| Message ID | 1394705630-12384-5-git-send-email-takahiro.akashi@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Thu, Mar 13, 2014 at 10:13:47AM +0000, AKASHI Takahiro wrote: > This patch implements arm64 specific part to support function tracers, > such as function (CONFIG_FUNCTION_TRACER), function_graph > (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler > (CONFIG_FUNCTION_PROFILER). > > With 'function' tracer, all the functions in the kernel are traced with > timestamps in ${sysfs}/tracing/trace. If function_graph tracer is > specified, call graph is generated. > > The kernel must be compiled with -pg option so that _mcount() is inserted > at the beginning of functions. This function is called on every function's > entry as long as tracing is enabled. > In addition, function_graph tracer also needs to be able to probe function's > exit. ftrace_graph_caller() & return_to_handler do this by faking link > register's value to intercept function's return path. > > More details on architecture specific requirements are described in > Documentation/trace/ftrace-design.txt. [...] > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > new file mode 100644 > index 0000000..0ac31c8 > --- /dev/null > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -0,0 +1,175 @@ > +/* > + * arch/arm64/kernel/entry-ftrace.S > + * > + * Copyright (C) 2013 Linaro Limited > + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + */ > + > +#include <linux/linkage.h> > +#include <asm/ftrace.h> > +#include <asm/insn.h> > + > +/* > + * Gcc with -pg will put the following code in the beginning of each function: > + * mov x0, x30 > + * bl _mcount > + * [function's body ...] > + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic > + * ftrace is enabled. > + * > + * Please note that x0 as an argument will not be used here because we can > + * get lr(x30) of instrumented function at any time by winding up call stack > + * as long as the kernel is compiled without -fomit-frame-pointer. > + * (or CONFIG_FRAME_POINTER, this is forced on arm64) > + * > + * stack layout after mcount_enter in _mcount(): > + * > + * current sp/fp => 0:+-----+ > + * in _mcount() | x29 | -> instrumented function's fp > + * +-----+ > + * | x30 | -> _mcount()'s lr (= instrumented function's pc) > + * old sp => +16:+-----+ > + * when instrumented | | > + * function calls | ... | > + * _mcount() | | > + * | | > + * instrumented => +xx:+-----+ > + * function's fp | x29 | -> parent's fp > + * +-----+ > + * | x30 | -> instrumented function's lr (= parent's pc) > + * +-----+ > + * | ... | I guess it's just the diff that's misaligning your ASCII art here? > +/* > + * void return_to_handler(void) > + * > + * Run ftrace_return_to_handler() before going back to parent. > + * @fp is checked against the value passed by ftrace_graph_caller() > + * only when CONFIG_FUNCTION_GRAPH_FP_TEST is enabled. > + */ > + .global return_to_handler > +return_to_handler: ENTRY(return_to_handler) > + str x0, [sp, #-16]! > + mov x0, x29 // parent's fp > + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); > + mov x30, x0 // restore the original return address > + ldr x0, [sp], #16 > + ret and an ENDPROC here. > +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > new file mode 100644 > index 0000000..a559ab8 > --- /dev/null > +++ b/arch/arm64/kernel/ftrace.c > @@ -0,0 +1,64 @@ > +/* > + * arch/arm64/kernel/ftrace.c > + * > + * Copyright (C) 2013 Linaro Limited > + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License version 2 as > + * published by the Free Software Foundation. > + */ > + > +#include <linux/ftrace.h> > +#include <linux/swab.h> > +#include <linux/uaccess.h> > + > +#include <asm/cacheflush.h> > +#include <asm/ftrace.h> > +#include <asm/insn.h> > + > +#ifdef CONFIG_FUNCTION_GRAPH_TRACER > +/* > + * function_graph tracer expects ftrace_return_to_handler() to