klp_reloc_needed() returns true for module exports to support
late-module patching. However, clone_reloc_klp() unconditionally
rejects symbols without a twin (i.e., new references added by the
patch), even when the symbol is a known export from Module.symvers.
Relax the check: allow new references to exported symbols by only
erroring on !twin when there is no export. The export metadata from
Module.symvers provides sufficient context to emit the klp-relocation
without a twin.
For a module export that isn't sufficient on its own though, as the
resulting klp relocation will only be resolved at patch-enable time if
the exporting module is loaded.
If the original (unpatched) module already depends on the exporting
module, the dependency is safe: the module loader ensures the dependency
is satisfied before the patched module can be loaded, so the
klp relocation target will exist.
However, if the patch introduces a reference to a module that the
original doesn't depend on, there is no such guarantee. The exporting
module could be absent or could be unloaded at any time, leading to a
relocation failure or use-after-free.
So also add a build-time check: when a new symbol reference (no twin)
targets a module export, verify that the original module already has at
least one UNDEF symbol resolving to that same exporting module. If not,
error out with a diagnostic message.
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/e0d725acb4774747f0e271308b4ca33daae2d5db.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
While cloning a reloc, klp diff calls find_export() to determine whether
the referenced symbol is exported. That decides whether the reference
needs a klp reloc, which object the klp symbol belongs to, and whether
the symbol's data needs to be copied into the patch module.
But find_export() matches purely on symbol name, so a static function or
variable which happens to share its name with an export is mistaken for
a reference to that export:
- klp_reloc_needed() creates a klp reloc pointing at the exporting
module's symbol rather than the local one. For a vmlinux export it
skips the klp reloc altogether, leaving a normal reloc which the
module loader resolves to the vmlinux symbol.
- clone_reloc() treats the symbol as external and clones it without
its data, leaving a dangling reference.
- validate_special_section_klp_reloc() attributes a static branch or
call key to the wrong module, and for a vmlinux export skips the
unsupported-key check entirely.
Exports are always global, so ignore local symbols in find_export().
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/dafc7c017d1f62e2190a20dc84a52fbfc4c70210.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
A klp relocation section is .klp.rela.<objname>.<secname>, where objname
is the object being patched.
klp-build wrongly derives objname from where the referenced symbol
lives, not where it's referenced. For a cross-module reference like
patched can_isotp code calling can.ko's can_rx_unregister(), that gives
.klp.rela.can..text rather than .klp.rela.can_isotp..text. Unless the
patch happens to patch can.ko as well, the relocation never gets applied
and the call goes off into the weeds.
Name the intermediate section __klp_relocs.<objname> so post-link can
read the patched object's name from there.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://lore.kernel.org/20260720145658.1103243-2-joe.lawrence@redhat.com
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/ee93a08f3e55e76ffa67d04e283917ddaa893f09.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Explicitly disallow the patching and referencing of init code/data.
Otherwise it could potentially introduce some odd edge cases depending
on whether the target object's init section has been freed yet (note
that the init code still exists in the target module when doing late
module patching).
Such edge cases include sympos calculation and the patching and/or
referencing of non-existent (init-freed) code/data. Not to mention the
inherent differences in behavior that occur when the init code is only
patched *some* of the time depending on module loading order or kernel
config.
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/516e14f84cfbffa27dc19d3dcf35097504097966.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
An x86 alternative with an empty replacement, e.g. the second entry of
ALTERNATIVE_2("orig", "repl", ft1, "", ft2)
has a replacementlen of zero. Its replacement offset still gets a
relocation, but the label it points at is the end of the previous
replacement, which is also the beginning of the *next* alternative's
replacement. The value is meaningless; get_alt_entry() already ignores
it for that reason.
klp diff doesn't ignore it. When such an alternative belongs to a
changed function, cloning its relocations drags in the unrelated
neighboring replacement, along with everything that replacement
references. On an x86 clang/lto build an empty alternative in
meminfo_proc_show() pulled in the replacement of an alternative in
proc_kcore_init(), silently emitting a klp relocation against init text
which has long since been freed by the time the patch is applied.
Add arch_alt_ignore_new_reloc() and skip such relocations when cloning.
This has to be arch specific: on arm64 a zero-length replacement instead
identifies an alternative callback, whose replacement offset points at
the callback function and must be preserved.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/7a885b70974795c3417f3358869e62aafd4ef783.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
create_fake_symbols() sizes each ANNOTATE_DATA_SPECIAL entry from the
offset of the next annotation, falling back to the end of the section
for the last entry. But the last entry is detected by a zero size,
which also happens for an *empty* entry: ALTERNATIVE(oldinstr, "", ft)
still annotates its zero-length replacement, at the same offset as the
next entry's annotation.
So every empty replacement gets a fake symbol spanning the entire rest
of .altinstr_replacement. That's harmless today only because
find_symbol_containing() picks the smaller of two overlapping symbols.
Track whether a next annotation was found rather than inferring it from
the size. A zero-length fake symbol is fine: find_symbol_containing()
skips those, so the properly sized symbol at the same offset still wins.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/913e691c5009397df832c7c9a18cd5cf71b42737.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Testing klp-build with arm64 produced the following linker error during
the original kernel build:
`__notrim.1' referenced in section `.klp.symid' of vmlinux.o: defined in discarded section `.no_trim_symbol' of vmlinux.o
symbol_get() puts a static __notrim[] in .no_trim_symbol, which GCC
names __notrim.1, __notrim.2, etc. Two or more built-in translation
units calling symbol_get() thus produce duplicate names, resulting in
corresponding .klp.symid references which trigger the above error.
Add .no_trim_symbol to the discarded section list so its symbols don't
get symids.
Note this issue is not specific to arm64: it just needs two built-in
symbol_get() callers. arm64 trips over it easily because it has KVM
always compiled in vmlinux, whereas on x86 it's typically a module.
Fixes: 029223d301 ("objtool/klp: Add .klp.symid for sympos disambiguation")
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/5a3cc4cded743167dd0878220201d80f7e48e5d7.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
find_sympos() calculates a sympos used by livepatch to disambiguate
duplicately-named symbols. For function symbols, there's a hack which
counts .text.unlikely symbols before other .text symbols, matching the
linker script's section ordering.
Not only is the hack fragile, data symbols can have the same problem.
So for example, adding a reference to pwq_cache in
ep_unregister_pollwait() can trigger a corrupt sympos and a relocation
to the wrong pwq_cache symbol in the livepatch module, resulting in a
crash or undefined behavior.
Remove the existing hack in favor of a fully deterministic solution,
using the new .klp.symid table to derive the symbol-to-id mapping from
the original vmlinux.o and the id-to-address mapping from the
corresponding vmlinux, which can then be used to determine the exact
sympos associated with the original vmlinux.
Modules don't need any special treatment: the .ko has the same
section/symbol ordering as the original whole-archive symbol table.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Ben Procknow <bprockno@redhat.com>
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: live-patching@vger.kernel.org
Link: https://lore.kernel.org/20260710153042.3156788-1-joe.lawrence@redhat.com
Link: https://lore.kernel.org/20260724221730.3126529-1-joe.lawrence@redhat.com
Link: https://patch.msgid.link/919785e3bf2245db02ff6391e735d9cb139170b1.1785727106.git.jpoimboe@kernel.org
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
When creating a klp reloc, klp-diff keeps the original relocation but
converts the referenced symbol to an UNDEF/WEAK placeholder tombstone
symbol, which gets fully disabled later by klp post-link. The tombstone
symbol is only needed to avoid confusing objtool when it does the final
run on the patch module.
However, for references to exported symbols, modpost sees the reference
to the tombstone symbol as a real reference to an exported symbol,
resulting in a false module dependency getting created.
