selftests/bpf: Add a test for objects stuck in free_by_rcu_ttracegrafted

Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first
free_bulk() starts RCU tasks trace GP and the rest of the elements are
freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear
in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and
waiting_for_gp_ttrace lists are empty.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 315 insertions, 0 deletions

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
new file mode 100755
index 000000000..ab0b8125c
--- /dev/null
+++ b/scripts/link-vmlinux.sh
@@ -0,0 +1,315 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# link vmlinux
+#
+# vmlinux is linked from the objects in vmlinux.a and $(KBUILD_VMLINUX_LIBS).
+# vmlinux.a contains objects that are linked unconditionally.
+# $(KBUILD_VMLINUX_LIBS) are archives which are linked conditionally
+# (not within --whole-archive), and do not require symbol indexes added.
+#
+# vmlinux
+#   ^
+#   |
+#   +--< vmlinux.a
+#   |
+#   +--< $(KBUILD_VMLINUX_LIBS)
+#   |    +--< lib/lib.a + more
+#   |
+#   +-< ${kallsymso} (see description in KALLSYMS section)
+#
+# vmlinux version (uname -v) cannot be updated during normal
+# descending-into-subdirs phase since we do not yet know if we need to
+# update vmlinux.
+# Therefore this step is delayed until just before final link of vmlinux.
+#
+# System.map is generated to document addresses of all kernel symbols
+
+# Error out on error
+set -e
+
+LD="$1"
+KBUILD_LDFLAGS="$2"
+LDFLAGS_vmlinux="$3"
+VMLINUX="$4"
+
+is_enabled() {
+	grep -q "^$1=y" include/config/auto.conf
+}
+
+# Nice output in kbuild format
+# Will be suppressed by "make -s"
+info()
+{
+	printf "  %-7s %s\n" "${1}" "${2}"
+}
+
+# Link of vmlinux
+# ${1} - output file
+vmlinux_link()
+{
+	local output=${1}
+	local objs
+	local libs
+	local ld
+	local ldflags
+	local ldlibs
+
+	info LD ${output}
+
+	# skip output file argument
+	shift
+
+	if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ||
+	   is_enabled CONFIG_KLP_BUILD; then
+		# Use vmlinux.o instead of performing the slow LTO link again.
+		objs=vmlinux.o
+		libs=
+	else
+		objs=vmlinux.a
+		libs="${KBUILD_VMLINUX_LIBS}"
+	fi
+
+	if is_enabled CONFIG_GENERIC_BUILTIN_DTB; then
+		objs="${objs} .builtin-dtbs.o"
+	fi
+
+	objs="${objs} .vmlinux.export.o"
+	objs="${objs} init/version-timestamp.o"
+
+	if [ "${SRCARCH}" = "um" ]; then
+		wl=-Wl,
+		ld="${CC}"
+		ldflags="${CFLAGS_vmlinux}"
+		ldlibs="-lutil -lrt -lpthread"
+	else
+		wl=
+		ld="${LD}"
+		ldflags="${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}"
+		ldlibs=
+	fi
+
+	ldflags="${ldflags} ${wl}--script=${objtree}/${KBUILD_LDS}"
+
+	# The kallsyms linking does not need debug symbols included.
+	if [ -n "${strip_debug}" ] ; then
+		ldflags="${ldflags} ${wl}--strip-debug"
+	fi
+
+	if [ -n "${generate_map}" ];  then
+		ldflags="${ldflags} ${wl}-Map=vmlinux.map"
+	fi
+
+	${ld} ${ldflags} -o ${output}					\
+		${wl}--whole-archive ${objs} ${wl}--no-whole-archive	\
+		${wl}--start-group ${libs} ${wl}--end-group		\
+		${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
+}
+
+# Check if kallsymso_prev and kallsymso differ
+# If symbol sizes within ${kallsymso} change, any symbols within vmlinux are
+# likely to shift, invalidating ${kallsymso}.
+# Since file size can remain unchanged even if symbol sizes change, compare the
+# actual symbols instead of relying on file size only.
+kallsymso_changed()
+{
+	${NM} -n "${kallsymso_prev}" > "${kallsymso_prev}.sym"
+	${NM} -n "${kallsymso}" > "${kallsymso}.sym"
+	! cmp -s "${kallsymso_prev}.sym" "${kallsymso}.sym"
+}
+
+# Create ${2}.o file with all symbols from the ${1} object file
+kallsyms()
+{
+	local kallsymopt;
+
+	if is_enabled CONFIG_KALLSYMS_ALL; then
+		kallsymopt="${kallsymopt} --all-symbols"
+	fi
+
+	if is_enabled CONFIG_64BIT || is_enabled CONFIG_RELOCATABLE; then
+		kallsymopt="${kallsymopt} --pc-relative"
+	fi
+
+	info KSYMS "${2}.S"
+	scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"
+
+	info AS "${2}.o"
+	${CC} ${NOSTDINC_FLAGS} ${LINUXINCLUDE} ${KBUILD_CPPFLAGS} \
+	      ${KBUILD_AFLAGS} ${KBUILD_AFLAGS_KERNEL} -c -o "${2}.o" "${2}.S"
+
+	kallsymso_prev="${kallsymso:-}"
+	kallsymso=${2}.o
+}
+
+# Perform kallsyms for the given temporary vmlinux.
+sysmap_and_kallsyms()
+{
+	mksysmap "${1}" "${1}.syms"
+	kallsyms "${1}.syms" "${1}.kallsyms"
+
+	kallsyms_sysmap=${1}.syms
+}
+
+# Create map file with all symbols from ${1}
+# See mksymap for additional details
+mksysmap()
+{
+	info NM ${2}
+	${NM} -n "${1}" | sed -f "${srctree}/scripts/mksysmap" > "${2}"
+}
+
+sorttable()
+{
+	${NM} -S ${1} > .tmp_vmlinux.nm-sort
+	${objtree}/scripts/sorttable -s .tmp_vmlinux.nm-sort ${1}
+}
+
+cleanup()
+{
+	rm -f .btf.*
+	rm -f .tmp_vmlinux.nm-sort
+	rm -f System.map
+	rm -f vmlinux
+	rm -f vmlinux.map
+}
+
+# Use "make V=1" to debug this script
+case "${KBUILD_VERBOSE}" in
+*1*)
+	set -x
+	;;
+esac
+
+if [ "$1" = "clean" ]; then
+	cleanup
+	exit 0
+fi
+
+${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o
+
+arch_vmlinux_o=
+if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
+	arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o
+fi
+
+btf_vmlinux_bin_o=
+btfids_vmlinux=
+kallsymso=
+strip_debug=
+generate_map=
+
+# Use "make UT=1" to trigger warnings on unused tracepoints
+case "${WARN_ON_UNUSED_TRACEPOINTS}" in
+*1*)
+	${objtree}/scripts/tracepoint-update vmlinux.o
+	;;
+esac
+
+if is_enabled CONFIG_KALLSYMS; then
+	true > .tmp_vmlinux0.syms
+	kallsyms .tmp_vmlinux0.syms .tmp_vmlinux0.kallsyms
+fi
+
+if is_enabled CONFIG_KALLSYMS || is_enabled CONFIG_DEBUG_INFO_BTF; then
+
+	# The kallsyms linking does not need debug symbols, but the BTF does.
+	if ! is_enabled CONFIG_DEBUG_INFO_BTF; then
+		strip_debug=1
+	fi
+
+	vmlinux_link .tmp_vmlinux1
+fi
+
+if is_enabled CONFIG_DEBUG_INFO_BTF; then
+	info BTF .tmp_vmlinux1
+	if ! ${CONFIG_SHELL} ${srctree}/scripts/gen-btf.sh .tmp_vmlinux1; then
+		echo >&2 "Failed to generate BTF for vmlinux"
+		echo >&2 "Try to disable CONFIG_DEBUG_INFO_BTF"
+		exit 1
+	fi
+	btf_vmlinux_bin_o=.tmp_vmlinux1.btf.o
+	btfids_vmlinux=.tmp_vmlinux1.BTF_ids
+fi
+
+if is_enabled CONFIG_KALLSYMS; then
+
+	# kallsyms support
+	# Generate section listing all symbols and add it into vmlinux
+	# It's a four step process:
+	# 0)  Generate a dummy __kallsyms with empty symbol list.
+	# 1)  Link .tmp_vmlinux1.kallsyms so it has all symbols and sections,
+	#     with a dummy __kallsyms.
+	#     Running kallsyms on that gives us .tmp_vmlinux1.kallsyms.o with
+	#     the right size
+	# 2)  Link .tmp_vmlinux2.kallsyms so it now has a __kallsyms section of
+	#     the right size, but due to the added section, some
+	#     addresses have shifted.
+	#     From here, we generate a correct .tmp_vmlinux2.kallsyms.o
+	# 3)  That link may have expanded the kernel image enough that
+	#     more linker branch stubs / trampolines had to be added, which
+	#     introduces new names, which further expands kallsyms. Do another
+	#     pass if that is the case. In theory it's possible this results
+	#     in even more stubs, but unlikely.
+	#     KALLSYMS_EXTRA_PASS=1 may also used to debug or work around
+	#     other bugs.
+	# 4)  The correct ${kallsymso} is linked into the final vmlinux.
+	#
+	# a)  Verify that the System.map from vmlinux matches the map from
+	#     ${kallsymso}.
+
+	# The kallsyms linking does not need debug symbols included.
+	strip_debug=1
+
+	sysmap_and_kallsyms .tmp_vmlinux1
+	size1=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
+
+	vmlinux_link .tmp_vmlinux2
+	sysmap_and_kallsyms .tmp_vmlinux2
+	size2=$(${CONFIG_SHELL} "${srctree}/scripts/file-size.sh" ${kallsymso})
+
+	# Due to alignment, file size of the kallsymso object file might remain
+	# unchanged even if individual symbols within change size. Changed
+	# symbol sizes can still shift other symbols, though. Therefore, don't
+	# rely on file size alone.
+	if [ $size1 -ne $size2 ] || kallsymso_changed || \
+			[ -n "${KALLSYMS_EXTRA_PASS}" ]; then
+		vmlinux_link .tmp_vmlinux3
+		sysmap_and_kallsyms .tmp_vmlinux3
+	fi
+fi
+
+strip_debug=
+
+if is_enabled CONFIG_VMLINUX_MAP; then
+	generate_map=1
+fi
+
+vmlinux_link "${VMLINUX}"
+
+if is_enabled CONFIG_DEBUG_INFO_BTF; then
+	info BTFIDS ${VMLINUX}
+	${RESOLVE_BTFIDS} --patch_btfids ${btfids_vmlinux} ${VMLINUX}
+fi
+
+mksysmap "${VMLINUX}" System.map
+
+if is_enabled CONFIG_BUILDTIME_TABLE_SORT; then
+	info SORTTAB "${VMLINUX}"
+	if ! sorttable "${VMLINUX}"; then
+		echo >&2 Failed to sort kernel tables
+		exit 1
+	fi
+fi
+
+# step a (see comment above)
+if is_enabled CONFIG_KALLSYMS; then
+	if ! cmp -s System.map "${kallsyms_sysmap}"; then
+		echo >&2 Inconsistent kallsyms data
+		echo >&2 'Try "make KALLSYMS_EXTRA_PASS=1" as a workaround'
+		exit 1
+	fi
+fi
+
+# For fixdep
+echo "${VMLINUX}: $0" > ".${VMLINUX}.d"