Commit 62e72449 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Dave Hansen
Browse files

x86/cpu: Make sure flag_is_changeable_p() is always being used 



When flag_is_changeable_p() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:

arch/x86/kernel/cpu/common.c:351:19: error: unused function 'flag_is_changeable_p' [-Werror,-Wunused-function]
  351 | static inline int flag_is_changeable_p(u32 flag)
      |                   ^~~~~~~~~~~~~~~~~~~~

Fix this by moving core around to make sure flag_is_changeable_p() is
always being used.

See also commit 6863f564 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

While at it, fix the argument type to be unsigned long along with
the local variables, although it currently only runs in 32-bit cases.
Besides that, makes it return boolean instead of int. This induces
the change of the returning type of have_cpuid_p() to be boolean
as well.

Suggested-by: default avatarDave Hansen <dave.hansen@intel.com>
Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarH. Peter Anvin (Intel) <hpa@zytor.com>
Link: https://lore.kernel.org/all/20241108153105.1578186-1-andriy.shevchenko%40linux.intel.com
parent 86e39b94

arch/x86/include/asm/cpuid.h

+5 −3
Original line number Diff line number Diff line
@@ -6,6 +6,8 @@ 
#ifndef _ASM_X86_CPUID_H

#define _ASM_X86_CPUID_H



#include <linux/types.h>



#include <asm/string.h>



struct cpuid_regs {
@@ -20,11 +22,11 @@ enum cpuid_regs_idx { 
};



#ifdef CONFIG_X86_32

extern int have_cpuid_p(void);

bool have_cpuid_p(void);

#else

static inline int have_cpuid_p(void)

static inline bool have_cpuid_p(void)

{

	return 1;

	return true;

}

#endif

static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,

arch/x86/kernel/cpu/common.c

+18 −21
Original line number Diff line number Diff line
@@ -275,21 +275,13 @@ static int __init x86_noinvpcid_setup(char *s) 
}

early_param("noinvpcid", x86_noinvpcid_setup);



#ifdef CONFIG_X86_32

static int cachesize_override = -1;

static int disable_x86_serial_nr = 1;



static int __init cachesize_setup(char *str)

{

	get_option(&str, &cachesize_override);

	return 1;

}

__setup("cachesize=", cachesize_setup);



/* Standard macro to see if a specific flag is changeable */

static inline int flag_is_changeable_p(u32 flag)

static inline bool flag_is_changeable_p(unsigned long flag)

{

	u32 f1, f2;

	unsigned long f1, f2;



	if (!IS_ENABLED(CONFIG_X86_32))

		return true;



	/*

	 * Cyrix and IDT cpus allow disabling of CPUID
@@ -312,11 +304,22 @@ static inline int flag_is_changeable_p(u32 flag) 
		      : "=&r" (f1), "=&r" (f2)

		      : "ir" (flag));



	return ((f1^f2) & flag) != 0;

	return (f1 ^ f2) & flag;

}



#ifdef CONFIG_X86_32

static int cachesize_override = -1;

static int disable_x86_serial_nr = 1;



static int __init cachesize_setup(char *str)

{

	get_option(&str, &cachesize_override);

	return 1;

}

__setup("cachesize=", cachesize_setup);



/* Probe for the CPUID instruction */

int have_cpuid_p(void)

bool have_cpuid_p(void)

{

	return flag_is_changeable_p(X86_EFLAGS_ID);

}
@@ -348,10 +351,6 @@ static int __init x86_serial_nr_setup(char *s) 
}

__setup("serialnumber", x86_serial_nr_setup);

#else

static inline int flag_is_changeable_p(u32 flag)

{

	return 1;

}

static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)

{

}
@@ -1087,7 +1086,6 @@ void get_cpu_address_sizes(struct cpuinfo_x86 *c) 


static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)

{

#ifdef CONFIG_X86_32

	int i;



	/*
@@ -1108,7 +1106,6 @@ static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c) 
				break;

			}

		}

#endif

}



#define NO_SPECULATION		BIT(0)