mirror of
https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git
synced 2026-10-28 18:51:56 -04:00
Merge branch 'perf-uprobes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull user-space probe instrumentation from Ingo Molnar: "The uprobes code originates from SystemTap and has been used for years in Fedora and RHEL kernels. This version is much rewritten, reviews from PeterZ, Oleg and myself shaped the end result. This tree includes uprobes support in 'perf probe' - but SystemTap (and other tools) can take advantage of user probe points as well. Sample usage of uprobes via perf, for example to profile malloc() calls without modifying user-space binaries. First boot a new kernel with CONFIG_UPROBE_EVENT=y enabled. If you don't know which function you want to probe you can pick one from 'perf top' or can get a list all functions that can be probed within libc (binaries can be specified as well): $ perf probe -F -x /lib/libc.so.6 To probe libc's malloc(): $ perf probe -x /lib64/libc.so.6 malloc Added new event: probe_libc:malloc (on 0x7eac0) You can now use it in all perf tools, such as: perf record -e probe_libc:malloc -aR sleep 1 Make use of it to create a call graph (as the flat profile is going to look very boring): $ perf record -e probe_libc:malloc -gR make [ perf record: Woken up 173 times to write data ] [ perf record: Captured and wrote 44.190 MB perf.data (~1930712 $ perf report | less 32.03% git libc-2.15.so [.] malloc | --- malloc 29.49% cc1 libc-2.15.so [.] malloc | --- malloc | |--0.95%-- 0x208eb1000000000 | |--0.63%-- htab_traverse_noresize 11.04% as libc-2.15.so [.] malloc | --- malloc | 7.15% ld libc-2.15.so [.] malloc | --- malloc | 5.07% sh libc-2.15.so [.] malloc | --- malloc | 4.99% python-config libc-2.15.so [.] malloc | --- malloc | 4.54% make libc-2.15.so [.] malloc | --- malloc | |--7.34%-- glob | | | |--93.18%-- 0x41588f | | | --6.82%-- glob | 0x41588f ... Or: $ perf report -g flat | less # Overhead Command Shared Object Symbol # ........ ............. ............. .......... # 32.03% git libc-2.15.so [.] malloc 27.19% malloc 29.49% cc1 libc-2.15.so [.] malloc 24.77% malloc 11.04% as libc-2.15.so [.] malloc 11.02% malloc 7.15% ld libc-2.15.so [.] malloc 6.57% malloc ... The core uprobes design is fairly straightforward: uprobes probe points register themselves at (inode:offset) addresses of libraries/binaries, after which all existing (or new) vmas that map that address will have a software breakpoint injected at that address. vmas are COW-ed to preserve original content. The probe points are kept in an rbtree. If user-space executes the probed inode:offset instruction address then an event is generated which can be recovered from the regular perf event channels and mmap-ed ring-buffer. Multiple probes at the same address are supported, they create a dynamic callback list of event consumers. The basic model is further complicated by the XOL speedup: the original instruction that is probed is copied (in an architecture specific fashion) and executed out of line when the probe triggers. The XOL area is a single vma per process, with a fixed number of entries (which limits probe execution parallelism). The API: uprobes are installed/removed via /sys/kernel/debug/tracing/uprobe_events, the API is integrated to align with the kprobes interface as much as possible, but is separate to it. Injecting a probe point is privileged operation, which can be relaxed by setting perf_paranoid to -1. You can use multiple probes as well and mix them with kprobes and regular PMU events or tracepoints, when instrumenting a task." Fix up trivial conflicts in mm/memory.c due to previous cleanup of unmap_single_vma(). * 'perf-uprobes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits) perf probe: Detect probe target when m/x options are absent perf probe: Provide perf interface for uprobes tracing: Fix kconfig warning due to a typo tracing: Provide trace events interface for uprobes tracing: Extract out common code for kprobes/uprobes trace events tracing: Modify is_delete, is_return from int to bool uprobes/core: Decrement uprobe count before the pages are unmapped uprobes/core: Make background page replacement logic account for rss_stat counters uprobes/core: Optimize probe hits with the help of a counter uprobes/core: Allocate XOL slots for uprobes use uprobes/core: Handle breakpoint and singlestep exceptions uprobes/core: Rename bkpt to swbp uprobes/core: Make order of function parameters consistent across functions uprobes/core: Make macro names consistent uprobes: Update copyright notices uprobes/core: Move insn to arch specific structure uprobes/core: Remove uprobe_opcode_sz uprobes/core: Make instruction tables volatile uprobes: Move to kernel/events/ uprobes/core: Clean up, refactor and improve the code ...
