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Commit 70c3856b authored by Eric B Munson's avatar Eric B Munson Committed by Arnaldo Carvalho de Melo
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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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarEric B Munson <ebmunson@us.ibm.com>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent cf103a14

tools/perf/util/symbol.c

+34 −3
Original line number Diff line number Diff line
@@ -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,

			 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;

	uint32_t idx;

	GElf_Ehdr ehdr;

	GElf_Shdr shdr;

	Elf_Data *syms;

	GElf_Shdr shdr, opdshdr;

	Elf_Data *syms, *opddata = NULL;

	GElf_Sym sym;

	Elf_Scn *sec, *sec_strndx;

	Elf_Scn *sec, *sec_strndx, *opdsec;

	Elf *elf;

	int nr = 0;

	size_t opdidx = 0;



	elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, 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;

	}



	opdsec = elf_section_by_name(elf, &ehdr, &opdshdr, ".opd", &opdidx);

	if (opdsec)

		opddata = elf_rawdata(opdsec, NULL);



	syms = elf_getdata(sec, NULL);

	if (syms == NULL)

		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))

			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);

		if (!sec)

			goto out_elf_end;