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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>
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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>
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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>
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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 70589843b36f ("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: 0d83da43b1e1 ("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>
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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>
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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>
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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>
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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>
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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>
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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>
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Add an is_cold_func() helper. No functional changes intended.
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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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>
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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>
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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>
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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>
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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>
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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>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool updates from Ingo Molnar:
- KLP support updates and fixes (Song Liu)
- KLP-build script updates and fixes (Joe Lawrence)
- Support Clang RAX DRAP sequence, to address clang false positive
(Josh Poimboeuf)
- Reorder ORC register numbering to match regular x86 register
numbering (Josh Poimboeuf)
- Misc cleanups (Wentong Tian, Song Liu)
* tag 'objtool-core-2026-04-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool/x86: Reorder ORC register numbering
objtool: Support Clang RAX DRAP sequence
livepatch/klp-build: report patch validation fuzz
livepatch/klp-build: add terminal color output
livepatch/klp-build: provide friendlier error messages
livepatch/klp-build: improve short-circuit validation
livepatch/klp-build: fix shellcheck complaints
livepatch/klp-build: add Makefile with check target
livepatch/klp-build: add grep-override function
livepatch/klp-build: switch to GNU patch and recountdiff
livepatch/klp-build: support patches that add/remove files
objtool/klp: Correlate locals to globals
objtool/klp: Match symbols based on demangled_name for global variables
objtool/klp: Remove .llvm suffix in demangle_name()
objtool/klp: Also demangle global objects
objtool/klp: Use sym->demangled_name for symbol_name hash
objtool/klp: Remove trailing '_' in demangle_name()
objtool/klp: Remove redundant strcmp() in correlate_symbols()
objtool: Use section/symbol type helpers
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correlate_symbols() will always try to match full name first. If there is
no match, try match only demangled_name.
In very rare cases, it is possible to have multiple foo.llvm.<hash> in
the same kernel. Whenever there is ambiguity like this, fail the klp diff.
Signed-off-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/20260305231531.3847295-7-song@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Confusingly, ERROR_INSN() shows "warning:" instead of "error:". Fix that.
Link: https://patch.msgid.link/c4fe793bb3d23fac2c636b2511059af1158410e2.1772681234.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 paravirt updates from Borislav Petkov:
- A nice cleanup to the paravirt code containing a unification of the
paravirt clock interface, taming the include hell by splitting the
pv_ops structure and removing of a bunch of obsolete code (Juergen
Gross)
* tag 'x86_paravirt_for_v7.0_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
x86/paravirt: Use XOR r32,r32 to clear register in pv_vcpu_is_preempted()
x86/paravirt: Remove trailing semicolons from alternative asm templates
x86/pvlocks: Move paravirt spinlock functions into own header
x86/paravirt: Specify pv_ops array in paravirt macros
x86/paravirt: Allow pv-calls outside paravirt.h
objtool: Allow multiple pv_ops arrays
x86/xen: Drop xen_mmu_ops
x86/xen: Drop xen_cpu_ops
x86/xen: Drop xen_irq_ops
x86/paravirt: Move pv_native_*() prototypes to paravirt.c
x86/paravirt: Introduce new paravirt-base.h header
x86/paravirt: Move paravirt_sched_clock() related code into tsc.c
x86/paravirt: Use common code for paravirt_steal_clock()
riscv/paravirt: Use common code for paravirt_steal_clock()
loongarch/paravirt: Use common code for paravirt_steal_clock()
arm64/paravirt: Use common code for paravirt_steal_clock()
arm/paravirt: Use common code for paravirt_steal_clock()
sched: Move clock related paravirt code to kernel/sched
paravirt: Remove asm/paravirt_api_clock.h
x86/paravirt: Move thunk macros to paravirt_types.h
...
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The klp_object_ext and klp_func_ext data, which are stored in the
__klp_objects and __klp_funcs sections, respectively, are not needed
after they are used to create the actual klp_object and klp_func
instances. This operation is implemented by the init function in
scripts/livepatch/init.c.
Prefix the two sections with ".init" so they are freed after the module
is initializated.
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>
Link: https://patch.msgid.link/20260123102825.3521961-3-petr.pavlu@suse.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Having a single large pv_ops array has the main disadvantage of needing all
prototypes of the single array members in one header file. This is adding up
to the need to include lots of otherwise unrelated headers.
In order to allow multiple smaller pv_ops arrays dedicated to one area of the
kernel each, allow multiple arrays in objtool.
For better performance limit the possible names of the arrays to start with
"pv_ops".
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260105110520.21356-19-jgross@suse.com
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When using the x32 toolchain, compilation fails because the printf
specifier "%lx" (long), doesn't match the type of the "checksum" variable
(long long). Fix this by changing the printf specifier to "%llx" and
casting "checksum" to unsigned long long.