be called > + * on the way back to parent. For this purpose, this function is called > + * in _mcount() or ftrace_caller() to replace return address (*parent) on > + * the call stack to return_to_handler. > + * > + * Note that @frame_pointer is used only for sanity check later. > + */ > +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; > + struct ftrace_graph_ent trace; > + int err; > + > + if (unlikely(atomic_read(¤t->tracing_graph_pause))) > + return; > + > + /* > + * Note: > + * No protection against faulting at *parent, which may be seen > + * on other archs. It's unlikely on AArch64. > + */ > + old = *parent; > + *parent = return_hooker; return_hook? People might take it personally otherwise ;) > + trace.func = self_addr; in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up tracing_graph_pause and setting the ret_stack with a comment saying: /* Make sure the tasks see the -1 first: */ Why don't we have a corresponding read-barrier here? Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Thu, 2014-03-13 at 17:08 +0000, Will Deacon wrote: > > + /* > > + * Note: > > + * No protection against faulting at *parent, which may be seen > > + * on other archs. It's unlikely on AArch64. > > + */ > > + old = *parent; > > + *parent = return_hooker; > > return_hook? People might take it personally otherwise ;) No, return_hooker is consistent with all the other archs. Hey, it's a rugby position! Note, which I was when I played. ;-) > > > + trace.func = self_addr; > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > tracing_graph_pause and setting the ret_stack with a comment saying: > > /* Make sure the tasks see the -1 first: */ > > Why don't we have a corresponding read-barrier here? The corresponding rmb is in kernel/trace/trace_function_graph ftrace_push_return_trace(). -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Thu, Mar 13, 2014 at 06:27:39PM +0000, Steven Rostedt wrote: > On Thu, 2014-03-13 at 17:08 +0000, Will Deacon wrote: > > > > + /* > > > + * Note: > > > + * No protection against faulting at *parent, which may be seen > > > + * on other archs. It's unlikely on AArch64. > > > + */ > > > + old = *parent; > > > + *parent = return_hooker; > > > > return_hook? People might take it personally otherwise ;) > > No, return_hooker is consistent with all the other archs. Hey, it's a > rugby position! Note, which I was when I played. ;-) Hehe, in which case your children will be able to execute that line of ftrace! > > > > > + trace.func = self_addr; > > > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > > tracing_graph_pause and setting the ret_stack with a comment saying: > > > > /* Make sure the tasks see the -1 first: */ > > > > Why don't we have a corresponding read-barrier here? > > The corresponding rmb is in kernel/trace/trace_function_graph > ftrace_push_return_trace(). Okey doke then, I guess we don't really care about tracing_graph_pause getting out-of-sync with curr_ret_stack. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Thu, 2014-03-13 at 18:37 +0000, Will Deacon wrote: > > > No, return_hooker is consistent with all the other archs. Hey, it's a > > rugby position! Note, which I was when I played. ;-) > > Hehe, in which case your children will be able to execute that line of > ftrace! > My kids already know I was :-) > > > > > > > + trace.func = self_addr; > > > > > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > > > tracing_graph_pause and setting the ret_stack with a comment saying: > > > > > > /* Make sure the tasks see the -1 first: */ > > > > > > Why don't we have a corresponding read-barrier here? > > > > The corresponding rmb is in kernel/trace/trace_function_graph > > ftrace_push_return_trace(). > > Okey doke then, I guess we don't really care about tracing_graph_pause > getting out-of-sync with curr_ret_stack. Yep, the tracing_graph_pause is more to prevent crazy stuff happening when an interrupt comes in. So it is just local cpu context, and doesn't have issues with other CPUS. If it takes a bit for the task to see it go to zero, the worse thing is that you might miss a few tracing functions until that gets synced. Which will probably happen by the time tracing is fully activated anyway. