Re: [PATCH 2/2] perf probe: Fall back to debuginfod query if debuginfo and source not found
From: Masami Hiramatsu
Date: Thu Sep 17 2020 - 22:47:57 EST
On Thu, 17 Sep 2020 21:40:22 -0300
Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
> Em Thu, Sep 17, 2020 at 01:44:52AM +0900, Masami Hiramatsu escreveu:
> > Since the perf-probe heavily depends on the debuginfo, debuginfod
> > gives us many benefits on the perf probe command on remote machine.
> > Especially, this will be helpful for the embedded devices which will
> > not have enough storage, or boot with a cross-build kernel whose
> > source code is in the host machine.
> > This will work as similar to the commit c7a14fdcb3fa ("perf build-ids:
> > Fall back to debuginfod query if debuginfo not found")
> >
> > Tested with:
> >
> > (host) $ cd PATH/TO/KBUILD/DIR/
> > (host) $ debuginfod -F .
> > ...
> >
> > (remote) # perf probe -L vfs_read
> > Failed to find the path for the kernel: No such file or directory
> > Error: Failed to show lines.
> >
> > (remote) # export DEBUGINFOD_URLS="http://$HOST_IP:8002/";
> > (remote) # perf probe -L vfs_read
> > <vfs_read@...>
> > 0 ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
> > {
> > 2 ssize_t ret;
> >
> > if (!(file->f_mode & FMODE_READ))
> > return -EBADF;
> > 6 if (!(file->f_mode & FMODE_CAN_READ))
> > return -EINVAL;
> > 8 if (unlikely(!access_ok(buf, count)))
> > return -EFAULT;
> >
> > 11 ret = rw_verify_area(READ, file, pos, count);
> > 12 if (ret)
> > return ret;
> > if (count > MAX_RW_COUNT)
> > ...
> >
> > (remote) # perf probe -a "vfs_read count"
> > Added new event:
> > probe:vfs_read (on vfs_read with count)
> >
> > (remote) # perf probe -l
> > probe:vfs_read (on vfs_read@ksrc/linux/fs/read_write.c with count)
> >
> >
> > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > ---
> > tools/perf/util/probe-event.c | 52 ++++++++++++++++++++++++++++++++++++-
> > tools/perf/util/probe-finder.c | 56 ++++++++++++++++++++++++++++++++++++----
> > tools/perf/util/probe-finder.h | 7 ++++-
> > 3 files changed, 107 insertions(+), 8 deletions(-)
> >
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 17831f186ab5..26733c8070a7 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -43,6 +43,10 @@
> > #include <linux/ctype.h>
> > #include <linux/zalloc.h>
> >
> > +#ifdef HAVE_DEBUGINFOD_SUPPORT
> > +#include <elfutils/debuginfod.h>
> > +#endif
> > +
> > #define PERFPROBE_GROUP "probe"
> >
> > bool probe_event_dry_run; /* Dry run flag */
> > @@ -338,6 +342,8 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso)
> >
> > map = machine__kernel_map(host_machine);
> > dso = map->dso;
> > + if (!dso->has_build_id)
> > + dso__read_running_kernel_build_id(dso, host_machine);
> >
> > vmlinux_name = symbol_conf.vmlinux_name;
> > dso->load_errno = 0;
> > @@ -453,6 +459,43 @@ static int get_alternative_line_range(struct debuginfo *dinfo,
> > return ret;
> > }
> >
> > +static struct debuginfo *open_from_debuginfod(struct dso *dso, struct nsinfo *nsi,
> > + bool silent)
> > +{
> > +#ifdef HAVE_DEBUGINFOD_SUPPORT
>
> Its better to have the whole function enclosed in the ifdef, to avoid:
>
> CC /tmp/build/perf/util/unwind-libunwind.o
> util/probe-event.c: In function 'open_from_debuginfod':
> util/probe-event.c:462:59: error: unused parameter 'dso' [-Werror=unused-parameter]
> 462 | static struct debuginfo *open_from_debuginfod(struct dso *dso, struct nsinfo *nsi,
> | ~~~~~~~~~~~~^~~
> util/probe-event.c:462:79: error: unused parameter 'nsi' [-Werror=unused-parameter]
> 462 | static struct debuginfo *open_from_debuginfod(struct dso *dso, struct nsinfo *nsi,
> | ~~~~~~~~~~~~~~~^~~
> util/probe-event.c:463:17: error: unused parameter 'silent' [-Werror=unused-parameter]
> 463 | bool silent)
> | ^
> CC /tmp/build/perf/util/zlib.o
> util/probe-finder.c: In function 'get_source_from_debuginfod':
> util/probe-finder.c:1988:51: error: unused parameter 'raw_path' [-Werror=unused-parameter]
> 1988 | static int get_source_from_debuginfod(const char *raw_path,
> | ~~~~~~~~~~~~^~~~~~~~
> util/probe-finder.c:1989:17: error: unused parameter 'sbuild_id' [-Werror=unused-parameter]
> 1989 | const char *sbuild_id, char **new_path)
> | ~~~~~~~~~~~~^~~~~~~~~
> util/probe-finder.c:1989:35: error: unused parameter 'new_path' [-Werror=unused-parameter]
> 1989 | const char *sbuild_id, char **new_path)
> | ~~~~~~~^~~~~~~~
> CC /tmp/build/perf/util/lzma.o
>
>
> I.e. please test with:
>
> [acme@quaco perf]$ grep DEBUGINFOD tools/perf/Makefile.perf
> # Define NO_LIBDEBUGINFOD if you do not want support debuginfod
> [acme@quaco perf]$
>
Oops, right. I forgot to install libdebuginfod also on host side...
Let me update the series.
Thank you,
> - Arnaldo
>
> > + debuginfod_client * c = debuginfod_begin();
> > + char sbuild_id[SBUILD_ID_SIZE + 1];
> > + struct debuginfo *ret = NULL;
> > + struct nscookie nsc;
> > + char *path;
> > + int fd;
> > +
> > + if (!c)
> > + return NULL;
> > +
> > + build_id__sprintf(dso->build_id, BUILD_ID_SIZE, sbuild_id);
> > + fd = debuginfod_find_debuginfo(c, (const unsigned char *)sbuild_id,
> > + 0, &path);
> > + if (fd >= 0)
> > + close(fd);
> > + debuginfod_end(c);
> > + if (fd < 0) {
> > + if (!silent)
> > + pr_debug("Failed to find debuginfo in debuginfod.\n");
> > + return NULL;
> > + }
> > + if (!silent)
> > + pr_debug("Load debuginfo from debuginfod (%s)\n", path);
> > +
> > + nsinfo__mountns_enter(nsi, &nsc);
> > + ret = debuginfo__new((const char *)path);
> > + nsinfo__mountns_exit(&nsc);
> > + return ret;
> > +#else
> > + return NULL;
> > +#endif
> > +}
> > +
> > /* Open new debuginfo of given module */
> > static struct debuginfo *open_debuginfo(const char *module, struct nsinfo *nsi,
> > bool silent)
> > @@ -472,6 +515,10 @@ static struct debuginfo *open_debuginfo(const char *module, struct nsinfo *nsi,
> > strcpy(reason, "(unknown)");
> > } else
> > dso__strerror_load(dso, reason, STRERR_BUFSIZE);
> > + if (dso)
> > + ret = open_from_debuginfod(dso, nsi, silent);
> > + if (ret)
> > + return ret;
> > if (!silent) {
> > if (module)
> > pr_err("Module %s is not loaded, please specify its full path name.\n", module);
> > @@ -959,6 +1006,7 @@ static int __show_line_range(struct line_range *lr, const char *module,
> > int ret;
> > char *tmp;
> > char sbuf[STRERR_BUFSIZE];
> > + char sbuild_id[SBUILD_ID_SIZE] = "";
> >
> > /* Search a line range */
> > dinfo = open_debuginfo(module, NULL, false);
> > @@ -971,6 +1019,8 @@ static int __show_line_range(struct line_range *lr, const char *module,
> > if (!ret)
> > ret = debuginfo__find_line_range(dinfo, lr);
> > }
> > + if (dinfo->build_id)
> > + build_id__sprintf(dinfo->build_id, BUILD_ID_SIZE, sbuild_id);
> > debuginfo__delete(dinfo);
> > if (ret == 0 || ret == -ENOENT) {
> > pr_warning("Specified source line is not found.\n");
> > @@ -982,7 +1032,7 @@ static int __show_line_range(struct line_range *lr, const char *module,
> >
> > /* Convert source file path */
> > tmp = lr->path;
> > - ret = get_real_path(tmp, lr->comp_dir, &lr->path);
> > + ret = find_source_path(tmp, sbuild_id, lr->comp_dir, &lr->path);
> >
> > /* Free old path when new path is assigned */
> > if (tmp != lr->path)
> > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > index 659024342e9a..a98590940003 100644
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -31,6 +31,10 @@
> > #include "probe-file.h"
> > #include "string2.h"
> >
> > +#ifdef HAVE_DEBUGINFOD_SUPPORT
> > +#include <elfutils/debuginfod.h>
> > +#endif
> > +
> > /* Kprobe tracer basic type is up to u64 */
> > #define MAX_BASIC_TYPE_BITS 64
> >
> > @@ -51,6 +55,7 @@ static const Dwfl_Callbacks offline_callbacks = {
> > static int debuginfo__init_offline_dwarf(struct debuginfo *dbg,
> > const char *path)
> > {
> > + GElf_Addr dummy;
> > int fd;
> >
> > fd = open(path, O_RDONLY);
> > @@ -70,6 +75,8 @@ static int debuginfo__init_offline_dwarf(struct debuginfo *dbg,
> > if (!dbg->dbg)
> > goto error;
> >
> > + dwfl_module_build_id(dbg->mod, &dbg->build_id, &dummy);
> > +
> > dwfl_report_end(dbg->dwfl, NULL, NULL);
> >
> > return 0;
> > @@ -942,6 +949,7 @@ static int probe_point_lazy_walker(const char *fname, int lineno,
> > /* Find probe points from lazy pattern */
> > static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
> > {
> > + char sbuild_id[SBUILD_ID_SIZE] = "";
> > int ret = 0;
> > char *fpath;
> >
> > @@ -949,7 +957,10 @@ static int find_probe_point_lazy(Dwarf_Die *sp_die, struct probe_finder *pf)
> > const char *comp_dir;
> >
> > comp_dir = cu_get_comp_dir(&pf->cu_die);
> > - ret = get_real_path(pf->fname, comp_dir, &fpath);
> > + if (pf->dbg->build_id)
