From 64917f4df048a0649ea7901c2321f020e71e6f24 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 17 Aug 2023 15:14:21 -0300 Subject: [PATCH] perf trace: Use heuristic when deciding if a syscall tracepoint "const char *" field is really a string 'perf trace' tries to find BPF progs associated with a syscall that have a signature that is similar to syscalls without one to try and reuse, so, for instance, the 'open' signature can be reused with many other syscalls that have as its first arg a string. It uses the tracefs events format file for finding a signature that can be reused, but then comes the "write" syscall with its second argument as a "const char *": # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_write/format name: sys_enter_write ID: 746 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1; field:int __syscall_nr; offset:8; size:4; signed:1; field:unsigned int fd; offset:16; size:8; signed:0; field:const char * buf; offset:24; size:8; signed:0; field:size_t count; offset:32; size:8; signed:0; print fmt: "fd: 0x%08lx, buf: 0x%08lx, count: 0x%08lx", ((unsigned long)(REC->fd)), ((unsigned long)(REC->buf)), ((unsigned long)(REC->count)) # Which isn't a string (the man page for glibc has buf as "void *"), so we have to use the name of the argument as an heuristic, to consider a string just args that are "const char *" and that have in its name the "path", "file", etc substrings. With that now it reuses: [root@quaco ~]# perf trace -v --max-events=1 |& grep Reus Reusing "open" BPF sys_enter augmenter for "stat" Reusing "open" BPF sys_enter augmenter for "lstat" Reusing "open" BPF sys_enter augmenter for "access" Reusing "connect" BPF sys_enter augmenter for "accept" Reusing "sendto" BPF sys_enter augmenter for "recvfrom" Reusing "connect" BPF sys_enter augmenter for "bind" Reusing "connect" BPF sys_enter augmenter for "getsockname" Reusing "connect" BPF sys_enter augmenter for "getpeername" Reusing "open" BPF sys_enter augmenter for "execve" Reusing "open" BPF sys_enter augmenter for "truncate" Reusing "open" BPF sys_enter augmenter for "chdir" Reusing "open" BPF sys_enter augmenter for "mkdir" Reusing "open" BPF sys_enter augmenter for "rmdir" Reusing "open" BPF sys_enter augmenter for "creat" Reusing "open" BPF sys_enter augmenter for "link" Reusing "open" BPF sys_enter augmenter for "unlink" Reusing "open" BPF sys_enter augmenter for "symlink" Reusing "open" BPF sys_enter augmenter for "readlink" Reusing "open" BPF sys_enter augmenter for "chmod" Reusing "open" BPF sys_enter augmenter for "chown" Reusing "open" BPF sys_enter augmenter for "lchown" Reusing "open" BPF sys_enter augmenter for "mknod" Reusing "open" BPF sys_enter augmenter for "statfs" Reusing "open" BPF sys_enter augmenter for "pivot_root" Reusing "open" BPF sys_enter augmenter for "chroot" Reusing "open" BPF sys_enter augmenter for "acct" Reusing "open" BPF sys_enter augmenter for "swapon" Reusing "open" BPF sys_enter augmenter for "swapoff" Reusing "open" BPF sys_enter augmenter for "delete_module" Reusing "open" BPF sys_enter augmenter for "setxattr" Reusing "open" BPF sys_enter augmenter for "lsetxattr" Reusing "openat" BPF sys_enter augmenter for "fsetxattr" Reusing "open" BPF sys_enter augmenter for "getxattr" Reusing "open" BPF sys_enter augmenter for "lgetxattr" Reusing "openat" BPF sys_enter augmenter for "fgetxattr" Reusing "open" BPF sys_enter augmenter for "listxattr" Reusing "open" BPF sys_enter augmenter for "llistxattr" Reusing "open" BPF sys_enter augmenter for "removexattr" Reusing "open" BPF sys_enter augmenter for "lremovexattr" Reusing "fsetxattr" BPF sys_enter augmenter for "fremovexattr" Reusing "open" BPF sys_enter augmenter for "mq_open" Reusing "open" BPF sys_enter augmenter for "mq_unlink" Reusing "fsetxattr" BPF sys_enter augmenter for "add_key" Reusing "fremovexattr" BPF sys_enter augmenter for "request_key" Reusing "fremovexattr" BPF sys_enter augmenter for "inotify_add_watch" Reusing "fremovexattr" BPF sys_enter augmenter for "mkdirat" Reusing "fremovexattr" BPF sys_enter augmenter for "mknodat" Reusing "fremovexattr" BPF sys_enter augmenter for "fchownat" Reusing "fremovexattr" BPF sys_enter augmenter for "futimesat" Reusing "fremovexattr" BPF sys_enter augmenter for "newfstatat" Reusing "fremovexattr" BPF sys_enter augmenter for "unlinkat" Reusing "fremovexattr" BPF sys_enter augmenter for "linkat" Reusing "open" BPF sys_enter augmenter for "symlinkat" Reusing "fremovexattr" BPF sys_enter augmenter for "readlinkat" Reusing "fremovexattr" BPF sys_enter augmenter for "fchmodat" Reusing "fremovexattr" BPF sys_enter augmenter for "faccessat" Reusing "fremovexattr" BPF sys_enter augmenter for "utimensat" Reusing "connect" BPF sys_enter augmenter for "accept4" Reusing "fremovexattr" BPF sys_enter augmenter for "name_to_handle_at" Reusing "fremovexattr" BPF sys_enter augmenter for "renameat2" Reusing "open" BPF sys_enter augmenter for "memfd_create" Reusing "fremovexattr" BPF sys_enter augmenter for "execveat" Reusing "fremovexattr" BPF sys_enter augmenter for "statx" [root@quaco ~]# Reviewed-by: Ian Rogers Cc: Adrian Hunter Cc: Alan Maguire Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lore.kernel.org/lkml/ZN5lrdeEdSMCn7hk@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-trace.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 3964cf4..e541d0e2 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -3398,6 +3398,19 @@ try_to_find_pair: if (strcmp(field->type, candidate_field->type)) goto next_candidate; + /* + * This is limited in the BPF program but sys_write + * uses "const char *" for its "buf" arg so we need to + * use some heuristic that is kinda future proof... + */ + if (strcmp(field->type, "const char *") == 0 && + !(strstr(field->name, "name") || + strstr(field->name, "path") || + strstr(field->name, "file") || + strstr(field->name, "root") || + strstr(field->name, "description"))) + goto next_candidate; + is_candidate = true; } -- 2.7.4