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Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/li…
…nux/kernel/git/tip/linux-2.6-tip * 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (470 commits) x86: Fix comments of register/stack access functions perf tools: Replace %m with %a in sscanf hw-breakpoints: Keep track of user disabled breakpoints tracing/syscalls: Make syscall events print callbacks static tracing: Add DEFINE_EVENT(), DEFINE_SINGLE_EVENT() support to docbook perf: Don't free perf_mmap_data until work has been done perf_event: Fix compile error perf tools: Fix _GNU_SOURCE macro related strndup() build error trace_syscalls: Remove unused syscall_name_to_nr() trace_syscalls: Simplify syscall profile trace_syscalls: Remove duplicate init_enter_##sname() trace_syscalls: Add syscall_nr field to struct syscall_metadata trace_syscalls: Remove enter_id exit_id trace_syscalls: Set event_enter_##sname->data to its metadata trace_syscalls: Remove unused event_syscall_enter and event_syscall_exit perf_event: Initialize data.period in perf_swevent_hrtimer() perf probe: Simplify event naming perf probe: Add --list option for listing current probe events perf probe: Add argv_split() from lib/argv_split.c perf probe: Move probe event utility functions to probe-event.c ...
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Original file line number | Diff line number | Diff line change |
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Kprobe-based Event Tracing | ||
========================== | ||
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Documentation is written by Masami Hiramatsu | ||
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Overview | ||
-------- | ||
These events are similar to tracepoint based events. Instead of Tracepoint, | ||
this is based on kprobes (kprobe and kretprobe). So it can probe wherever | ||
kprobes can probe (this means, all functions body except for __kprobes | ||
functions). Unlike the Tracepoint based event, this can be added and removed | ||
dynamically, on the fly. | ||
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To enable this feature, build your kernel with CONFIG_KPROBE_TRACING=y. | ||
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Similar to the events tracer, this doesn't need to be activated via | ||
current_tracer. Instead of that, add probe points via | ||
/sys/kernel/debug/tracing/kprobe_events, and enable it via | ||
/sys/kernel/debug/tracing/events/kprobes/<EVENT>/enabled. | ||
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Synopsis of kprobe_events | ||
------------------------- | ||
p[:[GRP/]EVENT] SYMBOL[+offs]|MEMADDR [FETCHARGS] : Set a probe | ||
r[:[GRP/]EVENT] SYMBOL[+0] [FETCHARGS] : Set a return probe | ||
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GRP : Group name. If omitted, use "kprobes" for it. | ||
EVENT : Event name. If omitted, the event name is generated | ||
based on SYMBOL+offs or MEMADDR. | ||
SYMBOL[+offs] : Symbol+offset where the probe is inserted. | ||
MEMADDR : Address where the probe is inserted. | ||
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FETCHARGS : Arguments. Each probe can have up to 128 args. | ||
%REG : Fetch register REG | ||
@ADDR : Fetch memory at ADDR (ADDR should be in kernel) | ||
@SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol) | ||
$stackN : Fetch Nth entry of stack (N >= 0) | ||
$stack : Fetch stack address. | ||
$argN : Fetch function argument. (N >= 0)(*) | ||
$retval : Fetch return value.(**) | ||
+|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***) | ||
NAME=FETCHARG: Set NAME as the argument name of FETCHARG. | ||
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(*) aN may not correct on asmlinkaged functions and at the middle of | ||
function body. | ||
(**) only for return probe. | ||
(***) this is useful for fetching a field of data structures. | ||
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Per-Probe Event Filtering | ||
------------------------- | ||
Per-probe event filtering feature allows you to set different filter on each | ||
probe and gives you what arguments will be shown in trace buffer. If an event | ||
name is specified right after 'p:' or 'r:' in kprobe_events, it adds an event | ||
under tracing/events/kprobes/<EVENT>, at the directory you can see 'id', | ||
'enabled', 'format' and 'filter'. | ||
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enabled: | ||
You can enable/disable the probe by writing 1 or 0 on it. | ||
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format: | ||
This shows the format of this probe event. | ||
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filter: | ||
You can write filtering rules of this event. | ||
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id: | ||
This shows the id of this probe event. | ||
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Event Profiling | ||
--------------- | ||
You can check the total number of probe hits and probe miss-hits via | ||
/sys/kernel/debug/tracing/kprobe_profile. | ||
The first column is event name, the second is the number of probe hits, | ||
the third is the number of probe miss-hits. | ||
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Usage examples | ||
-------------- | ||
To add a probe as a new event, write a new definition to kprobe_events | ||
as below. | ||
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echo p:myprobe do_sys_open dfd=$arg0 filename=$arg1 flags=$arg2 mode=$arg3 > /sys/kernel/debug/tracing/kprobe_events | ||
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This sets a kprobe on the top of do_sys_open() function with recording | ||
1st to 4th arguments as "myprobe" event. As this example shows, users can | ||
choose more familiar names for each arguments. | ||
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echo r:myretprobe do_sys_open $retval >> /sys/kernel/debug/tracing/kprobe_events | ||
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This sets a kretprobe on the return point of do_sys_open() function with | ||
recording return value as "myretprobe" event. | ||
You can see the format of these events via | ||
/sys/kernel/debug/tracing/events/kprobes/<EVENT>/format. | ||
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cat /sys/kernel/debug/tracing/events/kprobes/myprobe/format | ||
name: myprobe | ||
ID: 75 | ||
format: | ||
field:unsigned short common_type; offset:0; size:2; | ||
field:unsigned char common_flags; offset:2; size:1; | ||
field:unsigned char common_preempt_count; offset:3; size:1; | ||
field:int common_pid; offset:4; size:4; | ||
field:int common_tgid; offset:8; size:4; | ||
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field: unsigned long ip; offset:16;tsize:8; | ||
field: int nargs; offset:24;tsize:4; | ||
field: unsigned long dfd; offset:32;tsize:8; | ||
field: unsigned long filename; offset:40;tsize:8; | ||
field: unsigned long flags; offset:48;tsize:8; | ||
field: unsigned long mode; offset:56;tsize:8; | ||
