From 67fd18924647bdcafab18c2945a79ddea73653de Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Tue, 1 Feb 2022 23:08:26 -0800 Subject: perf tools: Try chroot'ed filename when opening dso/symbol Currently it doesn't handle tasks in chroot properly. As filenames in MMAP records base on their root directory, it's different than what perf tool can see from outside. Add filename_with_chroot() helper to deal with those cases. The function returns a new filename only if it's in a different root directory. Since it needs to access /proc for the process, it only works until the task exits. With this change, I can see symbols in my program like below. # perf record -o- chroot myroot myprog 3 | perf report -i- ... # # Overhead Command Shared Object Symbol # ........ ....... ................. ............................. # 99.83% myprog myprog [.] loop 0.04% chroot [kernel.kallsyms] [k] fxregs_fixup 0.04% chroot [kernel.kallsyms] [k] rsm_load_seg_32 ... Signed-off-by: Namhyung Kim Acked-by: Jiri Olsa Cc: Andi Kleen Cc: Ian Rogers Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20220202070828.143303-3-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/util.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'tools/perf/util/util.c') diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c index fb4f6616b5fa..f8571a66d063 100644 --- a/tools/perf/util/util.c +++ b/tools/perf/util/util.c @@ -431,3 +431,34 @@ void perf_debuginfod_setup(struct perf_debuginfod *di) pr_debug("DEBUGINFOD_URLS=%s\n", getenv("DEBUGINFOD_URLS")); } + +/* + * Return a new filename prepended with task's root directory if it's in + * a chroot. Callers should free the returned string. + */ +char *filename_with_chroot(int pid, const char *filename) +{ + char buf[PATH_MAX]; + char proc_root[32]; + char *new_name = NULL; + int ret; + + scnprintf(proc_root, sizeof(proc_root), "/proc/%d/root", pid); + ret = readlink(proc_root, buf, sizeof(buf) - 1); + if (ret <= 0) + return NULL; + + /* readlink(2) does not append a null byte to buf */ + buf[ret] = '\0'; + + if (!strcmp(buf, "/")) + return NULL; + + if (strstr(buf, "(deleted)")) + return NULL; + + if (asprintf(&new_name, "%s/%s", buf, filename) < 0) + return NULL; + + return new_name; +} -- cgit v1.2.3