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2025-10-16Merge branch 'objtool/core' of ↵Peter Zijlstra
https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux This series introduces new objtool features and a klp-build script to generate livepatch modules using a source .patch as input. 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 which injects #line directives into the source .patch to preserve the original line numbers at compile time. The primary user interface is the klp-build script which does the following: - Builds an original kernel with -function-sections and -fdata-sections, plus objtool function checksumming. - Applies the .patch file and rebuilds the kernel using the same options. - Runs 'objtool klp diff' to detect changed functions and generate intermediate binary diff objects. - Builds a kernel module which links the diff objects with some livepatch module init code (scripts/livepatch/init.c). - Finalizes the livepatch module (aka work around linker wreckage) using 'objtool klp post-link'. I've tested with a variety of patches on defconfig and Fedora-config kernels with both GCC and Clang.
2025-10-14livepatch/klp-build: Introduce klp-build script for generating livepatch modulesJosh Poimboeuf
Add a klp-build script which automates the generation of a livepatch module from a source .patch file by performing the following steps: - Builds an original kernel with -function-sections and -fdata-sections, plus objtool function checksumming. - Applies the .patch file and rebuilds the kernel using the same options. - Runs 'objtool klp diff' to detect changed functions and generate intermediate binary diff objects. - Builds a kernel module which links the diff objects with some livepatch module init code (scripts/livepatch/init.c). - Finalizes the livepatch module (aka work around linker wreckage) using 'objtool klp post-link'. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Add base objtool support for livepatch modulesJosh Poimboeuf
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>
2025-10-14objtool: Refactor prefix symbol creation codeJosh Poimboeuf
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>
2025-10-14objtool/klp: Add post-link subcommand to finalize livepatch modulesJosh Poimboeuf
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>
2025-10-14objtool/klp: Add --debug option to show cloning decisionsJosh Poimboeuf
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>
2025-10-14objtool/klp: Introduce klp diff subcommand for diffing object filesJosh Poimboeuf
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>
2025-10-14objtool/klp: Add --debug-checksum=<funcs> to show per-instruction checksumsJosh Poimboeuf
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>
2025-10-14objtool/klp: Add --checksum option to generate per-function checksumsJosh Poimboeuf
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>
2025-10-14objtool: Add annotype() helperJosh Poimboeuf
... 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>
2025-10-14objtool: Add elf_create_file()Josh Poimboeuf
Add interface to enable the creation of a new ELF file. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Add elf_create_reloc() and elf_init_reloc()Josh Poimboeuf
elf_create_rela_section() is quite limited in that it requires the caller to know how many relocations need to be allocated up front. In preparation for the objtool klp diff subcommand, allow an arbitrary number of relocations to be created and initialized on demand after section creation. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Add elf_create_data()Josh Poimboeuf
In preparation for the objtool klp diff subcommand, refactor elf_add_string() by adding a new elf_add_data() helper which allows the adding of arbitrary data to a section. Make both interfaces global so they can be used by the upcoming klp diff code. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Generalize elf_create_section()Josh Poimboeuf
In preparation for the objtool klp diff subcommand, broaden the elf_create_section() interface to give callers more control and reduce duplication of some subtle setup logic. While at it, make elf_create_rela_section() global so sections can be created by the upcoming klp diff code. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Generalize elf_create_symbol()Josh Poimboeuf
In preparation for the objtool klp diff subcommand, broaden the elf_create_symbol() interface to give callers more control and reduce duplication of some subtle setup logic. While at it, make elf_create_symbol() and elf_create_section_symbol() global so sections can be created by the upcoming klp diff code. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Simplify special symbol handling in elf_update_symbol()Josh Poimboeuf
!sym->sec isn't actually a thing: even STT_UNDEF and other special symbol types belong to NULL section 0. Simplify the initialization of 'shndx' accordingly. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Refactor add_jump_destinations()Josh Poimboeuf
The add_jump_destinations() logic is a bit weird and convoluted after being incrementally tweaked over the years. Refactor it to hopefully be more logical and straightforward. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Reindent check_options[]Josh Poimboeuf
Bring the cmdline check_options[] array back into vertical alignment for better readability. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Resurrect --backup optionJosh Poimboeuf
The --backup option was removed with the following commit: aa8b3e64fd39 ("objtool: Create backup on error and print args") ... which tied the backup functionality to --verbose, and only for warnings/errors. It's a bit inelegant and out of scope to tie that to --verbose. Bring back the old --backup option, but with the new behavior: only on warnings/errors, and print the args to make it easier to recreate. Suggested-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Rename --Werror to --werrorJosh Poimboeuf
