kernel: backport libcap workaround for BPF selftests

Recent libcap versions (>= 2.60) cause problems with BPF kselftests, so
backport an upstream patch that replaces libcap and drops the dependency.

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>
(cherry picked from commit 04981c716acab6b7a81f672f217e5c47ee42a0b6)

1 files changed, 123 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.15/060-v5.18-01-bpf-selftests-Add-helpers-to-directly-use-the-capget.patch b/target/linux/generic/backport-5.15/060-v5.18-01-bpf-selftests-Add-helpers-to-directly-use-the-capget.patch
new file mode 100644
index 0000000000..4d544a30f5
--- /dev/null
+++ b/target/linux/generic/backport-5.15/060-v5.18-01-bpf-selftests-Add-helpers-to-directly-use-the-capget.patch
@@ -0,0 +1,123 @@
+From 5287acc6f097c0c18e54401b611a877a3083b68c Mon Sep 17 00:00:00 2001
+From: Martin KaFai Lau <kafai@fb.com>
+Date: Wed, 16 Mar 2022 10:38:23 -0700
+Subject: [PATCH 1/3] bpf: selftests: Add helpers to directly use the capget
+ and capset syscall
+
+After upgrading to the newer libcap (>= 2.60),
+the libcap commit aca076443591 ("Make cap_t operations thread safe.")
+added a "__u8 mutex;" to the "struct _cap_struct".  It caused a few byte
+shift that breaks the assumption made in the "struct libcap" definition
+in test_verifier.c.
+
+The bpf selftest usage only needs to enable and disable the effective
+caps of the running task.  It is easier to directly syscall the
+capget and capset instead.  It can also remove the libcap
+library dependency.
+
+The cap_helpers.{c,h} is added.  One __u64 is used for all CAP_*
+bits instead of two __u32.
+
+Signed-off-by: Martin KaFai Lau <kafai@fb.com>
+Signed-off-by: Alexei Starovoitov <ast@kernel.org>
+Acked-by: John Fastabend <john.fastabend@gmail.com>
+Link: https://lore.kernel.org/bpf/20220316173823.2036955-1-kafai@fb.com
+---
+ tools/testing/selftests/bpf/cap_helpers.c | 67 +++++++++++++++++++++++
+ tools/testing/selftests/bpf/cap_helpers.h | 19 +++++++
+ 2 files changed, 86 insertions(+)
+ create mode 100644 tools/testing/selftests/bpf/cap_helpers.c
+ create mode 100644 tools/testing/selftests/bpf/cap_helpers.h
+
+--- /dev/null
++++ b/tools/testing/selftests/bpf/cap_helpers.c
+@@ -0,0 +1,67 @@
++// SPDX-License-Identifier: GPL-2.0
++#include "cap_helpers.h"
++
++/* Avoid including <sys/capability.h> from the libcap-devel package,
++ * so directly declare them here and use them from glibc.
++ */
++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);
++
++int cap_enable_effective(__u64 caps, __u64 *old_caps)
++{
++	struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
++	struct __user_cap_header_struct hdr = {
++		.version = _LINUX_CAPABILITY_VERSION_3,
++	};
++	__u32 cap0 = caps;
++	__u32 cap1 = caps >> 32;
++	int err;
++
++	err = capget(&hdr, data);
++	if (err)
++		return err;
++
++	if (old_caps)
++		*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
++
++	if ((data[0].effective & cap0) == cap0 &&
++	    (data[1].effective & cap1) == cap1)
++		return 0;
++
++	data[0].effective |= cap0;
++	data[1].effective |= cap1;
++	err = capset(&hdr, data);
++	if (err)
++		return err;
++
++	return 0;
++}
++
++int cap_disable_effective(__u64 caps, __u64 *old_caps)
++{
++	struct __user_cap_data_struct data[_LINUX_CAPABILITY_U32S_3];
++	struct __user_cap_header_struct hdr = {
++		.version = _LINUX_CAPABILITY_VERSION_3,
++	};
++	__u32 cap0 = caps;
++	__u32 cap1 = caps >> 32;
++	int err;
++
++	err = capget(&hdr, data);
++	if (err)
++		return err;
++
++	if (old_caps)
++		*old_caps = (__u64)(data[1].effective) << 32 | data[0].effective;
++
++	if (!(data[0].effective & cap0) && !(data[1].effective & cap1))
++		return 0;
++
++	data[0].effective &= ~cap0;
++	data[1].effective &= ~cap1;
++	err = capset(&hdr, data);
++	if (err)
++		return err;
++
++	return 0;
++}
+--- /dev/null
++++ b/tools/testing/selftests/bpf/cap_helpers.h
+@@ -0,0 +1,19 @@
++/* SPDX-License-Identifier: GPL-2.0 */
++#ifndef __CAP_HELPERS_H
++#define __CAP_HELPERS_H
++
++#include <linux/types.h>
++#include <linux/capability.h>
++
++#ifndef CAP_PERFMON
++#define CAP_PERFMON		38
++#endif
++
++#ifndef CAP_BPF
++#define CAP_BPF			39
++#endif
++
++int cap_enable_effective(__u64 caps, __u64 *old_caps);
++int cap_disable_effective(__u64 caps, __u64 *old_caps);
++
++#endif