perf tools: Improve kernel/modules symbol lookup

This removes the ovelapping of vmlinux addresses with modules,
using the ELF section name when using --vmlinux and creating a
unique DSO name when using /proc/kallsyms ([kernel].N).

This is done by creating multiple 'struct map' instances for
address ranges backed by DSOs that have just the symbols for that
range and a name that is derived from the ELF section name.o

Now it is possible to ask for just the symbols in some particular
kernel section:

$ perf report -m --vmlinux ../build/tip-recvmmsg/vmlinux \
	--dsos [kernel].vsyscall_fn | head -15
    52.73%             Xorg  [.] vread_hpet
    18.61%          firefox  [.] vread_hpet
    14.50%     npviewer.bin  [.] vread_hpet
     6.83%           compiz  [.] vread_hpet
     5.73%         glxgears  [.] vread_hpet
     0.63%             java  [.] vread_hpet
     0.30%   gnome-terminal  [.] vread_hpet
     0.23%             perf  [.] vread_hpet
     0.18%            xchat  [.] vread_hpet
$

Now we don't have to first lookup the list of modules and then, if
it fails, vmlinux symbols, its just a simple lookup for the map
then the symbols, just like for threads.

Reports generated using /proc/kallsyms and --vmlinux should provide
the same results, modulo the DSO name for sections other than
".text".

But they don't right now because things like:

 ffffffff81011c20-ffffffff81012068 system_call
 ffffffff81011c30-ffffffff81011c9b system_call_after_swapgs
 ffffffff81011c9c-ffffffff81011cb6 system_call_fastpath
 ffffffff81011cb7-ffffffff81011cbb ret_from_sys_call

I.e. overlapping symbols, again some ASM special case that we have
to fixup.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1254934136-8503-1-git-send-email-acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 201 insertions, 87 deletions

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index a6887f94dfe..faa84f5d4f5 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -26,27 +26,35 @@ enum dso_origin {
 
 static void dsos__add(struct dso *dso);
 static struct dso *dsos__find(const char *name);
+static struct map *map__new2(u64 start, struct dso *dso);
+static void kernel_maps__insert(struct map *map);
 
 static struct rb_root kernel_maps;
 
-static void dso__set_symbols_end(struct dso *self)
+static void dso__fixup_sym_end(struct dso *self)
 {
         struct rb_node *nd, *prevnd = rb_first(&self->syms);
+        struct symbol *curr, *prev;
 
         if (prevnd == NULL)
                 return;
 
+        curr = rb_entry(prevnd, struct symbol, rb_node);
+
         for (nd = rb_next(prevnd); nd; nd = rb_next(nd)) {
-                struct symbol *prev = rb_entry(prevnd, struct symbol, rb_node),
-                              *curr = rb_entry(nd, struct symbol, rb_node);
+                prev = curr;
+                curr = rb_entry(nd, struct symbol, rb_node);
 
                 if (prev->end == prev->start)
                         prev->end = curr->start - 1;
-                prevnd = nd;
         }
+
+        /* Last entry */
+        if (curr->end == curr->start)
+                curr->end = roundup(curr->start, 4096);
 }
 
-static void kernel_maps__fixup_sym_end(void)
+static void kernel_maps__fixup_end(void)
 {
         struct map *prev, *curr;
         struct rb_node *nd, *prevnd = rb_first(&kernel_maps);
@@ -55,13 +63,17 @@ static void kernel_maps__fixup_sym_end(void)
                 return;
 
         curr = rb_entry(prevnd, struct map, rb_node);
-        dso__set_symbols_end(curr->dso);
 
         for (nd = rb_next(prevnd); nd; nd = rb_next(nd)) {
                 prev = curr;
                 curr = rb_entry(nd, struct map, rb_node);
                 prev->end = curr->start - 1;
-                dso__set_symbols_end(curr->dso);
+        }
+
+        nd = rb_last(&curr->dso->syms);
+        if (nd) {
+                struct symbol *sym = rb_entry(nd, struct symbol, rb_node);
+                curr->end = sym->end;
         }
 }
 
@@ -200,13 +212,16 @@ size_t dso__fprintf(struct dso *self, FILE *fp)
         return ret;
 }
 
