unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
1
Fork 0
Code Pull requests 5 Wiki Activity

bpftool, musl compat: Replace nftw with FTW_ACTIONRETVAL

Browse source 
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@codewreck.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220424051022.2619648-4-asmadeus@codewreck.org
This commit is contained in:
Dominique Martinet 2022-04-24 14:10:21 +09:00 committed by Daniel Borkmann
parent 003fed595c
commit 93bc2e9e94
1 changed files with 59 additions and 57 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

116
tools/bpf/bpftool/perf.c
View file

@ -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)
{
struct dirent *proc_de, *pid_fd_de;
__u64 probe_offset, probe_addr;
__u32 len, prog_id, fd_type;
int err, pid = 0, fd = 0;
DIR *proc, *pid_fd;
int err, pid, fd;
const char *pch;
char buf[4096];
/* prefix always /proc */
pch = fpath + 5;
if (*pch == '\0')
return 0;
proc = opendir("/proc");
if (!proc)
return -1;
/* pid should be all numbers */
pch++;
while (isdigit(*pch)) {
pid = pid * 10 + *pch - '0';
pch++;
while ((proc_de = readdir(proc))) {
pid = 0;
pch = proc_de->d_name;
/* 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);