[PATCH v2 29/58] objtool/klp: Add test for vmlinux relocs in a patched module
From: Song Liu <song@kernel.org>
Date: 2026-09-14 06:28:04
Subsystem:
objtool, the rest · Maintainers:
Josh Poimboeuf, Peter Zijlstra, Linus Torvalds
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. Signed-off-by: Dylan Hatch <redacted> Assisted-by: Claude:claude-opus-5 Signed-off-by: Song Liu <song@kernel.org> --- .../generic/test-module-vmlinux-reloc.sh | 40 +++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100755 tools/objtool/tests/generic/test-module-vmlinux-reloc.sh
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"
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2.53.0-Meta