Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [PATCH 1/3] perf tools: Try chroot'ed filename when opening dso/symbol | Date | Fri, 28 Jan 2022 12:39:48 -0800 |
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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 <namhyung@kernel.org> --- 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(-)
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 <errno.h> #include <libgen.h> #include <stdlib.h> #include <string.h> #include <symbol.h> // filename__read_build_id +#include <unistd.h> 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 */ -- 2.35.0.rc2.247.g8bbb082509-goog
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