This commit is contained in:
Linus Torvalds
commit
654443e20d
30 changed files with 5048 additions and 979 deletions
113
Documentation/trace/uprobetracer.txt
Normal file
113
Documentation/trace/uprobetracer.txt
Normal file
|
|
@ -0,0 +1,113 @@
|
|||
Uprobe-tracer: Uprobe-based Event Tracing
|
||||
=========================================
|
||||
Documentation written by Srikar Dronamraju
|
||||
|
||||
Overview
|
||||
--------
|
||||
Uprobe based trace events are similar to kprobe based trace events.
|
||||
To enable this feature, build your kernel with CONFIG_UPROBE_EVENT=y.
|
||||
|
||||
Similar to the kprobe-event tracer, this doesn't need to be activated via
|
||||
current_tracer. Instead of that, add probe points via
|
||||
/sys/kernel/debug/tracing/uprobe_events, and enable it via
|
||||
/sys/kernel/debug/tracing/events/uprobes/<EVENT>/enabled.
|
||||
|
||||
However unlike kprobe-event tracer, the uprobe event interface expects the
|
||||
user to calculate the offset of the probepoint in the object
|
||||
|
||||
Synopsis of uprobe_tracer
|
||||
-------------------------
|
||||
p[:[GRP/]EVENT] PATH:SYMBOL[+offs] [FETCHARGS] : Set a probe
|
||||
|
||||
GRP : Group name. If omitted, use "uprobes" for it.
|
||||
EVENT : Event name. If omitted, the event name is generated
|
||||
based on SYMBOL+offs.
|
||||
PATH : path to an executable or a library.
|
||||
SYMBOL[+offs] : Symbol+offset where the probe is inserted.
|
||||
|
||||
FETCHARGS : Arguments. Each probe can have up to 128 args.
|
||||
%REG : Fetch register REG
|
||||
|
||||
Event Profiling
|
||||
---------------
|
||||
You can check the total number of probe hits and probe miss-hits via
|
||||
/sys/kernel/debug/tracing/uprobe_profile.
|
||||
The first column is event name, the second is the number of probe hits,
|
||||
the third is the number of probe miss-hits.
|
||||
|
||||
Usage examples
|
||||
--------------
|
||||
To add a probe as a new event, write a new definition to uprobe_events
|
||||
as below.
|
||||
|
||||
echo 'p: /bin/bash:0x4245c0' > /sys/kernel/debug/tracing/uprobe_events
|
||||
|
||||
This sets a uprobe at an offset of 0x4245c0 in the executable /bin/bash
|
||||
|
||||
echo > /sys/kernel/debug/tracing/uprobe_events
|
||||
|
||||
This clears all probe points.
|
||||
|
||||
The following example shows how to dump the instruction pointer and %ax
|
||||
a register at the probed text address. Here we are trying to probe
|
||||
function zfree in /bin/zsh
|
||||
|
||||
# cd /sys/kernel/debug/tracing/
|
||||
# cat /proc/`pgrep zsh`/maps | grep /bin/zsh | grep r-xp
|
||||
00400000-0048a000 r-xp 00000000 08:03 130904 /bin/zsh
|
||||
# objdump -T /bin/zsh | grep -w zfree
|
||||
0000000000446420 g DF .text 0000000000000012 Base zfree
|
||||
|
||||
0x46420 is the offset of zfree in object /bin/zsh that is loaded at
|
||||
0x00400000. Hence the command to probe would be :
|
||||
|
||||
# echo 'p /bin/zsh:0x46420 %ip %ax' > uprobe_events
|
||||
|
||||
Please note: User has to explicitly calculate the offset of the probepoint
|
||||
in the object. We can see the events that are registered by looking at the
|
||||
uprobe_events file.
|
||||
|
||||
# cat uprobe_events
|
||||
p:uprobes/p_zsh_0x46420 /bin/zsh:0x00046420 arg1=%ip arg2=%ax
|
||||
|
||||
The format of events can be seen by viewing the file events/uprobes/p_zsh_0x46420/format
|
||||
|
||||
# cat events/uprobes/p_zsh_0x46420/format
|
||||
name: p_zsh_0x46420
|
||||
ID: 922
|
||||
format:
|
||||
field:unsigned short common_type; offset:0; size:2; signed:0;
|
||||
field:unsigned char common_flags; offset:2; size:1; signed:0;
|
||||
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
|
||||
field:int common_pid; offset:4; size:4; signed:1;
|
||||
field:int common_padding; offset:8; size:4; signed:1;
|
||||
|
||||
field:unsigned long __probe_ip; offset:12; size:4; signed:0;
|
||||
field:u32 arg1; offset:16; size:4; signed:0;
|
||||
field:u32 arg2; offset:20; size:4; signed:0;
|
||||
|
||||
print fmt: "(%lx) arg1=%lx arg2=%lx", REC->__probe_ip, REC->arg1, REC->arg2
|
||||
|
||||
Right after definition, each event is disabled by default. For tracing these
|
||||
events, you need to enable it by:
|
||||
|
||||
# echo 1 > events/uprobes/enable
|
||||
|
||||
Lets disable the event after sleeping for some time.
|
||||
# sleep 20
|
||||
# echo 0 > events/uprobes/enable
|
||||
|
||||
And you can see the traced information via /sys/kernel/debug/tracing/trace.
|
||||
|
||||
# cat trace
|
||||
# tracer: nop
|
||||
#
|
||||
# TASK-PID CPU# TIMESTAMP FUNCTION
|
||||
# | | | | |
|
||||
zsh-24842 [006] 258544.995456: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
|
||||
zsh-24842 [007] 258545.000270: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
|
||||
zsh-24842 [002] 258545.043929: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
|
||||
zsh-24842 [004] 258547.046129: p_zsh_0x46420: (0x446420) arg1=446421 arg2=79
|
||||
|
||||
Each line shows us probes were triggered for a pid 24842 with ip being
|
||||
0x446421 and contents of ax register being 79.
|
||||
Loading…
Reference in a new issue