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print fmt: "(%lx) dfd=%lx filename=%lx flags=%lx mode=%lx", REC->ip, REC->dfd, REC->filename, REC->flags, REC->mode | ||
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You can see that the event has 4 arguments as in the expressions you specified. | ||
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echo > /sys/kernel/debug/tracing/kprobe_events | ||
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This clears all probe points. | ||
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Right after definition, each event is disabled by default. For tracing these | ||
events, you need to enable it. | ||
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echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable | ||
echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable | ||
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And you can see the traced information via /sys/kernel/debug/tracing/trace. | ||
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cat /sys/kernel/debug/tracing/trace | ||
# tracer: nop | ||
# | ||
# TASK-PID CPU# TIMESTAMP FUNCTION | ||
# | | | | | | ||
<...>-1447 [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0 | ||
<...>-1447 [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=fffffffffffffffe | ||
<...>-1447 [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6 | ||
<...>-1447 [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 | ||
<...>-1447 [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10 | ||
<...>-1447 [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3 | ||
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Each line shows when the kernel hits an event, and <- SYMBOL means kernel | ||
returns from SYMBOL(e.g. "sys_open+0x1b/0x1d <- do_sys_open" means kernel | ||
returns from do_sys_open to sys_open+0x1b). | ||
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Original file line number | Diff line number | Diff line change |
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#undef TRACE_SYSTEM | ||
#define TRACE_SYSTEM powerpc | ||
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#if !defined(_TRACE_POWERPC_H) || defined(TRACE_HEADER_MULTI_READ) | ||
#define _TRACE_POWERPC_H | ||
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#include <linux/tracepoint.h> | ||
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struct pt_regs; | ||
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TRACE_EVENT(irq_entry, | ||
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TP_PROTO(struct pt_regs *regs), | ||
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TP_ARGS(regs), | ||
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TP_STRUCT__entry( | ||
__field(struct pt_regs *, regs) | ||
), | ||
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TP_fast_assign( | ||
__entry->regs = regs; | ||
), | ||
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TP_printk("pt_regs=%p", __entry->regs) | ||
); | ||
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TRACE_EVENT(irq_exit, | ||
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TP_PROTO(struct pt_regs *regs), | ||
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TP_ARGS(regs), | ||
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TP_STRUCT__entry( | ||
__field(struct pt_regs *, regs) | ||
), | ||
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TP_fast_assign( | ||
__entry->regs = regs; | ||
), | ||
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TP_printk("pt_regs=%p", __entry->regs) | ||
); | ||
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TRACE_EVENT(timer_interrupt_entry, | ||
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TP_PROTO(struct pt_regs *regs), | ||
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TP_ARGS(regs), | ||
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TP_STRUCT__entry( | ||
__field(struct pt_regs *, regs) | ||
), | ||
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TP_fast_assign( | ||
__entry->regs = regs; | ||
), | ||
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TP_printk("pt_regs=%p", __entry->regs) | ||
); | ||
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TRACE_EVENT(timer_interrupt_exit, | ||
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TP_PROTO(struct pt_regs *regs), | ||
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TP_ARGS(regs), | ||
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TP_STRUCT__entry( | ||
__field(struct pt_regs *, regs) | ||
), | ||
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TP_fast_assign( | ||
__entry->regs = regs; | ||
), | ||
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TP_printk("pt_regs=%p", __entry->regs) | ||
); | ||
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#ifdef CONFIG_PPC_PSERIES | ||
extern void hcall_tracepoint_regfunc(void); | ||
extern void hcall_tracepoint_unregfunc(void); | ||
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TRACE_EVENT_FN(hcall_entry, | ||
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TP_PROTO(unsigned long opcode, unsigned long *args), | ||
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TP_ARGS(opcode, args), | ||
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TP_STRUCT__entry( | ||
__field(unsigned long, opcode) | ||
), | ||
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TP_fast_assign( | ||
__entry->opcode = opcode; | ||
), | ||
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TP_printk("opcode=%lu", __entry->opcode), | ||
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hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc | ||
); | ||
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TRACE_EVENT_FN(hcall_exit, | ||
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TP_PROTO(unsigned long opcode, unsigned long retval, | ||
unsigned long *retbuf), | ||
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TP_ARGS(opcode, retval, retbuf), | ||
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TP_STRUCT__entry( | ||
__field(unsigned long, opcode) | ||
__field(unsigned long, retval) | ||
), | ||
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TP_fast_assign( | ||
__entry->opcode = opcode; | ||
__entry->retval = retval; | ||
), | ||
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TP_printk("opcode=%lu retval=%lu", __entry->opcode, __entry->retval), | ||
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hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc | ||
); | ||
#endif | ||
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#endif /* _TRACE_POWERPC_H */ | ||
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#undef TRACE_INCLUDE_PATH | ||
#undef TRACE_INCLUDE_FILE | ||
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#define TRACE_INCLUDE_PATH asm | ||
#define TRACE_INCLUDE_FILE trace | ||
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#include <trace/define_trace.h> |
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