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, 79 insertions, 0 deletions

diff --git a/tools/testing/shared/shared.mk b/tools/testing/shared/shared.mk
new file mode 100644
index 000000000..5bcdf26c8
--- /dev/null
+++ b/tools/testing/shared/shared.mk
@@ -0,0 +1,79 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../../scripts/Makefile.arch
+
+CFLAGS += -I../shared -I. -I../../include -I../../arch/$(SRCARCH)/include \
+	  -I../../../lib -g -Og -Wall \
+	  -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined
+CFLAGS += $(EXTRA_CFLAGS)
+LDFLAGS += -fsanitize=address -fsanitize=undefined
+LDLIBS += -lpthread -lurcu
+LIBS := slab.o find_bit.o bitmap.o hweight.o vsprintf.o
+SHARED_OFILES = xarray-shared.o radix-tree.o idr.o linux.o $(LIBS)
+
+SHARED_DEPS = Makefile ../shared/shared.mk ../shared/*.h generated/map-shift.h \
+	generated/bit-length.h generated/autoconf.h \
+	../../include/linux/*.h \
+	../../include/asm/*.h \
+	../../arch/$(SRCARCH)/include/asm/*.h \
+	../../../include/linux/xarray.h \
+	../../../include/linux/maple_tree.h \
+	../../../include/linux/radix-tree.h \
+	../../../lib/radix-tree.h \
+	../../../include/linux/idr.h \
+	../../../lib/maple_tree.c \
+	../../../lib/test_maple_tree.c
+
+ifndef SHIFT
+	SHIFT=3
+endif
+
+ifeq ($(BUILD), 32)
+	CFLAGS += -m32
+	LDFLAGS += -m32
+LONG_BIT := 32
+endif
+
+ifndef LONG_BIT
+LONG_BIT := $(shell getconf LONG_BIT)
+endif
+
+%.o: ../shared/%.c
+	$(CC) -c $(CFLAGS) $< -o $@
+
+vpath %.c ../../lib
+
+$(SHARED_OFILES): $(SHARED_DEPS)
+
+radix-tree.c: ../../../lib/radix-tree.c
+	sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
+
+idr.c: ../../../lib/idr.c
+	sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@
+
+xarray-shared.o: ../shared/xarray-shared.c ../../../lib/xarray.c \
+	../../../lib/test_xarray.c
+
+maple-shared.o: ../shared/maple-shared.c ../../../lib/maple_tree.c \
+	../../../lib/test_maple_tree.c
+
+generated/autoconf.h:
+	@mkdir -p generated
+	cp ../shared/autoconf.h generated/autoconf.h
+
+generated/map-shift.h:
+	@mkdir -p generated
+	@if ! grep -qws $(SHIFT) generated/map-shift.h; then            \
+		echo "Generating $@";                                   \
+		echo "#define XA_CHUNK_SHIFT $(SHIFT)" >                \
+				generated/map-shift.h;                  \
+	fi
+
+generated/bit-length.h: FORCE
+	@mkdir -p generated
+	@if ! grep -qws CONFIG_$(LONG_BIT)BIT generated/bit-length.h; then   \
+		echo "Generating $@";                                        \
+		echo "#define CONFIG_$(LONG_BIT)BIT 1" > $@;                 \
+		echo "#define CONFIG_PHYS_ADDR_T_$(LONG_BIT)BIT 1" >> $@;    \
+	fi
+
+FORCE: ;