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 03/14/2014 02:08 AM, Will Deacon wrote: > On Thu, Mar 13, 2014 at 10:13:47AM +0000, AKASHI Takahiro wrote: >> This patch implements arm64 specific part to support function tracers, >> such as function (CONFIG_FUNCTION_TRACER), function_graph >> (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler >> (CONFIG_FUNCTION_PROFILER). >> >> With 'function' tracer, all the functions in the kernel are traced with >> timestamps in ${sysfs}/tracing/trace. If function_graph tracer is >> specified, call graph is generated. >> >> The kernel must be compiled with -pg option so that _mcount() is inserted >> at the beginning of functions. This function is called on every function's >> entry as long as tracing is enabled. >> In addition, function_graph tracer also needs to be able to probe function's >> exit. ftrace_graph_caller() & return_to_handler do this by faking link >> register's value to intercept function's return path. >> >> More details on architecture specific requirements are described in >> Documentation/trace/ftrace-design.txt. > > [...] You seem not to like this statement :-) >> diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S >> new file mode 100644 >> index 0000000..0ac31c8 >> --- /dev/null >> +++ b/arch/arm64/kernel/entry-ftrace.S >> @@ -0,0 +1,175 @@ >> +/* >> + * arch/arm64/kernel/entry-ftrace.S >> + * >> + * Copyright (C) 2013 Linaro Limited >> + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + */ >> + >> +#include <linux/linkage.h> >> +#include <asm/ftrace.h> >> +#include <asm/insn.h> >> + >> +/* >> + * Gcc with -pg will put the following code in the beginning of each function: >> + * mov x0, x30 >> + * bl _mcount >> + * [function's body ...] >> + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic >> + * ftrace is enabled. >> + * >> + * Please note that x0 as an argument will not be used here because we can >> + * get lr(x30) of instrumented function at any time by winding up call stack >> + * as long as the kernel is compiled without -fomit-frame-pointer. >> + * (or CONFIG_FRAME_POINTER, this is forced on arm64) >> + * >> + * stack layout after mcount_enter in _mcount(): >> + * >> + * current sp/fp => 0:+-----+ >> + * in _mcount() | x29 | -> instrumented function's fp >> + * +-----+ >> + * | x30 | -> _mcount()'s lr (= instrumented function's pc) >> + * old sp => +16:+-----+ >> + * when instrumented | | >> + * function calls | ... | >> + * _mcount() | | >> + * | | >> + * instrumented => +xx:+--- --+ >> + * function's fp | x29 | -> parent's fp >> + * +-----+ >> + * | x30 | -> instrumented function's lr (= parent's pc) >> + * +-----+ >> + * | ... | > > I guess it's just the diff that's misaligning your ASCII art here? Yes, I think so. Misaligned due to "tab" >> +/* >> + * void return_to_handler(void) >> + * >> + * Run ftrace_return_to_handler() before going back to parent. >> + * @fp is checked against the value passed by ftrace_graph_caller() >> + * only when CONFIG_FUNCTION_GRAPH_FP_TEST is enabled.a >> + */ >> + .global return_to_handler >> +return_to_handler: > > ENTRY(return_to_handler) Fix it. >> + str x0, [sp, #-16]! >> + mov x0, x29 // parent's fp >> + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); >> + mov x30, x0 // restore the original return address >> + ldr x0, [sp], #16 >> + ret > > and an ENDPROC here. Fix it. But please note that this (return_to_handler) is not a real function. Declaring it as ENDPROC is not very useful. >> +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ >> diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c >> new file mode 100644 >> index 0000000..a559ab8 >> --- /dev/null >> +++ b/arch/arm64/kernel/ftrace.c >> @@ -0,0 +1,64 @@ >> +/* >> + * arch/arm64/kernel/ftrace.c >> + * >> + * Copyright (C) 2013 Linaro Limited >> + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + */ >> + >> +#include <linux/ftrace.h> >> +#include <linux/swab.h> >> +#include <linux/uaccess.h> >> + >> +#include <asm/cacheflush.h> >> +#include <asm/ftrace.h> >> +#include <asm/insn.h> >> + >> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER >> +/* >> + * function_graph tracer expects ftrace_return_to_handler() to be called >> + * on the way back to parent. For this purpose, this function is called >> + * in _mcount() or ftrace_caller() to replace return address (*parent) on >> + * the call stack to return_to_handler. >> + * >> + * Note that @frame_pointer is used only for sanity check later. >> + */ >> +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; >> + struct ftrace_graph_ent trace; >> + int err; >> + >> + if (unlikely(atomic_read(¤t->tracing_graph_pause))) >> + return; >> + >> + /* >> + * Note: >> + * No protection against faulting at *parent, which may be seen >> + * on other archs. It's unlikely on AArch64. >> + */ >> + old = *parent; >> + *parent = return_hooker; > > return_hook? People might take it personally otherwise ;) I didn't know what "(return) hooker" means. Anyway, leave it as it is after you and Steven's discussion. >> + trace.func = self_addr; > > in kernel/ftrace/ftrace.c there's an smb_wmb() between setting up > tracing_graph_pause and setting the ret_stack with a comment saying: > > /* Make sure the tasks see the -1 first: */ > > Why don't we have a corresponding read-barrier here? I think Steven answered it. -Takahiro AKASHI > Will > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Fri, Mar 14, 2014 at 04:45:13AM +0000, AKASHI Takahiro wrote: > On 03/14/2014 02:08 AM, Will Deacon wrote: > > On Thu, Mar 13, 2014 at 10:13:47AM +0000, AKASHI Takahiro wrote: > >> This patch implements arm64 specific part to support function tracers, > >> such as function (CONFIG_FUNCTION_TRACER), function_graph > >> (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler > >> (CONFIG_FUNCTION_PROFILER). > >> > >> With 'function' tracer, all the functions in the kernel are traced with > >> timestamps in ${sysfs}/tracing/trace. If function_graph tracer is > >> specified, call graph is generated. > >> > >> The kernel must be compiled with -pg option so that _mcount() is inserted > >> at the beginning of functions. This function is called on every function's > >> entry as long as tracing is enabled. > >> In addition, function_graph tracer also needs to be able to probe function's > >> exit. ftrace_graph_caller() & return_to_handler do this by faking link > >> register's value to intercept function's return path. > >> > >> More details on architecture specific requirements are described in > >> Documentation/trace/ftrace-design.txt. > > > > [...] > > You seem not to like this statement :-) Huh? I was just using '[...]' to signify that I'd removed a lot of context (since the code all looked fine there). Otherwise, review emails can get really long. > >> + str x0, [sp, #-16]! > >> + mov x0, x29 // parent's fp > >> + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); > >> + mov x30, x0 // restore the original return address > >> + ldr x0, [sp], #16 > >> + ret > > > > and an ENDPROC here. > > Fix it. > But please note that this (return_to_handler) is not a real function. > Declaring it as ENDPROC is not very useful. Then use END(...). The opening macro was the main point, since that avoid the need for an explicit .globl. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On 03/14/2014 07:07 PM, Will Deacon wrote: > On Fri, Mar 14, 2014 at 04:45:13AM +0000, AKASHI Takahiro wrote: >> On 03/14/2014 02:08 AM, Will Deacon wrote: >>> On Thu, Mar 13, 2014 at 10:13:47AM +0000, AKASHI Takahiro wrote: >>>> This patch implements arm64 specific part to support function tracers, >>>> such as function (CONFIG_FUNCTION_TRACER), function_graph >>>> (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler >>>> (CONFIG_FUNCTION_PROFILER). >>>> >>>> With 'function' tracer, all the functions in the kernel are traced with >>>> timestamps in ${sysfs}/tracing/trace. If function_graph tracer is >>>> specified, call graph is generated. >>>> >>>> The kernel must be compiled with -pg option so that _mcount() is inserted >>>> at the beginning of functions. This function is called on every function's >>>> entry as long as tracing is enabled. >>>> In addition, function_graph tracer also needs to be able to probe function's >>>> exit. ftrace_graph_caller() & return_to_handler do this by faking link >>>> register's value to intercept function's return path. >>>> >>>> More details on architecture specific requirements are described in >>>> Documentation/trace/ftrace-design.txt. >>> >>> [...] >> >> You seem not to like this statement :-) > > Huh? I was just using '[...]' to signify that I'd removed a lot of context > (since the code all looked fine there). Otherwise, review emails can get > really long. Please ignore my comment. >>>> + str x0, [sp, #-16]! >>>> + mov x0, x29 // parent's fp >>>> + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); >>>> + mov x30, x0 // restore the original return address >>>> + ldr x0, [sp], #16 >>>> + ret >>> >>> and an ENDPROC here. >> >> Fix it. >> But please note that this (return_to_handler) is not a real function. >> Declaring it as ENDPROC is not very useful. > > Then use END(...). The opening macro was the main point, since that avoid > the need for an explicit .globl. Fix it. -Takahiro AKASHI > Will > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 340e344..6b3fef6 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -35,6 +35,8 @@ config ARM64 select HAVE_DMA_CONTIGUOUS select HAVE_EFFICIENT_UNALIGNED_ACCESS select HAVE_FTRACE_MCOUNT_RECORD + select HAVE_FUNCTION_TRACER + select HAVE_FUNCTION_GRAPH_TRACER select HAVE_GENERIC_DMA_COHERENT select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_MEMBLOCK diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h new file mode 100644 index 0000000..58ea595 --- /dev/null +++ b/arch/arm64/include/asm/ftrace.h @@ -0,0 +1,23 @@ +/* + * arch/arm64/include/asm/ftrace.h + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ +#ifndef __ASM_FTRACE_H +#define __ASM_FTRACE_H + +#include <asm/insn.h> + +#define MCOUNT_ADDR ((unsigned long)_mcount) +#define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE + +#ifndef __ASSEMBLY__ +extern void _mcount(unsigned long); +#endif /* __ASSEMBLY__ */ + +#endif /* __ASM_FTRACE_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 2d4554b..ac67fd0 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -5,6 +5,9 @@ CPPFLAGS_vmlinux.lds := -DTEXT_OFFSET=$(TEXT_OFFSET) AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET) +CFLAGS_REMOVE_ftrace.o = -pg +CFLAGS_REMOVE_insn.o = -pg + # Object file lists. arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \ entry-fpsimd.o process.o ptrace.o setup.o signal.o \ @@ -13,6 +16,7 @@ arm64-obj-y := cputable.o debug-monitors.o entry.o irq.o fpsimd.o \ arm64-obj-$(CONFIG_COMPAT) += sys32.o kuser32.o signal32.o \ sys_compat.o +arm64-obj-$(CONFIG_FUNCTION_TRACER) += ftrace.o entry-ftrace.o arm64-obj-$(CONFIG_MODULES) += arm64ksyms.o module.o arm64-obj-$(CONFIG_SMP) += smp.o smp_spin_table.o arm64-obj-$(CONFIG_HW_PERF_EVENTS) += perf_event.o diff --git a/arch/arm64/kernel/arm64ksyms.c b/arch/arm64/kernel/arm64ksyms.c index 338b568..7f0512f 100644 --- a/arch/arm64/kernel/arm64ksyms.c +++ b/arch/arm64/kernel/arm64ksyms.c @@ -56,3 +56,7 @@ EXPORT_SYMBOL(clear_bit); EXPORT_SYMBOL(test_and_clear_bit); EXPORT_SYMBOL(change_bit); EXPORT_SYMBOL(test_and_change_bit); + +#ifdef CONFIG_FUNCTION_TRACER +EXPORT_SYMBOL(_mcount); +#endif diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S new file mode 100644 index 0000000..0ac31c8 --- /dev/null +++ b/arch/arm64/kernel/entry-ftrace.S @@ -0,0 +1,175 @@ +/* + * arch/arm64/kernel/entry-ftrace.S + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/linkage.h> +#include <asm/ftrace.h> +#include <asm/insn.h> + +/* + * Gcc with -pg will put the following code in the beginning of each function: + * mov x0, x30 + * bl _mcount + * [function's body ...] + * "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic + * ftrace is enabled. + * + * Please note that x0 as an argument will not be used here because we can + * get lr(x30) of instrumented function at any time by winding up call stack + * as long as the kernel is compiled without -fomit-frame-pointer. + * (or CONFIG_FRAME_POINTER, this is forced on arm64) + * + * stack layout after mcount_enter in _mcount(): + * + * current sp/fp => 0:+-----+ + * in _mcount() | x29 | -> instrumented function's fp + * +-----+ + * | x30 | -> _mcount()'s lr (= instrumented function's pc) + * old sp => +16:+-----+ + * when instrumented | | + * function calls | ... | + * _mcount() | | + * | | + * instrumented => +xx:+-----+ + * function's fp | x29 | -> parent's fp + * +-----+ + * | x30 | -> instrumented function's lr (= parent's pc) + * +-----+ + * | ... | + */ + + .macro mcount_enter + stp x29, x30, [sp, #-16]! + mov x29, sp + .endm + + .macro mcount_exit + ldp x29, x30, [sp], #16 + ret + .endm + + .macro mcount_adjust_addr rd, rn + sub \rd, \rn, #AARCH64_INSN_SIZE + .endm + + /* for instrumented function's parent */ + .macro mcount_get_parent_fp reg + ldr \reg, [x29] + ldr \reg, [\reg] + .endm + + /* for instrumented function */ + .macro mcount_get_pc0 reg + mcount_adjust_addr \reg, x30 + .endm + + .macro mcount_get_pc reg + ldr \reg, [x29, #8] + mcount_adjust_addr \reg, \reg + .endm + + .macro mcount_get_lr reg + ldr \reg, [x29] + ldr \reg, [\reg, #8] + mcount_adjust_addr \reg, \reg + .endm + + .macro mcount_get_lr_addr reg + ldr \reg, [x29] + add \reg, \reg, #8 + .endm + +/* + * void _mcount(unsigned long return_address) + * @return_address: return address to instrumented function + * + * This function makes calls, if enabled, to: + * - tracer function to probe instrumented function's entry, + * - ftrace_graph_caller to set up an exit hook + */ +ENTRY(_mcount) +#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST + ldr x0, =ftrace_trace_stop + ldr x0, [x0] // if ftrace_trace_stop + ret // return; +#endif + mcount_enter + + ldr x0, =ftrace_trace_function + ldr x2, [x0] + adr x0, ftrace_stub + cmp x0, x2 // if (ftrace_trace_function + b.eq skip_ftrace_call // != ftrace_stub) { + + mcount_get_pc x0 // function's pc + mcount_get_lr x1 // function's lr (= parent's pc) + blr x2 // (*ftrace_trace_function)(pc, lr); + +#ifndef CONFIG_FUNCTION_GRAPH_TRACER +skip_ftrace_call: // return; + mcount_exit // } +#else + mcount_exit // return; + // } +skip_ftrace_call: + ldr x1, =ftrace_graph_return + ldr x2, [x1] // if ((ftrace_graph_return + cmp x0, x2 // != ftrace_stub) + b.ne ftrace_graph_caller + + ldr x1, =ftrace_graph_entry // || (ftrace_graph_entry + ldr x2, [x1] // != ftrace_graph_entry_stub)) + ldr x0, =ftrace_graph_entry_stub + cmp x0, x2 + b.ne ftrace_graph_caller // ftrace_graph_caller(); + + mcount_exit +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ +ENDPROC(_mcount) + +ENTRY(ftrace_stub) + ret +ENDPROC(ftrace_stub) + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +/* + * void ftrace_graph_caller(void) + * + * Called from _mcount() or ftrace_caller() when function_graph tracer is + * selected. + * This function w/ prepare_ftrace_return() fakes link register's value on + * the call stack in order to intercept instrumented function's return path + * and run return_to_handler() later on its exit. + */ +ENTRY(ftrace_graph_caller) + mcount_get_lr_addr x0 // pointer to function's saved lr + mcount_get_pc x1 // function's pc + mcount_get_parent_fp x2 // parent's fp + bl prepare_ftrace_return // prepare_ftrace_return(&lr, pc, fp) + + mcount_exit +ENDPROC(ftrace_graph_caller) + +/* + * void return_to_handler(void) + * + * Run ftrace_return_to_handler() before going back to parent. + * @fp is checked against the value passed by ftrace_graph_caller() + * only when CONFIG_FUNCTION_GRAPH_FP_TEST is enabled. + */ + .global return_to_handler +return_to_handler: + str x0, [sp, #-16]! + mov x0, x29 // parent's fp + bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp); + mov x30, x0 // restore the original return address + ldr x0, [sp], #16 + ret +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c new file mode 100644 index 0000000..a559ab8 --- /dev/null +++ b/arch/arm64/kernel/ftrace.c @@ -0,0 +1,64 @@ +/* + * arch/arm64/kernel/ftrace.c + * + * Copyright (C) 2013 Linaro Limited + * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/ftrace.h> +#include <linux/swab.h> +#include <linux/uaccess.h> + +#include <asm/cacheflush.h> +#include <asm/ftrace.h> +#include <asm/insn.h> + +#ifdef CONFIG_FUNCTION_GRAPH_TRACER +/* + * function_graph tracer expects ftrace_return_to_handler() to be called + * on the way back to parent. For this purpose, this function is called + * in _mcount() or ftrace_caller() to replace return address (*parent) on + * the call stack to return_to_handler. + * + * Note that @frame_pointer is used only for sanity check later. + */ +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; + struct ftrace_graph_ent trace; + int err; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + return; + + /* + * Note: + * No protection against faulting at *parent, which may be seen + * on other archs. It's unlikely on AArch64. + */ + old = *parent; + *parent = return_hooker; + + trace.func = self_addr; + trace.depth = current->curr_ret_stack + 1; + + /* Only trace if the calling function expects to */ + if (!ftrace_graph_entry(&trace)) { + *parent = old; + return; + } + + err = ftrace_push_return_trace(old, self_addr, &trace.depth, + frame_pointer); + if (err == -EBUSY) { + *parent = old; + return; + } +} +#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
This patch implements arm64 specific part to support function tracers, such as function (CONFIG_FUNCTION_TRACER), function_graph (CONFIG_FUNCTION_GRAPH_TRACER) and function profiler (CONFIG_FUNCTION_PROFILER). With 'function' tracer, all the functions in the kernel are traced with timestamps in ${sysfs}/tracing/trace. If function_graph tracer is specified, call graph is generated. The kernel must be compiled with -pg option so that _mcount() is inserted at the beginning of functions. This function is called on every function's entry as long as tracing is enabled. In addition, function_graph tracer also needs to be able to probe function's exit. ftrace_graph_caller() & return_to_handler do this by faking link register's value to intercept function's return path. More details on architecture specific requirements are described in Documentation/trace/ftrace-design.txt. Reviewed-by: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com> Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org> --- arch/arm64/Kconfig | 2 + arch/arm64/include/asm/ftrace.h | 23 +++++ arch/arm64/kernel/Makefile | 4 + arch/arm64/kernel/arm64ksyms.c | 4 + arch/arm64/kernel/entry-ftrace.S | 175 ++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/ftrace.c | 64 ++++++++++++++ 6 files changed, 272 insertions(+) create mode 100644 arch/arm64/include/asm/ftrace.h create mode 100644 arch/arm64/kernel/entry-ftrace.S create mode 100644 arch/arm64/kernel/ftrace.c