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perf symbols: Function descriptor symbol lookup 

Currently symbol resolution does not work for 64-bit programs on architectures
that use function descriptors such as ppc64.

The problem is that a symbol doesn't point to a text address, it points to a
data area that contains (amongst other things) a pointer to the text address.

We look for a section called ".opd" which is the function descriptor area. To
create the full symbol table, when we see a symbol in the function descriptor
section we load the first pointer and use that as the text address.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1276523793-15422-1-git-send-email-ebmunson@us.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Eric B Munson <ebmunson@us.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Eric B Munson 2010-06-14 14:56:33 +01:00 committed by Arnaldo Carvalho de Melo
parent cf103a14dd
commit 70c3856b2f
1 changed files with 34 additions and 3 deletions
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37
tools/perf/util/symbol.c
View File

@ -933,6 +933,25 @@ static bool elf_sec__is_a(GElf_Shdr *self, Elf_Data *secstrs, enum map_type type
} }
} }
static size_t elf_addr_to_index(Elf *elf, GElf_Addr addr)
{
Elf_Scn *sec = NULL;
GElf_Shdr shdr;
size_t cnt = 1;
while ((sec = elf_nextscn(elf, sec)) != NULL) {
gelf_getshdr(sec, &shdr);
if ((addr >= shdr.sh_addr) &&
(addr < (shdr.sh_addr + shdr.sh_size)))
return cnt;
++cnt;
}
return -1;
}
static int dso__load_sym(struct dso *self, struct map *map, const char *name, static int dso__load_sym(struct dso *self, struct map *map, const char *name,
int fd, symbol_filter_t filter, int kmodule) int fd, symbol_filter_t filter, int kmodule)
{ {
@ -944,12 +963,13 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
int err = -1; int err = -1;
uint32_t idx; uint32_t idx;
GElf_Ehdr ehdr; GElf_Ehdr ehdr;
GElf_Shdr shdr; GElf_Shdr shdr, opdshdr;
Elf_Data *syms; Elf_Data *syms, *opddata = NULL;
GElf_Sym sym; GElf_Sym sym;
Elf_Scn *sec, *sec_strndx; Elf_Scn *sec, *sec_strndx, *opdsec;
Elf *elf; Elf *elf;
int nr = 0; int nr = 0;
size_t opdidx = 0;
elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
if (elf == NULL) { if (elf == NULL) {
@ -969,6 +989,10 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
goto out_elf_end; goto out_elf_end;
} }
opdsec = elf_section_by_name(elf, &ehdr, &opdshdr, ".opd", &opdidx);
if (opdsec)
opddata = elf_rawdata(opdsec, NULL);
syms = elf_getdata(sec, NULL); syms = elf_getdata(sec, NULL);
if (syms == NULL) if (syms == NULL)
goto out_elf_end; goto out_elf_end;
@ -1013,6 +1037,13 @@ static int dso__load_sym(struct dso *self, struct map *map, const char *name,
if (!is_label && !elf_sym__is_a(&sym, map->type)) if (!is_label && !elf_sym__is_a(&sym, map->type))
continue; continue;
if (opdsec && sym.st_shndx == opdidx) {
u32 offset = sym.st_value - opdshdr.sh_addr;
u64 *opd = opddata->d_buf + offset;
sym.st_value = *opd;
sym.st_shndx = elf_addr_to_index(elf, sym.st_value);
}
sec = elf_getscn(elf, sym.st_shndx); sec = elf_getscn(elf, sym.st_shndx);
if (!sec) if (!sec)
goto out_elf_end; goto out_elf_end;