selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 107 insertions, 0 deletions

diff --git a/tools/perf/util/setup.py b/tools/perf/util/setup.py
new file mode 100644
index 000000000..a0ce76624
--- /dev/null
+++ b/tools/perf/util/setup.py
@@ -0,0 +1,107 @@
+from os import getenv, path
+from subprocess import Popen, PIPE
+from re import sub
+import shlex
+
+cc = getenv("CC")
+assert cc, "Environment variable CC not set"
+
+# Check if CC has options, as is the case in yocto, where it uses CC="cc --sysroot..."
+cc_tokens = cc.split()
+if len(cc_tokens) > 1:
+    cc = cc_tokens[0]
+    cc_options = " ".join([str(e) for e in cc_tokens[1:]]) + " "
+else:
+    cc_options = ""
+
+# ignore optional stderr could be None as it is set to PIPE to avoid that.
+# mypy: disable-error-code="union-attr"
+cc_is_clang = b"clang version" in Popen([cc, "-v"], stderr=PIPE).stderr.readline()
+
+srctree = getenv('srctree')
+assert srctree, "Environment variable srctree, for the Linux sources, not set"
+src_feature_tests  = f'{srctree}/tools/build/feature'
+
+def clang_has_option(option):
+    error_substrings = (
+        b"unknown argument",
+        b"is not supported",
+        b"unknown warning option"
+    )
+    cmd = shlex.split(f"{cc} {cc_options} {option}") + [
+        "-o", "/dev/null",
+        path.join(src_feature_tests, "test-hello.c")
+    ]
+    cc_output = Popen(cmd, stderr=PIPE).stderr.readlines()
+    return not any(any(error in line for error in error_substrings) for line in cc_output)
+
+if cc_is_clang:
+    from sysconfig import get_config_vars
+    vars = get_config_vars()
+    for var in ('CFLAGS', 'OPT'):
+        vars[var] = sub("-specs=[^ ]+", "", vars[var])
+        if not clang_has_option("-mcet"):
+            vars[var] = sub("-mcet", "", vars[var])
+        if not clang_has_option("-fcf-protection"):
+            vars[var] = sub("-fcf-protection", "", vars[var])
+        if not clang_has_option("-fstack-clash-protection"):
+            vars[var] = sub("-fstack-clash-protection", "", vars[var])
+        if not clang_has_option("-fstack-protector-strong"):
+            vars[var] = sub("-fstack-protector-strong", "", vars[var])
+        if not clang_has_option("-fno-semantic-interposition"):
+            vars[var] = sub("-fno-semantic-interposition", "", vars[var])
+        if not clang_has_option("-ffat-lto-objects"):
+            vars[var] = sub("-ffat-lto-objects", "", vars[var])
+        if not clang_has_option("-ftree-loop-distribute-patterns"):
+            vars[var] = sub("-ftree-loop-distribute-patterns", "", vars[var])
+        if not clang_has_option("-gno-variable-location-views"):
+            vars[var] = sub("-gno-variable-location-views", "", vars[var])
+
+from setuptools import setup, Extension
+
+from setuptools.command.build_ext   import build_ext   as _build_ext
+from setuptools.command.install_lib import install_lib as _install_lib
+
+class build_ext(_build_ext):
+    def finalize_options(self):
+        _build_ext.finalize_options(self)
+        self.build_lib  = build_lib
+        self.build_temp = build_tmp
+
+class install_lib(_install_lib):
+    def finalize_options(self):
+        _install_lib.finalize_options(self)
+        self.build_dir = build_lib
+
+
+# switch off several checks (need to be at the end of cflags list)
+extra_cflags = ['-fno-strict-aliasing', '-Wno-write-strings', '-Wno-unused-parameter', '-Wno-redundant-decls' ]
+if cc_is_clang:
+    extra_cflags += ["-Wno-unused-command-line-argument" ]
+    if clang_has_option("-Wno-cast-function-type-mismatch"):
+        extra_cflags += ["-Wno-cast-function-type-mismatch" ]
+else:
+    extra_cflags += ['-Wno-cast-function-type' ]
+
+# The python headers have mixed code with declarations (decls after asserts, for instance)
+extra_cflags += [ "-Wno-declaration-after-statement" ]
+
+src_perf  = f'{srctree}/tools/perf'
+build_lib = getenv('PYTHON_EXTBUILD_LIB')
+build_tmp = getenv('PYTHON_EXTBUILD_TMP')
+
+perf = Extension('perf',
+                 sources = [ src_perf + '/util/python.c' ],
+		         include_dirs = ['util/include'],
+		         extra_compile_args = extra_cflags,
+                 )
+
+setup(name='perf',
+      version='0.1',
+      description='Interface with the Linux profiling infrastructure',
+      author='Arnaldo Carvalho de Melo',
+      author_email='acme@redhat.com',
+      license='GPLv2',
+      url='http://perf.wiki.kernel.org',
+      ext_modules=[perf],
+      cmdclass={'build_ext': build_ext, 'install_lib': install_lib})