Further, for a reference to a tombstone symbol which is exported into a
module namespace, e.g. via EXPORT_SYMBOL_FOR_KVM_INTERNAL(), modpost
can't satisfy the dependency, resulting in a warning like the following:
module ... uses symbol kvm_flush_remote_tlbs from namespace
module:kvm-amd,kvm-intel, but does not import it.
Rename the placeholder tombstone symbols to ".klp.tombstone.<name>" so
modpost no longer recognizes them.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Ben Procknow <bprockno@redhat.com>
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: live-patching@vger.kernel.org
Link: https://lore.kernel.org/20260720145658.1103243-5-joe.lawrence@redhat.com
Link: https://patch.msgid.link/9548393f4d89ec3b498f4f69aa6ef6b9bb7150fe.1785727106.git.jpoimboe@kernel.org
Module.symvers contains build-tree object paths as module identifiers
(e.g., "arch/x86/kvm/kvm") rather than runtime module names ("kvm").
Objtool's clone_reloc_klp() uses this field directly for exported
symbols, while unexported symbols correctly go through __find_modname().
This means that exported symbol relocations may land in a .klp.rela
section named with the build path rather than the module name. That is
a crash waiting to happen: the kernel's livepatch loader silently skips
this relocation because it doesn't match the expected klp_object name.
The unresolved relocation sits in the newly activated code, crashing
when executed.
Normalize export->mod at Module.symvers read time using the same logic
as __find_modname() (refactored into a shared normalize_modname()
helper).
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Ben Procknow <bprockno@redhat.com>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Cc: live-patching@vger.kernel.org
Link: https://patch.msgid.link/dbe1b72931bd3c31b751fd0729613d9f2226fff6.1785727106.git.jpoimboe@kernel.org
When .modinfo has no "name=" tag, __find_modname() falls back to
converting the object's build-tree path to a runtime module name by
stripping directory components, converting '-' to '_' and truncating the
file extension.
It does all that in a single pass over the entire path, so the first dot
anywhere in the path ends the name. For an object built in a directory
whose name contains a dot, e.g. "drivers/foo-1.0/bar.o", the result is a
bogus module name.
Strip the directory components up front so only the basename is scanned
for the extension separator.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Sashiko <sashiko-bot@kernel.org>
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/9017b4609553bed16674e8f924d34691cbc2b2c1.1785727106.git.jpoimboe@kernel.org
Cache the dont_correlate() result once per symbol at the start of
correlate_symbols(). This reduces klp diff time on an arm64 LTO
vmlinux.o from 2m51s to 35s.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Only create prefix symbols for functions that have
__patchable_function_entries entries, since those are the only C
functions where prefix NOPs are intentional.
This both simplifies the detection and makes it more accurate.
Note that assembly functions using SYM_TYPED_FUNC_START() can also have
prefixed NOPs, but that macro already creates their __cfi_ symbols.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
With CFI+CALL_PADDING, Clang places .Ltmp labels at the start of the NOP
padding (offset 5) between the __cfi_ prefix and the function entry
point. get_func_prefix() only checks the immediately previous symbol,
so the intervening .Ltmp label causes it to miss the __cfi_ prefix
symbol.
This results in klp-diff not cloning the kCFI type hash into the
livepatch module, causing a CFI failure at module load when calling
callback functions through indirect calls:
CFI failure at __klp_enable_patch+0xab/0x140
(target: pre_patch_callback+0x0/0x80 [livepatch_combined];
expected type: 0xde073954)
Instead of walking backward through the section's symbol list, just use
find_func_containing() for the byte before the function. This works now
that __cfi_ symbols are being grown by objtool to fill the padding.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
For all CONFIG_CFI+CONFIG_CALL_PADDING configs, for C functions, the
__cfi_ symbols only cover the 5-byte kCFI type hash. After that there
also N bytes of NOP padding between the hash and the function entry
which aren't associated with any symbol.