Fixes: a3493b33384a ("objtool/klp: Add --debug-checksum=<funcs> to show per-instruction checksums")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/a1158c99-fe0e-a218-4b5b-ffac212489f6@redhat.com
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overflows
When the kernel build fails due to an objtool segfault, the error
message is a bit obtuse and confusing:
make[5]: *** [scripts/Makefile.build:503: drivers/scsi/qla2xxx/qla2xxx.o] Error 139
^^^^^^^^^
make[5]: *** Deleting file 'drivers/scsi/qla2xxx/qla2xxx.o'
make[4]: *** [scripts/Makefile.build:556: drivers/scsi/qla2xxx] Error 2
make[3]: *** [scripts/Makefile.build:556: drivers/scsi] Error 2
make[2]: *** [scripts/Makefile.build:556: drivers] Error 2
make[1]: *** [/home/jpoimboe/git/linux/Makefile:2013: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2
Add a signal handler to objtool which prints an error message like if
the local stack has overflown (for which there's a chance as objtool
makes heavy use of recursion):
drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool stack overflow!
or:
drivers/scsi/qla2xxx/qla2xxx.o: error: SIGSEGV: objtool crash!
Also, re-raise the signal so the core dump still gets triggered.
[ mingo: Applied a build fix, added more comments and prettified the code. ]
Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: David Laight <david.laight.linux@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/mi4tihk4dbncn7belrhp6ooudhpw4vdggerktu5333w3gqf3uf@vqlhc3y667mg
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Add the --wide option to provide a wide output when disassembling.
With this option, the disassembly of alternatives is displayed
side-by-side instead of one above the other.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-30-alexandre.chartre@oracle.com
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Add a function to get the name of a CPU feature. The function is
architecture dependent and currently only implemented for x86. The
feature names are automatically generated from the cpufeatures.h
include file.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@oracle.com
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Each alternative of a group alternative depends on a specific
feature and flags. Provide access to the feature/flags for each
alternative as an attribute (feature) in struct alt_group.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-26-alexandre.chartre@oracle.com
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Add the --disas=<function-pattern> actions to disassemble the specified
functions. The function pattern can be a single function name (e.g.
--disas foo to disassemble the function with the name "foo"), or a shell
wildcard pattern (e.g. --disas foo* to disassemble all functions with a
name starting with "foo").
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-18-alexandre.chartre@oracle.com
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When tracing function validation, improve the reporting of
alternative instruction by more clearly showing the different
alternatives beginning and end.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-16-alexandre.chartre@oracle.com
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Add the disas_alt_name() and disas_alt_type_name() to provide a
name and a type name for an alternative. This will be used to
better name alternatives when tracing their execution.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-15-alexandre.chartre@oracle.com
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Alternative code, including jump table and exception table, is represented
with the same struct alternative structure. But there is no obvious way to
identify whether the struct represents alternative instructions, a jump
table or an exception table.
So add a type to struct alternative to clearly identify the type of
alternative.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-14-alexandre.chartre@oracle.com
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When tracing function validation, instruction state changes can
report changes involving registers. These registers are reported
with the name "r<num>" (e.g. "r3"). Print the CPU specific register
name instead of a generic name (e.g. print "rbx" instead of "r3"
on x86).
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-13-alexandre.chartre@oracle.com
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During function validation, objtool maintains a per-instruction state,
in particular to track call frame information. When tracing validation,
print any instruction state changes.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-12-alexandre.chartre@oracle.com
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Add an option to trace and have information during the validation
of specified functions. Functions are specified with the --trace
option which can be a single function name (e.g. --trace foo to
trace the function with the name "foo"), or a shell wildcard
pattern (e.g. --trace foo* to trace all functions with a name
starting with "foo").
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-11-alexandre.chartre@oracle.com
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When an instruction warning (WARN_INSN) or backtrace (BT_INSN) is issued,
disassemble the instruction to provide more context.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-8-alexandre.chartre@oracle.com
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Print symbols referenced during disassembly instead of just printing
raw addresses. Also handle address relocation.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-6-alexandre.chartre@oracle.com
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objtool executes the objdump command to disassemble code. Use libopcodes
instead to have more control about the disassembly scope and output.
If libopcodes is not present then objtool is built without disassembly
support.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-4-alexandre.chartre@oracle.com
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Create a structure to store information for disassembling functions.
For now, it is just a wrapper around an objtool file.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-3-alexandre.chartre@oracle.com
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objtool disassembles functions which have warnings. Move the code
to do that to a dedicated file. The code is just moved, it is not
changed.
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-2-alexandre.chartre@oracle.com
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The objtool .cold child/parent correlation is done in two phases: first
in elf_add_symbol() and later in add_jump_destinations().
The first phase is rather crude and can pick the wrong parent if there
are duplicates with the same name.
The second phase usually fixes that, but only if the parent has a direct
jump to the child. It does *not* work if the only branch from the
parent to the child is an alternative or jump table entry.
Make the first phase more robust by looking for the parent in the same
STT_FILE as the child.
