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Subject: Re: [PATCH] powerpc/perfctr: Check oprofile_cpu_type for NULL
	before using it
From: Michael Ellerman <michael@ellerman.id.au>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
In-Reply-To: <1249531356.18245.73.camel@pasglop>
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Date: Thu, 06 Aug 2009 21:03:06 +1000
Message-Id: <1249556586.4800.79.camel@concordia>
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Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>, Ingo Molnar <mingo@elte.hu>,
	Paul Mackerras <paulus@samba.org>, David Woodhouse <dwmw2@infradead.org>
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On Thu, 2009-08-06 at 14:02 +1000, Benjamin Herrenschmidt wrote:
> If the current CPU doesn't support performance counters,
> cur_cpu_spec->oprofile_cpu_type can be NULL. The current
> perfctr modules don't test for that case and would thus
> crash.

> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||
..
> +	if (!cur_cpu_spec->oprofile_cpu_type ||

Typing it seven times didn't make you think "how about a helper?" :)

Perhaps:

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cput
index 80f315e..956cbc3 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -123,6 +123,11 @@ struct cpu_spec {
 
 extern struct cpu_spec         *cur_cpu_spec;
 
+static inline int oprofile_cpu_type_matches(const char *s)
+{
+       return s && (strcmp(cur_cpu_spec->oprofile_cpu_type, s) == 0);
+}
+
 extern unsigned int __start___ftr_fixup, __stop___ftr_fixup;
 
 extern struct cpu_spec *identify_cpu(unsigned long offset, unsigned int pvr);


And then callsites become:

 static int init_mpc7450_pmu(void)
 {
        if (!oprofile_cpu_type_matches("ppc/7450"))
                return -ENODEV;


cheers