Commit 2ee08a89 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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
parents 1c3b68f0 3b19e22c

arch/x86/include/asm/elf.h

+4 −5
Original line number Diff line number Diff line
@@ -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 */

arch/x86/include/asm/fsgsbase.h

+2 −2
Original line number Diff line number Diff line
@@ -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;

}

arch/x86/include/asm/segment.h

+36 −23
Original line number Diff line number Diff line
@@ -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"

	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__ */

arch/x86/kernel/process_32.c

+1 −1
Original line number Diff line number Diff line
@@ -61,7 +61,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode, 
{

	unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;

	unsigned long d0, d1, d2, d3, d6, d7;

	unsigned short gs;

	unsigned int gs;



	savesegment(gs, gs);

arch/x86/kernel/process_64.c

+4 −4
Original line number Diff line number Diff line
@@ -104,10 +104,10 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode, 
		return;

	}



	asm("movl %%ds,%0" : "=r" (ds));

	asm("movl %%es,%0" : "=r" (es));

	asm("movl %%fs,%0" : "=r" (fsindex));

	asm("movl %%gs,%0" : "=r" (gsindex));

	savesegment(ds, ds);

	savesegment(es, es);

	savesegment(fs, fsindex);

	savesegment(gs, gsindex);



	rdmsrq(MSR_FS_BASE, fs);

	rdmsrq(MSR_GS_BASE, gs);