[LTP] [PATCH 0/1] Test brk vma code path

[LTP] [PATCH 0/1] Test brk vma code path

[Liam Howlett]

The brk system call uses a slightly different code path through the
kernel to expand/contract across VMAs.  This new test is written to
force the VMA to create a two new entries and shrink back across VMA
boundaries.

Liam R. Howlett (1):
  brk02: Add test for removing more than one VMA

 testcases/kernel/syscalls/brk/brk02.c | 49 +++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 testcases/kernel/syscalls/brk/brk02.c

-- 
2.28.0

[LTP] [PATCH 1/1] brk02: Add test for removing more than one VMA

[Liam Howlett]

When brk expands, it attempts to expand a VMA.  This expansion will
succeed depending on the anonymous VMA chain and if the vma flags are
compatible.  This test expands brk() then calls mprotect to ensure the
next brk call will create a new VMA, then it calls brk a final time to
restore the first brk address.  The test is the final brk call which
will remove more than an entire VMA from the vm area.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 testcases/kernel/syscalls/brk/brk02.c | 49 +++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 testcases/kernel/syscalls/brk/brk02.c

diff --git a/testcases/kernel/syscalls/brk/brk02.c b/testcases/kernel/syscalls/brk/brk02.c
new file mode 100644
index 000000000..834fe9f2f
--- /dev/null
+++ b/testcases/kernel/syscalls/brk/brk02.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021 Liam R. Howlett <liam.howlett@oracle.com>
+ *
+ *  
+ *  Expand the brk by 2 pages to ensure there is a newly created VMA and not
+ *  expanding the original due to multiple anon pages.  mprotect that new VMA
+ *  then brk back to the original address therefore causing a munmap of at
+ *  least one full VMA.
+ */
+
+#include <unistd.h>
+#include <stdint.h>
+#include <sys/mman.h>
+
+#include "tst_test.h"
+
+void brk_down_vmas(void)
+{
+	void *brk_addr = sbrk(0);
+	unsigned long page_size = getpagesize();
+	void *addr = brk_addr + page_size;
+
+	if (brk(addr))
+		return;
+
+	addr += page_size;
+	if (brk(addr))
+		return;
+
+	if (mprotect(addr - page_size, page_size,
+			PROT_READ|PROT_WRITE|PROT_EXEC))
+		return;
+
+	addr += page_size;
+	if (brk(addr))
+		return;
+
+	if (brk(brk_addr))
+		return;
+
+
+
+	tst_res(TPASS, "munmap two VMAs of brk() passed.");
+}
+
+static struct tst_test test = {
+	.test_all = brk_down_vmas,
+};
-- 
2.28.0

[LTP] [PATCH 1/1] brk02: Add test for removing more than one VMA

[Petr Vorel]

Hi Liam,

thanks for your patch. Minor notes below.

> When brk expands, it attempts to expand a VMA.  This expansion will
> succeed depending on the anonymous VMA chain and if the vma flags are
> compatible.  This test expands brk() then calls mprotect to ensure the
> next brk call will create a new VMA, then it calls brk a final time to
> restore the first brk address.  The test is the final brk call which
> will remove more than an entire VMA from the vm area.

> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
>  testcases/kernel/syscalls/brk/brk02.c | 49 +++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)
>  create mode 100644 testcases/kernel/syscalls/brk/brk02.c

> diff --git a/testcases/kernel/syscalls/brk/brk02.c b/testcases/kernel/syscalls/brk/brk02.c
> new file mode 100644
> index 000000000..834fe9f2f
> --- /dev/null
> +++ b/testcases/kernel/syscalls/brk/brk02.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2021 Liam R. Howlett <liam.howlett@oracle.com>
> + *
> + *  
nit: blank line
> + *  Expand the brk by 2 pages to ensure there is a newly created VMA and not
> + *  expanding the original due to multiple anon pages.  mprotect that new VMA
> + *  then brk back to the original address therefore causing a munmap of at
> + *  least one full VMA.
> + */
> +
> +#include <unistd.h>
> +#include <stdint.h>
nit: Not sure if <stdint.h> is needed.

> +#include <sys/mman.h>
> +
> +#include "tst_test.h"
> +
> +void brk_down_vmas(void)
> +{
> +	void *brk_addr = sbrk(0);
> +	unsigned long page_size = getpagesize();
> +	void *addr = brk_addr + page_size;
> +
> +	if (brk(addr))
> +		return;
> +
> +	addr += page_size;
> +	if (brk(addr))
> +		return;
You need to add tst_ret(TFAIL, "failed due ..."); before each return otherwise
you get error:
tst_test.c:1080: TBROK: Test haven't reported results!

