From: Arnaldo Carvalho de Melo <a...@redhat.com>
Allowing one to hook into the syscalls:sys_enter_NAME tracepoints,
an example is provided that hooks into the 'openat' syscall.
Using it with the probe:vfs_getname probe into getname_flags to get the
filename args as it is copied from userspace:
# perf probe -l
probe:vfs_getname (on getname_flags:73@acme/git/linux/fs/namei.c with
pathname)
# perf trace -e probe:*getname,tools/perf/examples/bpf/sys_enter_openat.c cat
/etc/passwd > /dev/null
0.000 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.preload"
0.022 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafbe8da8, flags:
CLOEXEC
0.027 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/ld.so.cache"
0.054 syscalls:sys_enter_openat:dfd: CWD, filename: 0xafdf0ce0, flags:
CLOEXEC
0.057 probe:vfs_getname:(ffffffffbd2a8983) pathname="/lib64/libc.so.6"
0.316 probe:vfs_getname:(ffffffffbd2a8983)
pathname="/usr/lib/locale/locale-archive"
0.375 syscalls:sys_enter_openat:dfd: CWD, filename: 0xe2b2b0b4
0.379 probe:vfs_getname:(ffffffffbd2a8983) pathname="/etc/passwd"
#
Cc: Adrian Hunter <adrian.hun...@intel.com>
Cc: David Ahern <dsah...@gmail.com>
Cc: Jiri Olsa <jo...@kernel.org>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Wang Nan <wangn...@huawei.com>
Link: https://lkml.kernel.org/n/tip-2po9jcqv1qgj0koxlg8kk...@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
---
tools/perf/examples/bpf/sys_enter_openat.c | 33 ++++++++++++++++++++++++++++++
tools/perf/include/bpf/bpf.h | 3 +++
2 files changed, 36 insertions(+)
create mode 100644 tools/perf/examples/bpf/sys_enter_openat.c
diff --git a/tools/perf/examples/bpf/sys_enter_openat.c
b/tools/perf/examples/bpf/sys_enter_openat.c
new file mode 100644
index 000000000000..9cd124b09392
--- /dev/null
+++ b/tools/perf/examples/bpf/sys_enter_openat.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hook into 'openat' syscall entry tracepoint
+ *
+ * Test it with:
+ *
+ * perf trace -e tools/perf/examples/bpf/sys_enter_openat.c cat /etc/passwd >
/dev/null
+ *
+ * It'll catch some openat syscalls related to the dynamic linked and
+ * the last one should be the one for '/etc/passwd'.
+ *
+ * The syscall_enter_openat_args can be used to get the syscall fields
+ * and use them for filtering calls, i.e. use in expressions for
+ * the return value.
+ */
+
+#include <bpf.h>
+
+struct syscall_enter_openat_args {
+ unsigned long long unused;
+ long syscall_nr;
+ long dfd;
+ char *filename_ptr;
+ long flags;
+ long mode;
+};
+
+int syscall_enter(openat)(struct syscall_enter_openat_args *args)
+{
+ return 1;
+}
+
+license(GPL);
diff --git a/tools/perf/include/bpf/bpf.h b/tools/perf/include/bpf/bpf.h
index a63aa6241b7f..2873cdde293f 100644
--- a/tools/perf/include/bpf/bpf.h
+++ b/tools/perf/include/bpf/bpf.h
@@ -9,6 +9,9 @@
#define probe(function, vars) \
SEC(#function "=" #function " " #vars) function
+#define syscall_enter(name) \
+ SEC("syscalls:sys_enter_" #name) syscall_enter_ ## name
+
#define license(name) \
char _license[] SEC("license") = #name; \
int _version SEC("version") = LINUX_VERSION_CODE;
--
2.14.4
