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From: Robin Jarry <rjarry@redhat.com>
To: dev@dpdk.org
Cc: Robin Jarry <rjarry@redhat.com>,
Olivier Matz <olivier.matz@6wind.com>
Subject: [PATCH] usertools/pmdinfo: remove dependency to ldd
Date: Thu, 13 Oct 2022 15:41:25 +0200
Message-Id: <20221013134125.448437-1-rjarry@redhat.com>
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Some environments (buildroot) do not have the ldd utility installed by
default. However, ldd is often only a wrapper shell script that actually
checks that the arguments are valid ELF files and executes them with
the LD_TRACE_LOADED_OBJECTS=1 variable set in the environment.
Since ld.so is the actual ELF interpreter which is loaded first when
executing a program, executing any dynamic ELF program/library with that
variable set will cause all dependent dynamic libraries to be printed
and ld.so will exit before even running main.
Excerpt from ld.so(7) man page:
LD_TRACE_LOADED_OBJECTS
If set (to any value), causes the program to list its dynamic
dependencies, as if run by ldd(1), instead of running normally.
Change dpdk-pmdinfo.py to actually "execute" the files provided on the
command line with LD_TRACE_LOADED_OBJECTS=1 set. Ensure that the files
are valid dynamically executable ELF programs to avoid obscure and
confusing errors.
Reported-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: Robin Jarry <rjarry@redhat.com>
---
doc/guides/tools/pmdinfo.rst | 4 ++--
usertools/dpdk-pmdinfo.py | 34 +++++++++++++++++++++++-----------
2 files changed, 25 insertions(+), 13 deletions(-)
diff --git a/doc/guides/tools/pmdinfo.rst b/doc/guides/tools/pmdinfo.rst
index a9217de4eef2..1406b9c442eb 100644
--- a/doc/guides/tools/pmdinfo.rst
+++ b/doc/guides/tools/pmdinfo.rst
@@ -37,8 +37,8 @@ Arguments
.. option:: ELF_FILE
- DPDK application binary or dynamic library.
- Any linked ``librte_*.so`` library (as reported by ``ldd``) will also be analyzed.
+ Executable DPDK application binary or dynamic library.
+ Any linked ``librte_*.so`` library (as reported by ``ld.so``) will also be analyzed.
Can be specified multiple times.
Environment Variables
diff --git a/usertools/dpdk-pmdinfo.py b/usertools/dpdk-pmdinfo.py
index 67d023a04711..01bb90666bcc 100755
--- a/usertools/dpdk-pmdinfo.py
+++ b/usertools/dpdk-pmdinfo.py
@@ -97,9 +97,9 @@ def parse_args() -> argparse.Namespace:
"elf_files",
metavar="ELF_FILE",
nargs="+",
- type=existing_file,
+ type=executable_elf_file,
help="""
- DPDK application binary or dynamic library.
+ Executable DPDK application binary or dynamic library.
""",
)
return parser.parse_args()
@@ -180,14 +180,24 @@ def get_plugin_libs(binaries: Iterable[Path]) -> Iterator[Path]:
# ----------------------------------------------------------------------------
-def existing_file(value: str) -> Path:
+def executable_elf_file(value: str) -> Path:
"""
- Argparse type= callback to ensure an argument points to a valid file path.
+ Argparse type= callback to ensure an argument points to a valid ELF file
+ path which can be executed.
"""
- path = Path(value)
- if not path.is_file():
- raise argparse.ArgumentTypeError(f"{value}: No such file")
- return path
+ try:
+ with open(value, "rb") as f:
+ elf = ELFFile(f)
+ if elf.header.e_type not in ("ET_DYN", "ET_EXEC"):
+ raise ELFError(f"unknown type: {elf.header.e_type!r}")
+ if not os.access(value, os.X_OK):
+ raise OSError("is not executable")
+ except ELFError as e:
+ raise argparse.ArgumentTypeError(f"{value}: invalid ELF: {e}") from e
+ except OSError as e:
+ raise argparse.ArgumentTypeError(f"{value}: {e}") from e
+
+ return Path(value)
# ----------------------------------------------------------------------------
@@ -270,7 +280,7 @@ def get_elf_strings(path: Path, section: str, prefix: str) -> Iterator[str]:
# ----------------------------------------------------------------------------
-LDD_LIB_RE = re.compile(
+LOADED_OBJECT_RE = re.compile(
r"""
^ # beginning of line
\t # tab
@@ -290,14 +300,16 @@ def get_needed_libs(path: Path) -> Iterator[Path]:
"""
Extract the dynamic library dependencies from an ELF executable.
"""
+ env = os.environ.copy()
+ env["LD_TRACE_LOADED_OBJECTS"] = "1"
with subprocess.Popen(
- ["ldd", str(path)], stdout=subprocess.PIPE, stderr=subprocess.PIPE
+ [str(path)], stdout=subprocess.PIPE, stderr=subprocess.PIPE, env=env
) as proc:
out, err = proc.communicate()
if proc.returncode != 0:
err = err.decode("utf-8").splitlines()[-1].strip()
raise Exception(f"cannot read ELF file: {err}")
- for match in LDD_LIB_RE.finditer(out.decode("utf-8")):
+ for match in LOADED_OBJECT_RE.finditer(out.decode("utf-8")):
libname, libpath = match.groups()
if libname.startswith("librte_"):
libpath = Path(libpath)
--
2.37.3