kernel/linux.git/arch/x86/include/asm/segment.h, branch linux-7.1.y

x86/asm/segment: Implement loadsegment()/savesegment() macros with static inline helpers

2026-03-30T07:10:16+00:00

Convert the __loadsegment_simple() and savesegment() macro implementations into static inline helper functions generated via small helper macros. Historically loadsegment() and savesegment() relied on macros that embedded inline assembly. This approach obscures types, complicates debugging, and makes the call sites harder for the compiler and static analysis tools to reason about. This change is purely mechanical and does not alter the generated code, but improves readability, type safety, and compiler visibility of the helpers. Suggested-by: H. Peter Anvin Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://patch.msgid.link/20260330055823.5793-4-ubizjak@gmail.com

x86/asm/segment: Use ASM_INPUT_RM in __loadsegment_fs()

2026-03-30T07:10:16+00:00

Use the ASM_INPUT_RM macro in __loadsegment_fs() to work around Clang problems with the "rm" asm constraint. Clang seems to always chose the memory input, while it is almost always the worst choice. Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Acked-by: Nathan Chancellor Cc: Linus Torvalds Cc: H. Peter Anvin Link: https://patch.msgid.link/20260330055823.5793-3-ubizjak@gmail.com

x86/asm/segment: Remove unnecessary "memory" clobber from savesegment()

2026-03-30T07:10:15+00:00

The savesegment() macro uses inline assembly to copy a segment register into a general-purpose register: movl %seg, reg This instruction does not access memory, yet the inline asm currently declares a "memory" clobber, which unnecessarily acts as a compiler barrier and may inhibit optimization. Remove the "memory" clobber and mark the asm as `asm volatile` instead. Segment register loads in the kernel are implemented using `asm volatile`, so the compiler will not schedule segment register reads before those loads. Using `asm volatile` preserves the intended ordering with other segment register operations without imposing an unnecessary global memory barrier. No functional change intended. Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: H. Peter Anvin Link: https://patch.msgid.link/20260330055823.5793-2-ubizjak@gmail.com

x86/segment: Use MOVL when reading segment registers

2026-01-20T11:34:58+00:00

Use MOVL when reading segment registers to avoid 0x66 operand-size override insn prefix. The segment value is always 16-bit and gets zero-extended to the full 32-bit size. Example: 4e4: 66 8c c0 mov %es,%ax 4e7: 66 89 83 80 0b 00 00 mov %ax,0xb80(%rbx) 4e4: 8c c0 mov %es,%eax 4e6: 66 89 83 80 0b 00 00 mov %ax,0xb80(%rbx) Also, use the %k0 modifier which generates the SImode (signed integer) register name for the target register. [ bp: Extend and clarify commit message. ] Signed-off-by: Uros Bizjak Signed-off-by: Borislav Petkov (AMD) Reviewed-by: H. Peter Anvin (Intel) Tested-by: Michael Kelley Link: https://patch.msgid.link/20260105090422.6243-1-ubizjak@gmail.com

x86/vdso: Fix output operand size of RDPID

2025-08-26T17:33:19+00:00

RDPID instruction outputs to a word-sized register (64-bit on x86_64 and 32-bit on x86_32). Use an unsigned long variable to store the correct size. LSL outputs to 32-bit register, use %k operand prefix to always print the 32-bit name of the register. Use RDPID insn mnemonic while at it as the minimum binutils version of 2.30 supports it. [ bp: Merge two patches touching the same function into a single one. ] Fixes: ffebbaedc861 ("x86/vdso: Introduce helper functions for CPU and node number") Signed-off-by: Uros Bizjak Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/20250616095315.230620-1-ubizjak@gmail.com

x86/headers: Replace ASSEMBLY with ASSEMBLER in non-UAPI headers

2025-03-19T10:47:30+00:00

While the GCC and Clang compilers already define __ASSEMBLER__ automatically when compiling assembly code, __ASSEMBLY__ is a macro that only gets defined by the Makefiles in the kernel. This can be very confusing when switching between userspace and kernelspace coding, or when dealing with UAPI headers that rather should use __ASSEMBLER__ instead. So let's standardize on the __ASSEMBLER__ macro that is provided by the compilers now. This is mostly a mechanical patch (done with a simple "sed -i" statement), with some manual tweaks in , and that mentioned this macro in comments with some missing underscores. Signed-off-by: Thomas Huth Signed-off-by: Ingo Molnar Cc: Brian Gerst Cc: Juergen Gross Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250314071013.1575167-38-thuth@redhat.com

x86/vdso: Choose the right GDT_ENTRY_CPUNODE for 32-bit getcpu() on 64-bit kernel

2023-08-08T07:31:43+00:00

The vDSO getcpu() reads CPU ID from the GDT_ENTRY_CPUNODE entry when the RDPID instruction is not available. And GDT_ENTRY_CPUNODE is defined as 28 on 32-bit Linux kernel and 15 on 64-bit. But the 32-bit getcpu() on 64-bit Linux kernel is compiled with 32-bit Linux kernel GDT_ENTRY_CPUNODE, i.e., 28, beyond the 64-bit Linux kernel GDT limit. Thus, it just fails _silently_. When BUILD_VDSO32_64 is defined, choose the 64-bit Linux kernel GDT definitions to compile the 32-bit getcpu(). Fixes: 877cff5296faa6e ("x86/vdso: Fake 32bit VDSO build on 64bit compile for vgetcpu") Reported-by: kernel test robot Reported-by: Shan Kang Signed-off-by: Xin Li Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230322061758.10639-1-xin3.li@intel.com Link: https://lore.kernel.org/oe-lkp/202303020903.b01fd1de-yujie.liu@intel.com

x86/cpu: Provide the full setup for getcpu() on x86-32

2023-02-06T14:48:54+00:00

setup_getcpu() configures two things: - it writes the current CPU & node information into MSR_TSC_AUX - it writes the same information as a GDT entry. By using the "full" setup_getcpu() on i386 it is possible to read the CPU information in userland via RDTSCP() or via LSL from the GDT. Provide an GDT_ENTRY_CPUNODE for x86-32 and make the setup function unconditionally available. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Reviewed-by: Roland Mainz Link: https://lore.kernel.org/r/20221125094216.3663444-2-bigeasy@linutronix.de

x86/signal/32: Merge native and compat 32-bit signal code

2022-10-19T07:58:49+00:00

There are significant differences between signal handling on 32-bit vs. 64-bit, like different structure layouts and legacy syscalls. Instead of duplicating that code for native and compat, merge both versions into one file. Signed-off-by: Brian Gerst Signed-off-by: Borislav Petkov Acked-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/20220606203802.158958-8-brgerst@gmail.com Signed-off-by: Borislav Petkov

x86: Remove __USER32_DS