Re: [PATCH 3/3] selftests/mseal_system_mappings: Test vdso unmap and remap

From: Chris Down

Date: Tue Oct 27 2026 - 12:44:53 EST

Lorenzo Stoakes (ARM) writes:
Sorry, in mm we require commit messages. Even for tests :)

Sure thing, I'll add one.

On Tue, Oct 27, 2026 at 07:43:25PM +0800, Chris Down wrote:
Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
---
.../mseal_system_mappings/sysmap_is_sealed.c | 92 +++++++++++++++++++
1 file changed, 92 insertions(+)

diff --git a/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c b/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c
index ea75ad537620..83b4fadfbfe7 100644
--- a/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c
+++ b/tools/testing/selftests/mseal_system_mappings/sysmap_is_sealed.c

Why on earth does 'mseal_system_mappings' have its own directory...??

Ugh I don't know how I let this stuff go on the original series :/

Please, for the love of all that's sacred, move these tests over to
tools/selftests/mm/. This is an mm feature, for our sins...

You can do the move as a prerequisite patch in the series.

Will do, I'll make the move the first patch.

(And, again, I really do insist on your change doing some cleanup here as
well rather than extending this stuff.)

Yep, see my reply to 1/3.

@@ -10,6 +10,7 @@
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
+#include <sys/mman.h>
#include <sys/utsname.h>
#include <zlib.h>

@@ -232,4 +233,95 @@ TEST_F(basic, check_sealed)
EXPECT_EQ(expected, sealed);
};

+static bool find_vdso(unsigned long *start, unsigned long *end)
+{
+ char line[MAX_LINE_LEN];
+ bool found = false;
+ FILE *maps;
+
+ maps = fopen("/proc/self/maps", "r");
+ if (!maps)
+ return false;
+
+ while (fgets(line, sizeof(line), maps)) {
+ if (strstr(line, "[vdso]") &&
+ sscanf(line, "%lx-%lx", start, end) == 2) {
+ found = true;
+ break;
+ }
+ }
+
+ fclose(maps);
+ return found;
+}

There's shared code for this kind of thing, please don't duplicate a
/proc/self/maps thing if unnecessary. Also there's a nicer ioctl interface for
all this.

See vm_utils.[ch].

Oh thank you! I will use that.

I mean arguably this is an mremap test that belongs with mremap? I guess
debatable...

Hmm, I'd lean towards keeping it with the sysmap test, since it's really testing that the seal is enforced on these mappings rather than anything about mremap() itself, but I don't feel strongly if you insist, just let me know.

This all just seems like work that should have been done in the past when this
feature was proposed, and doesn't depend on your changes at all AFAICT? Maybe I
missed it though.

Valuable in itself, but probably worth sending separately as a result? Otherwise
it's a little disconnected from the actual change you're making.

Yeah, it doesn't depend on it. I can send it separately on top of the move if you like, I just don't like touching things without tests where possible.

Thanks for the review!