> > + build_id__sprintf(pf->dbg->build_id,
> > + BUILD_ID_SIZE, sbuild_id);
> > + ret = find_source_path(pf->fname, sbuild_id, comp_dir, &fpath);
> > if (ret < 0) {
> > pr_warning("Failed to find source file path.\n");
> > return ret;
> > @@ -1448,7 +1459,7 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
> > struct probe_trace_event **tevs)
> > {
> > struct trace_event_finder tf = {
> > - .pf = {.pev = pev, .callback = add_probe_trace_event},
> > + .pf = {.pev = pev, .dbg = dbg, .callback = add_probe_trace_event},
> > .max_tevs = probe_conf.max_probes, .mod = dbg->mod};
> > int ret, i;
> >
> > @@ -1618,7 +1629,7 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg,
> > struct variable_list **vls)
> > {
> > struct available_var_finder af = {
> > - .pf = {.pev = pev, .callback = add_available_vars},
> > + .pf = {.pev = pev, .dbg = dbg, .callback = add_available_vars},
> > .mod = dbg->mod,
> > .max_vls = probe_conf.max_probes};
> > int ret;
> > @@ -1973,17 +1984,52 @@ int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr)
> > return (ret < 0) ? ret : lf.found;
> > }
> >
> > +/* debuginfod doesn't require the comp_dir but buildid is required */
> > +static int get_source_from_debuginfod(const char *raw_path,
> > + const char *sbuild_id, char **new_path)
> > +{
> > +#ifdef HAVE_DEBUGINFOD_SUPPORT
> > + debuginfod_client * c = debuginfod_begin();
> > + const char *p = raw_path;
> > + int fd;
> > +
> > + if (!c)
> > + return -ENOMEM;
> > +
> > + fd = debuginfod_find_source(c, (const unsigned char *)sbuild_id,
> > + 0, p, new_path);
> > + pr_debug("Search %s from debuginfod -> %d\n", p, fd);
> > + if (fd >= 0)
> > + close(fd);
> > + debuginfod_end(c);
> > + if (fd < 0) {
> > + pr_debug("Failed to find %s in debuginfod (%s)\n",
> > + raw_path, sbuild_id);
> > + return -ENOENT;
> > + }
> > + pr_debug("Got a source %s\n", *new_path);
> > +
> > + return 0;
> > +#else
> > + return -ENOTSUP;
> > +#endif
> > +}
> > /*
> > * Find a src file from a DWARF tag path. Prepend optional source path prefix
> > * and chop off leading directories that do not exist. Result is passed back as
> > * a newly allocated path on success.
> > * Return 0 if file was found and readable, -errno otherwise.
> > */
> > -int get_real_path(const char *raw_path, const char *comp_dir,
> > - char **new_path)
> > +int find_source_path(const char *raw_path, const char *sbuild_id,
> > + const char *comp_dir, char **new_path)
> > {
> > const char *prefix = symbol_conf.source_prefix;
> >
> > + if (sbuild_id && !prefix) {
> > + if (!get_source_from_debuginfod(raw_path, sbuild_id, new_path))
> > + return 0;
> > + }
> > +
> > if (!prefix) {
> > if (raw_path[0] != '/' && comp_dir)
> > /* If not an absolute path, try to use comp_dir */
> > diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
> > index 11be10080613..2febb5875678 100644
> > --- a/tools/perf/util/probe-finder.h
> > +++ b/tools/perf/util/probe-finder.h
> > @@ -4,6 +4,7 @@
> >
> > #include <stdbool.h>
> > #include "intlist.h"
> > +#include "build-id.h"
> > #include "probe-event.h"
> > #include <linux/ctype.h>
> >
> > @@ -32,6 +33,7 @@ struct debuginfo {
> > Dwfl_Module *mod;
> > Dwfl *dwfl;
> > Dwarf_Addr bias;
> > + const unsigned char *build_id;
> > };
> >
> > /* This also tries to open distro debuginfo */
> > @@ -59,11 +61,12 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg,
> > struct variable_list **vls);
> >
> > /* Find a src file from a DWARF tag path */
> > -int get_real_path(const char *raw_path, const char *comp_dir,
> > - char **new_path);
> > +int find_source_path(const char *raw_path, const char *sbuild_id,
> > + const char *comp_dir, char **new_path);
> >
> > struct probe_finder {
> > struct perf_probe_event *pev; /* Target probe event */
> > + struct debuginfo *dbg;
> >
> > /* Callback when a probe point is found */
> > int (*callback)(Dwarf_Die *sc_die, struct probe_finder *pf);
> >
>
> --
>
> - Arnaldo
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>