> +
> +	if (mprotect(addr - page_size, page_size,
> +			PROT_READ|PROT_WRITE|PROT_EXEC))
> +		return;
> +
> +	addr += page_size;
> +	if (brk(addr))
> +		return;
> +
> +	if (brk(brk_addr))
> +		return;
> +
> +
> +
Please remove these blank lines.
> +	tst_res(TPASS, "munmap two VMAs of brk() passed.");
> +}
> +
> +static struct tst_test test = {
> +	.test_all = brk_down_vmas,
> +};

Kind regards,
Petr

[LTP] [PATCH 1/1] brk02: Add test for removing more than one VMA

[Liam Howlett]

Petr,

Thank you for looking at this patch.


* Petr Vorel <pvorel@suse.cz> [210212 05:27]:
> Hi Liam,
> 
> thanks for your patch. Minor notes below.
> 
> > When brk expands, it attempts to expand a VMA.  This expansion will
> > succeed depending on the anonymous VMA chain and if the vma flags are
> > compatible.  This test expands brk() then calls mprotect to ensure the
> > next brk call will create a new VMA, then it calls brk a final time to
> > restore the first brk address.  The test is the final brk call which
> > will remove more than an entire VMA from the vm area.
> 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> > ---
> >  testcases/kernel/syscalls/brk/brk02.c | 49 +++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >  create mode 100644 testcases/kernel/syscalls/brk/brk02.c
> 
> > diff --git a/testcases/kernel/syscalls/brk/brk02.c b/testcases/kernel/syscalls/brk/brk02.c
> > new file mode 100644
> > index 000000000..834fe9f2f
> > --- /dev/null
> > +++ b/testcases/kernel/syscalls/brk/brk02.c
> > @@ -0,0 +1,49 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (c) 2021 Liam R. Howlett <liam.howlett@oracle.com>
> > + *
> > + *  
> nit: blank line
Will do.

> > + *  Expand the brk by 2 pages to ensure there is a newly created VMA and not
> > + *  expanding the original due to multiple anon pages.  mprotect that new VMA
> > + *  then brk back to the original address therefore causing a munmap of at
> > + *  least one full VMA.
> > + */
> > +
> > +#include <unistd.h>
> > +#include <stdint.h>
> nit: Not sure if <stdint.h> is needed.

It is not, thank you.  I will fix it.

> 
> > +#include <sys/mman.h>
> > +
> > +#include "tst_test.h"
> > +
> > +void brk_down_vmas(void)
> > +{
> > +	void *brk_addr = sbrk(0);
> > +	unsigned long page_size = getpagesize();
> > +	void *addr = brk_addr + page_size;
> > +
> > +	if (brk(addr))
> > +		return;
> > +
> > +	addr += page_size;
> > +	if (brk(addr))
> > +		return;
> You need to add tst_ret(TFAIL, "failed due ..."); before each return otherwise
> you get error:
> tst_test.c:1080: TBROK: Test haven't reported results!

I believe you mean tst_res().  I will fix it.

> 
> > +
> > +	if (mprotect(addr - page_size, page_size,
> > +			PROT_READ|PROT_WRITE|PROT_EXEC))
> > +		return;
> > +
> > +	addr += page_size;
> > +	if (brk(addr))
> > +		return;
> > +
> > +	if (brk(brk_addr))
> > +		return;
> > +
> > +
> > +
> Please remove these blank lines.

Will do.

Thank you,
Liam

> > +	tst_res(TPASS, "munmap two VMAs of brk() passed.");
> > +}
> > +
> > +static struct tst_test test = {
> > +	.test_all = brk_down_vmas,
> > +};
> 
> Kind regards,
> Petr

[LTP] [PATCH 1/1] brk02: Add test for removing more than one VMA

[Petr Vorel]

Hi Liam,

> > > +	addr += page_size;
> > > +	if (brk(addr))
> > > +		return;
> > You need to add tst_ret(TFAIL, "failed due ..."); before each return otherwise
> > you get error:
> > tst_test.c:1080: TBROK: Test haven't reported results!

> I believe you mean tst_res().  I will fix it.
Yes, sorry for typo.

Thanks for your work!

Kind regards,
Petr