kernel.git/arch/x86/entry/entry.S, branch linux-6.19.y

Merge tag 'x86_misc_for_6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-12-02T22:16:42Z

Pull misc x86 updates from Dave Hansen: "The most significant are some changes to ensure that symbols exported for KVM are used only by KVM modules themselves, along with some related cleanups. In true x86/misc fashion, the other patch is completely unrelated and just enhances an existing pr_warn() to make it clear to users how they have tainted their kernel when something is mucking with MSRs. Summary: - Make MSR-induced taint easier for users to track down - Restrict KVM-specific exports to KVM itself" * tag 'x86_misc_for_6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Restrict KVM-induced symbol exports to KVM modules where obvious/possible x86/mm: Drop unnecessary export of "ptdump_walk_pgd_level_debugfs" x86/mtrr: Drop unnecessary export of "mtrr_state" x86/bugs: Drop unnecessary export of "x86_spec_ctrl_base" x86/msr: Add CPU_OUT_OF_SPEC taint name to "unrecognized" pr_warn(msg)

x86_64/bug: Implement __WARN_printf()

2025-11-24T19:23:05Z

The basic idea is to have __WARN_printf() be a vararg function such that the compiler can do the optimal calling convention for us. This function body will be a #UD and then set up a va_list in the exception from pt_regs. But because the trap will be in a called function, the bug_entry must be passed in. Have that be the first argument, with the format tucked away inside the bug_entry. The comments should clarify the real fun details. The big downside is that all WARNs will now show: RIP: 0010:__WARN_trap:+0 One possible solution is to simply discard the top frame when unwinding. A follow up patch takes care of this slightly differently by abusing the x86 static_call implementation. This changes (with the next patches): WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, "corrupted preempt_count: %s/%d/0x%x\n", from: cmpl $2, %ecx #, _7 jne .L1472 ... .L1472: cmpb $0, __already_done.11(%rip) je .L1513 ... .L1513 movb $1, __already_done.11(%rip) movl 1424(%r14), %edx # _15->pid, _15->pid leaq 1912(%r14), %rsi #, _17 movq $.LC43, %rdi #, call __warn_printk # ud2 .pushsection __bug_table,"aw" 2: .long 1b - . # bug_entry::bug_addr .long .LC1 - . # bug_entry::file .word 5093 # bug_entry::line .word 2313 # bug_entry::flags .org 2b + 12 .popsection .pushsection .discard.annotate_insn,"M", @progbits, 8 .long 1b - . .long 8 # ANNOTYPE_REACHABLE .popsection into: cmpl $2, %ecx #, _7 jne .L1442 #, ... .L1442: lea (2f)(%rip), %rdi 1: .pushsection __bug_table,"aw" 2: .long 1b - . # bug_entry::bug_addr .long .LC43 - . # bug_entry::format .long .LC1 - . # bug_entry::file .word 5093 # bug_entry::line .word 2323 # bug_entry::flags .org 2b + 16 .popsection movl 1424(%r14), %edx # _19->pid, _19->pid leaq 1912(%r14), %rsi #, _13 ud1 (%edx), %rdi Notably, by pushing everything into the exception handler it can take care of the ONCE thing. Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20251110115758.213813530@infradead.org

x86: Restrict KVM-induced symbol exports to KVM modules where obvious/possible

2025-11-12T23:29:38Z

Extend KVM's export macro framework to provide EXPORT_SYMBOL_FOR_KVM(), and use the helper macro to export symbols for KVM throughout x86 if and only if KVM will build one or more modules, and only for those modules. To avoid unnecessary exports when CONFIG_KVM=m but kvm.ko will not be built (because no vendor modules are selected), let arch code #define EXPORT_SYMBOL_FOR_KVM to suppress/override the exports. Note, the set of symbols to restrict to KVM was generated by manual search and audit; any "misses" are due to human error, not some grand plan. Signed-off-by: Sean Christopherson Signed-off-by: Dave Hansen Acked-by: Kai Huang Tested-by: Kai Huang Link: https://patch.msgid.link/20251112173944.1380633-5-seanjc%40google.com

x86/bugs: Rename MDS machinery to something more generic

2025-06-16T16:45:18Z

It will be used by other x86 mitigations. No functional changes. Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Pawan Gupta

x86/bugs: Use SBPB in write_ibpb() if applicable

2025-04-09T10:41:30Z

write_ibpb() does IBPB, which (among other things) flushes branch type predictions on AMD. If the CPU has SRSO_NO, or if the SRSO mitigation has been disabled, branch type flushing isn't needed, in which case the lighter-weight SBPB can be used. The 'x86_pred_cmd' variable already keeps track of whether IBPB or SBPB should be used. Use that instead of hardcoding IBPB. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/17c5dcd14b29199b75199d67ff7758de9d9a4928.1744148254.git.jpoimboe@kernel.org

x86/bugs: Rename entry_ibpb() to write_ibpb()

2025-04-09T10:41:29Z

There's nothing entry-specific about entry_ibpb(). In preparation for calling it from elsewhere, rename it to write_ibpb(). Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/1e54ace131e79b760de3fe828264e26d0896e3ac.1744148254.git.jpoimboe@kernel.org

x86/stackprotector/64: Only export __ref_stack_chk_guard on CONFIG_SMP

2025-03-19T10:26:58Z

The __ref_stack_chk_guard symbol doesn't exist on UP: :4:15: error: ‘__ref_stack_chk_guard’ undeclared here (not in a function) Fix the #ifdef around the entry.S export. Signed-off-by: Ingo Molnar Cc: Brian Gerst Cc: Ard Biesheuvel Cc: Uros Bizjak Link: https://lore.kernel.org/r/20250123190747.745588-8-brgerst@gmail.com

Merge branch 'x86/asm' into x86/core, to pick up dependent commits

2025-03-04T19:29:35Z

Signed-off-by: Ingo Molnar

x86/stackprotector/64: Convert to normal per-CPU variable

2025-02-18T09:15:09Z

Older versions of GCC fixed the location of the stack protector canary at %gs:40. This constraint forced the percpu section to be linked at absolute address 0 so that the canary could be the first data object in the percpu section. Supporting the zero-based percpu section requires additional code to handle relocations for RIP-relative references to percpu data, extra complexity to kallsyms, and workarounds for linker bugs due to the use of absolute symbols. GCC 8.1 supports redefining where the canary is located, allowing it to become a normal percpu variable instead of at a fixed location. This removes the constraint that the percpu section must be zero-based. Signed-off-by: Brian Gerst Signed-off-by: Ingo Molnar Reviewed-by: Ard Biesheuvel Reviewed-by: Uros Bizjak Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250123190747.745588-8-brgerst@gmail.com

x86/cfi: Clean up linkage

2025-02-14T09:32:05Z

With the introduction of kCFI the addition of ENDBR to SYM_FUNC_START* no longer suffices to make the function indirectly callable. This now requires the use of SYM_TYPED_FUNC_START. As such, remove the implicit ENDBR from SYM_FUNC_START* and add some explicit annotations to fix things up again. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Sami Tolvanen Link: https://lore.kernel.org/r/20250207122546.409116003@infradead.org