Commit b10f7430 authored by Stephen Brennan's avatar Stephen Brennan Committed by Namhyung Kim
Browse files

perf symbol: Support .gnu_debugdata for symbols 



Fedora introduced a "MiniDebuginfo" feature, in which an LZMA-compressed
ELF file is placed inside a section named ".gnu_debugdata". This file
contains nothing but a symbol table, which can be used to supplement the
.dynsym section which only contains required symbols for runtime.

It is supported by GDB for stack traces, but it should be useful for
tracing as well. Implement support for loading symbols from
.gnu_debugdata.

Signed-off-by: default avatarStephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250307232206.2102440-4-stephen.s.brennan@oracle.com


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent 71fa411f

tools/perf/util/dso.c

+3 −0
Original line number Diff line number Diff line
@@ -67,6 +67,7 @@ char dso__symtab_origin(const struct dso *dso) 
		[DSO_BINARY_TYPE__GUEST_KMODULE]		= 'G',

		[DSO_BINARY_TYPE__GUEST_KMODULE_COMP]		= 'M',

		[DSO_BINARY_TYPE__GUEST_VMLINUX]		= 'V',

		[DSO_BINARY_TYPE__GNU_DEBUGDATA]		= 'n',

	};



	if (dso == NULL || dso__symtab_type(dso) == DSO_BINARY_TYPE__NOT_FOUND)
@@ -93,6 +94,7 @@ bool dso__is_object_file(const struct dso *dso) 
	case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO:

	case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO:

	case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:

	case DSO_BINARY_TYPE__GNU_DEBUGDATA:

	case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:

	case DSO_BINARY_TYPE__GUEST_KMODULE:

	case DSO_BINARY_TYPE__GUEST_KMODULE_COMP:
@@ -224,6 +226,7 @@ int dso__read_binary_type_filename(const struct dso *dso, 
	case DSO_BINARY_TYPE__VMLINUX:

	case DSO_BINARY_TYPE__GUEST_VMLINUX:

	case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:

	case DSO_BINARY_TYPE__GNU_DEBUGDATA:

		__symbol__join_symfs(filename, size, dso__long_name(dso));

		break;

tools/perf/util/dso.h

+1 −0
Original line number Diff line number Diff line
@@ -33,6 +33,7 @@ enum dso_binary_type { 
	DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,

	DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO,

	DSO_BINARY_TYPE__BUILDID_DEBUGINFO,

	DSO_BINARY_TYPE__GNU_DEBUGDATA,

	DSO_BINARY_TYPE__SYSTEM_PATH_DSO,

	DSO_BINARY_TYPE__GUEST_KMODULE,

	DSO_BINARY_TYPE__GUEST_KMODULE_COMP,

tools/perf/util/symbol-elf.c

+104 −2
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <unistd.h>

#include <inttypes.h>



#include "compress.h"

#include "dso.h"

#include "map.h"

#include "maps.h"
@@ -1228,6 +1229,81 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr) 
	       ehdr.e_type == ET_DYN;

}



static Elf *read_gnu_debugdata(struct dso *dso, Elf *elf, const char *name, int *fd_ret)

{

	Elf *elf_embedded;

	GElf_Ehdr ehdr;

	GElf_Shdr shdr;

	Elf_Scn *scn;

	Elf_Data *scn_data;

	FILE *wrapped;

	size_t shndx;

	char temp_filename[] = "/tmp/perf.gnu_debugdata.elf.XXXXXX";

	int ret, temp_fd;



	if (gelf_getehdr(elf, &ehdr) == NULL) {

		pr_debug("%s: cannot read %s ELF file.\n", __func__, name);

		*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;

		return NULL;

	}



	scn = elf_section_by_name(elf, &ehdr, &shdr, ".gnu_debugdata", &shndx);

	if (!scn) {

		*dso__load_errno(dso) = -ENOENT;

		return NULL;

	}



	if (shdr.sh_type == SHT_NOBITS) {

		pr_debug("%s: .gnu_debugdata of ELF file %s has no data.\n", __func__, name);