The NOPs can be replaced with actual code at runtime. Without a symbol,
unwinders and tooling have no way of knowing where those bytes belong.
Grow the existing __cfi_* symbols to fill that gap.
Note that assembly functions with SYM_TYPED_FUNC_START() aren't affected
by this issue, their __cfi_ symbols also cover the padding.
Also, CONFIG_PREFIX_SYMBOLS has no reason to exist: CONFIG_CALL_PADDING
is what causes the compiler to emit NOP padding before function entry
(via -fpatchable-function-entry), so it's the right condition for
creating prefix symbols.
Remove CONFIG_PREFIX_SYMBOLS, as it's no longer needed. Simplify the
LONGEST_SYM_KUNIT_TEST dependency accordingly. Rework objtool's
arguments a bit to handle the variety of prefix/cfi-related cases.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
When computing klp checksums, instructions with non-relocated jump/call
destination offsets are problematic because the offset values can change
when surrounding code has moved, causing the function to be incorrectly
marked as changed.
Specifically, that includes jumps from alternatives to the end of the
alternative, which from objtool's perspective are jumps to the end of
the alternative instruction block in the original function.
Note that 'jump_dest' jumps don't include sibling calls (those use
call_dest), nor do they include jumps to/from .cold sub functions (those
are cross-section and need a reloc).
Fix it by hashing the opcode bytes (excluding the immediate operand)
along with a position-independent representation of the destination.
For calls, use the function name, and for jumps, use the destination's
offset within its function.
[Note the "9 bit hole" comment was wrong: it has been 8 bits since
commit 70589843b3 ("objtool: Add option to trace function validation")
added the 'trace' field. Adding the 4-bit 'immediate_len' field now
leaves a 4-bit hole.]
Fixes: 0d83da43b1 ("objtool/klp: Add --checksum option to generate per-function checksums")
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Alternative replacement instructions awkwardly have insn->sym set to the
function they get patched to rather than the symbol (or rather lack
thereof) they belong to in the file.
This makes it difficult to know where a given instruction actually
lives.
Add a new insn_sym() helper which preserves the existing semantic of
insn->sym. Rename insn->sym to insn->_sym, which contains the actual
ELF binary symbol (or NULL, for alternative replacements) an instruction
lives in.
The private insn->_sym value will be needed for a subsequent patch.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Add debugging messages to show how duplicate symbols get correlated, and
split the --debug feature into --debug-correlate and --debug-clone.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Rewrite the symbol correlation code, using a tiered list of
deterministic strategies in a loop. For duplicately named symbols, each
tier applies a filter with the goal of finding a 1:1 deterministic
correlation between the original and patched version of the symbol.
The three matching strategies are:
find_twin(): A funnel of progressively tighter filters. Candidates
with the same demangled name are counted at four levels: name, scope
(local-vs-global), file (strict file association), and checksum
(unchanged functions). The widest level that yields a 1:1 match wins,
narrower levels are only tried when the wider level is ambiguous.
find_twin_suffixed(): Uses already-correlated LLVM symbol pairs to map
.llvm.<hash> suffixes from orig to patched. Because all promoted
symbols from the same TU share the same hash, one correlated pair
seeds the mapping for the entire TU.
find_twin_positional(): Last resort, matches symbols by position among
same-named candidates, similar to livepatch sympos. Used for data
objects like __quirk variables where no deterministic filter can
distinguish the candidates.
Overall this works much better than the existing algorithm, particularly
with LTO kernels.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Start checksumming data objects in preparation for revamping the
correlation algorithm.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
The checksum functionality has been moved to "objtool klp checksum"
which is now used by klp-build. Remove the now-dead --checksum and
--debug-checksum options from the default objtool command.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Move the checksum functionality out of the main objtool command into a
new "objtool klp checksum" subcommand.
This has the benefit of making the code (and the patch generation
process itself) more modular.
For bisectability, both "objtool --checksum" and "objtool klp checksum"
work for now. The former will be removed after klp-build has been
converted to use the new subcommand.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
decode_sections() relies on CFI and cfi_hash initialization done
separately in check(), making it unusable outside of check().
Consolidate the initialization into decode_sections() and rename it to
decode_file(), and make it global along with free_insns() and
insn_reloc() for use by other objtool components -- namely, the checksum
code which will be moving to another file.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
In preparation for porting the checksum code to other arches, make its
functionality independent from the CFG reverse engineering code.
Move it into a standalone calculate_checksums() function which iterates
all functions and instructions directly, rather than being called inline
from do_validate_branch().
Since checksum_update_insn() is no longer called during CFG traversal,
it needs to manually iterate the alternatives.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Improve readability with a new is_alias_sym() helper.
No functional changes intended.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Clang generates anonymous data sections named .data..Lanon.<hash>.
These need section-symbol references in the same way as .data..Lubsan
(GCC) and .data..L__unnamed_ (Clang UBSAN) sections. Without this,
convert_reloc_sym() fails when processing relocations that reference
these sections.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
If an object file has no functions, objtool has nothing to checksum, so
it doesn't create the .discard.sym_checksum symbol.
Then when 'objtool klp diff' reads symbol checksums, it errors out due
to the missing .discard.sym_checksum section.
Instead, just create an empty checksum section to signal to
read_sym_checksums() that the file has been processed.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Instead of installing libsubcmd headers to a build output directory and
including from there, include directly from tools/lib/ where they
already exist. This fixes clangd indexing which otherwise can't find
libsubcmd headers.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Section symbols aren't grouped after their corresponding FILE symbols.
Their sym->file should really be NULL rather than whatever random FILE
happened to be last.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
In find_reloc_by_dest_range(), hash collisions can cause a high-offset
relocation to appear when probing a low-offset hash bucket.
Only return early when the best match found so far genuinely belongs to
the current bucket (its offset is within the bucket's stride range).
Otherwise, continue scanning later buckets which may contain
lower-offset matches.
This ensures the first reloc in the range gets returned.
Fixes: 74b873e49d ("objtool: Optimize find_rela_by_dest_range()")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Use the section symbol's index instead of the old symbol's index when
updating the ELF relocation entry in convert_reloc_sym_to_secsym().
Found by Sashiko review.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Clang aggregates UBSAN type descriptors into shared anonymous
.data..L__unnamed_* sections. This data is used by UBSAN trap handlers.
When a changed function has an UBSAN bounds check, klp-diff clones the
entire UBSAN data section associated with the TU. Relocations within
the cloned section that reference named rodata objects in .rodata.cst*
(like 'exponent', 'pirq_ali_set.irqmap') become KLP relocations because
those objects now get correlated.
That results in a .klp.rela.vmlinux..data section which can easily have
thousands of KLP relocs, most of which are completely superfluous, used
by functions which aren't cloned to the patch module.
The .rodata.cst* sections are SHF_MERGE constant pool sections
containing small fixed-size data (lookup tables, bitmasks) that is only
read by value. Pointer identity is never relevant for these objects, so
correlating them is unnecessary.
Exclude .rodata.cst* objects from correlation so they get cloned as
local data instead of generating KLP relocations.
It might be possible to someday treat UBSAN data sections as special
sections, and only extract the few needed entries. But this works for
now.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
klp-diff treats all rodata as uncorrelated, so any reference to it uses
a duplicated copy rather than using a KLP reloc.
For the contents of the data itself, a duplicated copy is fine.
However, pointer comparisons (e.g., f->f_op == &foo_ops) are broken.
Fix it by correlating non-anonymous rodata objects.
Also, use a new find_symbol_containing_inclusive() helper for matching
the end of a symbol so bounds calculations don't get broken, for the
case where an array or other symbol's ending address is used as part of
a bounds calculation.
