linux-kernel - Re: [PATCH v2 02/22] ARM: add self test for runtime patch mechanism

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Date:	Sun, 12 Aug 2012 23:19:48 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Cyril Chemparathy <cyril@...com>
cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	arnd@...db.de, catalin.marinas@....com, grant.likely@...retlab.ca,
	linux@....linux.org.uk, will.deacon@....com
Subject: Re: [PATCH v2 02/22] ARM: add self test for runtime patch
 mechanism

On Sun, 12 Aug 2012, Cyril Chemparathy wrote:

> On 08/11/12 22:35, Nicolas Pitre wrote:
> > On Fri, 10 Aug 2012, Cyril Chemparathy wrote:
> > 
> > > This patch adds basic sanity tests to ensure that the instruction patching
> > > results in valid instruction encodings.  This is done by verifying the
> > > output
> > > of the patch process against a vector of assembler generated instructions
> > > at
> > > init time.
> > > 
> > > Signed-off-by: Cyril Chemparathy <cyril@...com>
> > > ---
> [...]
> > > +	__asm__ __volatile__ (
> > > +		"	.irp	shift1, 0, 6, 12, 18\n"
> > > +		"	.irp	shift2, 0, 1, 2, 3, 4, 5\n"
> > > +		"	add     r1, r2, #(0x41 << (\\shift1 + \\shift2))\n"
> > > +		"	.endr\n"
> > > +		"	.endr\n"
> > 
> > 
> > Maybe adding a "add r1, r2 #0x81 << 24" here might be a good thing since
> > this is the most used case but missing from the above.
> > 
> 
> Indeed.  I've now replaced this with something a bit more extensive. Does the
> following look better?
> 
> +struct patch_test_imm8 {
> +       u16     imm;
> +       u16     shift;
> +       u32     insn;
> +};
> +
> +static void __init __used __naked __patch_test_code_imm8(void)
> +{
> +       __asm__ __volatile__ (
> +
> +               /* a single test case */
> +               "       .macro          test_one, imm, sft\n"
> +               "       .hword          \\imm\n"
> +               "       .hword          \\sft\n"
> +               "       add             r1, r2, #(\\imm << \\sft)\n"
> +               "       .endm\n"
> +
> +               /* a sequence of tests at 'inc' increments of shift */
> +               "       .macro          test_seq, imm, sft, max, inc\n"
> +               "       test_one        \\imm, \\sft\n"
> +               "       .if             \\sft < \\max\n"
> +               "       test_seq        \\imm, (\\sft + \\inc), \\max,
> \\inc\n"
> +               "       .endif\n"
> +               "       .endm\n"
> +
> +               /* an empty record to mark the end */
> +               "       .macro          test_end\n"
> +               "       .hword          0, 0\n"
> +               "       .word           0\n"
> +               "       .endm\n"
> +
> +               /* finally generate the test sequences */
> +               "       test_seq        0x41, 0, 24, 1\n"
> +               "       test_seq        0x81, 0, 24, 2\n"
> +               "       test_end\n"
> +               : : :
> +       );
> +}

Yes, this is certainly quite extensive.  :-)


Nicolas
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