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Message-Id: <20220424051022.2619648-4-asmadeus@codewreck.org>
Date: Sun, 24 Apr 2022 14:10:21 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
KP Singh <kpsingh@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Yonghong Song <yhs@...com>, Song Liu <songliubraving@...com>,
Martin KaFai Lau <kafai@...com>,
Andrii Nakryiko <andrii@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Dominique Martinet <asmadeus@...ewreck.org>
Subject: [PATCH 3/4] tools/bpf: musl compat: replace nftw with FTW_ACTIONRETVAL
musl nftw implementation does not support FTW_ACTIONRETVAL.
There have been multiple attempts at pushing the feature in musl
upstream but it has been refused or ignored all the times:
https://www.openwall.com/lists/musl/2021/03/26/1
https://www.openwall.com/lists/musl/2022/01/22/1
In this case we only care about /proc/<pid>/fd/<fd>, so it's not
too difficult to reimplement directly instead, and the new
implementation makes 'bpftool perf' slightly faster because it doesn't
needlessly stat/readdir unneeded directories (54ms -> 13ms on my machine)
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
---
Alternatively alpine has one package where they reimplemented nftw with
FTW_ACTIONRETVAL support locally, so if reaaallly needed we could do the
same here.. But honestly doing two readdirs is probably just as simple
for this particular case.
tools/bpf/bpftool/perf.c | 116 ++++++++++++++++++++-------------------
1 file changed, 59 insertions(+), 57 deletions(-)
diff --git a/tools/bpf/bpftool/perf.c b/tools/bpf/bpftool/perf.c
index 50de087b0db7..de793872544e 100644
--- a/tools/bpf/bpftool/perf.c
+++ b/tools/bpf/bpftool/perf.c
@@ -11,7 +11,7 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
-#include <ftw.h>
+#include <dirent.h>
#include <bpf/bpf.h>
@@ -147,81 +147,83 @@ static void print_perf_plain(int pid, int fd, __u32 prog_id, __u32 fd_type,
}
}
-static int show_proc(const char *fpath, const struct stat *sb,
- int tflag, struct FTW *ftwbuf)
+static int show_proc(void)
{
__u64 probe_offset, probe_addr;
__u32 len, prog_id, fd_type;
- int err, pid = 0, fd = 0;
+ int err, pid, fd;
+ DIR *proc, *pid_fd;
+ struct dirent *proc_de, *pid_fd_de;
const char *pch;
char buf[4096];
- /* prefix always /proc */
- pch = fpath + 5;
- if (*pch == '\0')
- return 0;
+ proc = opendir("/proc");
+ if (!proc)
+ return -1;
+ while ((proc_de = readdir(proc))) {
+ pid = 0;
+ pch = proc_de->d_name;
- /* pid should be all numbers */
- pch++;
- while (isdigit(*pch)) {
- pid = pid * 10 + *pch - '0';
- pch++;
+ /* pid should be all numbers */
+ while (isdigit(*pch)) {
+ pid = pid * 10 + *pch - '0';
+ pch++;
+ }
+ if (*pch != '\0')
+ continue;
+
+ err = snprintf(buf, sizeof(buf), "/proc/%s/fd", proc_de->d_name);
+ if (err < 0 || err >= (int)sizeof(buf))
+ continue;
+
+ pid_fd = opendir(buf);
+ if (!pid_fd)
+ continue;
+
+ while ((pid_fd_de = readdir(pid_fd))) {
+ fd = 0;
+ pch = pid_fd_de->d_name;
+
+ /* fd should be all numbers */
+ while (isdigit(*pch)) {
+ fd = fd * 10 + *pch - '0';
+ pch++;
+ }
+ if (*pch != '\0')
+ continue;
+
+ /* query (pid, fd) for potential perf events */
+ len = sizeof(buf);
+ err = bpf_task_fd_query(pid, fd, 0, buf, &len, &prog_id, &fd_type,
+ &probe_offset, &probe_addr);
+ if (err < 0)
+ continue;
+
+ if (json_output)
+ print_perf_json(pid, fd, prog_id, fd_type, buf, probe_offset,
+ probe_addr);
+ else
+ print_perf_plain(pid, fd, prog_id, fd_type, buf, probe_offset,
+ probe_addr);
+ }
+ closedir(pid_fd);
}
- if (*pch == '\0')
- return 0;
- if (*pch != '/')
- return FTW_SKIP_SUBTREE;
-
- /* check /proc/<pid>/fd directory */
- pch++;
- if (strncmp(pch, "fd", 2))
- return FTW_SKIP_SUBTREE;
- pch += 2;
- if (*pch == '\0')
- return 0;
- if (*pch != '/')
- return FTW_SKIP_SUBTREE;
-
- /* check /proc/<pid>/fd/<fd_num> */
- pch++;
- while (isdigit(*pch)) {
- fd = fd * 10 + *pch - '0';
- pch++;
- }
- if (*pch != '\0')
- return FTW_SKIP_SUBTREE;
-
- /* query (pid, fd) for potential perf events */
- len = sizeof(buf);
- err = bpf_task_fd_query(pid, fd, 0, buf, &len, &prog_id, &fd_type,
- &probe_offset, &probe_addr);
- if (err < 0)
- return 0;
-
- if (json_output)
- print_perf_json(pid, fd, prog_id, fd_type, buf, probe_offset,
- probe_addr);
- else
- print_perf_plain(pid, fd, prog_id, fd_type, buf, probe_offset,
- probe_addr);
-
+ closedir(proc);
return 0;
}
static int do_show(int argc, char **argv)
{
- int flags = FTW_ACTIONRETVAL | FTW_PHYS;
- int err = 0, nopenfd = 16;
+ int err;
if (!has_perf_query_support())
return -1;
if (json_output)
jsonw_start_array(json_wtr);
- if (nftw("/proc", show_proc, nopenfd, flags) == -1) {
- p_err("%s", strerror(errno));
- err = -1;
- }
+
+ err = show_proc();
+
if (json_output)
jsonw_end_array(json_wtr);
--
2.35.1
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