREAKPOINT_LEN_EXECUTE)
- return ret;
+ /* Type */
+ switch (x86_type) {
+ case X86_BREAKPOINT_EXECUTE:
+ *gen_type = HW_BREAKPOINT_X;
break;
- case HW_BREAKPOINT_WRITE:
+ case X86_BREAKPOINT_WRITE:
+ *gen_type = HW_BREAKPOINT_W;
break;
- case HW_BREAKPOINT_RW:
+ case X86_BREAKPOINT_RW:
+ *gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
break;
default:
- return ret;
+ return -EINVAL;
}
- switch (bp->info.len) {
+ return 0;
+}
+
+
+static int arch_build_bp_info(struct perf_event *bp)
+{
+ struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+ info->address = bp->attr.bp_addr;
+
+ /* Len */
+ switch (bp->attr.bp_len) {
case HW_BREAKPOINT_LEN_1:
- align = 0;
+ info->len = X86_BREAKPOINT_LEN_1;
break;
case HW_BREAKPOINT_LEN_2:
- align = 1;
+ info->len = X86_BREAKPOINT_LEN_2;
break;
case HW_BREAKPOINT_LEN_4:
- align = 3;
+ info->len = X86_BREAKPOINT_LEN_4;
break;
#ifdef CONFIG_X86_64
case HW_BREAKPOINT_LEN_8:
+ info->len = X86_BREAKPOINT_LEN_8;
+ break;
+#endif
+ default:
+ return -EINVAL;
+ }
+
+ /* Type */
+ switch (bp->attr.bp_type) {
+ case HW_BREAKPOINT_W:
+ info->type = X86_BREAKPOINT_WRITE;
+ break;
+ case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+ info->type = X86_BREAKPOINT_RW;
+ break;
+ case HW_BREAKPOINT_X:
+ info->type = X86_BREAKPOINT_EXECUTE;
+ break;
+ 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);
+ unsigned int align;
+ int ret;
+
+
+ ret = arch_build_bp_info(bp);
+ if (ret)
+ return ret;
+
+ ret = -EINVAL;
+
+ if (info->type == X86_BREAKPOINT_EXECUTE)
+ /*
+ * Ptrace-refactoring code
+ * For now, we'll allow instruction breakpoint only for user-space
+ * addresses
+ */
+ if ((!arch_check_va_in_userspace(info->address, info->len)) &&
+ info->len != X86_BREAKPOINT_EXECUTE)
+ return ret;
+
+ switch (info->len) {
+ case X86_BREAKPOINT_LEN_1:
+ align = 0;
+ break;
+ case X86_BREAKPOINT_LEN_2:
+ align = 1;
+ break;
+ case X86_BREAKPOINT_LEN_4:
+ align = 3;
+ break;
+#ifdef CONFIG_X86_64
+ case X86_BREAKPOINT_LEN_8:
align = 7;
break;
#endif
@@ -246,8 +351,8 @@ int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp,
return ret;
}
- if (bp->triggered)
- ret = arch_store_info(bp, tsk);
+ if (bp->callback)
+ ret = arch_store_info(bp);
if (ret < 0)
return ret;
@@ -255,44 +360,47 @@ int arch_validate_hwbkpt_settings(struct hw_breakpoint *bp,
* Check that the low-order bits of the address are appropriate
* for the alignment implied by len.
*/
- if (bp->info.address & align)
+ if (info->address & align)
return -EINVAL;
/* Check that the virtual address is in the proper range */
if (tsk) {
- if (!arch_check_va_in_userspace(bp->info.address, bp->info.len))
+ if (!arch_check_va_in_userspace(info->address, info->len))
return -EFAULT;
} else {
- if (!arch_check_va_in_kernelspace(bp->info.address,
- bp->info.len))
+ if (!arch_check_va_in_kernelspace(info->address, info->len))
return -EFAULT;
}
+
return 0;
}
-void arch_update_user_hw_breakpoint(int pos, struct task_struct *tsk)
+/*
+ * Release the user breakpoints used by ptrace
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
{
- struct thread_struct *thread = &(tsk->thread);
- struct hw_breakpoint *bp = thread->hbp[pos];
-
- thread->debugreg7 &= ~dr7_masks[pos];
- if (bp) {
- thread->debugreg[pos] = bp->info.address;
- thread->debugreg7 |= encode_dr7(pos, bp->info.len,
- bp->info.type);
- } else
- thread->debugreg[pos] = 0;
+ int i;
+ struct thread_struct *t = &tsk->thread;
+
+ for (i = 0; i < HBP_NUM; i++) {
+ unregister_hw_breakpoint(t->ptrace_bps[i]);
+ t->ptrace_bps[i] = NULL;
+ }
}
-void arch_flush_thread_hw_breakpoint(struct task_struct *tsk)
+#ifdef CONFIG_KVM
+void hw_breakpoint_restore(void)
{
- int i;
- struct thread_struct *thread = &(tsk->thread);
-
- thread->debugreg7 = 0;
- for (i = 0; i < HBP_NUM; i++)
- thread->debugreg[i] = 0;
+ set_debugreg(__get_cpu_var(cpu_debugreg[0]), 0);
+ set_debugreg(__get_cpu_var(cpu_debugreg[1]), 1);
+ set_debugreg(__get_cpu_var(cpu_debugreg[2]), 2);
+ set_debugreg(__get_cpu_var(cpu_debugreg[3]), 3);
+ set_debugreg(current->thread.debugreg6, 6);
+ set_debugreg(__get_cpu_var(dr7), 7);
}
+EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
+#endif
/*
* Handle debug exception notifications.
@@ -313,7 +421,7 @@ void arch_flush_thread_hw_breakpoint(struct task_struct *tsk)
static int __kprobes hw_breakpoint_handler(struct die_args *args)
{
int i, cpu, rc = NOTIFY_STOP;
- struct hw_breakpoint *bp;
+ struct perf_event *bp;
unsigned long dr7, dr6;
unsigned long *dr6_p;
@@ -325,10 +433,6 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
if ((dr6 & DR_TRAP_BITS) == 0)
return NOTIFY_DONE;
- /* Lazy debug register switching */
- if (!test_tsk_thread_flag(current, TIF_DEBUG))
- arch_uninstall_thread_hw_breakpoint();
-
get_debugreg(dr7, 7);
/* Disable breakpoints during exception handling */
set_debugreg(0UL, 7);
@@ -344,17 +448,18 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
for (i = 0; i < HBP_NUM; ++i) {
if (likely(!(dr6 & (DR_TRAP0 << i))))
continue;
+
/*
- * Find the corresponding hw_breakpoint structure and
- * invoke its triggered callback.
+ * 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.
*/
- if (i >= hbp_kernel_pos)
- bp = per_cpu(this_hbp_kernel[i], cpu);
- else {
- bp = current->thread.hbp[i];
- if (bp)
- rc = NOTIFY_DONE;
- }
+ rcu_read_lock();
+
+ bp = per_cpu(bp_per_reg[i], cpu);
+ if (bp)
+ rc = NOTIFY_DONE;
/*
* Reset the 'i'th TRAP bit in dr6 to denote completion of
* exception handling
@@ -362,19 +467,23 @@ static int __kprobes hw_breakpoint_handler(struct die_args *args)
(*dr6_p) &= ~(DR_TRAP0 << i);
/*
* 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.
+ * or due to concurrent perf counter removing.
*/
- if (!bp)
- continue;
+ if (!bp) {
+ rcu_read_unlock();
+ break;
+ }
+
+ (bp->callback)(bp, args->regs);
- (bp->triggered)(bp, args->regs);
+ rcu_read_unlock();
}
if (dr6 & (~DR_TRAP_BITS))
rc = NOTIFY_DONE;
set_debugreg(dr7, 7);
put_cpu();
+
return rc;
}
@@ -389,3 +498,13 @@ int __kprobes hw_breakpoint_exceptions_notify(
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 */
+}
generated by cgit (git 2.34.1) at 2024-06-11 08:59:27 +0000