		*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;

		return NULL;

	}



	scn_data = elf_rawdata(scn, NULL);

	if (!scn_data) {

		pr_debug("%s: error reading .gnu_debugdata of %s: %s\n", __func__,

			 name, elf_errmsg(-1));

		*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;

		return NULL;

	}



	wrapped = fmemopen(scn_data->d_buf, scn_data->d_size, "r");

	if (!wrapped) {

		pr_debug("%s: fmemopen: %s\n", __func__, strerror(errno));

		*dso__load_errno(dso) = -errno;

		return NULL;

	}



	temp_fd = mkstemp(temp_filename);

	if (temp_fd < 0) {

		pr_debug("%s: mkstemp: %s\n", __func__, strerror(errno));

		*dso__load_errno(dso) = -errno;

		fclose(wrapped);

		return NULL;

	}

	unlink(temp_filename);



	ret = lzma_decompress_stream_to_file(wrapped, temp_fd);

	fclose(wrapped);

	if (ret < 0) {

		*dso__load_errno(dso) = -errno;

		close(temp_fd);

		return NULL;

	}



	elf_embedded = elf_begin(temp_fd, PERF_ELF_C_READ_MMAP, NULL);

	if (!elf_embedded) {

		pr_debug("%s: error reading .gnu_debugdata of %s: %s\n", __func__,

			 name, elf_errmsg(-1));

		*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;

		close(temp_fd);

		return NULL;

	}

	pr_debug("%s: using .gnu_debugdata of %s\n", __func__, name);

	*fd_ret = temp_fd;

	return elf_embedded;

}



int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,

		 enum dso_binary_type type)

{
@@ -1256,6 +1332,19 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name, 
		goto out_close;

	}



	if (type == DSO_BINARY_TYPE__GNU_DEBUGDATA) {

		int new_fd;

		Elf *embedded = read_gnu_debugdata(dso, elf, name, &new_fd);



		if (!embedded)

			goto out_close;



		elf_end(elf);

		close(fd);

		fd = new_fd;

		elf = embedded;

	}



	if (gelf_getehdr(elf, &ehdr) == NULL) {

		*dso__load_errno(dso) = DSO_LOAD_ERRNO__INVALID_ELF;

		pr_debug("%s: cannot get elf header.\n", __func__);
@@ -1854,10 +1943,23 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss, 
					     kmodule, 1);

		if (err < 0)

			return err;

		err += nr;

		nr += err;

	}



	/*

	 * The .gnu_debugdata is a special situation: it contains a symbol

	 * table, but the runtime file may also contain dynsym entries which are

	 * not present there. We need to load both.

	 */

	if (syms_ss->type == DSO_BINARY_TYPE__GNU_DEBUGDATA && runtime_ss->dynsym) {

		err = dso__load_sym_internal(dso, map, runtime_ss, runtime_ss,

					     kmodule, 1);

		if (err < 0)

			return err;

		nr += err;

	}



	return nr;

}



static int elf_read_maps(Elf *elf, bool exe, mapfn_t mapfn, void *data)

tools/perf/util/symbol.c

+2 −0
Original line number Diff line number Diff line
@@ -85,6 +85,7 @@ static enum dso_binary_type binary_type_symtab[] = { 
	DSO_BINARY_TYPE__FEDORA_DEBUGINFO,

	DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,

	DSO_BINARY_TYPE__BUILDID_DEBUGINFO,

	DSO_BINARY_TYPE__GNU_DEBUGDATA,

	DSO_BINARY_TYPE__SYSTEM_PATH_DSO,

	DSO_BINARY_TYPE__GUEST_KMODULE,

	DSO_BINARY_TYPE__GUEST_KMODULE_COMP,
@@ -1717,6 +1718,7 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod, 
	case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO:

	case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:

	case DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO:

	case DSO_BINARY_TYPE__GNU_DEBUGDATA:

		return !kmod && dso__kernel(dso) == DSO_SPACE__USER;



	case DSO_BINARY_TYPE__KALLSYMS: