From 65b0aac4125c18280efbda38174ec14bcef887b2 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Wed, 16 Sep 2026 11:43:22 -0700 Subject: objtool/klp: Add test for vmlinux relocs in a patched module The kernel refuses a module-targeted klp relocation which names a vmlinux symbol. An EXPORT_SYMBOL_FOR_MODULES() symbol needs a klp relocation, so patching a module function that references one only loads if klp diff files that relocation under vmlinux rather than under the patched module. This fails at load, not at build: klp-build produces a module and static checks of it find nothing wrong. Hence the assertion on which object the relocation is filed against. Reported by Dylan Hatch, whose mod-ns-lp branch carries the kernel-side half of this case. Co-developed-by: Dylan Hatch Signed-off-by: Dylan Hatch Signed-off-by: Song Liu Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Assisted-by: Claude:claude-opus-5 Link: https://patch.msgid.link/20260916184351.2720310-30-song@kernel.org --- .../tests/generic/test-module-vmlinux-reloc.sh | 40 ++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100755 tools/objtool/tests/generic/test-module-vmlinux-reloc.sh (limited to 'tools/objtool') diff --git a/tools/objtool/tests/generic/test-module-vmlinux-reloc.sh b/tools/objtool/tests/generic/test-module-vmlinux-reloc.sh new file mode 100755 index 000000000000..635a75f6b8ba --- /dev/null +++ b/tools/objtool/tests/generic/test-module-vmlinux-reloc.sh @@ -0,0 +1,40 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Patching a module, where the patched code references a vmlinux symbol which +# needs a klp relocation. +# +# The kernel does not allow a module-targeted klp relocation to reference a +# vmlinux symbol, and a symbol exported with EXPORT_SYMBOL_FOR_MODULES gets a +# klp relocation. Put together, filing that relocation under the patched +# module produces a patch the kernel refuses to apply to its target. +# +# So it goes under vmlinux instead, and is applied when the patch module loads +# rather than when the patched module does. That is the opposite of the rule +# for a reference to a module's symbol, which test-module-object covers; this +# is the other branch of the same decision. + +. "$(dirname "$0")/../lib.sh" + +setup +# The object being patched is a module ... +build_module_pair cross_module.c klp_testmod + +# ... and the symbol it references belongs to vmlinux, exported in a way that +# still requires a klp relocation. +export_syms +add_exports_ns vmlinux module:kvm other_mod_func +run_diff + +# Filed against vmlinux, applied when the patch loads. +assert_section __klp_relocs.vmlinux +assert_klp_sym other_mod_func vmlinux + +# Not against the patched module: that is the relocation the kernel rejects. +assert_no_section __klp_relocs.klp_testmod + +run_post_link +assert_klp_rela vmlinux .text.target +assert_no_section ".klp.rela.klp_testmod..text.target" + +pass "klp relocation to a vmlinux symbol filed under vmlinux, not the patched module" -- cgit v1.2.3