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Enhance readelf relocs support
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@djphoenix
djphoenix committed May 26, 2019
1 parent 9400184 commit a0fbe67
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Showing 2 changed files with 141 additions and 66 deletions.
182 changes: 116 additions & 66 deletions src/readelf/readelf.cpp
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Expand Up @@ -104,21 +104,52 @@ static uint64_t readelf_dylink_dynamic_find(Process *process,
return 0;
}

static bool readelf_dylink_process_reloc(Process *process, uintptr_t start, const ELF64RELA &ent,
uintptr_t symtab, uintptr_t syment, uintptr_t strtab) {
if (ent.sym == 0) return 0;
ELF64SYM sym;
process->readData(&sym, symtab + syment * ent.sym, sizeof(sym));
if (!sym.name) return 0;

uintptr_t addr = 0;
char *name = process->readString(strtab + sym.name);
ELF64_SYM_BIND bind = ELF64_SYM_BIND(sym.info >> 4);
uintptr_t ptr = readelf_find_load_addr(process, start, ent.addr);

bool allownull = bind == STB_WEAK;
addr = process->getSymbolByName(name);
if (!addr) addr = process->linkLibrary(name);

if (!allownull && addr == 0) {
printf("Cannot link symbol: %s\n", name);
delete name;
return 0;
}
delete name;

addr += ent.add;
switch (ent.type) {
case R_X86_64_JUMP_SLOT:
case R_X86_64_GLOB_DAT:
process->writeData(ptr, &addr, sizeof(addr));
break;
default:
printf("UNHANDLED REL@%#lx: %x => %x+%#lx\n", ent.addr, ent.type, ent.sym, ent.add);
return 0;
}
return 1;
}

static bool readelf_dylink_handle_dynamic_jmprel(Process *process,
uintptr_t start,
uintptr_t dyntbl,
size_t dynsz,
uintptr_t jmprel) {
uintptr_t symtab =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMTAB);
uintptr_t pltrel =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_PLTREL);
uintptr_t pltrelsz =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_PLTRELSZ);
uintptr_t syment =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
uintptr_t symtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMTAB);
uintptr_t pltrel = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_PLTREL);
uintptr_t pltrelsz = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_PLTRELSZ);
uintptr_t syment = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
if (syment == 0) syment = sizeof(ELF64SYM);
if (jmprel == 0 || symtab == 0) return 0;
switch (pltrel) {
Expand All @@ -131,7 +162,6 @@ static bool readelf_dylink_handle_dynamic_jmprel(Process *process,
default: return 0;
}
ELF64RELA rel;
ELF64SYM sym;
Memory::zero(&rel, sizeof(rel));
while (pltrelsz) {
switch (pltrel) {
Expand All @@ -147,35 +177,54 @@ static bool readelf_dylink_handle_dynamic_jmprel(Process *process,
break;
default: return 0;
}
uintptr_t addr = 0;
if (rel.sym != 0) {
process->readData(&sym, symtab + syment * rel.sym, sizeof(sym));
if (sym.name) {
char *name = process->readString(strtab + sym.name);
addr = process->linkLibrary(name);
if (addr == 0) {
printf("Cannot link symbol: %s\n", name);
delete name;
return 0;
}
delete name;
} else {
return 0;
}
} else {
return 0;
}
addr += rel.add;
uintptr_t ptr = readelf_find_load_addr(process, start, rel.addr);
switch (rel.type) {
case R_X86_64_JUMP_SLOT:
process->writeData(ptr, &addr, sizeof(addr));
break;
default:
printf("UNHANDLED REL@%#lx: %x/%x+%#lx\n",
rel.addr, rel.type, rel.sym, rel.add);
return 0;
}
if (!readelf_dylink_process_reloc(process, start, rel, symtab, syment, strtab)) return 0;
}
return 1;
}

static bool readelf_dylink_handle_dynamic_rel(Process *process,
uintptr_t start,
uintptr_t dyntbl,
size_t dynsz,
uintptr_t rel) {
uintptr_t sz = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_RELSZ);
uintptr_t entsz = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_RELENT);
uintptr_t symtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMTAB);
uintptr_t syment = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
if (sz == 0 || entsz != sizeof(ELF64REL)) return 0;
ELF64RELA ent;
ent.add = 0;
while (sz) {
process->readData(&ent, rel, sizeof(ELF64REL));

if (!readelf_dylink_process_reloc(process, start, ent, symtab, syment, strtab)) return 0;

