mmap() a file with a good offset and then munmap() it. a non-zero offset is passed to test the 6th argument of my_syscall6(). Note, it is not easy to find a unique file for mmap() in different scenes, so, a file list is used to search the right one: - /dev/zero: is commonly used to allocate anonymous memory and is likely present and readable - /proc/1/exe: for 'run' and 'run-user' target, 'run-user' can not find '/proc/self/exe' - /proc/self/exe: for 'libc-test' target, normal program 'libc-test' has no permission to access '/proc/1/exe' - argv0: the path of the program itself, let it pass even with worst case scene: no procfs and no /dev/zero Suggested-by: Willy Tarreau <w@xxxxxx> Link: https://lore.kernel.org/lkml/20230702193306.GK16233@xxxxxx/ Suggested-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx> Link: https://lore.kernel.org/lkml/bff82ea6-610b-4471-a28b-6c76c28604a6@xxxxxxxx/ Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx> --- tools/testing/selftests/nolibc/nolibc-test.c | 60 ++++++++++++++++++++ 1 file changed, 60 insertions(+) diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 8644e415cb66..a7191b637b85 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -595,6 +595,65 @@ static int test_stat_timestamps(void) return 0; } +int test_mmap_munmap(void) +{ + int ret, fd, i; + void *mem; + size_t page_size, file_size, length; + off_t offset, pa_offset; + struct stat stat_buf; + const char * const files[] = { + "/dev/zero", + "/proc/1/exe", "/proc/self/exe", + argv0, + NULL + }; + + page_size = getpagesize(); + if (page_size < 0) + return -1; + + /* find a right file to mmap, existed and accessible */ + for (i = 0; files[i] != NULL; i++) { + ret = fd = open(files[i], O_RDONLY); + if (ret == -1) + continue; + else + break; + } + if (ret == -1) + return ret; + + ret = stat(files[i], &stat_buf); + if (ret == -1) + goto end; + + /* file size of the special /dev/zero is 0, let's assign one manually */ + if (i == 0) + file_size = 3*page_size; + else + file_size = stat_buf.st_size; + + offset = file_size - 1; + if (offset < 0) + offset = 0; + length = file_size - offset; + pa_offset = offset & ~(page_size - 1); + + mem = mmap(NULL, length + offset - pa_offset, PROT_READ, MAP_SHARED, fd, pa_offset); + if (mem == MAP_FAILED) { + ret = -1; + goto end; + } + + ret = munmap(mem, length + offset - pa_offset); + +end: + close(fd); + return ret; +} + + /* Run syscall tests between IDs <min> and <max>. * Return 0 on success, non-zero on failure. */ @@ -671,6 +730,7 @@ int run_syscall(int min, int max) CASE_TEST(mkdir_root); EXPECT_SYSER(1, mkdir("/", 0755), -1, EEXIST); break; CASE_TEST(mmap_bad); EXPECT_PTRER(1, mmap(NULL, 0, PROT_READ, MAP_PRIVATE, 0, 0), MAP_FAILED, EINVAL); break; CASE_TEST(munmap_bad); EXPECT_SYSER(1, munmap((void *)1, 0), -1, EINVAL); break; + CASE_TEST(mmap_munmap_good); EXPECT_SYSZR(1, test_mmap_munmap()); break; CASE_TEST(open_tty); EXPECT_SYSNE(1, tmp = open("/dev/null", 0), -1); if (tmp != -1) close(tmp); break; CASE_TEST(open_blah); EXPECT_SYSER(1, tmp = open("/proc/self/blah", 0), -1, ENOENT); if (tmp != -1) close(tmp); break; CASE_TEST(poll_null); EXPECT_SYSZR(1, poll(NULL, 0, 0)); break; -- 2.25.1
