netdev - [PATCH 1/3] samples: bpf: fix bpf programs with kprobe/sys

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Message-Id: <20200626081720.5546-1-danieltimlee@gmail.com>
Date:   Fri, 26 Jun 2020 17:17:18 +0900
From:   "Daniel T. Lee" <danieltimlee@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Andrii Nakryiko <andriin@...com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH 1/3] samples: bpf: fix bpf programs with kprobe/sys_connect event

Currently, BPF programs with kprobe/sys_connect does not work properly.

Commit 34745aed515c ("samples/bpf: fix kprobe attachment issue on x64")
This commit modifies the bpf_load behavior of kprobe events in the x64
architecture. If the current kprobe event target starts with "sys_*",
add the prefix "__x64_" to the front of the event.

Appending "__x64_" prefix with kprobe/sys_* event was appropriate as a
solution to most of the problems caused by the commit below.

    commit d5a00528b58c ("syscalls/core, syscalls/x86: Rename struct
    pt_regs-based sys_*() to __x64_sys_*()")

However, there is a problem with the sys_connect kprobe event that does
not work properly. For __sys_connect event, parameters can be fetched
normally, but for __x64_sys_connect, parameters cannot be fetched.

Because of this problem, this commit fixes the sys_connect event by
specifying the __sys_connect directly and this will bypass the
"__x64_" appending rule of bpf_load.

Fixes: 34745aed515c ("samples/bpf: fix kprobe attachment issue on x64")
Signed-off-by: Daniel T. Lee <danieltimlee@...il.com>
---
 samples/bpf/map_perf_test_kern.c         | 2 +-
 samples/bpf/test_map_in_map_kern.c       | 2 +-
 samples/bpf/test_probe_write_user_kern.c | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/samples/bpf/map_perf_test_kern.c b/samples/bpf/map_perf_test_kern.c
index 1bb1fdb9cdf8..69ecd717d998 100644
--- a/samples/bpf/map_perf_test_kern.c
+++ b/samples/bpf/map_perf_test_kern.c
@@ -159,7 +159,7 @@ int stress_percpu_hmap_alloc(struct pt_regs *ctx)
 	return 0;
 }
 
-SEC("kprobe/sys_connect")
+SEC("kprobe/__sys_connect")
 int stress_lru_hmap_alloc(struct pt_regs *ctx)
 {
 	char fmt[] = "Failed at stress_lru_hmap_alloc. ret:%dn";
diff --git a/samples/bpf/test_map_in_map_kern.c b/samples/bpf/test_map_in_map_kern.c
index 6cee61e8ce9b..b1562ba2f025 100644
--- a/samples/bpf/test_map_in_map_kern.c
+++ b/samples/bpf/test_map_in_map_kern.c
@@ -102,7 +102,7 @@ static __always_inline int do_inline_hash_lookup(void *inner_map, u32 port)
 	return result ? *result : -ENOENT;
 }
 
-SEC("kprobe/sys_connect")
+SEC("kprobe/__sys_connect")
 int trace_sys_connect(struct pt_regs *ctx)
 {
 	struct sockaddr_in6 *in6;
diff --git a/samples/bpf/test_probe_write_user_kern.c b/samples/bpf/test_probe_write_user_kern.c
index 6579639a83b2..9b3c3918c37d 100644
--- a/samples/bpf/test_probe_write_user_kern.c
+++ b/samples/bpf/test_probe_write_user_kern.c
@@ -26,7 +26,7 @@ struct {
  * This example sits on a syscall, and the syscall ABI is relatively stable
  * of course, across platforms, and over time, the ABI may change.
  */
-SEC("kprobe/sys_connect")
+SEC("kprobe/__sys_connect")
 int bpf_prog1(struct pt_regs *ctx)
 {
 	struct sockaddr_in new_addr, orig_addr = {};
-- 
2.25.1