[PATCH 3/4] ARM: hw-breakpoint: add new ptrace requests for hw-breakpoint interaction
Will Deacon
will.deacon at arm.com
Tue Aug 10 09:10:57 EDT 2010
For debuggers to take advantage of the hw-breakpoint framework in the kernel,
it is necessary to expose the API calls via a ptrace interface.
This patch exposes the hardware breakpoints framework as a collection of
virtual registers, accesible using PTRACE_SETHBPREGS and PTRACE_GETHBPREGS
requests. The breakpoints are stored in the debug_info struct of the running
thread.
Cc: Russell King - ARM Linux <linux at arm.linux.org.uk>
Cc: Frederic Weisbecker <fweisbec at gmail.com>
Cc: S. Karthikeyan <informkarthik at gmail.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
arch/arm/include/asm/processor.h | 4 +
arch/arm/include/asm/ptrace.h | 2 +
arch/arm/kernel/hw_breakpoint.c | 13 +++
arch/arm/kernel/ptrace.c | 223 ++++++++++++++++++++++++++++++++++++++
4 files changed, 242 insertions(+), 0 deletions(-)
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 7bed3da..67357ba 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -19,6 +19,7 @@
#ifdef __KERNEL__
+#include <asm/hw_breakpoint.h>
#include <asm/ptrace.h>
#include <asm/types.h>
@@ -41,6 +42,9 @@ struct debug_entry {
struct debug_info {
int nsaved;
struct debug_entry bp[2];
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ struct perf_event *hbp[ARM_MAX_HBP_SLOTS];
+#endif
};
struct thread_struct {
diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index 9dcb11e..21560e4 100644
--- a/arch/arm/include/asm/ptrace.h
+++ b/arch/arm/include/asm/ptrace.h
@@ -29,6 +29,8 @@
#define PTRACE_SETCRUNCHREGS 26
#define PTRACE_GETVFPREGS 27
#define PTRACE_SETVFPREGS 28
+#define PTRACE_GETHBPREGS 29
+#define PTRACE_SETHBPREGS 30
/*
* PSR bits
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 9fe8843..d36ff92 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -674,6 +674,19 @@ out:
return ret;
}
+static int hw_breakpoint_thread_notify(struct notifier_block *self,
+ unsigned long cmd, void *t)
+{
+ if (cmd == THREAD_NOTIFY_FLUSH)
+ flush_ptrace_hw_breakpoint(current);
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block hw_breakpoint_thread_notifier_block = {
+ .notifier_call = hw_breakpoint_thread_notify,
+};
+
/*
* One-time initialisation.
*/
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 3f562a7..c442941 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -19,6 +19,8 @@
#include <linux/init.h>
#include <linux/signal.h>
#include <linux/uaccess.h>
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
#include <asm/pgtable.h>
#include <asm/system.h>
@@ -751,6 +753,216 @@ static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
}
#endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+/*
+ * Convert a virtual register number into an index for a thread_info
+ * breakpoint array. Breakpoints are identified using positive numbers
+ * whilst watchpoints are negative. The registers are laid out as pairs
+ * of (address, control), each pair mapping to a unique hw_breakpoint struct.
+ * Register 0 is reserved for describing resource information.
+ */
+static int ptrace_hbp_num_to_idx(long num)
+{
+ if (num < 0)
+ num = (ARM_MAX_BRP << 1) - num;
+ return (num - 1) >> 1;
+}
+
+/*
+ * Returns the virtual register number for the address of the
+ * breakpoint at index idx.
+ */
+static long ptrace_hbp_idx_to_num(int idx)
+{
+ long mid = ARM_MAX_BRP << 1;
+ long num = (idx << 1) + 1;
+ return num > mid ? mid - num : num;
+}
+
+/*
+ * Handle hitting a HW-breakpoint.
