diff options
Diffstat (limited to 'arch/riscv/kernel/ftrace.c')
| -rw-r--r-- | arch/riscv/kernel/ftrace.c | 227 |
1 files changed, 227 insertions, 0 deletions
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c new file mode 100644 index 000000000..2086f6585 --- /dev/null +++ b/arch/riscv/kernel/ftrace.c @@ -0,0 +1,227 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + * Copyright (C) 2017 Andes Technology Corporation + */ + +#include <linux/ftrace.h> +#include <linux/uaccess.h> +#include <linux/memory.h> +#include <asm/cacheflush.h> +#include <asm/patch.h> + +#ifdef CONFIG_DYNAMIC_FTRACE +void ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) +{ + mutex_lock(&text_mutex); +} + +void ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) +{ + mutex_unlock(&text_mutex); +} + +static int ftrace_check_current_call(unsigned long hook_pos, + unsigned int *expected) +{ + unsigned int replaced[2]; + unsigned int nops[2] = {NOP4, NOP4}; + + /* we expect nops at the hook position */ + if (!expected) + expected = nops; + + /* + * Read the text we want to modify; + * return must be -EFAULT on read error + */ + if (copy_from_kernel_nofault(replaced, (void *)hook_pos, + MCOUNT_INSN_SIZE)) + return -EFAULT; + + /* + * Make sure it is what we expect it to be; + * return must be -EINVAL on failed comparison + */ + if (memcmp(expected, replaced, sizeof(replaced))) { + pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n", + (void *)hook_pos, expected[0], expected[1], replaced[0], + replaced[1]); + return -EINVAL; + } + + return 0; +} + +static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target, + bool enable) +{ + unsigned int call[2]; + unsigned int nops[2] = {NOP4, NOP4}; + + make_call(hook_pos, target, call); + + /* Replace the auipc-jalr pair at once. Return -EPERM on write error. */ + if (patch_text_nosync + ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE)) + return -EPERM; + + return 0; +} + +/* + * Put 5 instructions with 16 bytes at the front of function within + * patchable function entry nops' area. + * + * 0: REG_S ra, -SZREG(sp) + * 1: auipc ra, 0x? + * 2: jalr -?(ra) + * 3: REG_L ra, -SZREG(sp) + * + * So the opcodes is: + * 0: 0xfe113c23 (sd)/0xfe112e23 (sw) + * 1: 0x???????? -> auipc + * 2: 0x???????? -> jalr + * 3: 0xff813083 (ld)/0xffc12083 (lw) + */ +#if __riscv_xlen == 64 +#define INSN0 0xfe113c23 +#define INSN3 0xff813083 +#elif __riscv_xlen == 32 +#define INSN0 0xfe112e23 +#define INSN3 0xffc12083 +#endif + +#define FUNC_ENTRY_SIZE 16 +#define FUNC_ENTRY_JMP 4 + +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned int call[4] = {INSN0, 0, 0, INSN3}; + unsigned long target = addr; + unsigned long caller = rec->ip + FUNC_ENTRY_JMP; + + call[1] = to_auipc_insn((unsigned int)(target - caller)); + call[2] = to_jalr_insn((unsigned int)(target - caller)); + + if (patch_text_nosync((void *)rec->ip, call, FUNC_ENTRY_SIZE)) + return -EPERM; + + return 0; +} + +int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, + unsigned long addr) +{ + unsigned int nops[4] = {NOP4, NOP4, NOP4, NOP4}; + + if (patch_text_nosync((void *)rec->ip, nops, FUNC_ENTRY_SIZE)) + return -EPERM; + + return 0; +} + + +/* + * This is called early on, and isn't wrapped by + * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold + * text_mutex, which triggers a lockdep failure. SMP isn't running so we could + * just directly poke the text, but it's simpler to just take the lock + * ourselves. + */ +int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) +{ + int out; + + ftrace_arch_code_modify_prepare(); + out = ftrace_make_nop(mod, rec, MCOUNT_ADDR); + ftrace_arch_code_modify_post_process(); + + return out; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + int ret = __ftrace_modify_call((unsigned long)&ftrace_call, + (unsigned long)func, true); + if (!ret) { + ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call, + (unsigned long)func, true); + } + + return ret; +} +#endif + +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, + unsigned long addr) +{ + unsigned int call[2]; + unsigned long caller = rec->ip + FUNC_ENTRY_JMP; + int ret; + + make_call(caller, old_addr, call); + ret = ftrace_check_current_call(caller, call); + + if (ret) + return ret; + + return __ftrace_modify_call(caller, addr, true); +} +#endif + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +/* + * Most of this function is copied from arm64. + */ +void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, + unsigned long frame_pointer) +{ + unsigned long return_hooker = (unsigned long)&return_to_handler; + unsigned long old; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + /* + * We don't suffer access faults, so no extra fault-recovery assembly + * is needed here. + */ + old = *parent; + + if (!function_graph_enter(old, self_addr, frame_pointer, parent)) + *parent = return_hooker; +} + +#ifdef CONFIG_DYNAMIC_FTRACE +extern void ftrace_graph_call(void); +extern void ftrace_graph_regs_call(void); +int ftrace_enable_ftrace_graph_caller(void) +{ + int ret; + + ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call, + (unsigned long)&prepare_ftrace_return, true); + if (ret) + return ret; + + return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call, + (unsigned long)&prepare_ftrace_return, true); +} + +int ftrace_disable_ftrace_graph_caller(void) +{ + int ret; + + ret = __ftrace_modify_call((unsigned long)&ftrace_graph_call, + (unsigned long)&prepare_ftrace_return, false); + if (ret) + return ret; + + return __ftrace_modify_call((unsigned long)&ftrace_graph_regs_call, + (unsigned long)&prepare_ftrace_return, false); +} +#endif /* CONFIG_DYNAMIC_FTRACE */ +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |