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>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220202070828.143303-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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];
#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)
{
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);
}
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);
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;
+}
bool set;
};
void perf_debuginfod_setup(struct perf_debuginfod *di);
+
+char *filename_with_chroot(int pid, const char *filename);
#endif /* GIT_COMPAT_UTIL_H */