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/dso.c | 15 +++++++++++++-- tools/perf/util/dsos.c | 13 +++++++++++++ tools/perf/util/symbol.c | 10 ++++++++++ tools/perf/util/util.c | 31 +++++++++++++++++++++++++++++++ tools/perf/util/util.h | 2 ++ 5 files changed, 69 insertions(+), 2 deletions(-) (limited to 'tools') diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c index 9cc8a1772b4b..5ac13958d1bd 100644 --- a/tools/perf/util/dso.c +++ b/tools/perf/util/dso.c @@ -508,8 +508,19 @@ static int __open_dso(struct dso *dso, struct machine *machine) root_dir, name, PATH_MAX)) goto out; - if (!is_regular_file(name)) - goto out; + if (!is_regular_file(name)) { + char *new_name; + + if (errno != ENOENT || dso->nsinfo == NULL) + goto out; + + new_name = filename_with_chroot(dso->nsinfo->pid, name); + if (!new_name) + goto out; + + free(name); + name = new_name; + } if (dso__needs_decompress(dso)) { char newpath[KMOD_DECOMP_LEN]; diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c index 183a81d5b2f9..b97366f77bbf 100644 --- a/tools/perf/util/dsos.c +++ b/tools/perf/util/dsos.c @@ -2,12 +2,15 @@ #include "debug.h" #include "dsos.h" #include "dso.h" +#include "util.h" #include "vdso.h" #include "namespaces.h" +#include #include #include #include #include // filename__read_build_id +#include static int __dso_id__cmp(struct dso_id *a, struct dso_id *b) { @@ -76,6 +79,16 @@ bool __dsos__read_build_ids(struct list_head *head, bool with_hits) if (filename__read_build_id(pos->long_name, &pos->bid) > 0) { have_build_id = true; pos->has_build_id = true; + } else if (errno == ENOENT && pos->nsinfo) { + char *new_name = filename_with_chroot(pos->nsinfo->pid, + pos->long_name); + + if (new_name && filename__read_build_id(new_name, + &pos->bid) > 0) { + have_build_id = true; + pos->has_build_id = true; + } + free(new_name); } nsinfo__mountns_exit(&nsc); } diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index b2ed3140a1fa..34302c61d36b 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -1864,6 +1864,16 @@ int dso__load(struct dso *dso, struct map *map) nsinfo__mountns_exit(&nsc); is_reg = is_regular_file(name); + if (!is_reg && errno == ENOENT && dso->nsinfo) { + char *new_name = filename_with_chroot(dso->nsinfo->pid, + name); + if (new_name) { + is_reg = is_regular_file(new_name); + strlcpy(name, new_name, PATH_MAX); + free(new_name); + } + } + #ifdef HAVE_LIBBFD_SUPPORT if (is_reg) bfdrc = dso__load_bfd_symbols(dso, name); 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; +} diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h index 7b625cbd2dd8..0f78f1e7782d 100644 --- a/tools/perf/util/util.h +++ b/tools/perf/util/util.h @@ -77,4 +77,6 @@ struct perf_debuginfod { bool set; }; void perf_debuginfod_setup(struct perf_debuginfod *di); + +char *filename_with_chroot(int pid, const char *filename); #endif /* GIT_COMPAT_UTIL_H */ -- cgit v1.2.3-59-g8ed1b