[RFC PATCH 3/4] ARM: hw-breakpoint: add new ptrace requests for hw-breakpoint interaction
Will Deacon
will.deacon at arm.com
Tue Feb 2 11:22:27 EST 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 adds support for a debugger to insert, modify and remove hardware
breakpoints using PTRACE_SET_HWBKPT requests. The breakpoints are stored in
the debug_info struct of the running thread. A further request,
PTRACE_GET_HWBKPT can be used to query the number of hardware resources
available.
The ptrace interaction is controlled using a 32-bit word, as described in
arch/arm/include/asm/hw_breakpoint.h.
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/ptrace.c | 158 ++++++++++++++++++++++++++++++++++++++
3 files changed, 164 insertions(+), 0 deletions(-)
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 6a89567..ddb0953 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[HBP_NUM];
+#endif
};
struct thread_struct {
diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h
index eec6e89..ea35e4e 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_GET_HWBKPT 29
+#define PTRACE_SET_HWBKPT 30
/*
* PSR bits
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index a2ea385..1e02bc5 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>
@@ -707,6 +709,152 @@ static int ptrace_setvfpregs(struct task_struct *tsk, void __user *data)
}
#endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+/*
+ * Handle hitting a HW-breakpoint.
+ */
+static void ptrace_hwbreak_triggered(struct perf_event *bp, int unused,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
+{
+ struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
+ siginfo_t info;
+
+ info.si_signo = SIGTRAP;
+ info.si_errno = bp->attr.bp_type;
+ info.si_code = TRAP_HWBKPT;
+ info.si_addr = (void __user *)(bkpt->trigger);
+
+ force_sig_info(SIGTRAP, &info, current);
+}
+
+static int ptrace_insert_hwbkpt(struct task_struct *tsk, unsigned long addr,
+ u8 n, u8 len, u8 type)
+{
+ struct perf_event *bp;
+ struct thread_struct *t = &tsk->thread;
+ struct perf_event_attr attr;
+ int ret = 0;
+
+ /* Watchpoints live in the upper indices. */
+ if ((type & HW_BREAKPOINT_X) == 0)
+ n += ARM_MAX_BRP;
+
+ if (n >= HBP_NUM) {
+ ret = -ENOSPC;
+ goto out;
+ }
+
+ if (!t->debug.hbp[n]) {
+ /* New breakpoint. */
+ hw_breakpoint_init(&attr);
+ attr.bp_addr = addr;
+ attr.bp_len = len;
+ attr.bp_type = type;
+
+ bp = register_user_hw_breakpoint(&attr,
+ ptrace_hwbreak_triggered, tsk);
+ if (IS_ERR(bp))
+ ret = PTR_ERR(bp);
+ else
+ t->debug.hbp[n] = bp;
+ } else {
+ /* Existing breakpoint. */
+ bp = t->debug.hbp[n];
+ attr = bp->attr;
+ attr.bp_addr = addr;
+ attr.bp_len = len;
+ attr.disabled = 0;
+ ret = modify_user_hw_breakpoint(bp, &attr);
+ }
+
+out:
+ return ret;
+}
+
+static int ptrace_remove_hwbkpt(struct task_struct *tsk, u8 n, u8 type)
+{
+ struct perf_event *bp;
+ struct thread_struct *t = &tsk->thread;
+ struct perf_event_attr attr;
+ int ret = -EINVAL;
+
+ if ((type & HW_BREAKPOINT_X) == 0)
+ n += ARM_MAX_BRP;
+
+ if (n < HBP_NUM) {
+ bp = t->debug.hbp[n];
+ if (bp == NULL)
+ goto out;
+ attr = bp->attr;
+ attr.disabled = 1;
+ ret = modify_user_hw_breakpoint(bp, &attr);
+ } else {
+ ret = -ENOSPC;
+ }
+
+out:
+ return ret;
+}
+
+static int ptrace_get_hwbkpt(struct task_struct *tsk, long addr,
+ unsigned long __user *data)
+{
+ unsigned long num;
+ int ret = 0;
+
+ switch (addr) {
+ case PTRACE_HWBREAK_GET_NUM_BRPS:
+ num = ptrace_get_num_brps();
+ break;
+ case PTRACE_HWBREAK_GET_NUM_WRPS:
+ num = ptrace_get_num_wrps();
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ if (!ret && put_user(num, data))
+ ret = -EFAULT;
+
+ return ret;
+}
+
+static int ptrace_set_hwbkpt(struct task_struct *tsk, long addr,
+ unsigned long data)
+{
+ int ret;
+ u8 num, len, type;
+
+ /* Check version field. */
+ if (PTRACE_HWBREAK_VER(data) != 0) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* Extract data fields. */
+ num = PTRACE_HWBREAK_NUM(data);
+ len = PTRACE_HWBREAK_LEN(data);
+ type = PTRACE_HWBREAK_TYPE(data);
+
+ /* Insert or remove the breakpoint. */
+ switch (PTRACE_HWBREAK_OP(data)) {
+ case PTRACE_HWBREAK_OP_REMOVE:
+ ret = ptrace_remove_hwbkpt(tsk, num, type);
+ break;
+ case PTRACE_HWBREAK_OP_INSERT:
+ ret = ptrace_insert_hwbkpt(tsk, addr, num, len, type);
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+out:
+ return ret;
+}
+
+#endif
+
long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
int ret;
@@ -839,6 +987,16 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
break;
#endif
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+ case PTRACE_GET_HWBKPT:
+ ret = ptrace_get_hwbkpt(child, addr,
+ (unsigned long __user *)data);
+ break;
+ case PTRACE_SET_HWBKPT:
+ ret = ptrace_set_hwbkpt(child, addr, data);
+ break;
+#endif
+
default:
ret = ptrace_request(child, request, addr, data);
break;
--
1.6.5.7
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