-static int maps__load_kallsyms(symbol_filter_t filter, int use_modules, int v)
+/*
+ * Loads the function entries in /proc/kallsyms into kernel_map->dso,
+ * so that we can in the next step set the symbol ->end address and then
+ * call kernel_maps__split_kallsyms.
+ */
+static int kernel_maps__load_all_kallsyms(int v)
 {
-        struct map *map = kernel_map;
         char *line = NULL;
         size_t n;
         FILE *file = fopen("/proc/kallsyms", "r");
-        int count = 0;
 
         if (file == NULL)
                 goto out_failure;
@@ -216,7 +231,7 @@ static int maps__load_kallsyms(symbol_filter_t filter, int use_modules, int v)
                 struct symbol *sym;
                 int line_len, len;
                 char symbol_type;
-                char *module, *symbol_name;
+                char *symbol_name;
 
                 line_len = getline(&line, &n, file);
                 if (line_len < 0)
@@ -241,20 +256,55 @@ static int maps__load_kallsyms(symbol_filter_t filter, int use_modules, int v)
                         continue;
 
                 symbol_name = line + len + 2;
-                module = strchr(symbol_name, '\t');
-                if (module) {
-                        char *module_name_end;
+                /*
+                 * Will fix up the end later, when we have all symbols sorted.
+                 */
+                sym = symbol__new(start, 0, symbol_name,
+                                  kernel_map->dso->sym_priv_size, v);
 
+                if (sym == NULL)
+                        goto out_delete_line;
+
+                dso__insert_symbol(kernel_map->dso, sym);
+        }
+
+        free(line);
+        fclose(file);
+
+        return 0;
+
+out_delete_line:
+        free(line);
+out_failure:
+        return -1;
+}
+
+/*
+ * Split the symbols into maps, making sure there are no overlaps, i.e. the
+ * kernel range is broken in several maps, named [kernel].N, as we don't have
+ * the original ELF section names vmlinux have.
+ */
+static int kernel_maps__split_kallsyms(symbol_filter_t filter, int use_modules)
+{
+        struct map *map = kernel_map;
+        struct symbol *pos;
+        int count = 0;
+        struct rb_node *next = rb_first(&kernel_map->dso->syms);
+        int kernel_range = 0;
+
+        while (next) {
+                char *module;
+
+                pos = rb_entry(next, struct symbol, rb_node);
+                next = rb_next(&pos->rb_node);
+
+                module = strchr(pos->name, '\t');
+                if (module) {
                         if (!use_modules)
-                                continue;
-                        *module = '\0';
-                        module = strchr(module + 1, '[');
-                        if (!module)
-                                continue;
-                        module_name_end = strchr(module + 1, ']');
-                        if (!module_name_end)
-                                continue;
-                        *(module_name_end + 1) = '\0';
+                                goto delete_symbol;
+
+                        *module++ = '\0';
+
                         if (strcmp(map->dso->name, module)) {
                                 map = kernel_maps__find_by_dso_name(module);
                                 if (!map) {
@@ -263,50 +313,77 @@ static int maps__load_kallsyms(symbol_filter_t filter, int use_modules, int v)
                                         return -1;
                                 }
                         }
-                        start = map->map_ip(map, start);
-                } else
-                        map = kernel_map;
-                /*
-                 * Well fix up the end later, when we have all sorted.
-                 */
-                sym = symbol__new(start, 0, symbol_name,
-                                  map->dso->sym_priv_size, v);
+                        /*
+                         * So that we look just like we get from .ko files,
+                         * i.e. not prelinked, relative to map->start.
+                         */
+                        pos->start = map->map_ip(map, pos->start);
+                        pos->end   = map->map_ip(map, pos->end);
+                } else if (map != kernel_map) {
+                        char dso_name[PATH_MAX];
+                        struct dso *dso;
+
+                        snprintf(dso_name, sizeof(dso_name), "[kernel].%d",
+                                 kernel_range++);
+
+                        dso = dso__new(dso_name,
+                                       kernel_map->dso->sym_priv_size);
+                        if (dso == NULL)
+                                return -1;
+
+                        map = map__new2(pos->start, dso);
+                        if (map == NULL) {
+                                dso__delete(dso);
+                                return -1;
+                        }
 
-                if (sym == NULL)
-                        goto out_delete_line;
+                        map->map_ip = vdso__map_ip;
+                        kernel_maps__insert(map);
+                        ++kernel_range;
+                }
 
-                if (filter && filter(map, sym))
-                        symbol__delete(sym, map->dso->sym_priv_size);
-                else {
-                        dso__insert_symbol(map->dso, sym);
+                if (filter && filter(map, pos)) {
+delete_symbol:
+                        rb_erase(&pos->rb_node, &kernel_map->dso->syms);
+                        symbol__delete(pos, kernel_map->dso->sym_priv_size);
+                } else {
+                        if (map != kernel_map) {
+                                rb_erase(&pos->rb_node, &kernel_map->dso->syms);
+                                dso__insert_symbol(map->dso, pos);
+                        }
                         count++;
                 }
         }
 
