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locking/refcount: Consolidate implementations of refcount_t

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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>
This commit is contained in:
Will Deacon
2019-11-21 11:59:00 +00:00
committed by Ingo Molnar
parent 65b0085524
commit fb041bb7c0
11 changed files with 59 additions and 308 deletions
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49
arch/x86/mm/extable.c
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@@ -44,55 +44,6 @@ __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)