While these are really two distinct changes, they need to be done in the
same patch so as to avoid introducing bisection regressions.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Inline section_reference_needed() and is_reloc_allowed() into
convert_reloc_sym() and remove the redundant is_reloc_allowed() check in
clone_reloc().
Move the is_sec_sym() checks into the convert callees so they become
no-ops when the reloc is already in the right format. This allows
convert_reloc_sym() to unconditionally dispatch to the right converter
based on section type.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Move the sec->rodata marking from check.c to elf.c so it's set during
ELF reading rather than during the check pipeline. This makes the
rodata flag available to all objtool users, including klp-diff which
reads ELF files directly without running check().
Add an is_rodata_sec() helper to elf.h for consistency with
is_text_sec() and is_string_sec().
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Objtool has some hacks which NOP out certain calls/jumps and replace
their relocations with R_X86_64_NONE. The klp-diff relocation
extraction code will error out when trying to copy these relocations due
to their negative addend, which would only makes sense for a PC-relative
branch instruction. Just ignore them.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
.kcfi_traps contains references to kCFI trap instruction locations.
When a KCFI type check fails at an indirect call, the trap handler looks
up the faulting address in this section.
Add it to the special sections list so the entries get extracted for the
changed functions they reference.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Objtool is failing to extract text annotations which reference
.altinstr_replacement instructions:
1) Alternative replacement fake symbols are NOTYPE rather than FUNC,
and they don't have sym->included set, thus they aren't recognized
by should_keep_special_sym().
2) .discard.annotate_insn gets processed before .altinstr_replacement,
so the referenced (fake) symbols don't have clones yet.
Fix the first issue by checking for a valid clone instead of
sym->included and by accepting NOTYPE symbols when processing
.discard.annotate_insn.
Fix the second issue by deferring text annotation processing until after
the other special sections have been cloned.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
The XXH3 state allocated in checksum_init() is never freed. Free it in
checksum_finish().
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Fix NULL dereference when cloning a symbol from an empty section.
sec->data is only populated for sections with non-zero size.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
When a section is empty (e.g. only zero-length alternative
replacements), there are no symbols to convert a section symbol
reference to. Skip the reloc instead of erroring out.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
find_symbol_by_name() only returns the first match, so
--debug-checksum=<func> silently ignores any subsequent duplicately
named functions after the first.
Fix that, along with a new for_each_sym_by_name() helper.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Convert the callback-based iterate_sym_by_demangled_name() with a new
for_each_sym_by_demangled_name() macro. This eliminates the callback
struct/function and makes the code more compact and readable.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
create_fake_symbols() has two phases: creating symbols from
ANNOTATE_DATA_SPECIAL entries, and a fallback that uses sh_entsize for
special sections like .static_call_sites.
When .discard.annotate_data is absent, the function returns early,
skipping the entsize fallback and silently allowing unsupported
module-local static call keys through.
Fix it by jumping to the entsize phase instead of returning early.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Assisted-by: Claude:claude-4-opus
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Clang emits various .L-prefixed local symbols beyond .Ltmp*, such as
.L__const.* for local constant data. These are assembler-local labels
not present in kallsyms, so they can never be resolved at module load
time.
Broaden the check from .Ltmp* to all .L* symbols so they get cloned into
the patch module instead.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Clang LTO uses __UNIQUE_ID() to generate some uniquely named wrapper
functions, like initstubs. If they're uncorrelated, prevent them from
being reported as new functions and included unnecessarily.
Note that dont_correlate() already includes prefix functions, so prefix
functions are still being ignored here.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
With LTO, the initcall infrastructure generates __initstub__kmod_*
wrapper functions in .init.text. These are the LTO equivalent of
__initcall__kmod_* data pointers, which are already excluded from
correlation.
These are __init functions whose memory is freed after boot, so there's
no reason to include or reference them in a livepatch module.
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