The objtool --Werror option name is stylistically inconsistent: halfway between GCC's single-dash capitalized -Werror and objtool's double-dash --lowercase convention, making it unnecessarily hard to remember. Make the 'W' lower case (--werror) for consistency with objtool's other options. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Avoid emptying lists for duplicate sectionsJosh Poimboeuf
When a to-be-created section already exists, there's no point in emptying the various lists if their respective sections already exist. In fact it's better to leave them intact as they might get used later. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Simplify reloc offset calculation in unwind_read_hints()Josh Poimboeuf
Simplify the relocation offset calculation in unwind_read_hints(), similar to other conversions which have already been done. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Mark prefix functionsJosh Poimboeuf
In preparation for the objtool klp diff subcommand, introduce a flag to identify __pfx_*() and __cfi_*() functions in advance so they don't need to be manually identified every time a check is needed. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix weak symbol hole detection for .cold functionsJosh Poimboeuf
When ignore_unreachable_insn() looks for weak function holes which jump to their .cold functions, it assumes the parent function comes before the corresponding .cold function in the symbol table. That's not necessarily the case with -ffunction-sections. Mark all the holes beforehand (including .cold functions) so the ordering of the discovery doesn't matter. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Mark .cold subfunctionsJosh Poimboeuf
Introduce a flag to identify .cold subfunctions so they can be detected easier and faster. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Add section/symbol type helpersJosh Poimboeuf
Add some helper macros to improve readability. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Convert elf iterator macros to use 'struct elf'Josh Poimboeuf
'struct objtool_file' is specific to the check code and doesn't belong in the elf code which is supposed to be objtool_file-agnostic. Convert the elf iterator macros to use 'struct elf' instead. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Remove .parainstructions referenceJosh Poimboeuf
The .parainstructions section no longer exists since the following commit: 60bc276b129e ("x86/paravirt: Switch mixed paravirt/alternative calls to alternatives"). Remove the reference to it. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Clean up compiler flag usageJosh Poimboeuf
KBUILD_HOSTCFLAGS and KBUILD_HOSTLDFLAGS aren't defined when objtool is built standalone. Also, the EXTRA_WARNINGS flags are rather arbitrary. Make things simpler and more consistent by specifying compiler flags explicitly and tweaking the warnings. Also make a few code tweaks to make the new warnings happy. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Const string cleanupJosh Poimboeuf
Use 'const char *' where applicable. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Check for missing annotation entries in read_annotate()Josh Poimboeuf
Add a sanity check to make sure none of the relocations for the .discard.annotate_insn section have gone missing. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix "unexpected end of section" warning for alternativesJosh Poimboeuf
Due to the short circuiting logic in next_insn_to_validate(), control flow may silently transition from .altinstr_replacement to .text without a corresponding nested call to validate_branch(). As a result the validate_branch() 'sec' variable doesn't get reinitialized, which can trigger a confusing "unexpected end of section" warning which blames .altinstr_replacement rather than the offending fallthrough function. Fix that by not caching the section. There's no point in doing that anyway. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix __pa_symbol() relocation handlingJosh Poimboeuf
__pa_symbol() generates a relocation which refers to a physical address. Convert it to back its virtual form before calculating the addend. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix x86 addend calculationJosh Poimboeuf
On x86, arch_dest_reloc_offset() hardcodes the addend adjustment to four, but the actual adjustment depends on the relocation type. Fix that. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix weak symbol detectionJosh Poimboeuf
find_symbol_hole_containing() fails to find a symbol hole (aka stripped weak symbol) if its section has no symbols before the hole. This breaks weak symbol detection if -ffunction-sections is enabled. Fix that by allowing the interval tree to contain section symbols, which are always at offset zero for a given section. Fixes a bunch of (-ffunction-sections) warnings like: vmlinux.o: warning: objtool: .text.__x64_sys_io_setup+0x10: unreachable instruction Fixes: 4adb23686795 ("objtool: Ignore extra-symbol code") Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix interval tree insertion for zero-length symbolsJosh Poimboeuf
Zero-length symbols get inserted in the wrong spot. Fix that. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Add empty symbols to the symbol tree againJosh Poimboeuf
The following commit 5da6aea375cd ("objtool: Fix find_{symbol,func}_containing()") fixed the issue where overlapping symbols weren't getting sorted properly in the symbol tree. Therefore the workaround to skip adding empty symbols from the following commit a2e38dffcd93 ("objtool: Don't add empty symbols to the rbtree") is no longer needed. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Remove error handling boilerplateJosh Poimboeuf
