linux-kernel - [PATCH 03/13] MIPS: cpu-probe: ingenic: Fix broken BUG

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Date:   Mon,  3 Aug 2020 19:01:14 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Paul Burton <paulburton@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        周琰杰 <zhouyanjie@...yeetech.com>,
        od@...c.me, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH 03/13] MIPS: cpu-probe: ingenic: Fix broken BUG_ON

The previous code was doing:
BUG_ON(!__builtin_constant_p(cpu_has_counter) || cpu_has_counter);

This only worked as the "cpu_has_counter" macro was overridden in
<cpu-feature-overrides.h>. The default "cpu_has_counter" macro is
non-constant, which triggered the BUG_ON() independently of the value
returned by the macro.

What we want to check here, is that *if* the macro was overridden to a
compile-time constant, then must be defined to zero, otherwise it's a
bug.

So the correct check is:
BUG_ON(__builtin_constant_p(cpu_has_counter) && cpu_has_counter);

Signed-off-by: Paul Cercueil <paul@...pouillou.net>
---
 arch/mips/kernel/cpu-probe.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index a07e66a6e063..6be23f205e74 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -2123,7 +2123,7 @@ static inline void cpu_probe_ingenic(struct cpuinfo_mips *c, unsigned int cpu)
 
 	/* XBurst does not implement the CP0 counter. */
 	c->options &= ~MIPS_CPU_COUNTER;
-	BUG_ON(!__builtin_constant_p(cpu_has_counter) || cpu_has_counter);
+	BUG_ON(__builtin_constant_p(cpu_has_counter) && cpu_has_counter);
 
 	/* XBurst has virtually tagged icache */
 	c->icache.flags |= MIPS_CACHE_VTAG;
-- 
2.27.0