Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

Daniel Borkmann says:

====================
pull-request: bpf-next 2022-07-09

We've added 94 non-merge commits during the last 19 day(s) which contain
a total of 125 files changed, 5141 insertions(+), 6701 deletions(-).

The main changes are:

1) Add new way for performing BTF type queries to BPF, from Daniel Müller.

2) Add inlining of calls to bpf_loop() helper when its function callback is
   statically known, from Eduard Zingerman.

3) Implement BPF TCP CC framework usability improvements, from Jörn-Thorben Hinz.

4) Add LSM flavor for attaching per-cgroup BPF programs to existing LSM
   hooks, from Stanislav Fomichev.

5) Remove all deprecated libbpf APIs in prep for 1.0 release, from Andrii Nakryiko.

6) Add benchmarks around local_storage to BPF selftests, from Dave Marchevsky.

7) AF_XDP sample removal (given move to libxdp) and various improvements around AF_XDP
   selftests, from Magnus Karlsson & Maciej Fijalkowski.

8) Add bpftool improvements for memcg probing and bash completion, from Quentin Monnet.

9) Add arm64 JIT support for BPF-2-BPF coupled with tail calls, from Jakub Sitnicki.

10) Sockmap optimizations around throughput of UDP transmissions which have been
    improved by 61%, from Cong Wang.

11) Rework perf's BPF prologue code to remove deprecated functions, from Jiri Olsa.

12) Fix sockmap teardown path to avoid sleepable sk_psock_stop, from John Fastabend.

13) Fix libbpf's cleanup around legacy kprobe/uprobe on error case, from Chuang Wang.

14) Fix libbpf's bpf_helpers.h to work with gcc for the case of its sec/pragma
    macro, from James Hilliard.

15) Fix libbpf's pt_regs macros for riscv to use a0 for RC register, from Yixun Lan.

16) Fix bpftool to show the name of type BPF_OBJ_LINK, from Yafang Shao.

* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (94 commits)
  selftests/bpf: Fix xdp_synproxy build failure if CONFIG_NF_CONNTRACK=m/n
  bpf: Correctly propagate errors up from bpf_core_composites_match
  libbpf: Disable SEC pragma macro on GCC
  bpf: Check attach_func_proto more carefully in check_return_code
  selftests/bpf: Add test involving restrict type qualifier
  bpftool: Add support for KIND_RESTRICT to gen min_core_btf command
  MAINTAINERS: Add entry for AF_XDP selftests files
  selftests, xsk: Rename AF_XDP testing app
  bpf, docs: Remove deprecated xsk libbpf APIs description
  selftests/bpf: Add benchmark for local_storage RCU Tasks Trace usage
  libbpf, riscv: Use a0 for RC register
  libbpf: Remove unnecessary usdt_rel_ip assignments
  selftests/bpf: Fix few more compiler warnings
  selftests/bpf: Fix bogus uninitialized variable warning
  bpftool: Remove zlib feature test from Makefile
  libbpf: Cleanup the legacy uprobe_event on failed add/attach_event()
  libbpf: Fix wrong variable used in perf_event_uprobe_open_legacy()
  libbpf: Cleanup the legacy kprobe_event on failed add/attach_event()
  selftests/bpf: Add type match test against kernel's task_struct
  selftests/bpf: Add nested type to type based tests
  ...
====================

Link: https://lore.kernel.org/r/20220708233145.32365-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 69 insertions, 3 deletions

diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c
index a0d4acd7c54a..067e9ea59e3b 100644
--- a/tools/bpf/bpftool/common.c
+++ b/tools/bpf/bpftool/common.c
@@ -13,14 +13,17 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
-#include <linux/limits.h>
-#include <linux/magic.h>
 #include <net/if.h>
 #include <sys/mount.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/vfs.h>
 
+#include <linux/filter.h>
+#include <linux/limits.h>
+#include <linux/magic.h>
+#include <linux/unistd.h>
+
 #include <bpf/bpf.h>
 #include <bpf/hashmap.h>
 #include <bpf/libbpf.h> /* libbpf_num_possible_cpus */
@@ -73,11 +76,73 @@ static bool is_bpffs(char *path)
 	return (unsigned long)st_fs.f_type == BPF_FS_MAGIC;
 }
 
+/* Probe whether kernel switched from memlock-based (RLIMIT_MEMLOCK) to
+ * memcg-based memory accounting for BPF maps and programs. This was done in
+ * commit 97306be45fbe ("Merge branch 'switch to memcg-based memory
+ * accounting'"), in Linux 5.11.
+ *
+ * Libbpf also offers to probe for memcg-based accounting vs rlimit, but does
+ * so by checking for the availability of a given BPF helper and this has
+ * failed on some kernels with backports in the past, see commit 6b4384ff1088
+ * ("Revert "bpftool: Use libbpf 1.0 API mode instead of RLIMIT_MEMLOCK"").
+ * Instead, we can probe by lowering the process-based rlimit to 0, trying to
+ * load a BPF object, and resetting the rlimit. If the load succeeds then
+ * memcg-based accounting is supported.
+ *
+ * This would be too dangerous to do in the library, because multithreaded
+ * applications might attempt to load items while the rlimit is at 0. Given
+ * that bpftool is single-threaded, this is fine to do here.
+ */
+static bool known_to_need_rlimit(void)
+{
+	struct rlimit rlim_init, rlim_cur_zero = {};
+	struct bpf_insn insns[] = {
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	size_t insn_cnt = ARRAY_SIZE(insns);
+	union bpf_attr attr;
+	int prog_fd, err;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	attr.insns = ptr_to_u64(insns);
+	attr.insn_cnt = insn_cnt;
+	attr.license = ptr_to_u64("GPL");
+
+	if (getrlimit(RLIMIT_MEMLOCK, &rlim_init))
+		return false;
+
+	/* Drop the soft limit to zero. We maintain the hard limit to its
+	 * current value, because lowering it would be a permanent operation
+	 * for unprivileged users.
+	 */
+	rlim_cur_zero.rlim_max = rlim_init.rlim_max;
+	if (setrlimit(RLIMIT_MEMLOCK, &rlim_cur_zero))
+		return false;
+
+	/* Do not use bpf_prog_load() from libbpf here, because it calls
+	 * bump_rlimit_memlock(), interfering with the current probe.
+	 */
+	prog_fd = syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
+	err = errno;
+
+	/* reset soft rlimit to its initial value */
+	setrlimit(RLIMIT_MEMLOCK, &rlim_init);
+
+	if (prog_fd < 0)
+		return err == EPERM;
+
+	close(prog_fd);
+	return false;
+}
+
 void set_max_rlimit(void)
 {
 	struct rlimit rinf = { RLIM_INFINITY, RLIM_INFINITY };
 
-	setrlimit(RLIMIT_MEMLOCK, &rinf);
+	if (known_to_need_rlimit())
+		setrlimit(RLIMIT_MEMLOCK, &rinf);
 }
 
 static int
@@ -251,6 +316,7 @@ const char *get_fd_type_name(enum bpf_obj_type type)
 		[BPF_OBJ_UNKNOWN]	= "unknown",
 		[BPF_OBJ_PROG]		= "prog",
 		[BPF_OBJ_MAP]		= "map",
+		[BPF_OBJ_LINK]		= "link",
 	};
 
 	if (type < 0 || type >= ARRAY_SIZE(names) || !names[type])