Up to a certain point in objtool's execution, all errors are fatal and return -1. When propagating such errors, just return -1 directly instead of trying to propagate the original return code. This helps make the code more compact and the behavior more explicit. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Propagate elf_truncate_section() error in elf_write()Josh Poimboeuf
Properly check and propagate the return value of elf_truncate_section() to avoid silent failures. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix broken error handling in read_symbols()Josh Poimboeuf
The free(sym) call in the read_symbols() error path is fundamentally broken: 'sym' doesn't point to any allocated block. If triggered, things would go from bad to worse. Remove the free() and simplify the error paths. Freeing memory isn't necessary here anyway, these are fatal errors which lead to an immediate exit(). Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Make find_symbol_containing() less arbitraryJosh Poimboeuf
In the rare case of overlapping symbols, find_symbol_containing() just returns the first one it finds. Make it slightly less arbitrary by returning the smallest symbol with size > 0. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14interval_tree: Sync interval_tree_generic.h with toolsJosh Poimboeuf
The following commit made an improvement to interval_tree_generic.h, but didn't sync it to the tools copy: 19811285784f ("lib/interval_tree: skip the check before go to the right subtree") Sync it, and add it to objtool's sync-check.sh so they are more likely to stay in sync going forward. Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Fix standalone --hacks=jump_labelDylan Hatch
The objtool command line 'objtool --hacks=jump_label foo.o' on its own should be expected to rewrite jump labels to NOPs. This means the add_special_section_alts() code path needs to run when only this option is provided. This is mainly relevant in certain debugging situations, but could potentially also fix kernel builds in which objtool is run with --hacks=jump_label but without --orc, --stackval, --uaccess, or --hacks=noinstr. Fixes: de6fbcedf5ab ("objtool: Read special sections with alts only when specific options are selected") Signed-off-by: Dylan Hatch <dylanbhatch@google.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool: Remove unneeded semicolonChen Ni
Remove unnecessary semicolons reported by Coccinelle/coccicheck and the semantic patch at scripts/coccinelle/misc/semicolon.cocci. Signed-off-by: Chen Ni <nichen@iscas.ac.cn> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
2025-10-14objtool/x86: Fix NOP decodePeter Zijlstra
For x86_64 the kernel consistently uses 2 instructions for all NOPs: 90 - NOP 0f 1f /0 - NOPL Notably: - REP NOP is PAUSE, not a NOP instruction. - 0f {0c...0f} is reserved space, except for 0f 0d /1, which is PREFETCHW, not a NOP. - 0f {19,1c...1f} is reserved space, except for 0f 1f /0, which is NOPL. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
2025-10-14objtool/x86: Add UDB supportPeter Zijlstra
Per commit 85a2d4a890dc ("x86,ibt: Use UDB instead of 0xEA"), make sure objtool also recognises UDB as a #UD instruction. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
2025-10-14objtool/x86: Remove 0xea hackPeter Zijlstra
Was properly fixed in the decoder with commit 4b626015e1bf ("x86/insn: Stop decoding i64 instructions in x86-64 mode at opcode") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
2025-10-11Merge tag 'x86_core_for_v6.18_rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull more x86 updates from Borislav Petkov: - Remove a bunch of asm implementing condition flags testing in KVM's emulator in favor of int3_emulate_jcc() which is written in C - Replace KVM fastops with C-based stubs which avoids problems with the fastop infra related to latter not adhering to the C ABI due to their special calling convention and, more importantly, bypassing compiler control-flow integrity checking because they're written in asm - Remove wrongly used static branches and other ugliness accumulated over time in hyperv's hypercall implementation with a proper static function call to the correct hypervisor call variant - Add some fixes and modifications to allow running FRED-enabled kernels in KVM even on non-FRED hardware - Add kCFI improvements like validating indirect calls and prepare for enabling kCFI with GCC. Add cmdline params documentation and other code cleanups - Use the single-byte 0xd6 insn as the official #UD single-byte undefined opcode instruction as agreed upon by both x86 vendors - Other smaller cleanups and touchups all over the place * tag 'x86_core_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) x86,retpoline: Optimize patch_retpoline() x86,ibt: Use UDB instead of 0xEA x86/cfi: Remove __noinitretpoline and __noretpoline x86/cfi: Add "debug" option to "cfi=" bootparam x86/cfi: Standardize on common "CFI:" prefix for CFI reports x86/cfi: Document the "cfi=" bootparam options x86/traps: Clarify KCFI instruction layout compiler_types.h: Move __nocfi out of compiler-specific header objtool: Validate kCFI calls x86/fred: KVM: VMX: Always use FRED for IRQs when CONFIG_X86_FRED=y x86/fred: Play nice with invoking asm_fred_entry_from_kvm() on non-FRED hardware x86/fred: Install system vector handlers even if FRED isn't fully enabled x86/hyperv: Use direct call to hypercall-page x86/hyperv: Clean up hv_do_hypercall() KVM: x86: Remove fastops KVM: x86: Convert em_salc() to C KVM: x86: Introduce EM_ASM_3WCL KVM: x86: Introduce EM_ASM_1SRC2 KVM: x86: Introduce EM_ASM_2CL KVM: x86: Introduce EM_ASM_2W ...
