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arm64: support single-step and breakpoint handler hooks
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> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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@ -62,6 +62,27 @@ struct task_struct;
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#define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */
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#define DBG_HOOK_HANDLED 0
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#define DBG_HOOK_ERROR 1
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struct step_hook {
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struct list_head node;
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int (*fn)(struct pt_regs *regs, unsigned int esr);
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};
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void register_step_hook(struct step_hook *hook);
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void unregister_step_hook(struct step_hook *hook);
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struct break_hook {
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struct list_head node;
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u32 esr_val;
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u32 esr_mask;
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int (*fn)(struct pt_regs *regs, unsigned int esr);
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};
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void register_break_hook(struct break_hook *hook);
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void unregister_break_hook(struct break_hook *hook);
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u8 debug_monitors_arch(void);
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void enable_debug_monitors(enum debug_el el);
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@ -187,6 +187,48 @@ static void clear_regs_spsr_ss(struct pt_regs *regs)
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regs->pstate = spsr;
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}
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/* EL1 Single Step Handler hooks */
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static LIST_HEAD(step_hook);
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DEFINE_RWLOCK(step_hook_lock);
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void register_step_hook(struct step_hook *hook)
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{
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write_lock(&step_hook_lock);
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list_add(&hook->node, &step_hook);
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write_unlock(&step_hook_lock);
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}
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void unregister_step_hook(struct step_hook *hook)
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{
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write_lock(&step_hook_lock);
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list_del(&hook->node);
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write_unlock(&step_hook_lock);
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}
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/*
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* Call registered single step handers
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* There is no Syndrome info to check for determining the handler.
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* So we call all the registered handlers, until the right handler is
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* found which returns zero.
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*/
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static int call_step_hook(struct pt_regs *regs, unsigned int esr)
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{
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struct step_hook *hook;
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int retval = DBG_HOOK_ERROR;
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read_lock(&step_hook_lock);
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list_for_each_entry(hook, &step_hook, node) {
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retval = hook->fn(regs, esr);
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if (retval == DBG_HOOK_HANDLED)
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break;
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}
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read_unlock(&step_hook_lock);
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return retval;
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}
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static int single_step_handler(unsigned long addr, unsigned int esr,
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struct pt_regs *regs)
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{
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@ -214,7 +256,9 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
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*/
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user_rewind_single_step(current);
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} else {
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/* TODO: route to KGDB */
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if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
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return 0;
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pr_warning("Unexpected kernel single-step exception at EL1\n");
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/*
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* Re-enable stepping since we know that we will be
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@ -226,11 +270,53 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
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return 0;
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}
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/*
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* Breakpoint handler is re-entrant as another breakpoint can
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* hit within breakpoint handler, especically in kprobes.
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* Use reader/writer locks instead of plain spinlock.
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*/
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static LIST_HEAD(break_hook);
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DEFINE_RWLOCK(break_hook_lock);
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void register_break_hook(struct break_hook *hook)
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{
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write_lock(&break_hook_lock);
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list_add(&hook->node, &break_hook);
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write_unlock(&break_hook_lock);
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}
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void unregister_break_hook(struct break_hook *hook)
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{
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write_lock(&break_hook_lock);
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list_del(&hook->node);
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write_unlock(&break_hook_lock);
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}
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static int call_break_hook(struct pt_regs *regs, unsigned int esr)
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{
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struct break_hook *hook;
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int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL;
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read_lock(&break_hook_lock);
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list_for_each_entry(hook, &break_hook, node)
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if ((esr & hook->esr_mask) == hook->esr_val)
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fn = hook->fn;
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read_unlock(&break_hook_lock);
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return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
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}
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static int brk_handler(unsigned long addr, unsigned int esr,
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struct pt_regs *regs)
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{
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siginfo_t info;
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if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
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return 0;
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pr_warn("unexpected brk exception at %lx, esr=0x%x\n",
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(long)instruction_pointer(regs), esr);
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if (!user_mode(regs))
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return -EFAULT;
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@ -288,6 +288,8 @@ el1_dbg:
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/*
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* Debug exception handling
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*/
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cmp x24, #ESR_EL1_EC_BRK64 // if BRK64
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cinc x24, x24, eq // set bit '0'
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tbz x24, #0, el1_inv // EL1 only
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mrs x0, far_el1
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mov x2, sp // struct pt_regs
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