linux-kernel - [PATCH 3.16 042/366] powerpc/lib: Fix the feature fixup tests to actually work

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Date:   Sun, 11 Nov 2018 19:49:05 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Michael Ellerman" <mpe@...erman.id.au>
Subject: [PATCH 3.16 042/366] powerpc/lib: Fix the feature fixup tests to
 actually work

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Ellerman <mpe@...erman.id.au>

commit cad0e39023b43d94d5e38dfd55c103e15bdd093d upstream.

The code patching code has always been a bit confused about whether
it's best to use void *, unsigned int *, char *, etc. to point to
instructions. In fact in the feature fixups tests we use both unsigned
int[] and u8[] in different places.

Unfortunately the tests that use unsigned int[] calculate the size of
the code blocks using subtraction of those unsigned int pointers, and
then pass the result to memcmp(). This means we're only comparing 1/4
of the bytes we need to, because we need to multiply by
sizeof(unsigned int) to get the number of *bytes*.

The result is that the tests do all the patching and then only compare
some of the resulting code, so patching bugs that only effect that
last 3/4 of the code could slip through undetected. It turns out that
hasn't been happening, although one test had a bad expected case (see
previous commit).

Fix it for now by multiplying the size by 4 in the affected functions.

Fixes: 362e7701fd18 ("powerpc: Add self-tests of the feature fixup code")
Epic-brown-paper-bag-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/lib/feature-fixups.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -170,7 +170,7 @@ void test_basic_patching(void)
 	extern unsigned int end_ftr_fixup_test1[];
 	extern unsigned int ftr_fixup_test1_orig[];
 	extern unsigned int ftr_fixup_test1_expected[];
-	int size = end_ftr_fixup_test1 - ftr_fixup_test1;
+	int size = 4 * (end_ftr_fixup_test1 - ftr_fixup_test1);
 
 	fixup.value = fixup.mask = 8;
 	fixup.start_off = calc_offset(&fixup, ftr_fixup_test1 + 1);
@@ -202,7 +202,7 @@ static void test_alternative_patching(vo
 	extern unsigned int ftr_fixup_test2_orig[];
 	extern unsigned int ftr_fixup_test2_alt[];
 	extern unsigned int ftr_fixup_test2_expected[];
-	int size = end_ftr_fixup_test2 - ftr_fixup_test2;
+	int size = 4 * (end_ftr_fixup_test2 - ftr_fixup_test2);
 
 	fixup.value = fixup.mask = 0xF;
 	fixup.start_off = calc_offset(&fixup, ftr_fixup_test2 + 1);
@@ -234,7 +234,7 @@ static void test_alternative_case_too_bi
 	extern unsigned int end_ftr_fixup_test3[];
 	extern unsigned int ftr_fixup_test3_orig[];
 	extern unsigned int ftr_fixup_test3_alt[];
-	int size = end_ftr_fixup_test3 - ftr_fixup_test3;
+	int size = 4 * (end_ftr_fixup_test3 - ftr_fixup_test3);
 
 	fixup.value = fixup.mask = 0xC;
 	fixup.start_off = calc_offset(&fixup, ftr_fixup_test3 + 1);
@@ -261,7 +261,7 @@ static void test_alternative_case_too_sm
 	extern unsigned int ftr_fixup_test4_orig[];
 	extern unsigned int ftr_fixup_test4_alt[];
 	extern unsigned int ftr_fixup_test4_expected[];
-	int size = end_ftr_fixup_test4 - ftr_fixup_test4;
+	int size = 4 * (end_ftr_fixup_test4 - ftr_fixup_test4);
 	unsigned long flag;
 
 	/* Check a high-bit flag */
@@ -295,7 +295,7 @@ static void test_alternative_case_with_b
 	extern unsigned int ftr_fixup_test5[];
 	extern unsigned int end_ftr_fixup_test5[];
 	extern unsigned int ftr_fixup_test5_expected[];
-	int size = end_ftr_fixup_test5 - ftr_fixup_test5;
+	int size = 4 * (end_ftr_fixup_test5 - ftr_fixup_test5);
 
 	check(memcmp(ftr_fixup_test5, ftr_fixup_test5_expected, size) == 0);
 }
@@ -305,7 +305,7 @@ static void test_alternative_case_with_e
 	extern unsigned int ftr_fixup_test6[];
 	extern unsigned int end_ftr_fixup_test6[];
 	extern unsigned int ftr_fixup_test6_expected[];
-	int size = end_ftr_fixup_test6 - ftr_fixup_test6;
+	int size = 4 * (end_ftr_fixup_test6 - ftr_fixup_test6);
 
 	check(memcmp(ftr_fixup_test6, ftr_fixup_test6_expected, size) == 0);
 }