2025-10-01Merge tag 'kbuild-6.18-1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux Pull Kbuild updates from Nathan Chancellor: - Extend modules.builtin.modinfo to include module aliases from MODULE_DEVICE_TABLE for builtin modules so that userspace tools (such as kmod) can verify that a particular module alias will be handled by a builtin module - Bump the minimum version of LLVM for building the kernel to 15.0.0 - Upgrade several userspace API checks in headers_check.pl to errors - Unify and consolidate CONFIG_WERROR / W=e handling - Turn assembler and linker warnings into errors with CONFIG_WERROR / W=e - Respect CONFIG_WERROR / W=e when building userspace programs (userprogs) - Enable -Werror unconditionally when building host programs (hostprogs) - Support copy_file_range() and data segment alignment in gen_init_cpio to improve performance on filesystems that support reflinks such as btrfs and XFS - Miscellaneous small changes to scripts and configuration files * tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (47 commits) modpost: Initialize builtin_modname to stop SIGSEGVs Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds kbuild: vmlinux.unstripped should always depend on .vmlinux.export.o modpost: Create modalias for builtin modules modpost: Add modname to mod_device_table alias scsi: Always define blogic_pci_tbl structure kbuild: extract modules.builtin.modinfo from vmlinux.unstripped kbuild: keep .modinfo section in vmlinux.unstripped kbuild: always create intermediate vmlinux.unstripped s390: vmlinux.lds.S: Reorder sections KMSAN: Remove tautological checks objtool: Drop noinstr hack for KCSAN_WEAK_MEMORY lib/Kconfig.debug: Drop CLANG_VERSION check from DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT riscv: Remove ld.lld version checks from many TOOLCHAIN_HAS configs riscv: Unconditionally use linker relaxation riscv: Remove version check for LTO_CLANG selects powerpc: Drop unnecessary initializations in __copy_inst_from_kernel_nofault() mips: Unconditionally select ARCH_HAS_CURRENT_STACK_POINTER arm64: Remove tautological LLVM Kconfig conditions ARM: Clean up definition of ARM_HAS_GROUP_RELOCS ...
2025-09-30Merge tag 'x86_apic_for_v6.18_rc1' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 SEV and apic updates from Borislav Petkov: - Add functionality to provide runtime firmware updates for the non-x86 parts of an AMD platform like the security processor (ASP) firmware, modules etc, for example. The intent being that these updates are interim, live fixups before a proper BIOS update can be attempted - Add guest support for AMD's Secure AVIC feature which gives encrypted guests the needed protection against a malicious hypervisor generating unexpected interrupts and injecting them into such guest, thus interfering with its operation in an unexpected and negative manner. The advantage of this scheme is that the guest determines which interrupts and when to accept them vs leaving that to the benevolence (or not) of the hypervisor - Strictly separate the startup code from the rest of the kernel where former is executed from the initial 1:1 mapping of memory. The problem was that the toolchain-generated version of the code was being executed from a different mapping of memory than what was "assumed" during code generation, needing an ever-growing pile of fixups for absolute memory references which are invalid in the early, 1:1 memory mapping during boot. The major advantage of this is that there's no need to check the 1:1 mapping portion of the code for absolute relocations anymore and get rid of the RIP_REL_REF() macro sprinkling all over the place. For more info, see Ard's very detailed writeup on this [1] - The usual cleanups and fixes Link: https://lore.kernel.org/r/CAMj1kXEzKEuePEiHB%2BHxvfQbFz0sTiHdn4B%2B%2BzVBJ2mhkPkQ4Q@mail.gmail.com [1] * tag 'x86_apic_for_v6.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits) x86/boot: Drop erroneous __init annotation from early_set_pages_state() crypto: ccp - Add AMD Seamless Firmware Servicing (SFS) driver crypto: ccp - Add new HV-Fixed page allocation/free API x86/sev: Add new dump_rmp parameter to snp_leak_pages() API x86/startup/sev: Document the CPUID flow in the boot #VC handler objtool: Ignore __pi___cfi_ prefixed symbols x86/sev: Zap snp_abort() x86/apic/savic: Do not use snp_abort() x86/boot: Get rid of the .head.text section x86/boot: Move startup code out of __head section efistub/x86: Remap inittext read-execute when needed x86/boot: Create a confined code area for startup code x86/kbuild: Incorporate boot/startup/ via Kbuild makefile x86/boot: Revert "Reject absolute references in .head.text" x86/boot: Check startup code for absence of absolute relocations objtool: Add action to check for absence of absolute relocations x86/sev: Export startup routines for later use x86/sev: Move __sev_[get|put]_ghcb() into separate noinstr object x86/sev: Provide PIC aliases for SEV related data objects x86/boot: Provide PIC aliases for 5-level paging related constants ...