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Athira Rajeev 556b58c191 perf probe: Pick the correct dwarf die while adding probe points 
Perf probe on vfs_fstatat fails as below on a powerpc system

  $ ./perf probe -nf --max-probes=512 -a 'vfs_fstatat $params'
  Segmentation fault (core dumped)

This is observed while running perftool-testsuite_probe testcase.

While running with verbose, its observed that segfault happens
at:

   synthesize_probe_trace_arg ()
   synthesize_probe_trace_command ()
   probe_file.add_event ()
   apply_perf_probe_events ()
   __cmd_probe ()
   cmd_probe ()
   run_builtin ()
   handle_internal_command ()
   main ()

Code in synthesize_probe_trace_arg() access a null value and results in
segfault. Data structure which is null:
struct probe_trace_arg arg->value

We are hitting a case where arg->value is null in probe point:
"vfs_fstatat $params". This is happening since 'commit e896474fe4
("getname_maybe_null() - the third variant of pathname copy-in")'
Before the commit, probe point for vfs_fstatat was getting added only
for one location:

  Writing event: p:probe/vfs_fstatat _text+6345404 dfd=%gpr3:s32 filename=%gpr4:x64 stat=%gpr5:x64 flags=%gpr6:s32

With this change, vfs_fstatat code is inlined for other locations in the
code:
  Probe point found: __do_sys_lstat64+48
  Probe point found: __do_sys_stat64+48
  Probe point found: __do_sys_newlstat+48
  Probe point found: __do_sys_newstat+48
  Probe point found: vfs_fstatat+0

When trying to find matching dwarf information entry (DIE)
from the debuginfo, the code incorrectly picks DIE which is
not referring to vfs_fstatat. Snippet from dwarf entry in vmlinux
debuginfo file.

The main abstract die is:
 <1><4214883>: Abbrev Number: 147 (DW_TAG_subprogram)
    <4214885>   DW_AT_external    : 1
    <4214885>   DW_AT_name        : (indirect string, offset: 0x17b9f3): vfs_fstatat

With formal parameters:
 <2><4214896>: Abbrev Number: 51 (DW_TAG_formal_parameter)
    <4214897>   DW_AT_name        : dfd
 <2><42148a3>: Abbrev Number: 23 (DW_TAG_formal_parameter)
    <42148a4>   DW_AT_name        : (indirect string, offset: 0x8fda9): filename
 <2><42148b0>: Abbrev Number: 23 (DW_TAG_formal_parameter)
    <42148b1>   DW_AT_name        : (indirect string, offset: 0x16bd9c): stat
 <2><42148bd>: Abbrev Number: 23 (DW_TAG_formal_parameter)
    <42148be>   DW_AT_name        : (indirect string, offset: 0x39832b): flags

While collecting variables/parameters for a probe point, the function
copy_variables_cb() also looks at dwarf debug entries based on the
instruction address. Snippet

        if (dwarf_haspc(die_mem, vf->pf->addr))
                return DIE_FIND_CB_CONTINUE;
        else
                return DIE_FIND_CB_SIBLING;

But incase of inlined function instance for vfs_fstatat, there are two
entries which has the instruction address entry point as same.

Instance 1: which is for vfs_fstatat and DW_AT_abstract_origin points to
0x4214883 (reference above for main abstract die)

 <3><42131fa>: Abbrev Number: 59 (DW_TAG_inlined_subroutine)
    <42131fb>   DW_AT_abstract_origin: <0x4214883>
    <42131ff>   DW_AT_entry_pc    : 0xc00000000062b1e0

Instance 2: which is not for vfs_fstatat but for getname

 <5><4213270>: Abbrev Number: 39 (DW_TAG_inlined_subroutine)
    <4213271>   DW_AT_abstract_origin: <0x4215b6b>
    <4213275>   DW_AT_entry_pc    : 0xc00000000062b1e0

But the copy_variables_cb() continues to add parameters from second
instance also based on the dwarf_haspc() check. This results in
formal parameters for getname also appended to params. But while
filling in the args->value for these parameters, since these args
are not part of dwarf with offset "42131fa". Hence value will be
null. This incorrect args results in segfault when value field is
accessed.

Save the dwarf dieoffset of the actual DW_TAG_subprogram as part of
"struct probe_finder". In copy_variables_cb(), include check to make
sure the DW_AT_abstract_origin points to the correct entry if the
dwarf_haspc() matches the instruction address.

Signed-off-by: Athira Rajeev <atrajeev@linux.ibm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://lore.kernel.org/r/20250225123042.37263-1-atrajeev@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
2025-02-26 14:25:14 -08:00
arch sh updates for v6.14 2025-02-02 10:40:27 -08:00
block block-6.14-20250131 2025-01-31 11:49:30 -08:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
Documentation 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
drivers 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
fs assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
include assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
init Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
io_uring io_uring-6.14-20250131 2025-01-31 11:29:23 -08:00
ipc treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
kernel 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
lib 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
net assorted stuff for this merge window 2025-02-01 15:07:56 -08:00
rust Kbuild updates for v6.14 2025-01-31 12:07:07 -08:00
samples AT_EXECVE_CHECK update for v6.14-rc1 (fix1) 2025-01-31 17:12:31 -08:00
scripts 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
security treewide: const qualify ctl_tables where applicable 2025-01-28 13:48:37 +01:00
sound sound fixes for 6.14-rc1 2025-01-31 09:17:02 -08:00
tools perf probe: Pick the correct dwarf die while adding probe points 2025-02-26 14:25:14 -08:00
usr kbuild: Drop support for include/asm-<arch> in headers_check.pl 2024-12-21 11:43:17 +09:00
virt Merge branch 'kvm-mirror-page-tables' into HEAD 2025-01-20 07:15:58 -05:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-01-10 00:17:25 +01:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: use host dylib naming convention to support macOS 2025-01-10 01:01:24 +01:00
.mailmap 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
.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 Mainly individually changelogged singleton patches. The patch series in 2025-01-26 17:50:53 -08:00
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 21 hotfixes. 8 are cc:stable and the remainder address post-6.13 issues. 2025-02-01 09:49:20 -08:00
Makefile Linux 6.14-rc1 2025-02-02 15:39:26 -08:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.