Commit ee6214ce authored by Sandeepa Prabhu's avatar Sandeepa Prabhu Committed by Catalin Marinas
Browse files

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: default avatarSandeepa Prabhu <sandeepa.prabhu@linaro.org>
Signed-off-by: default avatarDeepak Saxena <dsaxena@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 26920dd2
......@@ -62,6 +62,27 @@ struct task_struct;
#define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */
#define DBG_HOOK_HANDLED 0
#define DBG_HOOK_ERROR 1
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);
......
......@@ -187,6 +187,48 @@ static void clear_regs_spsr_ss(struct pt_regs *regs)
regs->pstate = spsr;
}
/* EL1 Single Step Handler hooks */
static LIST_HEAD(step_hook);
DEFINE_RWLOCK(step_hook_lock);
void register_step_hook(struct step_hook *hook)
{
write_lock(&step_hook_lock);
list_add(&hook->node, &step_hook);
write_unlock(&step_hook_lock);
}
void unregister_step_hook(struct step_hook *hook)
{
write_lock(&step_hook_lock);
list_del(&hook->node);
write_unlock(&step_hook_lock);
}
/*
* 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 = DBG_HOOK_ERROR;
read_lock(&step_hook_lock);
list_for_each_entry(hook, &step_hook, node) {
retval = hook->fn(regs, esr);
if (retval == DBG_HOOK_HANDLED)
break;
}
read_unlock(&step_hook_lock);
return retval;
}
static int single_step_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
......@@ -214,7 +256,9 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
*/
user_rewind_single_step(current);
} else {
/* TODO: route to KGDB */
if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED)
return 0;
pr_warning("Unexpected kernel single-step exception at EL1\n");
/*
* Re-enable stepping since we know that we will be
......@@ -226,11 +270,53 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
return 0;
}
/*
* Breakpoint handler is re-entrant as another breakpoint can
* hit within breakpoint handler, especically in kprobes.
* Use reader/writer locks instead of plain spinlock.
*/
static LIST_HEAD(break_hook);
DEFINE_RWLOCK(break_hook_lock);
void register_break_hook(struct break_hook *hook)
{
write_lock(&break_hook_lock);
list_add(&hook->node, &break_hook);
write_unlock(&break_hook_lock);
}
void unregister_break_hook(struct break_hook *hook)
{
write_lock(&break_hook_lock);
list_del(&hook->node);
write_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;
read_lock(&break_hook_lock);
list_for_each_entry(hook, &break_hook, node)
if ((esr & hook->esr_mask) == hook->esr_val)
fn = hook->fn;
read_unlock(&break_hook_lock);
return fn ? fn(regs, esr) : DBG_HOOK_ERROR;
}
static int brk_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
siginfo_t info;
if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED)
return 0;
pr_warn("unexpected brk exception at %lx, esr=0x%x\n",
(long)instruction_pointer(regs), esr);
if (!user_mode(regs))
return -EFAULT;
......
......@@ -288,6 +288,8 @@ el1_dbg:
/*
* Debug exception handling
*/
cmp x24, #ESR_EL1_EC_BRK64 // if BRK64
cinc x24, x24, eq // set bit '0'
tbz x24, #0, el1_inv // EL1 only
mrs x0, far_el1
mov x2, sp // struct pt_regs
......
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