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

On Fri, 2024-03-15 at 07:14 +0000, Christophe Leroy wrote:

Le 15/03/2024 à 03:57, Benjamin Gray a écrit :

quoted

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 <redacted>
---
  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?

quoted

+	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;
  }