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-rw-r--r--arch/loongarch/kernel/ftrace_dyn.c341
1 files changed, 341 insertions, 0 deletions
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
new file mode 100644
index 0000000000..73858c9029
--- /dev/null
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -0,0 +1,341 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Based on arch/arm64/kernel/ftrace.c
+ *
+ * Copyright (C) 2022 Loongson Technology Corporation Limited
+ */
+
+#include <linux/ftrace.h>
+#include <linux/kprobes.h>
+#include <linux/uaccess.h>
+
+#include <asm/inst.h>
+#include <asm/module.h>
+
+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(&current->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 *)&regs->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 */