kernel/tools/objtool/arch/x86/special.c, branch linux-rolling-stable

objtool: Add Function to get the name of a CPU feature

2025-11-24T19:39:47Z

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 Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://patch.msgid.link/20251121095340.464045-27-alexandre.chartre@oracle.com

objtool: Add section/symbol type helpers

2025-10-14T21:45:25Z

Add some helper macros to improve readability. Acked-by: Petr Mladek Tested-by: Joe Lawrence Signed-off-by: Josh Poimboeuf

objtool: Fix false-positive "ignoring unreachables" warning

2025-04-10T20:55:00Z

There's no need to try to automatically disable unreachable warnings if they've already been manually disabled due to CONFIG_KCOV quirks. This avoids a spurious warning with a KCOV kernel: fs/smb/client/cifs_unicode.o: warning: objtool: cifsConvertToUTF16.part.0+0xce5: ignoring unreachables due to jump table quirk Fixes: eeff7ac61526 ("objtool: Warn when disabling unreachable warnings") Reported-by: kernel test robot Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/5eb28eeb6a724b7d945a961cfdcf8d41e6edf3dc.1744238814.git.jpoimboe@kernel.org Closes: https://lore.kernel.org/r/202504090910.QkvTAR36-lkp@intel.com/

objtool: Fix X86_FEATURE_SMAP alternative handling

2025-03-25T08:20:26Z

For X86_FEATURE_SMAP alternatives which replace NOP with STAC or CLAC, uaccess validation skips the NOP branch to avoid following impossible code paths, e.g. where a STAC would be patched but a CLAC wouldn't. However, it's not safe to assume an X86_FEATURE_SMAP alternative is patching STAC/CLAC. There can be other alternatives, like static_cpu_has(), where both branches need to be validated. Fix that by repurposing ANNOTATE_IGNORE_ALTERNATIVE for skipping either original instructions or new ones. This is a more generic approach which enables the removal of the feature checking hacks and the insn->ignore bit. Fixes the following warnings: arch/x86/mm/fault.o: warning: objtool: do_user_addr_fault+0x8ec: __stack_chk_fail() missing __noreturn in .c/.h or NORETURN() in noreturns.h arch/x86/mm/fault.o: warning: objtool: do_user_addr_fault+0x8f1: unreachable instruction [ mingo: Fix up conflicts with recent x86 changes. ] Fixes: ea24213d8088 ("objtool: Add UACCESS validation") Reported-by: kernel test robot Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/de0621ca242130156a55d5d74fed86994dfa4c9c.1742852846.git.jpoimboe@kernel.org Closes: https://lore.kernel.org/oe-kbuild-all/202503181736.zkZUBv4N-lkp@intel.com/

objtool: Warn when disabling unreachable warnings

2025-03-25T08:20:25Z

Print a warning when disabling the unreachable warnings (due to a GCC bug). This will help determine if recent GCCs still have the issue and alert us if any other issues might be silently lurking behind the unreachable disablement. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/df243063787596e6031367e6659e7e43409d6c6d.1742852846.git.jpoimboe@kernel.org

objtool: Allow arch code to discover jump table size

2024-12-02T11:24:29Z

In preparation for adding support for annotated jump tables, where ELF relocations and symbols are used to describe the locations of jump tables in the executable, refactor the jump table discovery logic so the table size can be returned from arch_find_switch_table(). Signed-off-by: Ard Biesheuvel Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241011170847.334429-12-ardb+git@google.com

x86/alternatives: Add nested alternatives macros

2024-06-11T15:13:08Z

Instead of making increasingly complicated ALTERNATIVE_n() implementations, use a nested alternative expression. The only difference between: ALTERNATIVE_2(oldinst, newinst1, flag1, newinst2, flag2) and ALTERNATIVE(ALTERNATIVE(oldinst, newinst1, flag1), newinst2, flag2) is that the outer alternative can add additional padding when the inner alternative is the shorter one, which then results in alt_instr::instrlen being inconsistent. However, this is easily remedied since the alt_instr entries will be consecutive and it is trivial to compute the max(alt_instr::instrlen) at runtime while patching. Specifically, after this the ALTERNATIVE_2 macro, after CPP expansion (and manual layout), looks like this: .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2 740: 740: \oldinstr ; 741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ; 742: .pushsection .altinstructions,"a" ; altinstr_entry 740b,743f,\ft_flags1,742b-740b,744f-743f ; .popsection ; .pushsection .altinstr_replacement,"ax" ; 743: \newinstr1 ; 744: .popsection ; ; 741: .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ; 742: .pushsection .altinstructions,"a" ; altinstr_entry 740b,743f,\ft_flags2,742b-740b,744f-743f ; .popsection ; .pushsection .altinstr_replacement,"ax" ; 743: \newinstr2 ; 744: .popsection ; .endm The only label that is ambiguous is 740, however they all reference the same spot, so that doesn't matter. NOTE: obviously only @oldinstr may be an alternative; making @newinstr an alternative would mean patching .altinstr_replacement which very likely isn't what is intended, also the labels will be confused in that case. [ bp: Debug an issue where it would match the wrong two insns and and consider them nested due to the same signed offsets in the .alternative section and use instr_va() to compare the full virtual addresses instead. - Use new labels to denote that the new, nested alternatives are being used when staring at preprocessed output. - Use the %c constraint everywhere instead of %P and document the difference for future reference. ] Signed-off-by: Peter Zijlstra Co-developed-by: Borislav Petkov (AMD) Signed-off-by: Borislav Petkov (AMD) Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230628104952.GA2439977@hirez.programming.kicks-ass.net

x86/bugs: Rename CONFIG_RETPOLINE => CONFIG_MITIGATION_RETPOLINE

2024-01-10T09:52:28Z

Step 5/10 of the namespace unification of CPU mitigations related Kconfig options. [ mingo: Converted a few more uses in comments/messages as well. ] Suggested-by: Josh Poimboeuf Signed-off-by: Breno Leitao Signed-off-by: Ingo Molnar Reviewed-by: Ariel Miculas Acked-by: Josh Poimboeuf Cc: Linus Torvalds Link: https://lore.kernel.org/r/20231121160740.1249350-6-leitao@debian.org

Merge tag 'objtool-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-06-27T22:05:41Z

Pull objtool updates from Ingo Molar: "Build footprint & performance improvements: - Reduce memory usage with CONFIG_DEBUG_INFO=y In the worst case of an allyesconfig+CONFIG_DEBUG_INFO=y kernel, DWARF creates almost 200 million relocations, ballooning objtool's peak heap usage to 53GB. These patches reduce that to 25GB. On a distro-type kernel with kernel IBT enabled, they reduce objtool's peak heap usage from 4.2GB to 2.8GB. These changes also improve the runtime significantly. Debuggability improvements: - Add the unwind_debug command-line option, for more extend unwinding debugging output - Limit unreachable warnings to once per function - Add verbose option for disassembling affected functions - Include backtrace in verbose mode - Detect missing __noreturn annotations - Ignore exc_double_fault() __noreturn warnings - Remove superfluous global_noreturns entries - Move noreturn function list to separate file - Add __kunit_abort() to noreturns Unwinder improvements: - Allow stack operations in UNWIND_HINT_UNDEFINED regions - drm/vmwgfx: Add unwind hints around RBP clobber Cleanups: - Move the x86 entry thunk restore code into thunk functions - x86/unwind/orc: Use swap() instead of open coding it - Remove unnecessary/unused variables Fixes for modern stack canary handling" * tag 'objtool-core-2023-06-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (42 commits) x86/orc: Make the is_callthunk() definition depend on CONFIG_BPF_JIT=y objtool: Skip reading DWARF section data objtool: Free insns when done objtool: Get rid of reloc->rel[a] objtool: Shrink elf hash nodes objtool: Shrink reloc->sym_reloc_entry objtool: Get rid of reloc->jump_table_start objtool: Get rid of reloc->addend objtool: Get rid of reloc->type objtool: Get rid of reloc->offset objtool: Get rid of reloc->idx objtool: Get rid of reloc->list objtool: Allocate relocs in advance for new rela sections objtool: Add for_each_reloc() objtool: Don't free memory in elf_close() objtool: Keep GElf_Rel[a] structs synced objtool: Add elf_create_section_pair() objtool: Add mark_sec_changed() objtool: Fix reloc_hash size objtool: Consolidate rel/rela handling ...

objtool: Get rid of reloc->addend

2023-06-07T17:03:23Z

Get the addend from the embedded GElf_Rel[a] struct. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 42.10G - After: peak heap memory consumption: 40.37G Link: https://lore.kernel.org/r/ad2354f95d9ddd86094e3f7687acfa0750657784.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf