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linux/Documentation/perf_counter/util/symbol.c
Arnaldo Carvalho de Melo 8ce998d669 perf_counter tools: Cover PLT symbols too
PLT, the Program Linking Table, is used with the dynamic linker to
allow PIC code in executables and shared objects to figure out
where functions are in other shared objects.

It is one of the sources of unknown/unresolved symbols - this patch
does what binutils figures out when you ask it to disassembly.
(objdump -S)

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Stephane Eranian <eranian@googlemail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-06-03 09:58:52 +02:00

553 lines
12 KiB
C

#include "util.h"
#include "../perf.h"
#include "string.h"
#include "symbol.h"
#include <libelf.h>
#include <gelf.h>
#include <elf.h>
static struct symbol *symbol__new(uint64_t start, uint64_t len,
const char *name, unsigned int priv_size)
{
size_t namelen = strlen(name) + 1;
struct symbol *self = malloc(priv_size + sizeof(*self) + namelen);
if (self != NULL) {
if (priv_size) {
memset(self, 0, priv_size);
self = ((void *)self) + priv_size;
}
self->start = start;
self->end = start + len;
memcpy(self->name, name, namelen);
}
return self;
}
static void symbol__delete(struct symbol *self, unsigned int priv_size)
{
free(((void *)self) - priv_size);
}
static size_t symbol__fprintf(struct symbol *self, FILE *fp)
{
return fprintf(fp, " %llx-%llx %s\n",
self->start, self->end, self->name);
}
struct dso *dso__new(const char *name, unsigned int sym_priv_size)
{
struct dso *self = malloc(sizeof(*self) + strlen(name) + 1);
if (self != NULL) {
strcpy(self->name, name);
self->syms = RB_ROOT;
self->sym_priv_size = sym_priv_size;
}
return self;
}
static void dso__delete_symbols(struct dso *self)
{
struct symbol *pos;
struct rb_node *next = rb_first(&self->syms);
while (next) {
pos = rb_entry(next, struct symbol, rb_node);
next = rb_next(&pos->rb_node);
rb_erase(&pos->rb_node, &self->syms);
symbol__delete(pos, self->sym_priv_size);
}
}
void dso__delete(struct dso *self)
{
dso__delete_symbols(self);
free(self);
}
static void dso__insert_symbol(struct dso *self, struct symbol *sym)
{
struct rb_node **p = &self->syms.rb_node;
struct rb_node *parent = NULL;
const uint64_t ip = sym->start;
struct symbol *s;
while (*p != NULL) {
parent = *p;
s = rb_entry(parent, struct symbol, rb_node);
if (ip < s->start)
p = &(*p)->rb_left;
else
p = &(*p)->rb_right;
}
rb_link_node(&sym->rb_node, parent, p);
rb_insert_color(&sym->rb_node, &self->syms);
}
struct symbol *dso__find_symbol(struct dso *self, uint64_t ip)
{
struct rb_node *n;
if (self == NULL)
return NULL;
n = self->syms.rb_node;
while (n) {
struct symbol *s = rb_entry(n, struct symbol, rb_node);
if (ip < s->start)
n = n->rb_left;
else if (ip > s->end)
n = n->rb_right;
else
return s;
}
return NULL;
}
size_t dso__fprintf(struct dso *self, FILE *fp)
{
size_t ret = fprintf(fp, "dso: %s\n", self->name);
struct rb_node *nd;
for (nd = rb_first(&self->syms); nd; nd = rb_next(nd)) {
struct symbol *pos = rb_entry(nd, struct symbol, rb_node);
ret += symbol__fprintf(pos, fp);
}
return ret;
}
static int dso__load_kallsyms(struct dso *self, symbol_filter_t filter)
{
struct rb_node *nd, *prevnd;
char *line = NULL;
size_t n;
FILE *file = fopen("/proc/kallsyms", "r");
if (file == NULL)
goto out_failure;
while (!feof(file)) {
__u64 start;
struct symbol *sym;
int line_len, len;
char symbol_type;
line_len = getline(&line, &n, file);
if (line_len < 0)
break;
if (!line)
goto out_failure;
line[--line_len] = '\0'; /* \n */
len = hex2u64(line, &start);
len++;
if (len + 2 >= line_len)
continue;
symbol_type = toupper(line[len]);
/*
* We're interested only in code ('T'ext)
*/
if (symbol_type != 'T' && symbol_type != 'W')
continue;
/*
* Well fix up the end later, when we have all sorted.
*/
sym = symbol__new(start, 0xdead, line + len + 2,
self->sym_priv_size);
if (sym == NULL)
goto out_delete_line;
if (filter && filter(self, sym))
symbol__delete(sym, self->sym_priv_size);
else
dso__insert_symbol(self, sym);
}
/*
* Now that we have all sorted out, just set the ->end of all
* symbols
*/
prevnd = rb_first(&self->syms);
if (prevnd == NULL)
goto out_delete_line;
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->end = curr->start - 1;
prevnd = nd;
}
free(line);
fclose(file);
return 0;
out_delete_line:
free(line);
out_failure:
return -1;
}
/**
* elf_symtab__for_each_symbol - iterate thru all the symbols
*
* @self: struct elf_symtab instance to iterate
* @index: uint32_t index
* @sym: GElf_Sym iterator
*/
#define elf_symtab__for_each_symbol(syms, nr_syms, index, sym) \
for (index = 0, gelf_getsym(syms, index, &sym);\
index < nr_syms; \
index++, gelf_getsym(syms, index, &sym))
static inline uint8_t elf_sym__type(const GElf_Sym *sym)
{
return GELF_ST_TYPE(sym->st_info);
}
static inline int elf_sym__is_function(const GElf_Sym *sym)
{
return elf_sym__type(sym) == STT_FUNC &&
sym->st_name != 0 &&
sym->st_shndx != SHN_UNDEF &&
sym->st_size != 0;
}
static inline const char *elf_sym__name(const GElf_Sym *sym,
const Elf_Data *symstrs)
{
return symstrs->d_buf + sym->st_name;
}
static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
GElf_Shdr *shp, const char *name,
size_t *index)
{
Elf_Scn *sec = NULL;
size_t cnt = 1;
while ((sec = elf_nextscn(elf, sec)) != NULL) {
char *str;
gelf_getshdr(sec, shp);
str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
if (!strcmp(name, str)) {
if (index)
*index = cnt;
break;
}
++cnt;
}
return sec;
}
#define elf_section__for_each_rel(reldata, pos, pos_mem, idx, nr_entries) \
for (idx = 0, pos = gelf_getrel(reldata, 0, &pos_mem); \
idx < nr_entries; \
++idx, pos = gelf_getrel(reldata, idx, &pos_mem))
#define elf_section__for_each_rela(reldata, pos, pos_mem, idx, nr_entries) \
for (idx = 0, pos = gelf_getrela(reldata, 0, &pos_mem); \
idx < nr_entries; \
++idx, pos = gelf_getrela(reldata, idx, &pos_mem))
static int dso__synthesize_plt_symbols(struct dso *self, Elf *elf,
GElf_Ehdr *ehdr, Elf_Scn *scn_dynsym,
GElf_Shdr *shdr_dynsym,
size_t dynsym_idx)
{
uint32_t nr_rel_entries, idx;
GElf_Sym sym;
__u64 plt_offset;
GElf_Shdr shdr_plt;
struct symbol *f;
GElf_Shdr shdr_rel_plt;
Elf_Data *reldata, *syms, *symstrs;
Elf_Scn *scn_plt_rel, *scn_symstrs;
char sympltname[1024];
int nr = 0, symidx;
scn_plt_rel = elf_section_by_name(elf, ehdr, &shdr_rel_plt,
".rela.plt", NULL);
if (scn_plt_rel == NULL) {
scn_plt_rel = elf_section_by_name(elf, ehdr, &shdr_rel_plt,
".rel.plt", NULL);
if (scn_plt_rel == NULL)
return 0;
}
if (shdr_rel_plt.sh_link != dynsym_idx)
return 0;
if (elf_section_by_name(elf, ehdr, &shdr_plt, ".plt", NULL) == NULL)
return 0;
/*
* Fetch the relocation section to find the indexes to the GOT
* and the symbols in the .dynsym they refer to.
*/
reldata = elf_getdata(scn_plt_rel, NULL);
if (reldata == NULL)
return -1;
syms = elf_getdata(scn_dynsym, NULL);
if (syms == NULL)
return -1;
scn_symstrs = elf_getscn(elf, shdr_dynsym->sh_link);
if (scn_symstrs == NULL)
return -1;
symstrs = elf_getdata(scn_symstrs, NULL);
if (symstrs == NULL)
return -1;
nr_rel_entries = shdr_rel_plt.sh_size / shdr_rel_plt.sh_entsize;
plt_offset = shdr_plt.sh_offset;
if (shdr_rel_plt.sh_type == SHT_RELA) {
GElf_Rela pos_mem, *pos;
elf_section__for_each_rela(reldata, pos, pos_mem, idx,
nr_rel_entries) {
symidx = GELF_R_SYM(pos->r_info);
plt_offset += shdr_plt.sh_entsize;
gelf_getsym(syms, symidx, &sym);
snprintf(sympltname, sizeof(sympltname),
"%s@plt", elf_sym__name(&sym, symstrs));
f = symbol__new(plt_offset, shdr_plt.sh_entsize,
sympltname, self->sym_priv_size);
if (!f)
return -1;
dso__insert_symbol(self, f);
++nr;
}
} else if (shdr_rel_plt.sh_type == SHT_REL) {
GElf_Rel pos_mem, *pos;
elf_section__for_each_rel(reldata, pos, pos_mem, idx,
nr_rel_entries) {
symidx = GELF_R_SYM(pos->r_info);
plt_offset += shdr_plt.sh_entsize;
gelf_getsym(syms, symidx, &sym);
snprintf(sympltname, sizeof(sympltname),
"%s@plt", elf_sym__name(&sym, symstrs));
f = symbol__new(plt_offset, shdr_plt.sh_entsize,
sympltname, self->sym_priv_size);
if (!f)
return -1;
dso__insert_symbol(self, f);
++nr;
}
} else {
/*
* TODO: There are still one more shdr_rel_plt.sh_type
* I have to investigate, but probably should be ignored.
