diff options
Diffstat (limited to 'arch/loongarch/kernel/ftrace_dyn.c')
-rw-r--r-- | arch/loongarch/kernel/ftrace_dyn.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c new file mode 100644 index 000000000000..3b82bface840 --- /dev/null +++ b/arch/loongarch/kernel/ftrace_dyn.c @@ -0,0 +1,110 @@ +// 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/uaccess.h> + +#include <asm/inst.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; +} + +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; + + 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; + + 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; +} |