Re: [PATCH v1 1/3] powerpc/code-patching: Test patch_instructions() during boot

[Benjamin Gray <bgray@linux.ibm.com>]

On Fri, 2024-03-15 at 07:14 +0000, Christophe Leroy wrote:
> 
> 
> Le 15/03/2024 à 03:57, Benjamin Gray a écrit :
> > patch_instructions() introduces new behaviour with a couple of
> > variations. Test each case of
> > 
> >    * a repeated 32-bit instruction,
> >    * a repeated 64-bit instruction (ppc64), and
> >    * a copied sequence of instructions
> > 
> > for both on a single page and when it crosses a page boundary.
> > 
> > Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
> > ---
> >   arch/powerpc/lib/test-code-patching.c | 92
> > +++++++++++++++++++++++++++
> >   1 file changed, 92 insertions(+)
> > 
> > diff --git a/arch/powerpc/lib/test-code-patching.c
> > b/arch/powerpc/lib/test-code-patching.c
> > index c44823292f73..35a3756272df 100644
> > --- a/arch/powerpc/lib/test-code-patching.c
> > +++ b/arch/powerpc/lib/test-code-patching.c
> > @@ -347,6 +347,97 @@ static void __init
> > test_prefixed_patching(void)
> >   	check(!memcmp(iptr, expected, sizeof(expected)));
> >   }
> >   
> > +static void __init test_multi_instruction_patching(void)
> > +{
> > +	u32 code[256];
> 
> Build failure:
> 
>    CC      arch/powerpc/lib/test-code-patching.o
> arch/powerpc/lib/test-code-patching.c: In function 
> 'test_multi_instruction_patching':
> arch/powerpc/lib/test-code-patching.c:439:1: error: the frame size of
> 1040 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
>    439 | }
>        | ^
> cc1: all warnings being treated as errors
> make[4]: *** [scripts/Makefile.build:243: 
> arch/powerpc/lib/test-code-patching.o] Error 1
> 
> 
> I have to avoid big arrays on the stack.

All good, I can do that.

I do run my patches through a couple of 32-bit configs, but I didn't
see this error. Is this a standard config I should be testing with?

> 
> 
> > +	void *buf;
> > +	u32 *addr32;
> > +	u64 *addr64;
> > +	ppc_inst_t inst64 = ppc_inst_prefix(OP_PREFIX << 26 | 3UL
> > << 24, PPC_RAW_TRAP());
> > +	u32 inst32 = PPC_RAW_NOP();
> > +
> > +	buf = vzalloc(PAGE_SIZE * 8);
> > +	check(buf);
> > +	if (!buf)
> > +		return;
> > +
> > +	/* Test single page 32-bit repeated instruction */
> > +	addr32 = buf + PAGE_SIZE;
> > +	check(!patch_instructions(addr32 + 1, &inst32, 12, true));
> > +
> > +	check(addr32[0] == 0);
> > +	check(addr32[1] == inst32);
> > +	check(addr32[2] == inst32);
> > +	check(addr32[3] == inst32);
> > +	check(addr32[4] == 0);
> > +
> > +	/* Test single page 64-bit repeated instruction */
> > +	if (IS_ENABLED(CONFIG_PPC64)) {
> > +		check(ppc_inst_prefixed(inst64));
> > +
> > +		addr64 = buf + PAGE_SIZE * 2;
> > +		ppc_inst_write(code, inst64);
> > +		check(!patch_instructions((u32 *)(addr64 + 1),
> > code, 24, true));
> > +
> > +		check(addr64[0] == 0);
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[1]), inst64));
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[2]), inst64));
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[3]), inst64));
> > +		check(addr64[4] == 0);
> > +	}
> > +
> > +	/* Test single page memcpy */
> > +	addr32 = buf + PAGE_SIZE * 3;
> > +
> > +	for (int i = 0; i < ARRAY_SIZE(code); i++)
> > +		code[i] = i + 1;
> > +
> > +	check(!patch_instructions(addr32 + 1, code, sizeof(code),
> > false));
> > +
> > +	check(addr32[0] == 0);
> > +	check(!memcmp(&addr32[1], code, sizeof(code)));
> > +	check(addr32[ARRAY_SIZE(code) + 1] == 0);
> > +
> > +	/* Test multipage 32-bit repeated instruction */
> > +	addr32 = buf + PAGE_SIZE * 4 - 8;
> > +	check(!patch_instructions(addr32 + 1, &inst32, 12, true));
> > +
> > +	check(addr32[0] == 0);
> > +	check(addr32[1] == inst32);
> > +	check(addr32[2] == inst32);
> > +	check(addr32[3] == inst32);
> > +	check(addr32[4] == 0);
> > +
> > +	/* Test multipage 64-bit repeated instruction */
> > +	if (IS_ENABLED(CONFIG_PPC64)) {
> > +		check(ppc_inst_prefixed(inst64));
> > +
> > +		addr64 = buf + PAGE_SIZE * 5 - 8;
> > +		ppc_inst_write(code, inst64);
> > +		check(!patch_instructions((u32 *)(addr64 + 1),
> > code, 24, true));
> > +
> > +		check(addr64[0] == 0);
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[1]), inst64));
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[2]), inst64));
> > +		check(ppc_inst_equal(ppc_inst_read((u32
> > *)&addr64[3]), inst64));
> > +		check(addr64[4] == 0);
> > +	}
> > +
> > +	/* Test multipage memcpy */
> > +	addr32 = buf + PAGE_SIZE * 6 - 12;
> > +
> > +	for (int i = 0; i < ARRAY_SIZE(code); i++)
> > +		code[i] = i + 1;
> > +
> > +	check(!patch_instructions(addr32 + 1, code, sizeof(code),
> > false));
> > +
> > +	check(addr32[0] == 0);
> > +	check(!memcmp(&addr32[1], code, sizeof(code)));
> > +	check(addr32[ARRAY_SIZE(code) + 1] == 0);
> > +
> > +	vfree(buf);
> > +}
> > +
> >   static int __init test_code_patching(void)
> >   {
> >   	pr_info("Running code patching self-tests ...\n");
> > @@ -356,6 +447,7 @@ static int __init test_code_patching(void)
> >   	test_create_function_call();
> >   	test_translate_branch();
> >   	test_prefixed_patching();
> > +	test_multi_instruction_patching();
> >   
> >   	return 0;
> >   }