Re: [PATCH v6 4/8] perf: symbol: generalize vmlinux path searching

From: Adrian Hunter
Date: Wed Sep 11 2024 - 04:05:12 EST

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On 25/07/24 05:15, Changbin Du wrote:
> This generalizes the vmlinux path searching logic. Later we will add
> another instance for vdso.
>
> The search pattern is described by struct dso_filename_pattern, and the
> formatted paths are hold in struct dso_filename_paths.
>
> Signed-off-by: Changbin Du <changbin.du@xxxxxxxxxx>
> ---
> tools/perf/util/machine.c | 4 +-
> tools/perf/util/symbol.c | 112 +++++++++++++++++++++-----------------
> tools/perf/util/symbol.h | 8 ++-
> 3 files changed, 70 insertions(+), 54 deletions(-)
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 8477edefc299..68315520f15b 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -896,9 +896,9 @@ size_t machine__fprintf_vmlinux_path(struct machine *machine, FILE *fp)
> printed += fprintf(fp, "[0] %s\n", filename);
> }
>
> - for (i = 0; i < vmlinux_path__nr_entries; ++i) {
> + for (i = 0; i < vmlinux_paths.nr_entries; ++i) {
> printed += fprintf(fp, "[%d] %s\n", i + dso__has_build_id(kdso),
> - vmlinux_path[i]);
> + vmlinux_paths.paths[i]);
> }
> return printed;
> }
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index ad3b7b929e94..6bf75c98e1f2 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -48,8 +48,7 @@ static int dso__load_guest_kernel_sym(struct dso *dso, struct map *map);
> static int dso__load_vdso_sym(struct dso *dso, struct map *map);
> static bool symbol__is_idle(const char *name);
>
> -int vmlinux_path__nr_entries;
> -char **vmlinux_path;
> +struct dso_filename_paths vmlinux_paths;
>
> struct symbol_conf symbol_conf = {
> .nanosecs = false,
> @@ -2042,10 +2041,10 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map)
> char *filename = NULL;
>
> pr_debug("Looking at the vmlinux_path (%d entries long)\n",
> - vmlinux_path__nr_entries + 1);
> + vmlinux_paths.nr_entries + 1);
>
> - for (i = 0; i < vmlinux_path__nr_entries; ++i) {
> - err = dso__load_vmlinux(dso, map, vmlinux_path[i], false);
> + for (i = 0; i < vmlinux_paths.nr_entries; ++i) {
> + err = dso__load_vmlinux(dso, map, vmlinux_paths.paths[i], false);
> if (err > 0)
> goto out;
> }
> @@ -2209,7 +2208,7 @@ static int dso__load_kernel_sym(struct dso *dso, struct map *map)
> return err;
> }
>
> - if (!symbol_conf.ignore_vmlinux && vmlinux_path != NULL) {
> + if (!symbol_conf.ignore_vmlinux && vmlinux_paths.paths != NULL) {
> err = dso__load_vmlinux_path(dso, map);
> if (err > 0)
> return err;
> @@ -2284,57 +2283,55 @@ static int dso__load_guest_kernel_sym(struct dso *dso, struct map *map)
> return err;
> }
>
> -static void vmlinux_path__exit(void)
> -{
> - while (--vmlinux_path__nr_entries >= 0)
> - zfree(&vmlinux_path[vmlinux_path__nr_entries]);
> - vmlinux_path__nr_entries = 0;
> -
> - zfree(&vmlinux_path);
> -}
> -
> -static const char * const vmlinux_paths[] = {
> - "vmlinux",
> - "/boot/vmlinux"
> +struct dso_filename_pattern {
> + const char *pattern;
> + /*
> + * 0 for matching directly,
> + * 1 for matching by kernel_version,
> + * 2 for matching by kernel_version + arch.
> + */
> + int match_type;
> };
>
> -static const char * const vmlinux_paths_upd[] = {
> - "/boot/vmlinux-%s",
> - "/usr/lib/debug/boot/vmlinux-%s",
> - "/lib/modules/%s/build/vmlinux",
> - "/usr/lib/debug/lib/modules/%s/vmlinux",
> - "/usr/lib/debug/boot/vmlinux-%s.debug"
> +struct dso_filename_pattern vmlinux_patterns[] = {
> + {"vmlinux", 0},
> + {"/boot/vmlinux", 0},
> + {"/boot/vmlinux-%s", 1},
> + {"/usr/lib/debug/boot/vmlinux-%s", 1},
> + {"/lib/modules/%s/build/vmlinux", 1},
> + {"/usr/lib/debug/lib/modules/%s/vmlinux", 1},
> + {"/usr/lib/debug/boot/vmlinux-%s.debug", 1},
> };
>
> -static int vmlinux_path__add(const char *new_entry)
