Merge tag 'x86-asm-2026-04-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 asm from Ingo Molnar:
 "x86 asm cleanups by Uros Bizjak:

   - Remove unnecessary memory clobbers from FS/GS base (read-)
     accessors and savesegment()

   - Use ASM_INPUT_RM in __loadsegment_fs() to work around clang code
     generation problems

   - Implement loadsegment()/savesegment() macros with static inline
     helpers

   - Use savesegment() for segment register reads in ELF core dump and
     __show_regs()

   - Use correct type for 'gs' variable in __show_regs() to avoid
     zero-extension

   - Clean up 'sel' variable usage in do_set_thread_area()"

* tag 'x86-asm-2026-04-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tls: Clean up 'sel' variable usage in do_set_thread_area()
  x86/process/32: Use correct type for 'gs' variable in __show_regs() to avoid zero-extension
  x86/process/64: Use savesegment() in __show_regs() instead of inline asm
  x86/elf: Use savesegment() for segment register reads in ELF core dump
  x86/asm/segment: Implement loadsegment()/savesegment() macros with static inline helpers
  x86/asm/segment: Use ASM_INPUT_RM in __loadsegment_fs()
  x86/asm/segment: Remove unnecessary "memory" clobber from savesegment()
  x86/asm/fsgsbase: Remove unnecessary "memory" clobbers from FS/GS base (read-) accessors

3 files changed, 42 insertions, 30 deletions

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 2ba5f166e58f..c7f98977663c 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -187,7 +187,6 @@ void set_personality_ia32(bool);
 
 #define ELF_CORE_COPY_REGS(pr_reg, regs)			\
 do {								\
-	unsigned v;						\
 	(pr_reg)[0] = (regs)->r15;				\
 	(pr_reg)[1] = (regs)->r14;				\
 	(pr_reg)[2] = (regs)->r13;				\
@@ -211,10 +210,10 @@ do {								\
 	(pr_reg)[20] = (regs)->ss;				\
 	(pr_reg)[21] = x86_fsbase_read_cpu();			\
 	(pr_reg)[22] = x86_gsbase_read_cpu_inactive();		\
-	asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v;	\
-	asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v;	\
-	asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v;	\
-	asm("movl %%gs,%0" : "=r" (v)); (pr_reg)[26] = v;	\
+	savesegment(ds, (pr_reg)[23]);				\
+	savesegment(es, (pr_reg)[24]);				\
+	savesegment(fs, (pr_reg)[25]);				\
+	savesegment(gs, (pr_reg)[26]);				\
 } while (0);
 
 /* I'm not sure if we can use '-' here */
diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index ab2547f97c2c..70ff4ef457b1 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -25,7 +25,7 @@ static __always_inline unsigned long rdfsbase(void)
 {
 	unsigned long fsbase;
 
-	asm volatile("rdfsbase %0" : "=r" (fsbase) :: "memory");
+	asm volatile("rdfsbase %0" : "=r" (fsbase));
 
 	return fsbase;
 }
@@ -34,7 +34,7 @@ static __always_inline unsigned long rdgsbase(void)
 {
 	unsigned long gsbase;
 
-	asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");
+	asm volatile("rdgsbase %0" : "=r" (gsbase));
 
 	return gsbase;
 }
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index 9f5be2bbd291..dbd90fede5e7 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -302,19 +302,17 @@ extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_I
  * failure to fully clear the cached descriptor is only observable for
  * FS and GS.
  */
-#define __loadsegment_simple(seg, value)				\
-do {									\
-	unsigned short __val = (value);					\
-									\
-	asm volatile("						\n"	\
-		     "1:	movl %k0,%%" #seg "		\n"	\
+#define LOAD_SEGMENT(seg)						\
+static inline void __loadsegment_##seg(u16 value)			\
+{									\
+	asm volatile("1:	movl %k0,%%" #seg "\n"			\
 		     _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k0)\
-		     : "+r" (__val) : : "memory");			\
-} while (0)
+		     : "+r" (value) : : "memory");			\
+}
 
-#define __loadsegment_ss(value) __loadsegment_simple(ss, (value))
-#define __loadsegment_ds(value) __loadsegment_simple(ds, (value))
-#define __loadsegment_es(value) __loadsegment_simple(es, (value))
+LOAD_SEGMENT(ss)
+LOAD_SEGMENT(ds)
+LOAD_SEGMENT(es)
 
 #ifdef CONFIG_X86_32
 
@@ -322,33 +320,48 @@ do {									\
  * On 32-bit systems, the hidden parts of FS and GS are unobservable if
  * the selector is NULL, so there's no funny business here.
  */
-#define __loadsegment_fs(value) __loadsegment_simple(fs, (value))
-#define __loadsegment_gs(value) __loadsegment_simple(gs, (value))
+LOAD_SEGMENT(fs)
+LOAD_SEGMENT(gs)
 
 #else
 
-static inline void __loadsegment_fs(unsigned short value)
+static inline void __loadsegment_fs(u16 value)
 {
-	asm volatile("						\n"
-		     "1:	movw %0, %%fs			\n"
-		     "2:					\n"
-
+	asm volatile("1:	movw %0, %%fs\n"
+		     "2:\n"
 		     _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_CLEAR_FS)
-
-		     : : "rm" (value) : "memory");
+		     : : ASM_INPUT_RM (value) : "memory");
 }
 
 /* __loadsegment_gs is intentionally undefined.  Use load_gs_index instead. */
 
 #endif
 
-#define loadsegment(seg, value) __loadsegment_ ## seg (value)
+#undef LOAD_SEGMENT
+
+#define loadsegment(seg, val) __loadsegment_##seg(val)
 
 /*
  * Save a segment register away:
  */
-#define savesegment(seg, value)				\
-	asm("movl %%" #seg ",%k0" : "=r" (value) : : "memory")
+#define SAVE_SEGMENT(seg)				\
+static inline unsigned long __savesegment_##seg(void)	\
+{							\
+	unsigned long v;				\
+	asm volatile("movl %%" #seg ",%k0" : "=r" (v));	\
+	return v;					\
+}
+
+SAVE_SEGMENT(cs)
+SAVE_SEGMENT(ss)
+SAVE_SEGMENT(ds)
+SAVE_SEGMENT(es)
+SAVE_SEGMENT(fs)
+SAVE_SEGMENT(gs)
+
+#undef SAVE_SEGMENT
+
+#define savesegment(seg, var) ((var) = __savesegment_##seg())
 
 #endif /* !__ASSEMBLER__ */
 #endif /* __KERNEL__ */