*/
}
return nr;
}
static int dso__load_sym(struct dso *self, int fd, const char *name,
symbol_filter_t filter)
{
Elf_Data *symstrs;
uint32_t nr_syms;
int err = -1;
uint32_t index;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
Elf_Data *syms;
GElf_Sym sym;
Elf_Scn *sec, *sec_dynsym;
Elf *elf;
size_t dynsym_idx;
int nr = 0;
elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
if (elf == NULL) {
fprintf(stderr, "%s: cannot read %s ELF file.\n",
__func__, name);
goto out_close;
}
if (gelf_getehdr(elf, &ehdr) == NULL) {
fprintf(stderr, "%s: cannot get elf header.\n", __func__);
goto out_elf_end;
}
/*
* We need to check if we have a .dynsym, so that we can handle the
* .plt, synthesizing its symbols, that aren't on the symtabs (be it
* .dynsym or .symtab)
*/
sec_dynsym = elf_section_by_name(elf, &ehdr, &shdr,
".dynsym", &dynsym_idx);
if (sec_dynsym != NULL) {
nr = dso__synthesize_plt_symbols(self, elf, &ehdr,
sec_dynsym, &shdr,
dynsym_idx);
if (nr < 0)
goto out_elf_end;
}
/*
* But if we have a full .symtab (that is a superset of .dynsym) we
* should add the symbols not in the .dynsyn
*/
sec = elf_section_by_name(elf, &ehdr, &shdr, ".symtab", NULL);
if (sec == NULL) {
if (sec_dynsym == NULL)
goto out_elf_end;
sec = sec_dynsym;
gelf_getshdr(sec, &shdr);
}
syms = elf_getdata(sec, NULL);
if (syms == NULL)
goto out_elf_end;
sec = elf_getscn(elf, shdr.sh_link);
if (sec == NULL)
goto out_elf_end;
symstrs = elf_getdata(sec, NULL);
if (symstrs == NULL)
goto out_elf_end;
nr_syms = shdr.sh_size / shdr.sh_entsize;
elf_symtab__for_each_symbol(syms, nr_syms, index, sym) {
struct symbol *f;
if (!elf_sym__is_function(&sym))
continue;
sec = elf_getscn(elf, sym.st_shndx);
if (!sec)
goto out_elf_end;
gelf_getshdr(sec, &shdr);
sym.st_value -= shdr.sh_addr - shdr.sh_offset;
f = symbol__new(sym.st_value, sym.st_size,
elf_sym__name(&sym, symstrs),
self->sym_priv_size);
if (!f)
goto out_elf_end;
if (filter && filter(self, f))
symbol__delete(f, self->sym_priv_size);
else {
dso__insert_symbol(self, f);
nr++;
}
}
err = nr;
out_elf_end:
elf_end(elf);
out_close:
return err;
}
int dso__load(struct dso *self, symbol_filter_t filter)
{
int size = strlen(self->name) + sizeof("/usr/lib/debug%s.debug");
char *name = malloc(size);
int variant = 0;
int ret = -1;
int fd;
if (!name)
return -1;
more:
do {
switch (variant) {
case 0: /* Fedora */
snprintf(name, size, "/usr/lib/debug%s.debug", self->name);
break;
case 1: /* Ubuntu */
snprintf(name, size, "/usr/lib/debug%s", self->name);
break;
case 2: /* Sane people */
snprintf(name, size, "%s", self->name);
break;
default:
goto out;
}
variant++;
fd = open(name, O_RDONLY);
} while (fd < 0);
ret = dso__load_sym(self, fd, name, filter);
close(fd);
/*
* Some people seem to have debuginfo files _WITHOUT_ debug info!?!?
*/
if (!ret)
goto more;
out:
free(name);
return ret;
}
static int dso__load_vmlinux(struct dso *self, const char *vmlinux,
symbol_filter_t filter)
{
int err, fd = open(vmlinux, O_RDONLY);
if (fd < 0)
return -1;
err = dso__load_sym(self, fd, vmlinux, filter);
close(fd);
return err;
}
int dso__load_kernel(struct dso *self, const char *vmlinux, symbol_filter_t filter)
{
int err = -1;
if (vmlinux)
err = dso__load_vmlinux(self, vmlinux, filter);
if (err)
err = dso__load_kallsyms(self, filter);
return err;
}
void symbol__init(void)
{
elf_version(EV_CURRENT);
}