On 3 October 2013 22:23, Will Deacon will.deacon@arm.com wrote:
On Tue, Oct 01, 2013 at 04:57:56PM +0100, Sandeepa Prabhu wrote:
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 route software breakpoint (BRK64) exception to do_debug_exception()
Signed-off-by: Sandeepa Prabhu sandeepa.prabhu@linaro.org Signed-off-by: Deepak Saxena dsaxena@linaro.org
arch/arm64/include/asm/debug-monitors.h | 23 +++++++++ arch/arm64/kernel/debug-monitors.c | 85 +++++++++++++++++++++++++++++++-- arch/arm64/kernel/entry.S | 2 + 3 files changed, 107 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index a2232d0..8e354b3 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/rculist.h>
#ifdef __KERNEL__
#define DBG_ESR_EVT(x) (((x) >> 27) & 0x7) @@ -62,6 +64,27 @@ struct task_struct;
#define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */
+#define DEBUG_HOOK_HANDLED 0 +#define DEBUG_HOOK_ERROR 1
Cosmetic: we use DBG vs DEBUG in the rest of this header.
Ok, I'll change it to DBG_*
+struct step_hook {
struct list_head node;int (*fn)(struct pt_regs *regs, unsigned int esr);+};
+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_val;u32 esr_mask;int (*fn)(struct pt_regs *regs, unsigned int esr);+};
+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..fbbf824 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -188,6 +188,43 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) regs->pstate = spsr; }
+/* EL1 Single Step Handler hooks */ +static LIST_HEAD(step_hook);
+void register_step_hook(struct step_hook *hook) +{
list_add_rcu(&hook->node, &step_hook);+}
This isn't safe against concurrent registrations. Why don't you use an rwlock instead? Then you take the writer lock here...
+/*
- 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) +{
struct step_hook *hook;int retval = DEBUG_HOOK_ERROR;rcu_read_lock();... and the reader lock here.
Hmm, rwlock sounds good, there wont be lock contention when concurrent handlers on different CPU. I will change it to rwlocks, can be used for call_break_hook as well instead of normal spin-lock to reduce contention.
list_for_each_entry_rcu(hook, &step_hook, node) {retval = hook->fn(regs, esr);if (retval == DEBUG_HOOK_HANDLED)break;}rcu_read_unlock();return retval;+}
static int single_step_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { @@ -215,8 +252,11 @@ 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 */Useless comment.
I will re-frame, how about simple "Call registered single step hook functions" ?
if (call_step_hook(regs, esr) == DEBUG_HOOK_HANDLED)return 0;pr_warn("unexpected single step exception at %lx!\n", addr);Why have you reworded this warning?
oops, mistake it was debug change to print addr, revert it in next version.
/* * Re-enable stepping since we know that we will be * returning to regs.@@ -227,11 +267,50 @@ static int single_step_handler(unsigned long addr, unsigned int esr, return 0; }
+static LIST_HEAD(break_hook); +static DEFINE_RAW_SPINLOCK(break_hook_lock);
+void register_break_hook(struct break_hook *hook) +{
raw_spin_lock(&break_hook_lock);list_add(&hook->node, &break_hook);raw_spin_unlock(&break_hook_lock);+}
+void unregister_break_hook(struct break_hook *hook) +{
raw_spin_lock(&break_hook_lock);list_del(&hook->node);raw_spin_unlock(&break_hook_lock);+}
+static int call_break_hook(struct pt_regs *regs, unsigned int esr) +{
struct break_hook *hook;int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;raw_spin_lock(&break_hook_lock);list_for_each_entry(hook, &break_hook, node)if ((esr & hook->esr_mask) == hook->esr_val)fn = hook->fn;raw_spin_unlock(&break_hook_lock);return fn ? fn(regs, esr) : DEBUG_HOOK_ERROR;+}
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) == DEBUG_HOOK_HANDLED)return 0;pr_warn("unexpected brk exception at %llx, esr=0x%x\n",instruction_pointer(regs), esr);%lx for the pc.
Hmm, shall correct it in v4.
Will