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Add method to update btf_var_secinfo.offset

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Bpf loader needs to fix btf_var_secinfo.offset based on ELF's string
section.

Bug: 403381101
Test: boot
Change-Id: I8382d0ee3e0fa7f0a3b825eca9cdcf40ccce9532
This commit is contained in:
Motomu Utsumi 2025-03-18 15:08:15 +09:00 • committed by Maciej Żenczykowski
commit efe33319f7
1 changed files with 55 additions and 0 deletions
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55
bpf/loader/NetBpfLoad.cpp
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@ -668,6 +668,61 @@ static int setBtfDatasecSize(ifstream &elfFile, struct btf *btf,
return 0;
}
static int getSymOffsetByName(ifstream &elfFile, const char *name, int *off) {
vector<Elf64_Sym> symtab;
int ret = readSymTab(elfFile, 1 /* sort */, symtab);
if (ret) return ret;
for (int i = 0; i < (int)symtab.size(); i++) {
string s;
ret = getSymName(elfFile, symtab[i].st_name, s);
if (ret) continue;
if (!strcmp(s.c_str(), name)) {
*off = symtab[i].st_value;
return 0;
}
}
return -1;
}
static int setBtfVarOffset(ifstream &elfFile, struct btf *btf,
struct btf_type *datasecBt) {
int i, vars = btf_vlen(datasecBt);
struct btf_var_secinfo *vsi;
const char *datasecName = btf__name_by_offset(btf, datasecBt->name_off);
if (!datasecName) {
ALOGE("Couldn't resolve section name, errno: %d", errno);
return -errno;
}
for (i = 0, vsi = btf_var_secinfos(datasecBt); i < vars; i++, vsi++) {
const struct btf_type *varBt = btf__type_by_id(btf, vsi->type);
if (!varBt || !btf_is_var(varBt)) {
ALOGE("Found non VAR kind btf_type, section: %s id: %d", datasecName,
vsi->type);
return -1;
}
const struct btf_var *var = btf_var(varBt);
if (var->linkage == BTF_VAR_STATIC) continue;
const char *varName = btf__name_by_offset(btf, varBt->name_off);
if (!varName) {
ALOGE("Failed to resolve var name, section: %s", datasecName);
return -1;
}
int off;
int ret = getSymOffsetByName(elfFile, varName, &off);
if (ret) {
ALOGE("No offset found in symbol table, section: %s, var: %s, ret: %d",
datasecName, varName, ret);
return ret;
}
vsi->offset = off;
}
return 0;
}
static int createMaps(const char* elfPath, ifstream& elfFile, vector<unique_fd>& mapFds,
const char* prefix, const unsigned int bpfloader_ver) {
int ret;