Fixes the following objtool warnings in an AutoFDO build with a large
CLANG_AUTOFDO_PROFILE profile:
vmlinux.o: warning: objtool: rdev_add_key() falls through to next function rdev_add_key.cold()
vmlinux.o: warning: objtool: rdev_set_default_key() falls through to next function rdev_set_default_key.cold()
Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/82c7b52e40efa75dd10e1c550cc75c1ce10ac2c9.1763671318.git.jpoimboe@kernel.org
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Copy from
54da6a092431 ("locking: Introduce __cleanup() based infrastructure")
the bits which mark the variable with a cleanup attribute unused so that my
clang 15 can dispose of it properly instead of warning that it is unused which
then fails the build due to -Werror.
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20251031114919.GBaQSiPxZrziOs3RCW@fat_crate.local
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In preparation for klp-build, enable "classic" objtool to work on
livepatch modules:
- Avoid duplicate symbol/section warnings for prefix symbols and the
.static_call_sites and __mcount_loc sections which may have already
been extracted by klp diff.
- Add __klp_funcs to the IBT function pointer section whitelist.
- Prevent KLP symbols from getting incorrectly classified as cold
subfunctions.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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The prefix symbol creation code currently ignores all errors, presumably
because some functions don't have the leading NOPs.
Shuffle the code around a bit, improve the error handling and document
why some errors are ignored.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Livepatch needs some ELF magic which linkers don't like:
- Two relocation sections (.rela*, .klp.rela*) for the same text
section.
- Use of SHN_LIVEPATCH to mark livepatch symbols.
Unfortunately linkers tend to mangle such things. To work around that,
klp diff generates a linker-compliant intermediate binary which encodes
the relevant KLP section/reloc/symbol metadata.
After module linking, the .ko then needs to be converted to an actual
livepatch module. Introduce a new klp post-link subcommand to do so.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a --debug option to klp diff which prints cloning decisions and an
indented dependency tree for all cloned symbols and relocations. This
helps visualize which symbols and relocations were included and why.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a new klp diff subcommand which performs a binary diff between two
object files and extracts changed functions into a new object which can
then be linked into a livepatch module.
This builds on concepts from the longstanding out-of-tree kpatch [1]
project which began in 2012 and has been used for many years to generate
livepatch modules for production kernels. However, this is a complete
rewrite which incorporates hard-earned lessons from 12+ years of
maintaining kpatch.
Key improvements compared to kpatch-build:
- Integrated with objtool: Leverages objtool's existing control-flow
graph analysis to help detect changed functions.
- Works on vmlinux.o: Supports late-linked objects, making it
compatible with LTO, IBT, and similar.
- Simplified code base: ~3k fewer lines of code.
- Upstream: No more out-of-tree #ifdef hacks, far less cruft.
- Cleaner internals: Vastly simplified logic for symbol/section/reloc
inclusion and special section extraction.
- Robust __LINE__ macro handling: Avoids false positive binary diffs
caused by the __LINE__ macro by introducing a fix-patch-lines script
(coming in a later patch) which injects #line directives into the
source .patch to preserve the original line numbers at compile time.
Note the end result of this subcommand is not yet functionally complete.
Livepatch needs some ELF magic which linkers don't like:
- Two relocation sections (.rela*, .klp.rela*) for the same text
section.
- Use of SHN_LIVEPATCH to mark livepatch symbols.
Unfortunately linkers tend to mangle such things. To work around that,
klp diff generates a linker-compliant intermediate binary which encodes
the relevant KLP section/reloc/symbol metadata.
After module linking, a klp post-link step (coming soon) will clean up
the mess and convert the linked .ko into a fully compliant livepatch
module.
Note this subcommand requires the diffed binaries to have been compiled
with -ffunction-sections and -fdata-sections, and processed with
'objtool --checksum'. Those constraints will be handled by a klp-build
script introduced in a later patch.
Without '-ffunction-sections -fdata-sections', reliable object diffing
would be infeasible due to toolchain limitations:
- For intra-file+intra-section references, the compiler might
occasionally generated hard-coded instruction offsets instead of
relocations.
- Section-symbol-based references can be ambiguous:
- Overlapping or zero-length symbols create ambiguity as to which
symbol is being referenced.
- A reference to the end of a symbol (e.g., checking array bounds)
can be misinterpreted as a reference to the next symbol, or vice
versa.
A potential future alternative to '-ffunction-sections -fdata-sections'
would be to introduce a toolchain option that forces symbol-based
(non-section) relocations.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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Add a --debug-checksum=<funcs> option to the check subcommand to print
the calculated checksum of each instruction in the given functions.
This is useful for determining where two versions of a function begin to
diverge.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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In preparation for the objtool klp diff subcommand, add a command-line
option to generate a unique checksum for each function. This will
enable detection of functions which have changed between two versions of
an object file.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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... for reading annotation types.
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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