Re: [PATCH] selftests: clone3: Use the capget and capset syscall directly

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On 10/11/24 00:59, zhouyuhang wrote:

On 2024/10/10 23:50, Shuah Khan wrote:
On 10/10/24 06:16, zhouyuhang wrote:
From: zhouyuhang <zhouyuhang@xxxxxxxxxx>

The libcap commit aca076443591 ("Make cap_t operations thread safe.") added a
__u8 mutex at the beginning of the struct _cap_struct,it changes the offset of
the members in the structure that breaks the assumption made in the "struct libcap"
definition in clone3_cap_checkpoint_restore.c.So use the capget and capset syscall
directly and remove the libcap library dependency like the commit 663af70aabb7
("bpf: selftests: Add helpers to directly use the capget and capset syscall") does.


NIT: grammar and comma spacing. Please fix those for readability.
e.g: Change "struct _cap_struct,it" to "struct _cap_struct, it"
Fix others as well.


Thanks, I'll fix it in V2


Signed-off-by: zhouyuhang <zhouyuhang@xxxxxxxxxx>
---
  tools/testing/selftests/clone3/Makefile       |  1 -
  .../clone3/clone3_cap_checkpoint_restore.c    | 60 +++++++++----------
  2 files changed, 28 insertions(+), 33 deletions(-)

diff --git a/tools/testing/selftests/clone3/Makefile b/tools/testing/selftests/clone3/Makefile
index 84832c369a2e..59d26e8da8d2 100644
--- a/tools/testing/selftests/clone3/Makefile
+++ b/tools/testing/selftests/clone3/Makefile
@@ -1,6 +1,5 @@
  # SPDX-License-Identifier: GPL-2.0
  CFLAGS += -g -std=gnu99 $(KHDR_INCLUDES)
-LDLIBS += -lcap
    TEST_GEN_PROGS := clone3 clone3_clear_sighand clone3_set_tid \
      clone3_cap_checkpoint_restore
diff --git a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
index 3c196fa86c99..111912e2aead 100644
--- a/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
+++ b/tools/testing/selftests/clone3/clone3_cap_checkpoint_restore.c
@@ -15,7 +15,7 @@
  #include <stdio.h>
  #include <stdlib.h>
  #include <stdbool.h>
-#include <sys/capability.h>
+#include <linux/capability.h>
  #include <sys/prctl.h>
  #include <sys/syscall.h>
  #include <sys/types.h>
@@ -27,6 +27,13 @@
  #include "../kselftest_harness.h"
  #include "clone3_selftests.h"
  +#ifndef CAP_CHECKPOINT_RESTORE
+#define CAP_CHECKPOINT_RESTORE 40
+#endif
+

Why is this necessary? This is defined in linux/capability.h.

+int capget(cap_user_header_t header, cap_user_data_t data);
+int capset(cap_user_header_t header, const cap_user_data_t data);

In general prototypes such as these should be defined in header
file. Why are we defining these here?

These are defined in sys/capability.h

I don't understand this change. You are removing sys/capability.h
which requires you to add these defines here. This doesn't
sound like a correct solution to me.


I tested it on my machine without libcap-dev installed, the /usr/include/linux/capability.h

is on this machine by default. Successfully compiled using #include <linux/capability.h>

but not with #include <sys/capability.h>. This patch removes libcap library dependencies.

And we don't use any part of sys/capability.h other than these two syscalls. So I think that's why it's necessary.

You are changing the code to not include sys/capability.h
What happens if sys/capability.h along with linux/capability.h

Do you see problems?

thanks,
-- Shuah




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