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, 39 insertions, 0 deletions

diff --git a/tools/objtool/Build b/tools/objtool/Build
new file mode 100644
index 000000000..59f948628
--- /dev/null
+++ b/tools/objtool/Build
@@ -0,0 +1,39 @@
+objtool-y += arch/$(SRCARCH)/
+
+objtool-y += weak.o
+
+objtool-y += check.o
+objtool-y += special.o
+objtool-y += builtin-check.o
+objtool-y += elf.o
+objtool-y += klp-symid.o
+objtool-y += objtool.o
+
+objtool-$(BUILD_DISAS) += disas.o
+objtool-$(BUILD_DISAS) += trace.o
+
+objtool-$(BUILD_ORC) += orc_gen.o orc_dump.o
+objtool-$(BUILD_KLP) += builtin-klp.o klp-checksum.o klp-diff.o \
+			klp-post-link.o klp-sympos.o
+
+objtool-y += libstring.o
+objtool-y += libctype.o
+objtool-y += str_error_r.o
+objtool-y += librbtree.o
+objtool-y += signal.o
+
+$(OUTPUT)libstring.o: ../lib/string.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)
+
+$(OUTPUT)libctype.o: ../lib/ctype.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)
+
+$(OUTPUT)str_error_r.o: ../lib/str_error_r.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)
+
+$(OUTPUT)librbtree.o: ../lib/rbtree.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)