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: Stephen Brennan <stephen.s.brennan@oracle.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250307232206.2102440-4-stephen.s.brennan@oracle.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 5c6e85fdae0de1defb86ebd94853cceb4072835b..7576e8e248386c36e167429cb5a28c1ed57b0c94 100644 (file)
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -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;
 

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index bb8e8f444054d821e1af57dec41a7a0bfdb486b0..84d5aac666aa1929321a5c1263f0292351ef897f 100644 (file)
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -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,

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 66fd1249660a3922ed602d179da85a1c4d6c7810..3fa92697c457b7421f0532a2e62365bd7ca6cf70 100644 (file)
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -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;
        }
 
-       return 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)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 315f74b5bac0609b20a60ea4237c6e04e4697647..11540219481ba8264dceb8b5b8a7a85fa172b66d 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -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: