This enables DYNAMIC_FTRACE configuration. ftrace_caller() is the entry function which is a replacement of _mcount(). If tracing is enabled on a function, the branch instruction to _mcount() is replaced to that of ftace_caller() and if disabled, replaced to nop.
See Documentation/trace/ftrace-design.txt
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/ftrace.h | 17 +++++++ arch/arm64/kernel/entry-ftrace.S | 39 +++++++++++++++ arch/arm64/kernel/ftrace.c | 103 ++++++++++++++++++++++++++++++++++++++ 4 files changed, 160 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3776319..c150430 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -23,6 +23,7 @@ config ARM64 select HAVE_DEBUG_KMEMLEAK select HAVE_DMA_API_DEBUG select HAVE_DMA_ATTRS + select HAVE_DYNAMIC_FTRACE select HAVE_FUNCTION_TRACER select HAVE_FUNCTION_GRAPH_TRACER select HAVE_GENERIC_DMA_COHERENT diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h index 0d5dfdb..37a379d 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -17,6 +17,23 @@
#ifndef __ASSEMBLY__ extern void _mcount(unsigned long); + +#ifdef CONFIG_DYNAMIC_FTRACE +struct dyn_arch_ftrace { + /* No extra data needed for arm64 */ +}; + +extern unsigned long ftrace_graph_call; + +static inline unsigned long ftrace_call_adjust(unsigned long addr) +{ + /* + * addr is the address of the mcount call instruction. + * recordmcount does the necessary offset calculation. + */ + return addr; +} +#endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* __ASSEMBLY__ */ #endif /* CONFIG_FUNCTION_TRACER */
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S index ae14ece..c35c650 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -88,6 +88,7 @@ add \reg, \reg, #8 .endm
+#ifndef CONFIG_DYNAMIC_FTRACE /* * void _mcount(unsigned long return_address) * @return_address: return address to instrumented function (callsite) @@ -132,6 +133,44 @@ skip_ftrace_call: #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ ENDPROC(_mcount)
+#else /* CONFIG_DYNAMIC_FTRACE */ +/* + * This code is executed only at boot time. + * Once after initialized, "bl _mcount" generated by gcc -pg option will be + * replaced to "nop" if tracing is disabled or "b ftrace_caller" if enabled. + */ +ENTRY(_mcount) + ret +ENDPROC(_mcount) + +/* + * void ftrace_caller(unsigned long return_address) + * @return_address: return address to instrumented function (callsite) + * + * Call any kind of tracer function and/or function graph tracer. + */ +ENTRY(ftrace_caller) + mcount_enter + + mcount_get_pc0 x0 // pc in callsite + mcount_get_lr x1 // callsite's lr (adjusted) + + .global ftrace_call +ftrace_call: // tracer(pc, lr); + nop // This will be replaced with "bl xxx" + // where xxx can be any kind of tracer. + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER + .global ftrace_graph_call +ftrace_graph_call: // ftrace_graph_caller(); + nop // If enabled, this will be replaced + // "b ftrace_graph_caller" +#endif + + mcount_exit +ENDPROC(ftrace_caller) +#endif /* CONFIG_DYNAMIC_FTRACE */ + ENTRY(ftrace_stub) ret ENDPROC(ftrace_stub) diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c index e779e16..da481c1 100644 --- a/arch/arm64/kernel/ftrace.c +++ b/arch/arm64/kernel/ftrace.c @@ -17,6 +17,76 @@ #include <asm/ftrace.h> #include <asm/insn.h>
+#ifdef CONFIG_DYNAMIC_FTRACE +/* FIXME: can be replaced by aarch64_insn_patch_text_nosync() */ +static int ftrace_modify_code(unsigned long pc, unsigned int old, + unsigned int new, bool validate) +{ + unsigned int replaced; + +#ifdef __AARCH64EB__ + old = swab32(old); + new = swab32(new); +#endif + + if (validate) { + if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) + return -EFAULT; + + if (replaced != old) + return -EINVAL; + } + + if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) + return -EPERM; + + flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); + + return 0; +} + +int ftrace_update_ftrace_func(ftrace_func_t func) +{ + unsigned long pc; + unsigned int new; + + pc = (unsigned long)&ftrace_call; + new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func, true); + + return ftrace_modify_code(pc, 0, new, false); +} + +int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long pc = rec->ip; + unsigned int old, new; + + old = aarch64_insn_gen_nop(); + new = aarch64_insn_gen_branch_imm(pc, addr, true); + + return ftrace_modify_code(pc, old, new, true); +} + +int ftrace_make_nop(struct module *mod, + struct dyn_ftrace *rec, unsigned long addr) +{ + unsigned long pc = rec->ip; + unsigned int old, new; + + old = aarch64_insn_gen_branch_imm(pc, addr, true); + new = aarch64_insn_gen_nop(); + + return ftrace_modify_code(pc, old, new, true); +} + +int __init ftrace_dyn_arch_init(void *data) +{ + *(unsigned long *)data = 0; + + return 0; +} +#endif /* CONFIG_DYNAMIC_FTRACE */ + #ifdef CONFIG_FUNCTION_GRAPH_TRACER void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, unsigned long frame_pointer) @@ -80,4 +150,37 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, return; } } + +#ifdef CONFIG_DYNAMIC_FTRACE +static int __ftrace_modify_caller(unsigned long *callsite, + void (*func) (void), bool enable) +{ + unsigned long pc = (unsigned long)callsite; + unsigned int branch, nop, old, new; + + branch = aarch64_insn_gen_branch_imm(pc, (unsigned long)func, false); + nop = aarch64_insn_gen_nop(); + old = enable ? nop : branch; + new = enable ? branch : nop; + + return ftrace_modify_code(pc, old, new, true); +} + +static int ftrace_modify_graph_caller(bool enable) +{ + return __ftrace_modify_caller(&ftrace_graph_call, + ftrace_graph_caller, + enable); +} + +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_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */