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Diffstat (limited to 'arch/arm64/kernel/debug-monitors.c')
-rw-r--r-- | arch/arm64/kernel/debug-monitors.c | 429 |
1 files changed, 429 insertions, 0 deletions
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c new file mode 100644 index 000000000..b056369fd --- /dev/null +++ b/arch/arm64/kernel/debug-monitors.c @@ -0,0 +1,429 @@ +/* + * ARMv8 single-step debug support and mdscr context switching. + * + * Copyright (C) 2012 ARM Limited + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * Author: Will Deacon <will.deacon@arm.com> + */ + +#include <linux/cpu.h> +#include <linux/debugfs.h> +#include <linux/hardirq.h> +#include <linux/init.h> +#include <linux/ptrace.h> +#include <linux/stat.h> +#include <linux/uaccess.h> + +#include <asm/debug-monitors.h> +#include <asm/cputype.h> +#include <asm/system_misc.h> + +/* Determine debug architecture. */ +u8 debug_monitors_arch(void) +{ + return read_cpuid(ID_AA64DFR0_EL1) & 0xf; +} + +/* + * MDSCR access routines. + */ +static void mdscr_write(u32 mdscr) +{ + unsigned long flags; + local_dbg_save(flags); + asm volatile("msr mdscr_el1, %0" :: "r" (mdscr)); + local_dbg_restore(flags); +} + +static u32 mdscr_read(void) +{ + u32 mdscr; + asm volatile("mrs %0, mdscr_el1" : "=r" (mdscr)); + return mdscr; +} + +/* + * Allow root to disable self-hosted debug from userspace. + * This is useful if you want to connect an external JTAG debugger. + */ +static u32 debug_enabled = 1; + +static int create_debug_debugfs_entry(void) +{ + debugfs_create_bool("debug_enabled", 0644, NULL, &debug_enabled); + return 0; +} +fs_initcall(create_debug_debugfs_entry); + +static int __init early_debug_disable(char *buf) +{ + debug_enabled = 0; + return 0; +} + +early_param("nodebugmon", early_debug_disable); + +/* + * Keep track of debug users on each core. + * The ref counts are per-cpu so we use a local_t type. + */ +static DEFINE_PER_CPU(int, mde_ref_count); +static DEFINE_PER_CPU(int, kde_ref_count); + +void enable_debug_monitors(enum debug_el el) +{ + u32 mdscr, enable = 0; + + WARN_ON(preemptible()); + + if (this_cpu_inc_return(mde_ref_count) == 1) + enable = DBG_MDSCR_MDE; + + if (el == DBG_ACTIVE_EL1 && + this_cpu_inc_return(kde_ref_count) == 1) + enable |= DBG_MDSCR_KDE; + + if (enable && debug_enabled) { + mdscr = mdscr_read(); + mdscr |= enable; + mdscr_write(mdscr); + } +} + +void disable_debug_monitors(enum debug_el el) +{ + u32 mdscr, disable = 0; + + WARN_ON(preemptible()); + + if (this_cpu_dec_return(mde_ref_count) == 0) + disable = ~DBG_MDSCR_MDE; + + if (el == DBG_ACTIVE_EL1 && + this_cpu_dec_return(kde_ref_count) == 0) + disable &= ~DBG_MDSCR_KDE; + + if (disable) { + mdscr = mdscr_read(); + mdscr &= disable; + mdscr_write(mdscr); + } +} + +/* + * OS lock clearing. + */ +static void clear_os_lock(void *unused) +{ + asm volatile("msr oslar_el1, %0" : : "r" (0)); +} + +static int os_lock_notify(struct notifier_block *self, + unsigned long action, void *data) +{ + int cpu = (unsigned long)data; + if (action == CPU_ONLINE) + smp_call_function_single(cpu, clear_os_lock, NULL, 1); + return NOTIFY_OK; +} + +static struct notifier_block os_lock_nb = { + .notifier_call = os_lock_notify, +}; + +static int debug_monitors_init(void) +{ + cpu_notifier_register_begin(); + + /* Clear the OS lock. */ + on_each_cpu(clear_os_lock, NULL, 1); + isb(); + local_dbg_enable(); + + /* Register hotplug handler. */ + __register_cpu_notifier(&os_lock_nb); + + cpu_notifier_register_done(); + return 0; +} +postcore_initcall(debug_monitors_init); + +/* + * Single step API and exception handling. + */ +static void set_regs_spsr_ss(struct pt_regs *regs) +{ + unsigned long spsr; + + spsr = regs->pstate; + spsr &= ~DBG_SPSR_SS; + spsr |= DBG_SPSR_SS; + regs->pstate = spsr; +} + +static void clear_regs_spsr_ss(struct pt_regs *regs) +{ + unsigned long spsr; + + spsr = regs->pstate; + spsr &= ~DBG_SPSR_SS; + regs->pstate = spsr; +} + +/* EL1 Single Step Handler hooks */ +static LIST_HEAD(step_hook); +static 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) +{ + siginfo_t info; + + /* + * If we are stepping a pending breakpoint, call the hw_breakpoint + * handler first. + */ + if (!reinstall_suspended_bps(regs)) + return 0; + + if (user_mode(regs)) { + info.si_signo = SIGTRAP; + info.si_errno = 0; + info.si_code = TRAP_HWBKPT; + info.si_addr = (void __user *)instruction_pointer(regs); + force_sig_info(SIGTRAP, &info, current); + + /* + * ptrace will disable single step unless explicitly + * asked to re-enable it. For other clients, it makes + * sense to leave it enabled (i.e. rewind the controls + * to the active-not-pending state). + */ + user_rewind_single_step(current); + } else { + 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 + * returning to regs. + */ + set_regs_spsr_ss(regs); + } + + 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); +static 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 (user_mode(regs)) { + info = (siginfo_t) { + .si_signo = SIGTRAP, + .si_errno = 0, + .si_code = TRAP_BRKPT, + .si_addr = (void __user *)instruction_pointer(regs), + }; + + force_sig_info(SIGTRAP, &info, current); + } else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) { + pr_warning("Unexpected kernel BRK exception at EL1\n"); + return -EFAULT; + } + + return 0; +} + +int aarch32_break_handler(struct pt_regs *regs) +{ + siginfo_t info; + u32 arm_instr; + u16 thumb_instr; + bool bp = false; + void __user *pc = (void __user *)instruction_pointer(regs); + + if (!compat_user_mode(regs)) + return -EFAULT; + + if (compat_thumb_mode(regs)) { + /* get 16-bit Thumb instruction */ + get_user(thumb_instr, (u16 __user *)pc); + thumb_instr = le16_to_cpu(thumb_instr); + if (thumb_instr == AARCH32_BREAK_THUMB2_LO) { + /* get second half of 32-bit Thumb-2 instruction */ + get_user(thumb_instr, (u16 __user *)(pc + 2)); + thumb_instr = le16_to_cpu(thumb_instr); + bp = thumb_instr == AARCH32_BREAK_THUMB2_HI; + } else { + bp = thumb_instr == AARCH32_BREAK_THUMB; + } + } else { + /* 32-bit ARM instruction */ + get_user(arm_instr, (u32 __user *)pc); + arm_instr = le32_to_cpu(arm_instr); + bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM; + } + + if (!bp) + return -EFAULT; + + info = (siginfo_t) { + .si_signo = SIGTRAP, + .si_errno = 0, + .si_code = TRAP_BRKPT, + .si_addr = pc, + }; + + force_sig_info(SIGTRAP, &info, current); + return 0; +} + +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"); + return 0; +} +arch_initcall(debug_traps_init); + +/* Re-enable single step for syscall restarting. */ +void user_rewind_single_step(struct task_struct *task) +{ + /* + * If single step is active for this thread, then set SPSR.SS + * to 1 to avoid returning to the active-pending state. + */ + if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) + set_regs_spsr_ss(task_pt_regs(task)); +} + +void user_fastforward_single_step(struct task_struct *task) +{ + if (test_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP)) + clear_regs_spsr_ss(task_pt_regs(task)); +} + +/* Kernel API */ +void kernel_enable_single_step(struct pt_regs *regs) +{ + WARN_ON(!irqs_disabled()); + set_regs_spsr_ss(regs); + mdscr_write(mdscr_read() | DBG_MDSCR_SS); + enable_debug_monitors(DBG_ACTIVE_EL1); +} + +void kernel_disable_single_step(void) +{ + WARN_ON(!irqs_disabled()); + mdscr_write(mdscr_read() & ~DBG_MDSCR_SS); + disable_debug_monitors(DBG_ACTIVE_EL1); +} + +int kernel_active_single_step(void) +{ + WARN_ON(!irqs_disabled()); + return mdscr_read() & DBG_MDSCR_SS; +} + +/* ptrace API */ +void user_enable_single_step(struct task_struct *task) +{ + set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); + set_regs_spsr_ss(task_pt_regs(task)); +} + +void user_disable_single_step(struct task_struct *task) +{ + clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); +} |