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Leo Yan cbc853c490 perf probe: Correct demangled symbols in C++ program 
[ Upstream commit 314909f13c ]

An issue can be observed when probe C++ demangled symbol with steps:

  # nm test_cpp_mangle | grep print_data
    0000000000000c94 t _GLOBAL__sub_I__Z10print_datai
    0000000000000afc T _Z10print_datai
    0000000000000b38 T _Z10print_dataR5Point

  # perf probe -x /home/niayan01/test_cpp_mangle -F --demangle
    ...
    print_data(Point&)
    print_data(int)
    ...

  # perf --debug verbose=3 probe -x test_cpp_mangle --add "test=print_data(int)"
    probe-definition(0): test=print_data(int)
    symbol:print_data(int) file:(null) line:0 offset:0 return:0 lazy:(null)
    0 arguments
    Open Debuginfo file: /home/niayan01/test_cpp_mangle
    Try to find probe point from debuginfo.
    Symbol print_data(int) address found : afc
    Matched function: print_data [2ccf]
    Probe point found: print_data+0
    Found 1 probe_trace_events.
    Opening /sys/kernel/tracing//uprobe_events write=1
    Opening /sys/kernel/tracing//README write=0
    Writing event: p:probe_test_cpp_mangle/test /home/niayan01/test_cpp_mangle:0xb38
    ...

When tried to probe symbol "print_data(int)", the log shows:

    Symbol print_data(int) address found : afc

The found address is 0xafc - which is right with verifying the output
result from nm. Afterwards when write event, the command uses offset
0xb38 in the last log, which is a wrong address.

The dwarf_diename() gets a common function name, in above case, it
returns string "print_data". As a result, the tool parses the offset
based on the common name. This leads to probe at the wrong symbol
"print_data(Point&)".

To fix the issue, use the die_get_linkage_name() function to retrieve
the distinct linkage name - this is the mangled name for the C++ case.
Based on this unique name, the tool can get a correct offset for
probing. Based on DWARF doc, it is possible the linkage name is missed
in the DIE, it rolls back to use dwarf_diename().

After:

  # perf --debug verbose=3 probe -x test_cpp_mangle --add "test=print_data(int)"
    probe-definition(0): test=print_data(int)
    symbol:print_data(int) file:(null) line:0 offset:0 return:0 lazy:(null)
    0 arguments
    Open Debuginfo file: /home/niayan01/test_cpp_mangle
    Try to find probe point from debuginfo.
    Symbol print_data(int) address found : afc
    Matched function: print_data [2d06]
    Probe point found: print_data+0
    Found 1 probe_trace_events.
    Opening /sys/kernel/tracing//uprobe_events write=1
    Opening /sys/kernel/tracing//README write=0
    Writing event: p:probe_test_cpp_mangle/test /home/niayan01/test_cpp_mangle:0xafc
    Added new event:
      probe_test_cpp_mangle:test (on print_data(int) in /home/niayan01/test_cpp_mangle)

    You can now use it in all perf tools, such as:

            perf record -e probe_test_cpp_mangle:test -aR sleep 1

  # perf --debug verbose=3 probe -x test_cpp_mangle --add "test2=print_data(Point&)"
    probe-definition(0): test2=print_data(Point&)
    symbol:print_data(Point&) file:(null) line:0 offset:0 return:0 lazy:(null)
    0 arguments
    Open Debuginfo file: /home/niayan01/test_cpp_mangle
    Try to find probe point from debuginfo.
    Symbol print_data(Point&) address found : b38
    Matched function: print_data [2ccf]
    Probe point found: print_data+0
    Found 1 probe_trace_events.
    Opening /sys/kernel/tracing//uprobe_events write=1
    Parsing probe_events: p:probe_test_cpp_mangle/test /home/niayan01/test_cpp_mangle:0x0000000000000afc
    Group:probe_test_cpp_mangle Event:test probe:p
    Opening /sys/kernel/tracing//README write=0
    Writing event: p:probe_test_cpp_mangle/test2 /home/niayan01/test_cpp_mangle:0xb38
    Added new event:
      probe_test_cpp_mangle:test2 (on print_data(Point&) in /home/niayan01/test_cpp_mangle)

    You can now use it in all perf tools, such as:

            perf record -e probe_test_cpp_mangle:test2 -aR sleep 1

Fixes: fb1587d869 ("perf probe: List probes with line number and file name")
Signed-off-by: Leo Yan <leo.yan@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20241012141432.877894-1-leo.yan@arm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-12-09 10:32:25 +01:00
arch arm64: dts: qcom: sc8180x: Add a SoC-specific compatible to cpufreq-hw 2024-12-09 10:32:22 +01:00
block block: fix bio_split_rw_at to take zone_write_granularity into account 2024-12-09 10:31:45 +01:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-09 10:31:48 +01:00
Documentation dt-bindings: clock: axi-clkgen: include AXI clk 2024-12-09 10:32:22 +01:00
drivers PCI: Fix reset_method_store() memory leak 2024-12-09 10:32:24 +01:00
fs f2fs: fix to account dirty data in __get_secs_required() 2024-12-09 10:32:25 +01:00
include netpoll: Use rcu_access_pointer() in netpoll_poll_lock 2024-12-09 10:32:12 +01:00
init initramfs: avoid filename buffer overrun 2024-12-09 10:31:44 +01:00
io_uring io_uring: fix possible deadlock in io_register_iowq_max_workers() 2024-11-17 15:08:58 +01:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel trace/trace_event_perf: remove duplicate samples on the first tracepoint event 2024-12-09 10:32:12 +01:00
lib lib/buildid: Fix build ID parsing logic 2024-11-22 15:38:36 +01:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/damon/core: copy nr_accesses when splitting region 2024-11-22 15:38:37 +01:00
net bpf: fix recursive lock when verdict program return SK_PASS 2024-12-09 10:32:12 +01:00
rust rust: sync: require T: Sync for LockedBy::access 2024-10-10 11:57:44 +02:00
samples bpf: Fix the xdp_adjust_tail sample prog issue 2024-12-09 10:32:02 +01:00
scripts checkpatch: always parse orig_commit in fixes tag 2024-12-09 10:32:18 +01:00
security ima: fix buffer overrun in ima_eventdigest_init_common 2024-11-22 15:38:34 +01:00
sound ALSA: 6fire: Release resources at card release 2024-12-09 10:32:11 +01:00
tools perf probe: Correct demangled symbols in C++ program 2024-12-09 10:32:25 +01:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock 2024-10-04 16:29:47 +02:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Remove *.orig pattern from .gitignore 2024-10-04 16:29:44 +02:00
.mailmap 20 hotfixes. 12 are cc:stable and the remainder address post-6.5 issues 2023-10-24 09:52:16 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS membarrier: riscv: Add full memory barrier in switch_mm() 2024-09-12 11:11:45 +02:00
Makefile Linux 6.6.63 2024-11-22 15:38:37 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.