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| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-08-02 20:24:27 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2026-08-03 07:12:39 +0200 |
| commit | 029223d301620bc4e1086696047b0d5d6eba5edd (patch) | |
| tree | d31f07a1a1ad20afbf2d64c40a715959d3f61217 /scripts | |
| parent | f5f762fc93d0b81d30b815a2f96320909ad10eb3 (diff) | |
| download | linux-029223d301620bc4e1086696047b0d5d6eba5edd.tar.gz linux-029223d301620bc4e1086696047b0d5d6eba5edd.zip | |
objtool/klp: Add .klp.symid for sympos disambiguation
Livepatch identifies a duplicate-named symbol by its position (sympos)
among same-named kallsyms entries, which for vmlinux are counted in
ascending address order in the final linked kernel. That order can't be
reliably derived from vmlinux.o: the final link reorders sub-sections
(.text.unlikely*, .data..*, etc).
Bridge the gap with a new .klp.symid section which can be used to
correlate symbols between vmlinux.o and vmlinux so that klp-diff can
reliably determine the sympos.
The table can't survive --gc-sections: keeping it alive would keep every
duplicate-named symbol's section alive, so the reference kernel would
stop matching the one which ships. klp-build rejects
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION instead. Nothing is lost today:
x86_64 is the only HAVE_KLP_BUILD arch and doesn't select
HAVE_LD_DEAD_CODE_DATA_ELIMINATION, arm64 and s390 have never selected
it either, and on powerpc, it's still EXPERIMENTAL and disabled by every
distro kernel.
This is the build-time half of reliable vmlinux sympos computation;
"objtool klp diff" will consume the table in a subsequent commit.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: live-patching@vger.kernel.org
Link: https://patch.msgid.link/64d50f077b569f47883c015cdb7079edb068efe8.1785727106.git.jpoimboe@kernel.org
Diffstat (limited to 'scripts')
| -rw-r--r-- | scripts/Makefile.vmlinux_o | 3 | ||||
| -rwxr-xr-x | scripts/livepatch/klp-build | 5 | ||||
| -rw-r--r-- | scripts/mod/modpost.c | 1 |
3 files changed, 9 insertions, 0 deletions
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o index 527352c222ff..24a3a4fd271c 100644 --- a/scripts/Makefile.vmlinux_o +++ b/scripts/Makefile.vmlinux_o @@ -47,6 +47,9 @@ endif vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION) += --noinstr \ $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret) +# Only used for builds initiated by klp-build +vmlinux-objtool-args-$(if $(KLP_SYMIDS),y) += --klp-symids + objtool-args = $(vmlinux-objtool-args-y) --link # Link of vmlinux.o used for section mismatch analysis diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index a8c103ce7763..f94e324ff53c 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -271,6 +271,9 @@ validate_config() { [[ -v CONFIG_GCC_PLUGIN_RANDSTRUCT ]] && \ die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported" + [[ -v CONFIG_LD_DEAD_CODE_DATA_ELIMINATION ]] && \ + die "kernel option 'CONFIG_LD_DEAD_CODE_DATA_ELIMINATION' not supported" + [[ -v CONFIG_AS_IS_LLVM ]] && \ [[ "$CONFIG_AS_VERSION" -lt 200000 ]] && \ die "Clang assembler version < 20 not supported" @@ -555,6 +558,8 @@ build_kernel() { # cmd+=("KBUILD_MODPOST_WARN=1") + cmd+=("KLP_SYMIDS=1") + if [[ -v VERBOSE ]]; then cmd+=("V=1") else diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index a7b72a81d248..027944fe35b4 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -767,6 +767,7 @@ static const char *const section_white_list[] = ".llvm.call-graph-profile", /* call graph */ "__llvm_covfun", "__llvm_covmap", + ".klp.symid", /* objtool --klp-symids */ NULL }; |