On 12/14/19 8:01 PM, Wenbo Zhang wrote:
> trace fstat events by tracepoint syscalls/sys_enter_newfstat, and handle
> events only produced by test_file_get_path, which call fstat on several
> different types of files to test bpf_get_file_path's feature.
>
> v4->v5: addressed Andrii's feedback
> - pass NULL for opts as bpf_object__open_file's PARAM2, as not really
> using any
> - modify patch subject to keep up with test code
> - as this test is single-threaded, so use getpid instead of SYS_gettid
> - remove unnecessary parens around check which after if (i < 3)
> - in kern use bpf_get_current_pid_tgid() >> 32 to fit getpid() in
> userspace part
> - with the patch adding helper as one patch series
>
> v3->v4: addressed Andrii's feedback
> - use a set of fd instead of fds array
> - use global variables instead of maps (in v3, I mistakenly thought that
> the bpf maps are global variables.)
> - remove uncessary global variable path_info_index
> - remove fd compare as the fstat's order is fixed
>
> v2->v3: addressed Andrii's feedback
> - use global data instead of perf_buffer to simplified code
>
> v1->v2: addressed Daniel's feedback
> - rename bpf_fd2path to bpf_get_file_path to be consistent with other
> helper's names
>
> Signed-off-by: Wenbo Zhang <ethercflow@xxxxxxxxx>
> ---
> .../selftests/bpf/prog_tests/get_file_path.c | 171 ++++++++++++++++++
> .../selftests/bpf/progs/test_get_file_path.c | 43 +++++
> 2 files changed, 214 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/get_file_path.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_get_file_path.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/get_file_path.c b/tools/testing/selftests/bpf/prog_tests/get_file_path.c
> new file mode 100644
> index 000000000000..7ec11e43e0fc
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/get_file_path.c
> @@ -0,0 +1,171 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <test_progs.h>
> +#include <sys/stat.h>
> +#include <linux/sched.h>
> +#include <sys/syscall.h>
> +
> +#define MAX_PATH_LEN 128
> +#define MAX_FDS 7
> +#define MAX_EVENT_NUM 16
> +
> +static struct file_path_test_data {
> + pid_t pid;
> + __u32 cnt;
> + __u32 fds[MAX_EVENT_NUM];
> + char paths[MAX_EVENT_NUM][MAX_PATH_LEN];
> +} src, dst;
> +
> +static inline int set_pathname(int fd)
In non-bpf .c file, typically we do not add 'inline' attribute.
It is up to compiler to decide whether it should be inlined.
> +{
> + char buf[MAX_PATH_LEN];
> +
> + snprintf(buf, MAX_PATH_LEN, "/proc/%d/fd/%d", src.pid, fd);
> + src.fds[src.cnt] = fd;
> + return readlink(buf, src.paths[src.cnt++], MAX_PATH_LEN);
> +}
> +
[...]
> diff --git a/tools/testing/selftests/bpf/progs/test_get_file_path.c b/tools/testing/selftests/bpf/progs/test_get_file_path.c
> new file mode 100644
> index 000000000000..eae663c1262a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_get_file_path.c
> @@ -0,0 +1,43 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <linux/ptrace.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include "bpf_helpers.h"
> +#include "bpf_tracing.h"
> +
> +#define MAX_PATH_LEN 128
> +#define MAX_EVENT_NUM 16
> +
> +static struct file_path_test_data {
> + pid_t pid;
> + __u32 cnt;
> + __u32 fds[MAX_EVENT_NUM];
> + char paths[MAX_EVENT_NUM][MAX_PATH_LEN];
> +} data;
> +
> +struct sys_enter_newfstat_args {
> + unsigned long long pad1;
> + unsigned long long pad2;
> + unsigned int fd;
> +};
The BTF generated vmlinux.h has the following structure,
struct trace_entry {
short unsigned int type;
unsigned char flags;
unsigned char preempt_count;
int pid;
};
struct trace_event_raw_sys_enter {
struct trace_entry ent;
long int id;
long unsigned int args[6];
char __data[0];
};
The third parameter type should be long, otherwise,
it may have issue on big endian machines?
