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coredump: fix parsing metadata without access to executable

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This was broken in a subtle way: we'd get an ELF ref, but not the right one,
so no metadata note would be found.
Change the parsing function to return 1 when it finds something, so that
we can return early only when that happens.
This commit is contained in:
Luca Boccassi
2021-11-29 11:25:48 +01:00
committed by Zbigniew Jędrzejewski-Szmek
parent ddf127cda4
commit c0775eb787
1 changed files with 32 additions and 34 deletions
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src/coredump/stacktrace.c
+32 -34
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@@ -127,11 +127,11 @@ static int parse_package_metadata(const char *name, JsonVariant *id_json, Elf *e
/* When iterating over PT_LOAD we will visit modules more than once */
if (set_contains(*c->modules, name))
return DWARF_CB_OK;
return 0;
r = elf_getphdrnum(elf, &n_program_headers);
if (r < 0) /* Not the handle we are looking for - that's ok, skip it */
return DWARF_CB_OK;
return 0;
/* Iterate over all program headers in that ELF object. These will have been copied by
* the kernel verbatim when the core file is generated. */
@@ -170,10 +170,8 @@ static int parse_package_metadata(const char *name, JsonVariant *id_json, Elf *e
_cleanup_(json_variant_unrefp) JsonVariant *v = NULL, *w = NULL;
r = json_parse(payload, 0, &v, NULL, NULL);
if (r < 0) {
log_error_errno(r, "json_parse on %s failed: %m", payload);
return DWARF_CB_ABORT;
}
if (r < 0)
return log_error_errno(r, "json_parse on %s failed: %m", payload);
/* First pretty-print to the buffer, so that the metadata goes as
* plaintext in the journal. */
@@ -186,40 +184,32 @@ static int parse_package_metadata(const char *name, JsonVariant *id_json, Elf *e
* so that it appears all nicely together in the logs/metadata. */
if (id_json) {
r = json_variant_merge(&v, id_json);
if (r < 0) {
log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
return DWARF_CB_ABORT;
}
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
}
/* Then we build a new object using the module name as the key, and merge it
* with the previous parses, so that in the end it all fits together in a single
* JSON blob. */
r = json_build(&w, JSON_BUILD_OBJECT(JSON_BUILD_PAIR(name, JSON_BUILD_VARIANT(v))));
if (r < 0) {
log_error_errno(r, "Failed to build JSON object: %m");
return DWARF_CB_ABORT;
}
if (r < 0)
return log_error_errno(r, "Failed to build JSON object: %m");
r = json_variant_merge(c->package_metadata, w);
if (r < 0) {
log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
return DWARF_CB_ABORT;
}
if (r < 0)
return log_error_errno(r, "json_variant_merge of package meta with buildid failed: %m");
/* Finally stash the name, so we avoid double visits. */
r = set_put_strdup(c->modules, name);
if (r < 0) {
log_error_errno(r, "set_put_strdup failed: %m");
return DWARF_CB_ABORT;
}
if (r < 0)
return log_error_errno(r, "set_put_strdup failed: %m");
return DWARF_CB_OK;
return 1;
}
}
}
/* Didn't find package metadata for this module - that's ok, just go to the next. */
return DWARF_CB_OK;
return 0;
}
static int module_callback(Dwfl_Module *mod, void **userdata, const char *name, Dwarf_Addr start, void *arg) {
@@ -268,17 +258,23 @@ static int module_callback(Dwfl_Module *mod, void **userdata, const char *name,
/* The .note.package metadata is more difficult. From the module, we need to get a reference
* to the ELF object first. We might be lucky and just get it from elfutils. */
elf = dwfl_module_getelf(mod, &bias);
if (elf)
return parse_package_metadata(name, id_json, elf, c);
if (elf) {
r = parse_package_metadata(name, id_json, elf, c);
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
return DWARF_CB_OK;
} else
elf = c->elf;
/* We did not get the ELF object. That is likely because we didn't get direct
* access to the executable, and the version of elfutils does not yet support
* parsing it out of the core file directly.
/* We did not get the ELF object, or it's just a reference to the core. That is likely
* because we didn't get direct access to the executable, and the version of elfutils does
* not yet support parsing it out of the core file directly.
* So fallback to manual extraction - get the PT_LOAD section from the core,
* and if it's the right one we can interpret it as an Elf object, and parse
* its notes manually. */
r = elf_getphdrnum(c->elf, &n_program_headers);
r = elf_getphdrnum(elf, &n_program_headers);
if (r < 0) {
log_warning("Could not parse number of program headers from core file: %s",
elf_errmsg(-1)); /* -1 retrieves the most recent error */
@@ -290,12 +286,12 @@ static int module_callback(Dwfl_Module *mod, void **userdata, const char *name,
Elf_Data *data;
/* The core file stores the ELF files in the PT_LOAD segment. */
program_header = gelf_getphdr(c->elf, i, &mem);
program_header = gelf_getphdr(elf, i, &mem);
if (!program_header || program_header->p_type != PT_LOAD)
continue;
/* Now get a usable Elf reference, and parse the notes from it. */
data = elf_getdata_rawchunk(c->elf,
data = elf_getdata_rawchunk(elf,
program_header->p_offset,
program_header->p_filesz,
ELF_T_NHDR);
@@ -306,8 +302,10 @@ static int module_callback(Dwfl_Module *mod, void **userdata, const char *name,
if (!memelf)
continue;
r = parse_package_metadata(name, id_json, memelf, c);
if (r != DWARF_CB_OK)
return r;
if (r < 0)
return DWARF_CB_ABORT;
if (r > 0)
break;
}
return DWARF_CB_OK;