kernel/linux.git/arch/x86/entry, branch v6.6.131

x86/xen: Move Xen upcall handler

2026-01-11T14:21:48+00:00

[ Upstream commit 1ab7b5ed44ba9bce581e225f40219b793bc779d6 ] Move the upcall handler to Xen-specific files. No functional changes. Signed-off-by: Brian Gerst Signed-off-by: Ingo Molnar Reviewed-by: Juergen Gross Reviewed-by: Sohil Mehta Cc: Andy Lutomirski Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Josh Poimboeuf Link: https://lore.kernel.org/r/20250314151220.862768-2-brgerst@gmail.com Stable-dep-of: e5aff444e3a7 ("x86/xen: Fix sparse warning in enlighten_pv.c") Signed-off-by: Sasha Levin

x86/vsyscall: Do not require X86_PF_INSTR to emulate vsyscall

2025-11-24T09:29:26+00:00

[ Upstream commit 8ba38a7a9a699905b84fa97578a8291010dec273 ] emulate_vsyscall() expects to see X86_PF_INSTR in PFEC on a vsyscall page fault, but the CPU does not report X86_PF_INSTR if neither X86_FEATURE_NX nor X86_FEATURE_SMEP are enabled. X86_FEATURE_NX should be enabled on nearly all 64-bit CPUs, except for early P4 processors that did not support this feature. Instead of explicitly checking for X86_PF_INSTR, compare the fault address to RIP. On machines with X86_FEATURE_NX enabled, issue a warning if RIP is equal to fault address but X86_PF_INSTR is absent. [ dhansen: flesh out code comments ] Originally-by: Dave Hansen Reported-by: Andrew Cooper Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Andrew Cooper Link: https://lore.kernel.org/all/bd81a98b-f8d4-4304-ac55-d4151a1a77ab@intel.com Link: https://lore.kernel.org/all/20250624145918.2720487-1-kirill.shutemov%40linux.intel.com Signed-off-by: Sasha Levin

x86/bugs: Rename MDS machinery to something more generic

2025-07-10T14:03:21+00:00

Commit f9af88a3d384c8b55beb5dc5483e5da0135fadbd upstream. It will be used by other x86 mitigations. No functional changes. Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Pawan Gupta Signed-off-by: Greg Kroah-Hartman

x86/stackprotector/64: Only export __ref_stack_chk_guard on CONFIG_SMP

2025-06-04T12:41:56+00:00

[ Upstream commit 91d5451d97ce35cbd510277fa3b7abf9caa4e34d ] 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 Signed-off-by: Sasha Levin

x86/its: Align RETs in BHB clear sequence to avoid thunking

2025-05-18T06:24:11+00:00

commit f0cd7091cc5a032c8870b4285305d9172569d126 upstream. The software mitigation for BHI is to execute BHB clear sequence at syscall entry, and possibly after a cBPF program. ITS mitigation thunks RETs in the lower half of the cacheline. This causes the RETs in the BHB clear sequence to be thunked as well, adding unnecessary branches to the BHB clear sequence. Since the sequence is in hot path, align the RET instructions in the sequence to avoid thunking. This is how disassembly clear_bhb_loop() looks like after this change: 0x44 <+4>: mov $0x5,%ecx 0x49 <+9>: call 0xffffffff81001d9b 0x4e <+14>: jmp 0xffffffff81001de5 0x53 <+19>: int3 ... 0x9b <+91>: call 0xffffffff81001dce 0xa0 <+96>: ret 0xa1 <+97>: int3 ... 0xce <+142>: mov $0x5,%eax 0xd3 <+147>: jmp 0xffffffff81001dd6 0xd5 <+149>: nop 0xd6 <+150>: sub $0x1,%eax 0xd9 <+153>: jne 0xffffffff81001dd3 0xdb <+155>: sub $0x1,%ecx 0xde <+158>: jne 0xffffffff81001d9b 0xe0 <+160>: ret 0xe1 <+161>: int3 0xe2 <+162>: int3 0xe3 <+163>: int3 0xe4 <+164>: int3 0xe5 <+165>: lfence 0xe8 <+168>: pop %rbp 0xe9 <+169>: ret Suggested-by: Andrew Cooper Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Alexandre Chartre Signed-off-by: Greg Kroah-Hartman

