[PATCH] AArch64: Add single-step and breakpoint handler hooks
Sandeepa Prabhu
sandeepa.prabhu at linaro.org
Tue Aug 6 02:12:06 EDT 2013
AArch64 Single Steping and Breakpoint debug exceptions will be
used by multiple debug framworks like kprobes & kgdb.
This patch implements the hooks for those frameworks to register
their own handlers for handling breakpoint and single step events.
Reworked the debug exception handler in entry.S: do_dbg to
pass the correct break/step address to the handlers, i.e. FAR_EL1 if
exception is watchpoint, ELR_EL1 for all other debug exceptions.
Signed-off-by: Sandeepa Prabhu <sandeepa.prabhu at linaro.org>
Signed-off-by: Deepak Saxena <dsaxena at linaro.org>
---
arch/arm64/include/asm/debug-monitors.h | 20 +++++++
arch/arm64/kernel/debug-monitors.c | 102 +++++++++++++++++++++++++++++++-
arch/arm64/kernel/entry.S | 6 +-
3 files changed, 124 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index a2232d0..aff3a76 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -16,6 +16,8 @@
#ifndef __ASM_DEBUG_MONITORS_H
#define __ASM_DEBUG_MONITORS_H
+#include <linux/list.h>
+
#ifdef __KERNEL__
#define DBG_ESR_EVT(x) (((x) >> 27) & 0x7)
@@ -62,6 +64,24 @@ struct task_struct;
#define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */
+struct step_hook {
+ struct list_head node;
+ int (*fn)(struct pt_regs *regs, unsigned int insn, unsigned long addr);
+};
+
+void register_step_hook(struct step_hook *hook);
+void unregister_step_hook(struct step_hook *hook);
+
+struct break_hook {
+ struct list_head node;
+ u32 esr_magic;
+ u32 esr_mask;
+ int (*fn)(struct pt_regs *regs, unsigned int insn, unsigned long addr);
+};
+
+void register_break_hook(struct break_hook *hook);
+void unregister_break_hook(struct break_hook *hook);
+
u8 debug_monitors_arch(void);
void enable_debug_monitors(enum debug_el el);
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index cbfacf7..2846327 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -188,6 +188,54 @@ static void clear_regs_spsr_ss(struct pt_regs *regs)
regs->pstate = spsr;
}
+/* EL1 Single Step Handler hooks */
+static LIST_HEAD(step_hook);
+static DEFINE_RAW_SPINLOCK(step_lock);
+
+void register_step_hook(struct step_hook *hook)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&step_lock, flags);
+ list_add(&hook->node, &step_hook);
+ raw_spin_unlock_irqrestore(&step_lock, flags);
+}
+
+void unregister_step_hook(struct step_hook *hook)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&step_lock, flags);
+ list_del(&hook->node);
+ raw_spin_unlock_irqrestore(&step_lock, flags);
+}
+
+/*
+ * Call registered single step handers
+ * There is no Syndrome info to check for determining the handler.
+ * So we call all the registered handlers, until the right handler is
+ * found which returns zero.
+ */
+static int call_step_hook(struct pt_regs *regs,
+ unsigned int esr, unsigned long addr)
+{
+ struct step_hook *hook;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&step_lock, flags);
+ list_for_each_entry(hook, &step_hook, node) {
+ raw_spin_unlock_irqrestore(&step_lock, flags);
+
+ if (hook->fn(regs, esr, addr) == 0)
+ return 0;
+
+ raw_spin_lock_irqsave(&step_lock, flags);
+ }
+ raw_spin_unlock_irqrestore(&step_lock, flags);
+
+ return 1;
+}
+
static int single_step_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
@@ -215,8 +263,11 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
*/
user_rewind_single_step(current);
} else {
- /* TODO: route to KGDB */
- pr_warning("Unexpected kernel single-step exception at EL1\n");
+ /* Call single step handlers for kgdb/kprobes */
+ if (call_step_hook(regs, addr, esr) == 0)
+ return 0;
+
+ pr_warn("unexpected single step exception at %lx!\n", addr);
/*
* Re-enable stepping since we know that we will be
* returning to regs.
@@ -227,11 +278,56 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
return 0;
}
+
+static LIST_HEAD(break_hook);
+static DEFINE_RAW_SPINLOCK(break_lock);
+
+void register_break_hook(struct break_hook *hook)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&break_lock, flags);
+ list_add(&hook->node, &break_hook);
+ raw_spin_unlock_irqrestore(&break_lock, flags);
+}
+
+void unregister_break_hook(struct break_hook *hook)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&break_lock, flags);
+ list_del(&hook->node);
+ raw_spin_unlock_irqrestore(&break_lock, flags);
+}
+
+static int call_break_hook(struct pt_regs *regs,
+ unsigned int esr, unsigned long addr)
+{
+ struct break_hook *hook;
+ unsigned long flags;
+ int (*fn)(struct pt_regs *regs,
+ unsigned int esr, unsigned long addr) = NULL;
+
+ raw_spin_lock_irqsave(&break_lock, flags);
+ list_for_each_entry(hook, &break_hook, node)
+ if ((esr & hook->esr_mask) == hook->esr_magic)
+ fn = hook->fn;
+ raw_spin_unlock_irqrestore(&break_lock, flags);
+
+ return fn ? fn(regs, esr, addr) : 1;
+}
+
static int brk_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
siginfo_t info;
+ /* Call single step handlers for kgdb/kprobes */
+ if (call_break_hook(regs, esr, addr) == 0)
+ return 0;
+
+ pr_warn("unexpected brk exception at %lx, esr=0x%x\n", addr, esr);
+
if (!user_mode(regs))
return -EFAULT;
@@ -291,7 +387,7 @@ static int __init debug_traps_init(void)
hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP,
TRAP_HWBKPT, "single-step handler");
hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
- TRAP_BRKPT, "ptrace BRK handler");
+ TRAP_BRKPT, "AArch64 BRK handler");
return 0;
}
arch_initcall(debug_traps_init);
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6ad781b..e7350bd 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -288,8 +288,12 @@ el1_dbg:
/*
* Debug exception handling
*/
+ mrs x25, far_el1 //far for watchpt
+ cmp x24, #ESR_EL1_EC_WATCHPT_EL1
+ csel x0, x25, x22, eq //addr: x25->far_el1, x22->elr_el1
+ b.ge do_dbg
tbz x24, #0, el1_inv // EL1 only
- mrs x0, far_el1
+do_dbg:
mov x2, sp // struct pt_regs
bl do_debug_exception
--
1.8.1.2
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