locking/refcount: Consolidate implementations of refcount_t

The generic implementation of refcount_t should be good enough for
everybody, so remove ARCH_HAS_REFCOUNT and REFCOUNT_FULL entirely,
leaving the generic implementation enabled unconditionally.

Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191121115902.2551-9-will@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 0 insertions, 132 deletions

diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 3ff577c0b102..5a0c14ebef70 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -139,9 +139,6 @@
 # define _ASM_EXTABLE_EX(from, to)				\
 	_ASM_EXTABLE_HANDLE(from, to, ex_handler_ext)
 
-# define _ASM_EXTABLE_REFCOUNT(from, to)			\
-	_ASM_EXTABLE_HANDLE(from, to, ex_handler_refcount)
-
 # define _ASM_NOKPROBE(entry)					\
 	.pushsection "_kprobe_blacklist","aw" ;			\
 	_ASM_ALIGN ;						\
@@ -170,9 +167,6 @@
 # define _ASM_EXTABLE_EX(from, to)				\
 	_ASM_EXTABLE_HANDLE(from, to, ex_handler_ext)
 
-# define _ASM_EXTABLE_REFCOUNT(from, to)			\
-	_ASM_EXTABLE_HANDLE(from, to, ex_handler_refcount)
-
 /* For C file, we already have NOKPROBE_SYMBOL macro */
 #endif
 
diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
deleted file mode 100644
index 232f856e0db0..000000000000
--- a/arch/x86/include/asm/refcount.h
+++ /dev/null
@@ -1,126 +0,0 @@
-#ifndef __ASM_X86_REFCOUNT_H
-#define __ASM_X86_REFCOUNT_H
-/*
- * x86-specific implementation of refcount_t. Based on PAX_REFCOUNT from
- * PaX/grsecurity.
- */
-#include <linux/refcount.h>
-#include <asm/bug.h>
-
-/*
- * This is the first portion of the refcount error handling, which lives in
- * .text.unlikely, and is jumped to from the CPU flag check (in the
- * following macros). This saves the refcount value location into CX for
- * the exception handler to use (in mm/extable.c), and then triggers the
- * central refcount exception. The fixup address for the exception points
- * back to the regular execution flow in .text.
- */
-#define _REFCOUNT_EXCEPTION				\
-	".pushsection .text..refcount\n"		\
-	"111:\tlea %[var], %%" _ASM_CX "\n"		\
-	"112:\t" ASM_UD2 "\n"				\
-	ASM_UNREACHABLE					\
-	".popsection\n"					\
-	"113:\n"					\
-	_ASM_EXTABLE_REFCOUNT(112b, 113b)
-
-/* Trigger refcount exception if refcount result is negative. */
-#define REFCOUNT_CHECK_LT_ZERO				\
-	"js 111f\n\t"					\
-	_REFCOUNT_EXCEPTION
-
-/* Trigger refcount exception if refcount result is zero or negative. */
-#define REFCOUNT_CHECK_LE_ZERO				\
-	"jz 111f\n\t"					\
-	REFCOUNT_CHECK_LT_ZERO
-
-/* Trigger refcount exception unconditionally. */
-#define REFCOUNT_ERROR					\
-	"jmp 111f\n\t"					\
-	_REFCOUNT_EXCEPTION
-
-static __always_inline void refcount_add(unsigned int i, refcount_t *r)
-{
-	asm volatile(LOCK_PREFIX "addl %1,%0\n\t"
-		REFCOUNT_CHECK_LT_ZERO
-		: [var] "+m" (r->refs.counter)
-		: "ir" (i)
-		: "cc", "cx");
-}
-
-static __always_inline void refcount_inc(refcount_t *r)
-{
-	asm volatile(LOCK_PREFIX "incl %0\n\t"
-		REFCOUNT_CHECK_LT_ZERO
-		: [var] "+m" (r->refs.counter)
-		: : "cc", "cx");
-}
-
-static __always_inline void refcount_dec(refcount_t *r)
-{
-	asm volatile(LOCK_PREFIX "decl %0\n\t"
-		REFCOUNT_CHECK_LE_ZERO
-		: [var] "+m" (r->refs.counter)
-		: : "cc", "cx");
-}
-
-static __always_inline __must_check
-bool refcount_sub_and_test(unsigned int i, refcount_t *r)
-{
-	bool ret = GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
-					 REFCOUNT_CHECK_LT_ZERO,
-					 r->refs.counter, e, "er", i, "cx");
-
-	if (ret) {
-		smp_acquire__after_ctrl_dep();
-		return true;
-	}
-
-	return false;
-}
-
-static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)
-{
-	bool ret = GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
-					 REFCOUNT_CHECK_LT_ZERO,
-					 r->refs.counter, e, "cx");
-
-	if (ret) {
-		smp_acquire__after_ctrl_dep();
-		return true;
-	}
-
-	return false;
-}
-
-static __always_inline __must_check
-bool refcount_add_not_zero(unsigned int i, refcount_t *r)
-{
-	int c, result;
-
-	c = atomic_read(&(r->refs));
-	do {
-		if (unlikely(c == 0))
-			return false;
-
-		result = c + i;
-
-		/* Did we try to increment from/to an undesirable state? */
-		if (unlikely(c < 0 || c == INT_MAX || result < c)) {
-			asm volatile(REFCOUNT_ERROR
-				     : : [var] "m" (r->refs.counter)
-				     : "cc", "cx");
-			break;
-		}
-
-	} while (!atomic_try_cmpxchg(&(r->refs), &c, result));
-
-	return c != 0;
-}
-
-static __always_inline __must_check bool refcount_inc_not_zero(refcount_t *r)
-{
-	return refcount_add_not_zero(1, r);
-}
-
-#endif