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

2025-05-02T05:50:59+00:00

[ Upstream commit fc9fd3f98423367c79e0bd85a9515df26dc1b3cc ] 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 Signed-off-by: Sasha Levin

x86/entry: Fix ORC unwinder for PUSH_REGS with save_ret=1

2025-04-10T12:37:31+00:00

[ Upstream commit 57e2428f8df8263275344566e02c277648a4b7f1 ] PUSH_REGS with save_ret=1 is used by interrupt entry helper functions that initially start with a UNWIND_HINT_FUNC ORC state. However, save_ret=1 means that we clobber the helper function's return address (and then later restore the return address further down on the stack); after that point, the only thing on the stack we can unwind through is the IRET frame, so use UNWIND_HINT_IRET_REGS until we have a full pt_regs frame. ( An alternate approach would be to move the pt_regs->di overwrite down such that it is the final step of pt_regs setup; but I don't want to rearrange entry code just to make unwinding a tiny bit more elegant. ) Fixes: 9e809d15d6b6 ("x86/entry: Reduce the code footprint of the 'idtentry' macro") Signed-off-by: Jann Horn Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Brian Gerst Cc: Juergen Gross Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Kees Cook Cc: Peter Zijlstra Cc: Josh Poimboeuf Link: https://lore.kernel.org/r/20250325-2025-03-unwind-fixes-v1-1-acd774364768@google.com Signed-off-by: Sasha Levin

x86/ptrace: Cleanup the definition of the pt_regs structure

2025-01-09T12:31:51+00:00

[ Upstream commit ee63291aa8287cb7ded767d340155fe8681fc075 ] struct pt_regs is hard to read because the member or section related comments are not aligned with the members. The 'cs' and 'ss' members of pt_regs are type of 'unsigned long' while in reality they are only 16-bit wide. This works so far as the remaining space is unused, but FRED will use the remaining bits for other purposes. To prepare for FRED: - Cleanup the formatting - Convert 'cs' and 'ss' to u16 and embed them into an union with a u64 - Fixup the related printk() format strings Suggested-by: Thomas Gleixner Originally-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Tested-by: Shan Kang Link: https://lore.kernel.org/r/20231205105030.8698-14-xin3.li@intel.com Stable-dep-of: dc81e556f2a0 ("x86/fred: Clear WFE in missing-ENDBRANCH #CPs") Signed-off-by: Sasha Levin

x86/stackprotector: Work around strict Clang TLS symbol requirements

2024-12-09T09:31:41+00:00

[ Upstream commit 577c134d311b9b94598d7a0c86be1f431f823003 ] GCC and Clang both implement stack protector support based on Thread Local Storage (TLS) variables, and this is used in the kernel to implement per-task stack cookies, by copying a task's stack cookie into a per-CPU variable every time it is scheduled in. Both now also implement -mstack-protector-guard-symbol=, which permits the TLS variable to be specified directly. This is useful because it will allow to move away from using a fixed offset of 40 bytes into the per-CPU area on x86_64, which requires a lot of special handling in the per-CPU code and the runtime relocation code. However, while GCC is rather lax in its implementation of this command line option, Clang actually requires that the provided symbol name refers to a TLS variable (i.e., one declared with __thread), although it also permits the variable to be undeclared entirely, in which case it will use an implicit declaration of the right type. The upshot of this is that Clang will emit the correct references to the stack cookie variable in most cases, e.g., 10d: 64 a1 00 00 00 00 mov %fs:0x0,%eax 10f: R_386_32 __stack_chk_guard However, if a non-TLS definition of the symbol in question is visible in the same compilation unit (which amounts to the whole of vmlinux if LTO is enabled), it will drop the per-CPU prefix and emit a load from a bogus address. Work around this by using a symbol name that never occurs in C code, and emit it as an alias in the linker script. Fixes: 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable") Signed-off-by: Ard Biesheuvel Signed-off-by: Brian Gerst Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Nathan Chancellor Tested-by: Nathan Chancellor Cc: stable@vger.kernel.org Link: https://github.com/ClangBuiltLinux/linux/issues/1854 Link: https://lore.kernel.org/r/20241105155801.1779119-2-brgerst@gmail.com Signed-off-by: Sasha Levin

x86/entry_32: Clear CPU buffers after register restore in NMI return

2024-10-22T13:46:34+00:00

commit 48a2440d0f20c826b884e04377ccc1e4696c84e9 upstream. CPU buffers are currently cleared after call to exc_nmi, but before register state is restored. This may be okay for MDS mitigation but not for RDFS. Because RDFS mitigation requires CPU buffers to be cleared when registers don't have any sensitive data. Move CLEAR_CPU_BUFFERS after RESTORE_ALL_NMI. Fixes: a0e2dab44d22 ("x86/entry_32: Add VERW just before userspace transition") Suggested-by: Dave Hansen Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/20240925-fix-dosemu-vm86-v7-2-1de0daca2d42%40linux.intel.com Signed-off-by: Greg Kroah-Hartman