Commit c6c973db authored by Uros Bizjak's avatar Uros Bizjak Committed by Borislav Petkov (AMD)
Browse files

x86/asm: Remove code depending on __GCC_ASM_FLAG_OUTPUTS__ 



The minimum supported GCC version is 8.1, which supports flag output operands
and always defines __GCC_ASM_FLAG_OUTPUTS__ macro.

Remove code depending on __GCC_ASM_FLAG_OUTPUTS__ and use the "=@ccCOND" flag
output operand directly.

Use the equivalent "=@ccz" instead of "=@cce" flag output operand for
CMPXCHG8B and CMPXCHG16B instructions. These instructions set a single flag
bit - the Zero flag - and "=@ccz" is used to distinguish the CC user from
comparison instructions, where set ZERO flag indeed means that the values are
equal.

Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20250905121723.GCaLrU04lP2A50PT-B@fat_crate.local
parent 13bdfb53

arch/x86/boot/bitops.h

+1 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ static inline bool variable_test_bit(int nr, const void *addr) 
	bool v;

	const u32 *p = addr;



	asm("btl %2,%1" CC_SET(c) : CC_OUT(c) (v) : "m" (*p), "Ir" (nr));

	asm("btl %2,%1" : "=@ccc" (v) : "m" (*p), "Ir" (nr));

	return v;

}

arch/x86/boot/boot.h

+4 −4
Original line number Diff line number Diff line
@@ -155,15 +155,15 @@ static inline void wrgs32(u32 v, addr_t addr) 
static inline bool memcmp_fs(const void *s1, addr_t s2, size_t len)

{

	bool diff;

	asm volatile("fs repe cmpsb" CC_SET(nz)

		     : CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));

	asm volatile("fs repe cmpsb"

		     : "=@ccnz" (diff), "+D" (s1), "+S" (s2), "+c" (len));

	return diff;

}

static inline bool memcmp_gs(const void *s1, addr_t s2, size_t len)

{

	bool diff;

	asm volatile("gs repe cmpsb" CC_SET(nz)

		     : CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));

	asm volatile("gs repe cmpsb"

		     : "=@ccnz" (diff), "+D" (s1), "+S" (s2), "+c" (len));

	return diff;

}

arch/x86/boot/string.c

+2 −2
Original line number Diff line number Diff line
@@ -32,8 +32,8 @@ 
int memcmp(const void *s1, const void *s2, size_t len)

{

	bool diff;

	asm("repe cmpsb" CC_SET(nz)

	    : CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));

	asm("repe cmpsb"

	    : "=@ccnz" (diff), "+D" (s1), "+S" (s2), "+c" (len));

	return diff;

}

arch/x86/include/asm/archrandom.h

+2 −4
Original line number Diff line number Diff line
@@ -23,8 +23,7 @@ static inline bool __must_check rdrand_long(unsigned long *v) 
	unsigned int retry = RDRAND_RETRY_LOOPS;

	do {

		asm volatile("rdrand %[out]"

			     CC_SET(c)

			     : CC_OUT(c) (ok), [out] "=r" (*v));

			     : "=@ccc" (ok), [out] "=r" (*v));

		if (ok)

			return true;

	} while (--retry);
@@ -35,8 +34,7 @@ static inline bool __must_check rdseed_long(unsigned long *v) 
{

	bool ok;

	asm volatile("rdseed %[out]"

		     CC_SET(c)

		     : CC_OUT(c) (ok), [out] "=r" (*v));

		     : "=@ccc" (ok), [out] "=r" (*v));

	return ok;

}

arch/x86/include/asm/asm.h

+0 −12
Original line number Diff line number Diff line
@@ -122,18 +122,6 @@ static __always_inline __pure void *rip_rel_ptr(void *p) 
}

#endif



/*

 * Macros to generate condition code outputs from inline assembly,

 * The output operand must be type "bool".

 */

#ifdef __GCC_ASM_FLAG_OUTPUTS__

# define CC_SET(c) "\n\t/* output condition code " #c "*/\n"

# define CC_OUT(c) "=@cc" #c

#else

# define CC_SET(c) "\n\tset" #c " %[_cc_" #c "]\n"

# define CC_OUT(c) [_cc_ ## c] "=qm"

#endif



#ifdef __KERNEL__



# include <asm/extable_fixup_types.h>