| /* |
| * 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/kprobes.h> |
| #include <linux/stat.h> |
| #include <linux/uaccess.h> |
| #include <linux/sched/task_stack.h> |
| |
| #include <asm/cpufeature.h> |
| #include <asm/cputype.h> |
| #include <asm/daifflags.h> |
| #include <asm/debug-monitors.h> |
| #include <asm/system_misc.h> |
| #include <asm/traps.h> |
| |
| /* Determine debug architecture. */ |
| u8 debug_monitors_arch(void) |
| { |
| return cpuid_feature_extract_unsigned_field(read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1), |
| ID_AA64DFR0_DEBUGVER_SHIFT); |
| } |
| |
| /* |
| * MDSCR access routines. |
| */ |
| static void mdscr_write(u32 mdscr) |
| { |
| unsigned long flags; |
| flags = local_daif_save(); |
| write_sysreg(mdscr, mdscr_el1); |
| local_daif_restore(flags); |
| } |
| NOKPROBE_SYMBOL(mdscr_write); |
| |
| static u32 mdscr_read(void) |
| { |
| return read_sysreg(mdscr_el1); |
| } |
| NOKPROBE_SYMBOL(mdscr_read); |
| |
| /* |
| * Allow root to disable self-hosted debug from userspace. |
| * This is useful if you want to connect an external JTAG debugger. |
| */ |
| static bool debug_enabled = true; |
| |
| 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 = false; |
| 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 dbg_active_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); |
| } |
| } |
| NOKPROBE_SYMBOL(enable_debug_monitors); |
| |
| void disable_debug_monitors(enum dbg_active_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); |
| } |
| } |
| NOKPROBE_SYMBOL(disable_debug_monitors); |
| |
| /* |
| * OS lock clearing. |
| */ |
| static int clear_os_lock(unsigned int cpu) |
| { |
| write_sysreg(0, oslar_el1); |
| isb(); |
| return 0; |
| } |
| |
| static int debug_monitors_init(void) |
| { |
| return cpuhp_setup_state(CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING, |
| "arm64/debug_monitors:starting", |
| clear_os_lock, NULL); |
| } |
| postcore_initcall(debug_monitors_init); |
| |
| /* |
| * Single step API and exception handling. |
| */ |
| static void set_regs_spsr_ss(struct pt_regs *regs) |
| { |
| regs->pstate |= DBG_SPSR_SS; |
| } |
| NOKPROBE_SYMBOL(set_regs_spsr_ss); |
| |
| static void clear_regs_spsr_ss(struct pt_regs *regs) |
| { |
| regs->pstate &= ~DBG_SPSR_SS; |
| } |
| NOKPROBE_SYMBOL(clear_regs_spsr_ss); |
| |
| /* EL1 Single Step Handler hooks */ |
| static LIST_HEAD(step_hook); |
| static DEFINE_SPINLOCK(step_hook_lock); |
| |
| void register_step_hook(struct step_hook *hook) |
| { |
| spin_lock(&step_hook_lock); |
| list_add_rcu(&hook->node, &step_hook); |
| spin_unlock(&step_hook_lock); |
| } |
| |
| void unregister_step_hook(struct step_hook *hook) |
| { |
| spin_lock(&step_hook_lock); |
| list_del_rcu(&hook->node); |
| spin_unlock(&step_hook_lock); |
| synchronize_rcu(); |
| } |
| |
| /* |
| * Call registered single step handlers |
| * 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; |
| |
| rcu_read_lock(); |
| |
| list_for_each_entry_rcu(hook, &step_hook, node) { |
| retval = hook->fn(regs, esr); |
| if (retval == DBG_HOOK_HANDLED) |
| break; |
| } |
| |
| rcu_read_unlock(); |
| |
| return retval; |
| } |
| NOKPROBE_SYMBOL(call_step_hook); |
| |
| static void send_user_sigtrap(int si_code) |
| { |
| struct pt_regs *regs = current_pt_regs(); |
| |
| if (WARN_ON(!user_mode(regs))) |
| return; |
| |
| if (interrupts_enabled(regs)) |
| local_irq_enable(); |
| |
| arm64_force_sig_fault(SIGTRAP, si_code, |
| (void __user *)instruction_pointer(regs), |
| "User debug trap"); |
| } |
| |
| static int single_step_handler(unsigned long addr, unsigned int esr, |
| struct pt_regs *regs) |
| { |
| bool handler_found = false; |
| |
| /* |
| * If we are stepping a pending breakpoint, call the hw_breakpoint |
| * handler first. |
| */ |
| if (!reinstall_suspended_bps(regs)) |
| return 0; |
| |
| #ifdef CONFIG_KPROBES |
| if (kprobe_single_step_handler(regs, esr) == DBG_HOOK_HANDLED) |
| handler_found = true; |
| #endif |