> +static int dso_filename_path__add(struct dso_filename_paths *paths, const char *new_entry)
> {
> - vmlinux_path[vmlinux_path__nr_entries] = strdup(new_entry);
> - if (vmlinux_path[vmlinux_path__nr_entries] == NULL)
> + paths->paths[paths->nr_entries] = strdup(new_entry);
> + if (paths->paths[paths->nr_entries] == NULL)
> return -1;
> - ++vmlinux_path__nr_entries;
> + ++paths->nr_entries;
>
> return 0;
> }
>
> -static int vmlinux_path__init(struct perf_env *env)
> +static void dso_filename_path__exit(struct dso_filename_paths *paths)
> {
> - struct utsname uts;
> - char bf[PATH_MAX];
> - char *kernel_version;
> - unsigned int i;
> + while (--paths->nr_entries >= 0)
> + zfree(&paths->paths[paths->nr_entries]);
> + paths->nr_entries = 0;
>
> - vmlinux_path = malloc(sizeof(char *) * (ARRAY_SIZE(vmlinux_paths) +
> - ARRAY_SIZE(vmlinux_paths_upd)));
> - if (vmlinux_path == NULL)
> - return -1;
> -
> - for (i = 0; i < ARRAY_SIZE(vmlinux_paths); i++)
> - if (vmlinux_path__add(vmlinux_paths[i]) < 0)
> - goto out_fail;
> + zfree(&paths->paths);
> +}
>
> - /* only try kernel version if no symfs was given */
> - if (symbol_conf.symfs[0] != 0)
> - return 0;
> +static int dso_filename_path__init(struct dso_filename_paths *paths,
> + struct dso_filename_pattern *patterns,
> + int nr_patterns,
> + struct perf_env *env)
> +{
> + struct utsname uts;
> + char bf[PATH_MAX];
> + const char *kernel_version;
> + const char *arch = perf_env__arch(env);
> + int i;
>
> if (env) {
> kernel_version = env->os_release;
> @@ -2345,16 +2342,28 @@ static int vmlinux_path__init(struct perf_env *env)
> kernel_version = uts.release;
> }
>
> - for (i = 0; i < ARRAY_SIZE(vmlinux_paths_upd); i++) {
> - snprintf(bf, sizeof(bf), vmlinux_paths_upd[i], kernel_version);
> - if (vmlinux_path__add(bf) < 0)
> + paths->paths = malloc(sizeof(char *) * nr_patterns);
> + if (paths->paths == NULL)
> + return -1;
> +
> + for (i = 0; i < nr_patterns; i++) {
> + if (patterns[i].match_type == 0)
> + strlcpy(bf, patterns[i].pattern, sizeof(bf));
> + else if (symbol_conf.symfs[0] == 0) {
> + /* only try kernel version if no symfs was given */
> + if (patterns[i].match_type == 1)
> + snprintf(bf, sizeof(bf), patterns[i].pattern, kernel_version);
> + else if (patterns[i].match_type == 2)
> + snprintf(bf, sizeof(bf), patterns[i].pattern, kernel_version, arch);
> + }
> + if (dso_filename_path__add(paths, bf) < 0)
> goto out_fail;
> }
>
> return 0;
>
> out_fail:
> - vmlinux_path__exit();
> + dso_filename_path__exit(paths);
> return -1;
> }
>
> @@ -2550,8 +2559,11 @@ int symbol__init(struct perf_env *env)
>
> symbol__elf_init();
>
> - if (symbol_conf.try_vmlinux_path && vmlinux_path__init(env) < 0)
> + if (symbol_conf.try_vmlinux_path &&
> + dso_filename_path__init(&vmlinux_paths, vmlinux_patterns,
> + ARRAY_SIZE(vmlinux_patterns), env) < 0) {
> return -1;
> + }
>
> if (symbol_conf.field_sep && *symbol_conf.field_sep == '.') {
> pr_err("'.' is the only non valid --field-separator argument\n");
> @@ -2628,7 +2640,7 @@ void symbol__exit(void)
> intlist__delete(symbol_conf.tid_list);
> intlist__delete(symbol_conf.pid_list);
> intlist__delete(symbol_conf.addr_list);
> - vmlinux_path__exit();
> + dso_filename_path__exit(&vmlinux_paths);
> symbol_conf.sym_list = symbol_conf.dso_list = symbol_conf.comm_list = NULL;
> symbol_conf.bt_stop_list = NULL;
> symbol_conf.initialized = false;
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 3fb5d146d9b1..30056884945b 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -101,8 +101,12 @@ static inline int __symbol__join_symfs(char *bf, size_t size, const char *path)
>
> #define symbol__join_symfs(bf, path) __symbol__join_symfs(bf, sizeof(bf), path)
>
> -extern int vmlinux_path__nr_entries;
> -extern char **vmlinux_path;
> +struct dso_filename_paths {
> + int nr_entries;
> + char **paths;
> +};

Feels a bit over engineered. We only need the nth path so
a simpler, more encapsulated API could be just:

const char *vdso_path(size_t i);

Also wonder why the paths cannot just be created by asprint().
e.g. notwithstanding that perf_env__os_release() does not exist:

#define MAX_VDSO_PATHS 8
static char *vdso_paths[MAX_VDSO_PATHS];
static size_t vdso_path__nr_entries;

static int vdso_path__init(struct perf_env *env)
{
const char *k = perf_env__os_release(env);
const char *a = perf_env__arch(env);
int i = 0;

#define PATH_INIT(fmt, ...) \
(i < MAX_VDSO_PATHS ? ({ \
int ret = asprintf(&vdso_paths[i], fmt, ##__VA_ARGS__); \
if (ret >= 0) { \
i += 1; \
ret = 0; \
} \
ret; \
}) : -1)

if (PATH_INIT("/lib/modules/%s/vdso/vdso.so", k) ||
PATH_INIT("/lib/modules/%s/vdso/vdso64.so", k) ||
PATH_INIT("/lib/modules/%s/vdso/vdso32.so", k) ||
PATH_INIT("/lib/modules/%s/build/arch/%s/vdso/vdso.so.dbg", k, a) ||
PATH_INIT("/lib/modules/%s/build/arch/%s/kernel/vdso/vdso.so.dbg", k, a) ||
PATH_INIT("/lib/modules/%s/build/arch/%s/entry/vdso/vdso32.so.dbg", k, a) ||
PATH_INIT("/lib/modules/%s/build/arch/%s/entry/vdso/vdso64.so.dbg", k, a))
goto out_err;

#undef PATH_INIT

vdso_path__nr_entries = i;
return 0;

out_err:
while (i)
zfree(&vdso_paths[--i]);
return -ENOMEM;
}

static void vdso_path__exit(void)
{
while (vdso_path__nr_entries)
zfree(&vdso_paths[--vdso_path__nr_entries]);
}

const char *vdso_path(size_t i)
{
if (i >= vdso_path__nr_entries)
return NULL;

return vdso_paths[i];
}

Next message: Adrian Hunter: "Re: [PATCH v6 5/8] perf: build-id: add support for build-id cache vdso debug"
Previous message: Jingyi Wang: "[PATCH v2 3/4] dt-bindings: soc: qcom: add qcom,qcs8300-imem compatible"
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