-        free(line);
-        fclose(file);
-
         return count;
+}
 
-out_delete_line:
-        free(line);
-out_failure:
-        return -1;
+
+static int kernel_maps__load_kallsyms(symbol_filter_t filter,
+                                      int use_modules, int v)
+{
+        if (kernel_maps__load_all_kallsyms(v))
+                return -1;
+
+        dso__fixup_sym_end(kernel_map->dso);
+
+        return kernel_maps__split_kallsyms(filter, use_modules);
 }
 
-static size_t kernel_maps__fprintf(FILE *fp)
+static size_t kernel_maps__fprintf(FILE *fp, int v)
 {
         size_t printed = fprintf(stderr, "Kernel maps:\n");
         struct rb_node *nd;
 
-        printed += map__fprintf(kernel_map, fp);
-        printed += dso__fprintf(kernel_map->dso, fp);
-
         for (nd = rb_first(&kernel_maps); nd; nd = rb_next(nd)) {
                 struct map *pos = rb_entry(nd, struct map, rb_node);
 
+                printed += fprintf(fp, "Map:");
                 printed += map__fprintf(pos, fp);
-                printed += dso__fprintf(pos->dso, fp);
+                if (v > 1) {
+                        printed += dso__fprintf(pos->dso, fp);
+                        printed += fprintf(fp, "--\n");
+                }
         }
 
         return printed + fprintf(stderr, "END kernel maps\n");
@@ -594,6 +671,9 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
                          int fd, symbol_filter_t filter, int kernel,
                          int kmodule, int v)
 {
+        struct map *curr_map = map;
+        struct dso *curr_dso = self;
+        size_t dso_name_len = strlen(self->short_name);
         Elf_Data *symstrs, *secstrs;
         uint32_t nr_syms;
         int err = -1;
@@ -660,10 +740,9 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
         elf_symtab__for_each_symbol(syms, nr_syms, idx, sym) {
                 struct symbol *f;
                 const char *elf_name;
-                char *demangled;
+                char *demangled = NULL;
                 int is_label = elf_sym__is_label(&sym);
                 const char *section_name;
-                u64 sh_offset = 0;
 
                 if (!is_label && !elf_sym__is_function(&sym))
                         continue;
@@ -677,14 +756,51 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
                 if (is_label && !elf_sec__is_text(&shdr, secstrs))
                         continue;
 
+                elf_name = elf_sym__name(&sym, symstrs);
                 section_name = elf_sec__name(&shdr, secstrs);
 
-                if ((kernel || kmodule)) {
-                        if (strstr(section_name, ".init"))
-                                sh_offset = shdr.sh_offset;
+                if (kernel || kmodule) {
+                        char dso_name[PATH_MAX];
+
+                        if (strcmp(section_name,
+                                   curr_dso->short_name + dso_name_len) == 0)
+                                goto new_symbol;
+
+                        if (strcmp(section_name, ".text") == 0) {
+                                curr_map = map;
+                                curr_dso = self;
+                                goto new_symbol;
+                        }
+
+                        snprintf(dso_name, sizeof(dso_name),
+                                 "%s%s", self->short_name, section_name);
+
+                        curr_map = kernel_maps__find_by_dso_name(dso_name);
+                        if (curr_map == NULL) {
+                                u64 start = sym.st_value;
+
+                                if (kmodule)
+                                        start += map->start + shdr.sh_offset;
+
+                                curr_dso = dso__new(dso_name, self->sym_priv_size);
+                                if (curr_dso == NULL)
+                                        goto out_elf_end;
+                                curr_map = map__new2(start, curr_dso);
+                                if (curr_map == NULL) {
+                                        dso__delete(curr_dso);
+                                        goto out_elf_end;
+                                }
+                                curr_map->map_ip = vdso__map_ip;
+                                curr_dso->origin = DSO__ORIG_KERNEL;
+                                kernel_maps__insert(curr_map);
+                                dsos__add(curr_dso);
+                        } else
+                                curr_dso = curr_map->dso;
+
+                        goto new_symbol;
                 }
 
