linux-kernel - Re: [PATCH v4 10/10] selftests/nolibc: add mmap and munmap test cases

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Message-Id: <20230622193249.1190336-1-falcon@tinylab.org>
Date:   Fri, 23 Jun 2023 03:32:49 +0800
From:   Zhangjin Wu <falcon@...ylab.org>
To:     thomas@...ch.de
Cc:     arnd@...db.de, david.laight@...lab.com, falcon@...ylab.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-riscv@...ts.infradead.org, w@....eu
Subject: Re: [PATCH v4 10/10] selftests/nolibc: add mmap and munmap test cases

Hi, Thomas

> On 2023-06-19 23:55:41+0800, Zhangjin Wu wrote:
> > Three mmap/munmap related test cases are added:
> > 
> > - mmap(NULL, 0, PROT_READ, MAP_PRIVATE, 0, 0), MAP_FAILED, EINVAL)
> > 
> >   The length argument must be greater than 0, otherwise, fail with -EINVAL.
> > 
> > - munmap((void *)-1, 4*1024), -1, EINVAL)
> > 
> >   Invalid (void *)-1 address fail with -EINVAL.
> > 
> > - test_mmap_munmap(4*1024)
> > 
> >   It finds a init file, mmap() it and then munmap().
> > 
> > Signed-off-by: Zhangjin Wu <falcon@...ylab.org>
> > ---
> >  tools/testing/selftests/nolibc/nolibc-test.c | 31 ++++++++++++++++++++
> >  1 file changed, 31 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> > index 80ab29e2887c..f7c0ca72cb28 100644
> > --- a/tools/testing/selftests/nolibc/nolibc-test.c
> > +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> > @@ -592,6 +592,34 @@ static int test_stat_timestamps(void)
> >  	return 0;
> >  }
> >  
> > +int test_mmap_munmap(int size)
> > +{
> > +	char init_files[5][20] = {"/init", "/sbin/init", "/etc/init", "/bin/init", "/bin/sh"};
> 
> Why not /proc/1/exe or even /proc/self/exe?
> 
> I know your other series tries to remove the procfs dependency, but
> we're not there yet :-).
> 

Yeah, '/proc/self/exe' is a choice, if so, the 'has_proc' should be added ;-)

> Also does it make sense to pass a size parameter?
> Why not use either PAGE_SIZE or the real size of the binary from
> fstat().
> 

Ok, as the manpage of mmap shows:

       For mmap(), offset must be a multiple of the underlying huge page
       size.  The system automatically aligns length to be a multiple of
       the underlying huge page size.

       For munmap(), addr, and length must both be a multiple of the
       underlying huge page size.

perhaps we should do further tests:

* the real size/length
* even > the real size
* the PAGE_SIZE
* not aligned with PAGE_SIZE

If such tests are required, the 'size' and even 'offset' arguments could be
provided to cover different combination or we do such tests internally, then,
the arguments are not required.

Thanks,
Zhangjin

> > +	int ret, fd, i;
> > +	void *mem;
> > +
> > +	for (i = 0; i < 5; i++) {
> > +		ret = fd = open(init_files[i], O_RDONLY);
> > +		if (ret < 0)
> > +			continue;
> > +		else
> > +			break;
> > +	}
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	mem = mmap(NULL, size, PROT_READ, MAP_SHARED, fd, 0);
> > +	if (mem == MAP_FAILED)
> > +		return -1;
> > +
> > +	ret = munmap(mem, size);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return close(fd);
> > +}
> > +
> > +
> >  /* Run syscall tests between IDs <min> and <max>.
> >   * Return 0 on success, non-zero on failure.
> >   */
> > @@ -666,6 +694,9 @@ int run_syscall(int min, int max)
> >  		CASE_TEST(lseek_m1);          EXPECT_SYSER(1, lseek(-1, 0, SEEK_SET), -1, EBADF); break;
> >  		CASE_TEST(lseek_0);           EXPECT_SYSER(1, lseek(0, 0, SEEK_SET), -1, ESPIPE); break;
> >  		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_good);         EXPECT_SYSZR(1, test_mmap_munmap(4*1024)); 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
> >