+ */
+static void ptrace_hbptriggered(struct perf_event *bp, int unused,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
+{
+ struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
+ long num;
+ int i;
+ siginfo_t info;
+
+ for (i = 0; i < ARM_MAX_HBP_SLOTS; ++i)
+ if (current->thread.debug.hbp[i] == bp)
+ break;
+
+ num = (i == ARM_MAX_HBP_SLOTS) ? 0 : ptrace_hbp_idx_to_num(i);
+
+ info.si_signo = SIGTRAP;
+ info.si_errno = (int)num;
+ info.si_code = TRAP_HWBKPT;
+ info.si_addr = (void __user *)(bkpt->trigger);
+
+ force_sig_info(SIGTRAP, &info, current);
+}
+
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+ int i;
+ struct thread_struct *t = &tsk->thread;
+
+ for (i = 0; i < ARM_MAX_HBP_SLOTS; i++) {
+ unregister_hw_breakpoint(t->debug.hbp[i]);
+ t->debug.hbp[i] = NULL;
+ }
+}
+
+static u32 ptrace_get_hbp_resource_info(void)
+{
+ u8 num_brps, num_wrps, debug_arch, wp_len;
+ u32 reg = 0;
+
+ num_brps = hw_breakpoint_slots(TYPE_INST);
+ num_wrps = hw_breakpoint_slots(TYPE_DATA);
+ debug_arch = arch_get_debug_arch();
+ wp_len = arch_get_max_wp_len();
+
+ reg |= debug_arch;
+ reg <<= 8;
+ reg |= wp_len;
+ reg <<= 8;
+ reg |= num_wrps;
+ reg <<= 8;
+ reg |= num_brps;
+
+ return reg;
+}
+
+static struct perf_event *ptrace_hbp_create(struct task_struct *tsk, int type)
+{
+ struct perf_event_attr attr;
+
+ ptrace_breakpoint_init(&attr);
+
+ /* Initialise fields to sane defaults. */
+ attr.bp_addr = 0;
+ attr.bp_len = HW_BREAKPOINT_LEN_4;
+ attr.bp_type = type;
+ attr.disabled = 1;
+
+ return register_user_hw_breakpoint(&attr, ptrace_hbptriggered, tsk);
+}
+
+static int ptrace_gethbpregs(struct task_struct *tsk, long num,
+ unsigned long __user *data)
+{
+ u32 reg;
+ int idx, ret = 0;
+ struct perf_event *bp;
+ struct arch_hw_breakpoint_ctrl arch_ctrl;
+
+ if (num == 0) {
+ reg = ptrace_get_hbp_resource_info();
+ } else {
+ idx = ptrace_hbp_num_to_idx(num);
+ if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ bp = tsk->thread.debug.hbp[idx];
+ if (!bp) {
+ reg = 0;
+ goto put;
+ }
+
+ arch_ctrl = counter_arch_bp(bp)->ctrl;
+
+ /*
+ * Fix up the len because we may have adjusted it
+ * to compensate for an unaligned address.
+ */
+ while (!(arch_ctrl.len & 0x1))
+ arch_ctrl.len >>= 1;
+
+ if (idx & 0x1)
+ reg = encode_ctrl_reg(arch_ctrl);
+ else
+ reg = bp->attr.bp_addr;
+ }
+
+put:
+ if (put_user(reg, data))
+ ret = -EFAULT;
+
+out:
+ return ret;
+}
+
+static int ptrace_sethbpregs(struct task_struct *tsk, long num,
+ unsigned long __user *data)
+{
+ int idx, gen_len, gen_type, implied_type, ret = 0;
+ u32 user_val;
+ struct perf_event *bp;
+ struct arch_hw_breakpoint_ctrl ctrl;
+ struct perf_event_attr attr;
+
+ if (num == 0)
+ goto out;
+ else if (num < 0)
+ implied_type = HW_BREAKPOINT_RW;
+ else
+ implied_type = HW_BREAKPOINT_X;
+
+ idx = ptrace_hbp_num_to_idx(num);
+ if (idx < 0 || idx >= ARM_MAX_HBP_SLOTS) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (get_user(user_val, data)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ bp = tsk->thread.debug.hbp[idx];
+ if (!bp) {
+ bp = ptrace_hbp_create(tsk, implied_type);
+ if (IS_ERR(bp)) {
+ ret = PTR_ERR(bp);
+ goto out;
+ }
+ tsk->thread.debug.hbp[idx] = bp;
+ }
+
+ attr = bp->attr;
+
+ if (num & 0x1) {
+ /* Address */
+ attr.bp_addr = user_val;
+ } else {
+ /* Control */
+ decode_ctrl_reg(user_val, &ctrl);
+ ret = arch_bp_generic_fields(ctrl, &gen_len, &gen_type);
+ if (ret)
+ goto out;
+
+ if ((gen_type & implied_type) != gen_type) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ attr.bp_len = gen_len;
+ attr.bp_type = gen_type;
+ attr.disabled = !ctrl.enabled;
+ }
+
+ ret = modify_user_hw_breakpoint(bp, &attr);
+out:
+ return ret;
+}
+#endif
+
long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
int ret;
@@ -820,6 +1032,17 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
break;
#endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ case PTRACE_GETHBPREGS:
+ ret = ptrace_gethbpregs(child, addr,
+ (unsigned long __user *)data);
+ break;
+ case PTRACE_SETHBPREGS:
+ ret = ptrace_sethbpregs(child, addr,
+ (unsigned long __user *)data);
+ break;
+#endif
+
default:
ret = ptrace_request(child, request, addr, data);
break;
--
1.6.3.3
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