// SPDX-License-Identifier: GPL-2.0 /* * Based on arch/arm64/kernel/ftrace.c * * Copyright (C) 2022 Loongson Technology Corporation Limited */ #include #include #include #include #include static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, bool validate) { u32 replaced; if (validate) { if (larch_insn_read((void *)pc, &replaced)) return -EFAULT; if (replaced != old) return -EINVAL; } if (larch_insn_patch_text((void *)pc, new)) return -EPERM; return 0; } #ifdef CONFIG_MODULES static bool reachable_by_bl(unsigned long addr, unsigned long pc) { long offset = (long)addr - (long)pc; return offset >= -SZ_128M && offset < SZ_128M; } static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr) { struct plt_entry *plt = mod->arch.ftrace_trampolines; if (addr == FTRACE_ADDR) return &plt[FTRACE_PLT_IDX]; if (addr == FTRACE_REGS_ADDR && IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS)) return &plt[FTRACE_REGS_PLT_IDX]; return NULL; } /* * Find the address the callsite must branch to in order to reach '*addr'. * * Due to the limited range of 'bl' instruction, modules may be placed too far * away to branch directly and we must use a PLT. * * Returns true when '*addr' contains a reachable target address, or has been * modified to contain a PLT address. Returns false otherwise. */ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr) { unsigned long pc = rec->ip + LOONGARCH_INSN_SIZE; struct plt_entry *plt; /* * If a custom trampoline is unreachable, rely on the ftrace_regs_caller * trampoline which knows how to indirectly reach that trampoline through * ops->direct_call. */ if (*addr != FTRACE_ADDR && *addr != FTRACE_REGS_ADDR && !reachable_by_bl(*addr, pc)) *addr = FTRACE_REGS_ADDR; /* * When the target is within range of the 'bl' instruction, use 'addr' * as-is and branch to that directly. */ if (reachable_by_bl(*addr, pc)) return true; /* * 'mod' is only set at module load time, but if we end up * dealing with an out-of-range condition, we can assume it * is due to a module being loaded far away from the kernel. * * NOTE: __module_text_address() must be called with preemption * disabled, but we can rely on ftrace_lock to ensure that 'mod' * retains its validity throughout the remainder of this code. */ if (!mod) { preempt_disable(); mod = __module_text_address(pc); preempt_enable(); } if (WARN_ON(!mod)) return false; plt = get_ftrace_plt(mod, *addr); if (!plt) { pr_err("ftrace: no module PLT for %ps\n", (void *)*addr); return false; } *addr = (unsigned long)plt; return true; } #else /* !CONFIG_MODULES */ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod, unsigned long *addr) { return true; } #endif #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { u32 old, new; unsigned long pc; pc = rec->ip + LOONGARCH_INSN_SIZE; if (!ftrace_find_callable_addr(rec, NULL, &addr)) return -EINVAL; if (!ftrace_find_callable_addr(rec, NULL, &old_addr)) return -EINVAL; new = larch_insn_gen_bl(pc, addr); old = larch_insn_gen_bl(pc, old_addr); return ftrace_modify_code(pc, old, new, true); } #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ int ftrace_update_ftrace_func(ftrace_func_t func) { u32 new; unsigned long pc; pc = (unsigned long)&ftrace_call; new = larch_insn_gen_bl(pc, (unsigned long)func); return ftrace_modify_code(pc, 0, new, false); } /* * The compiler has inserted 2 NOPs before the regular function prologue. * T series registers are available and safe because of LoongArch's psABI. * * At runtime, we can replace nop with bl to enable ftrace call and replace bl * with nop to disable ftrace call. The bl requires us to save the original RA * value, so it saves RA at t0 here. * * Details are: * * | Compiled | Disabled | Enabled | * +------------+------------------------+------------------------+ * | nop | move t0, ra | move t0, ra | * | nop | nop | bl ftrace_caller | * | func_body | func_body | func_body | * * The RA value will be recovered by ftrace_regs_entry, and restored into RA * before returning to the regular function prologue. When a function is not * being traced, the "move t0, ra" is not harmful. */ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { u32 old, new; unsigned long pc; pc = rec->ip; old = larch_insn_gen_nop(); new = larch_insn_gen_move(LOONGARCH_GPR_T0, LOONGARCH_GPR_RA); return ftrace_modify_code(pc, old, new, true); } int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { u32 old, new; unsigned long pc; pc = rec->ip + LOONGARCH_INSN_SIZE; if (!ftrace_find_callable_addr(rec, NULL, &addr)) return -EINVAL; old = larch_insn_gen_nop(); new = larch_insn_gen_bl(pc, addr); return ftrace_modify_code(pc, old, new, true); } int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { u32 old, new; unsigned long pc; pc = rec->ip + LOONGARCH_INSN_SIZE; if (!ftrace_find_callable_addr(rec, NULL, &addr)) return -EINVAL; new = larch_insn_gen_nop(); old = larch_insn_gen_bl(pc, addr); return ftrace_modify_code(pc, old, new, true); } void arch_ftrace_update_code(int command) { command |= FTRACE_MAY_SLEEP; ftrace_modify_all_code(command); } int __init ftrace_dyn_arch_init(void) { return 0; } #ifdef CONFIG_FUNCTION_GRAPH_TRACER void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent) { unsigned long old; unsigned long return_hooker = (unsigned long)&return_to_handler; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; old = *parent; if (!function_graph_enter(old, self_addr, 0, parent)) *parent = return_hooker; } #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) { struct pt_regs *regs = &fregs->regs; unsigned long *parent = (unsigned long *)®s->regs[1]; prepare_ftrace_return(ip, (unsigned long *)parent); } #else static int ftrace_modify_graph_caller(bool enable) { u32 branch, nop; unsigned long pc, func; extern void ftrace_graph_call(void); pc = (unsigned long)&ftrace_graph_call; func = (unsigned long)&ftrace_graph_caller; nop = larch_insn_gen_nop(); branch = larch_insn_gen_b(pc, func); if (enable) return ftrace_modify_code(pc, nop, branch, true); else return ftrace_modify_code(pc, branch, nop, true); } int ftrace_enable_ftrace_graph_caller(void) { return ftrace_modify_graph_caller(true); } int ftrace_disable_ftrace_graph_caller(void) { return ftrace_modify_graph_caller(false); } #endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ #ifdef CONFIG_KPROBES_ON_FTRACE /* Ftrace callback handler for kprobes -- called under preepmt disabled */ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *ops, struct ftrace_regs *fregs) { int bit; struct pt_regs *regs; struct kprobe *p; struct kprobe_ctlblk *kcb; bit = ftrace_test_recursion_trylock(ip, parent_ip); if (bit < 0) return; p = get_kprobe((kprobe_opcode_t *)ip); if (unlikely(!p) || kprobe_disabled(p)) goto out; regs = ftrace_get_regs(fregs); if (!regs) goto out; kcb = get_kprobe_ctlblk(); if (kprobe_running()) { kprobes_inc_nmissed_count(p); } else { unsigned long orig_ip = instruction_pointer(regs); instruction_pointer_set(regs, ip); __this_cpu_write(current_kprobe, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (!p->pre_handler || !p->pre_handler(p, regs)) { /* * Emulate singlestep (and also recover regs->csr_era) * as if there is a nop */ instruction_pointer_set(regs, (unsigned long)p->addr + MCOUNT_INSN_SIZE); if (unlikely(p->post_handler)) { kcb->kprobe_status = KPROBE_HIT_SSDONE; p->post_handler(p, regs, 0); } instruction_pointer_set(regs, orig_ip); } /* * If pre_handler returns !0, it changes regs->csr_era. We have to * skip emulating post_handler. */ __this_cpu_write(current_kprobe, NULL); } out: ftrace_test_recursion_unlock(bit); } NOKPROBE_SYMBOL(kprobe_ftrace_handler); int arch_prepare_kprobe_ftrace(struct kprobe *p) { p->ainsn.insn = NULL; return 0; } #endif /* CONFIG_KPROBES_ON_FTRACE */