-                if (self->adjust_symbols) {
+                if (curr_dso->adjust_symbols) {
                         if (v > 2)
                                 printf("adjusting symbol: st_value: %Lx sh_addr: %Lx sh_offset: %Lx\n",
                                         (u64)sym.st_value, (u64)shdr.sh_addr, (u64)shdr.sh_offset);
@@ -696,25 +812,29 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
                  * DWARF DW_compile_unit has this, but we don't always have access
                  * to it...
                  */
-                elf_name = elf_sym__name(&sym, symstrs);
                 demangled = bfd_demangle(NULL, elf_name, DMGL_PARAMS | DMGL_ANSI);
                 if (demangled != NULL)
                         elf_name = demangled;
-
-                f = symbol__new(sym.st_value + sh_offset, sym.st_size, elf_name,
-                                self->sym_priv_size, v);
+new_symbol:
+                f = symbol__new(sym.st_value, sym.st_size, elf_name,
+                                curr_dso->sym_priv_size, v);
                 free(demangled);
                 if (!f)
                         goto out_elf_end;
 
-                if (filter && filter(map, f))
-                        symbol__delete(f, self->sym_priv_size);
+                if (filter && filter(curr_map, f))
+                        symbol__delete(f, curr_dso->sym_priv_size);
                 else {
-                        dso__insert_symbol(self, f);
+                        dso__insert_symbol(curr_dso, f);
                         nr++;
                 }
         }
 
+        /*
+         * For misannotated, zeroed, ASM function sizes.
+         */
+        if (nr > 0)
+                dso__fixup_sym_end(self);
         err = nr;
 out_elf_end:
         elf_end(elf);
@@ -883,27 +1003,17 @@ static void kernel_maps__insert(struct map *map)
 
 struct symbol *kernel_maps__find_symbol(u64 ip, struct map **mapp)
 {
-        /*
-         * We can't have kernel_map in kernel_maps because it spans an address
-         * space that includes the modules. The right way to fix this is to
-         * create several maps, so that we don't have overlapping ranges with
-         * modules. For now lets look first on the kernel dso.
-         */
         struct map *map = maps__find(&kernel_maps, ip);
-        struct symbol *sym;
+
+        if (mapp)
+                *mapp = map;
 
         if (map) {
                 ip = map->map_ip(map, ip);
-                sym = map->dso->find_symbol(map->dso, ip);
-        } else {
-                map = kernel_map;
-                sym = map->dso->find_symbol(map->dso, ip);
+                return map->dso->find_symbol(map->dso, ip);
         }
 
-        if (mapp)
-                *mapp = map;
-
-        return sym;
+        return NULL;
 }
 
 struct map *kernel_maps__find_by_dso_name(const char *name)
@@ -994,6 +1104,14 @@ static int dsos__load_modules_sym_dir(char *dirname,
                         last = rb_last(&map->dso->syms);
                         if (last) {
                                 struct symbol *sym;
+                                /*
+                                 * We do this here as well, even having the
+                                 * symbol size found in the symtab because
+                                 * misannotated ASM symbols may have the size
+                                 * set to zero.
+                                 */
+                                dso__fixup_sym_end(map->dso);
+
                                 sym = rb_entry(last, struct symbol, rb_node);
                                 map->end = map->start + sym->end;
                         }
@@ -1163,17 +1281,11 @@ int dsos__load_kernel(const char *vmlinux, unsigned int sym_priv_size,
         }
 
         if (err <= 0)
-                err = maps__load_kallsyms(filter, use_modules, v);
+                err = kernel_maps__load_kallsyms(filter, use_modules, v);
 
         if (err > 0) {
                 struct rb_node *node = rb_first(&dso->syms);
                 struct symbol *sym = rb_entry(node, struct symbol, rb_node);
-                /*
-                 * Now that we have all sorted out, just set the ->end of all
-                 * symbols that still don't have it.
-                 */
-                dso__set_symbols_end(dso);
-                kernel_maps__fixup_sym_end();
 
                 kernel_map->start = sym->start;
                 node = rb_last(&dso->syms);
@@ -1181,14 +1293,16 @@ int dsos__load_kernel(const char *vmlinux, unsigned int sym_priv_size,
                 kernel_map->end = sym->end;
 
                 dso->origin = DSO__ORIG_KERNEL;
+                kernel_maps__insert(kernel_map);
                 /*
-                 * XXX See kernel_maps__find_symbol comment
-                 * kernel_maps__insert(kernel_map)
+                 * Now that we have all sorted out, just set the ->end of all
+                 * maps:
                  */
+                kernel_maps__fixup_end();
                 dsos__add(dso);
 
                 if (v > 0)
-                        kernel_maps__fprintf(stderr);
+                        kernel_maps__fprintf(stderr, v);
         }
 
         return err;