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>

1 files changed, 0 insertions, 49 deletions

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 4d75bc656f97..30bb0bd3b1b8 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -45,55 +45,6 @@ __visible bool ex_handler_fault(const struct exception_table_entry *fixup,
 EXPORT_SYMBOL_GPL(ex_handler_fault);
 
 /*
- * Handler for UD0 exception following a failed test against the
- * result of a refcount inc/dec/add/sub.
- */
-__visible bool ex_handler_refcount(const struct exception_table_entry *fixup,
-				   struct pt_regs *regs, int trapnr,
-				   unsigned long error_code,
-				   unsigned long fault_addr)
-{
-	/* First unconditionally saturate the refcount. */
-	*(int *)regs->cx = INT_MIN / 2;
-
-	/*
-	 * Strictly speaking, this reports the fixup destination, not
-	 * the fault location, and not the actually overflowing
-	 * instruction, which is the instruction before the "js", but
-	 * since that instruction could be a variety of lengths, just
-	 * report the location after the overflow, which should be close
-	 * enough for finding the overflow, as it's at least back in
-	 * the function, having returned from .text.unlikely.
-	 */
-	regs->ip = ex_fixup_addr(fixup);
-
-	/*
-	 * This function has been called because either a negative refcount
-	 * value was seen by any of the refcount functions, or a zero
-	 * refcount value was seen by refcount_dec().
-	 *
-	 * If we crossed from INT_MAX to INT_MIN, OF (Overflow Flag: result
-	 * wrapped around) will be set. Additionally, seeing the refcount
-	 * reach 0 will set ZF (Zero Flag: result was zero). In each of
-	 * these cases we want a report, since it's a boundary condition.
-	 * The SF case is not reported since it indicates post-boundary
-	 * manipulations below zero or above INT_MAX. And if none of the
-	 * flags are set, something has gone very wrong, so report it.
-	 */
-	if (regs->flags & (X86_EFLAGS_OF | X86_EFLAGS_ZF)) {
-		bool zero = regs->flags & X86_EFLAGS_ZF;
-
-		refcount_error_report(regs, zero ? "hit zero" : "overflow");
-	} else if ((regs->flags & X86_EFLAGS_SF) == 0) {
-		/* Report if none of OF, ZF, nor SF are set. */
-		refcount_error_report(regs, "unexpected saturation");
-	}
-
-	return true;
-}
-EXPORT_SYMBOL(ex_handler_refcount);
-
-/*
  * Handler for when we fail to restore a task's FPU state.  We should never get
  * here because the FPU state of a task using the FPU (task->thread.fpu.state)
  * should always be valid.  However, past bugs have allowed userspace to set