From: Sandeepa Prabhu sandeepa.prabhu@linaro.org
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@linaro.org Signed-off-by: Deepak Saxena dsaxena@linaro.org --- arch/arm64/include/asm/debug-monitors.h | 20 +++++++ arch/arm64/kernel/debug-monitors.c | 95 ++++++++++++++++++++++++++++++- arch/arm64/kernel/entry.S | 6 +- 3 files changed, 117 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index a2232d0..19e429e 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 esr, 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_val; + u32 esr_mask; + int (*fn)(struct pt_regs *regs, unsigned int esr, 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..d8a159e 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -188,6 +188,52 @@ 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) +{ + raw_spin_lock(&step_lock); + list_add(&hook->node, &step_hook); + raw_spin_unlock(&step_lock); +} + +void unregister_step_hook(struct step_hook *hook) +{ + raw_spin_lock(&step_lock); + list_del(&hook->node); + raw_spin_unlock(&step_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, unsigned long addr) +{ + struct step_hook *hook; + int (*fn)(struct pt_regs *regs, + unsigned int esr, unsigned long addr) = NULL; + + raw_spin_lock(&step_lock); + list_for_each_entry(hook, &step_hook, node) { + fn = hook->fn; + raw_spin_unlock(&step_lock); + + if (!fn(regs, esr, addr)) + return 0; + + raw_spin_lock(&step_lock); + } + raw_spin_unlock(&step_lock); + + return 1; +} + static int single_step_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { @@ -215,8 +261,11 @@ 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, esr, addr) == 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 +276,51 @@ 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) +{ + raw_spin_lock(&break_lock); + list_add(&hook->node, &break_hook); + raw_spin_unlock(&break_lock); +} + +void unregister_break_hook(struct break_hook *hook) +{ + raw_spin_lock(&break_lock); + list_del(&hook->node); + raw_spin_unlock(&break_lock); +} + +static int call_break_hook(struct pt_regs *regs, + unsigned int esr, unsigned long addr) +{ + struct break_hook *hook; + int (*fn)(struct pt_regs *regs, + unsigned int esr, unsigned long addr) = NULL; + + raw_spin_lock(&break_lock); + list_for_each_entry(hook, &break_hook, node) + if ((esr & hook->esr_mask) == hook->esr_val) + fn = hook->fn; + raw_spin_unlock(&break_lock); + + 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 +380,7 @@ 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 3881fd1..9589242 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -288,8 +288,12 @@ 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 + mrs x25, far_el1 // Watchpoint location + cmp x24, #ESR_EL1_EC_WATCHPT_EL1 + csel x0, x25, x22, eq // addr: x25->far_el1, x22->elr_el1 mov x2, sp // struct pt_regs bl do_debug_exception