| if (!handler_found && call_step_hook(regs, esr) == DBG_HOOK_HANDLED) |
| handler_found = true; |
| |
| if (!handler_found && user_mode(regs)) { |
| send_user_sigtrap(TRAP_TRACE); |
| |
| /* |
| * 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 (!handler_found) { |
| pr_warn("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; |
| } |
| NOKPROBE_SYMBOL(single_step_handler); |
| |
| /* |
| * 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_SPINLOCK(break_hook_lock); |
| |
| void register_break_hook(struct break_hook *hook) |
| { |
| spin_lock(&break_hook_lock); |
| list_add_rcu(&hook->node, &break_hook); |
| spin_unlock(&break_hook_lock); |
| } |
| |
| void unregister_break_hook(struct break_hook *hook) |
| { |
| spin_lock(&break_hook_lock); |
| list_del_rcu(&hook->node); |
| spin_unlock(&break_hook_lock); |
| synchronize_rcu(); |
| } |
| |
| 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; |
| |
| rcu_read_lock(); |
| list_for_each_entry_rcu(hook, &break_hook, node) |
| if ((esr & hook->esr_mask) == hook->esr_val) |
| fn = hook->fn; |
| rcu_read_unlock(); |
| |
| return fn ? fn(regs, esr) : DBG_HOOK_ERROR; |
| } |
| NOKPROBE_SYMBOL(call_break_hook); |
| |
| static int brk_handler(unsigned long addr, unsigned int esr, |
| struct pt_regs *regs) |
| { |
| bool handler_found = false; |
| |
| #ifdef CONFIG_KPROBES |
| if ((esr & BRK64_ESR_MASK) == BRK64_ESR_KPROBES) { |
| if (kprobe_breakpoint_handler(regs, esr) == DBG_HOOK_HANDLED) |
| handler_found = true; |
| } |
| #endif |
| if (!handler_found && call_break_hook(regs, esr) == DBG_HOOK_HANDLED) |
| handler_found = true; |
| |
| if (!handler_found && user_mode(regs)) { |
| send_user_sigtrap(TRAP_BRKPT); |
| } else if (!handler_found) { |
| pr_warn("Unexpected kernel BRK exception at EL1\n"); |
| return -EFAULT; |
| } |
| |
| return 0; |
| } |
| NOKPROBE_SYMBOL(brk_handler); |
| |
| int aarch32_break_handler(struct pt_regs *regs) |
| { |
| 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 */ |
| __le16 instr; |
| get_user(instr, (__le16 __user *)pc); |
| thumb_instr = le16_to_cpu(instr); |
| if (thumb_instr == AARCH32_BREAK_THUMB2_LO) { |
| /* get second half of 32-bit Thumb-2 instruction */ |
| get_user(instr, (__le16 __user *)(pc + 2)); |
| thumb_instr = le16_to_cpu(instr); |
| bp = thumb_instr == AARCH32_BREAK_THUMB2_HI; |
| } else { |
| bp = thumb_instr == AARCH32_BREAK_THUMB; |
| } |
| } else { |
| /* 32-bit ARM instruction */ |
| __le32 instr; |
| get_user(instr, (__le32 __user *)pc); |
| arm_instr = le32_to_cpu(instr); |
| bp = (arm_instr & ~0xf0000000) == AARCH32_BREAK_ARM; |
| } |
| |
| if (!bp) |
| return -EFAULT; |
| |
| send_user_sigtrap(TRAP_BRKPT); |
| return 0; |
| } |
| NOKPROBE_SYMBOL(aarch32_break_handler); |
| |
| static int __init debug_traps_init(void) |
| { |
| hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP, |
| TRAP_TRACE, "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)); |
| } |
| NOKPROBE_SYMBOL(user_rewind_single_step); |
| |
| 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); |
| } |
| NOKPROBE_SYMBOL(kernel_enable_single_step); |
| |
| void kernel_disable_single_step(void) |
| { |
| WARN_ON(!irqs_disabled()); |
| mdscr_write(mdscr_read() & ~DBG_MDSCR_SS); |
| disable_debug_monitors(DBG_ACTIVE_EL1); |
| } |
| NOKPROBE_SYMBOL(kernel_disable_single_step); |
| |
| int kernel_active_single_step(void) |
| { |
| WARN_ON(!irqs_disabled()); |
| return mdscr_read() & DBG_MDSCR_SS; |
| } |
| NOKPROBE_SYMBOL(kernel_active_single_step); |
| |
| /* ptrace API */ |
| void user_enable_single_step(struct task_struct *task) |
| { |
| struct thread_info *ti = task_thread_info(task); |
| |
| if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP)) |
| set_regs_spsr_ss(task_pt_regs(task)); |
| } |
| NOKPROBE_SYMBOL(user_enable_single_step); |
| |
| void user_disable_single_step(struct task_struct *task) |
| { |
| clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); |
| } |
| NOKPROBE_SYMBOL(user_disable_single_step); |