[PATCH] selftests/powerpc: Add test of memcmp at end of page
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-07-22 05:55:06
Update our memcmp selftest, to test the case where we're comparing up
to the end of a page and the subsequent page is not mapped. We have to
make sure we don't read off the end of the page and cause a fault.
We had a bug there in the past, fixed in commit
d9470757398a ("powerpc/64: Fix memcmp reading past the end of src/dest").
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
.../selftests/powerpc/stringloops/memcmp.c | 40 ++++++++++---------
1 file changed, 22 insertions(+), 18 deletions(-)
diff --git a/tools/testing/selftests/powerpc/stringloops/memcmp.c b/tools/testing/selftests/powerpc/stringloops/memcmp.c
index b1fa7546957f..e4605ca850dc 100644
--- a/tools/testing/selftests/powerpc/stringloops/memcmp.c
+++ b/tools/testing/selftests/powerpc/stringloops/memcmp.c@@ -2,6 +2,7 @@ #include <malloc.h> #include <stdlib.h> #include <string.h> +#include <sys/mman.h> #include <time.h> #include "utils.h"
@@ -13,6 +14,9 @@ #define LARGE_MAX_OFFSET 32 #define LARGE_SIZE_START 4096 +/* This is big enough to fit LARGE_SIZE and works on 4K & 64K kernels */ +#define MAP_SIZE (64 * 1024) + #define MAX_OFFSET_DIFF_S1_S2 48 int vmx_count;
@@ -68,25 +72,25 @@ static void test_one(char *s1, char *s2, unsigned long max_offset, static int testcase(bool islarge) { - char *s1; - char *s2; - unsigned long i; - - unsigned long comp_size = (islarge ? LARGE_SIZE : SIZE); - unsigned long alloc_size = comp_size + MAX_OFFSET_DIFF_S1_S2; - int iterations = islarge ? LARGE_ITERATIONS : ITERATIONS; - - s1 = memalign(128, alloc_size); - if (!s1) { - perror("memalign"); - exit(1); - } + unsigned long i, comp_size, alloc_size; + char *p, *s1, *s2; + int iterations; - s2 = memalign(128, alloc_size); - if (!s2) { - perror("memalign"); - exit(1); - } + comp_size = (islarge ? LARGE_SIZE : SIZE); + alloc_size = comp_size + MAX_OFFSET_DIFF_S1_S2; + iterations = islarge ? LARGE_ITERATIONS : ITERATIONS; + + p = mmap(NULL, 4 * MAP_SIZE, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + FAIL_IF(p == MAP_FAILED); + + /* Put s1/s2 at the end of a page */ + s1 = p + MAP_SIZE - alloc_size; + s2 = p + 3 * MAP_SIZE - alloc_size; + + /* And unmap the subsequent page to force a fault if we overread */ + munmap(p + MAP_SIZE, MAP_SIZE); + munmap(p + 3 * MAP_SIZE, MAP_SIZE); srandom(time(0));
--
2.25.1