rel += entsz;
sz -= entsz;
}
return 1;
}

static bool readelf_dylink_handle_dynamic_rela(Process *process,
uintptr_t start,
uintptr_t dyntbl,
size_t dynsz,
uintptr_t rela) {
uintptr_t sz = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_RELASZ);
uintptr_t entsz = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_RELAENT);
uintptr_t symtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMTAB);
uintptr_t syment = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
if (sz == 0 || entsz != sizeof(ELF64RELA)) return 0;
ELF64RELA ent;
while (sz) {
process->readData(&ent, rela, sizeof(ent));

if (!readelf_dylink_process_reloc(process, start, ent, symtab, syment, strtab)) return 0;

rela += entsz;
sz -= entsz;
}
return 1;
}
Expand All @@ -185,12 +234,9 @@ static bool readelf_dylink_handle_dynamic_symtab(Process *process,
uintptr_t dyntbl,
size_t dynsz,
uintptr_t symtab) {
uintptr_t syment =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
uintptr_t hashtab =
readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_HASH);
uintptr_t syment = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_SYMENT);
uintptr_t strtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_STRTAB);
uintptr_t hashtab = readelf_dylink_dynamic_find(process, dyntbl, dynsz, DT_HASH);
if (syment == 0 || strtab == 0 || hashtab == 0) return 0;
ELF64SYM sym;
struct {
Expand All @@ -204,12 +250,15 @@ static bool readelf_dylink_handle_dynamic_symtab(Process *process,
hashtab += sizeof(idx);
if (idx == 0) continue;
process->readData(&sym, symtab + syment * idx, sizeof(ELF64SYM));
if (sym.value == 0) continue;
if (sym.name == 0) continue;
uintptr_t ptr = readelf_find_load_addr(process, start, sym.value);
if (ptr == 0) continue;
char *name = process->readString(strtab + sym.name);
if (name && name[0] != 0) process->addSymbol(name, ptr);
if (name && name[0] != 0) {
uint8_t bind = sym.info >> 4;
if (bind == STB_GLOBAL)
process->addSymbol(name, ptr);
}
delete name;
}
return 1;
Expand All @@ -225,21 +274,29 @@ static bool readelf_dylink_handle_dynamic_table(Process *process,
process->readData(&dyn, dynptr, sizeof(ELF64_DYN));
switch (dyn.tag) {
case DT_JMPREL:
if (!readelf_dylink_handle_dynamic_jmprel(
process, start, dyntbl, dynsz, dyn.val)) return 0;
if (!readelf_dylink_handle_dynamic_jmprel(process, start, dyntbl, dynsz, dyn.val)) return 0;
break;
case DT_REL:
if (!readelf_dylink_handle_dynamic_rel(process, start, dyntbl, dynsz, dyn.val)) return 0;
break;
case DT_RELA:
if (!readelf_dylink_handle_dynamic_rela(process, start, dyntbl, dynsz, dyn.val)) return 0;
break;
case DT_PLTGOT:
case DT_PLTREL:
case DT_PLTRELSZ:
case DT_RELASZ:
case DT_RELAENT:
case DT_RELSZ:
case DT_RELENT:
case DT_SYMENT:
case DT_HASH:
case DT_GNU_HASH:
case DT_STRTAB:
case DT_STRSZ:
break;
case DT_SYMTAB:
if (!readelf_dylink_handle_dynamic_symtab(
process, start, dyntbl, dynsz, dyn.val)) return 0;
if (!readelf_dylink_handle_dynamic_symtab(process, start, dyntbl, dynsz, dyn.val)) return 0;
break;
case DT_NULL: break;
default:
Expand All @@ -262,10 +319,8 @@ static bool readelf_dylink_handle_dynamic(Process *process, uintptr_t start) {
for (phdr = phdr_base; phdr < phdr_top; phdr += sizeof(ELF64_PROG)) {
process->readData(&prog, phdr, sizeof(ELF64_PROG));
if (prog.type != PT_DYNAMIC) continue;
if (!readelf_dylink_fix_dynamic_table(
process, start, prog.vaddr, prog.filesz) ||
!readelf_dylink_handle_dynamic_table(
process, start, prog.vaddr, prog.filesz))
if (!readelf_dylink_fix_dynamic_table(process, start, prog.vaddr, prog.filesz) ||
!readelf_dylink_handle_dynamic_table(process, start, prog.vaddr, prog.filesz))
return 0;
}

Expand Down Expand Up @@ -313,17 +368,15 @@ size_t readelf(Process *process, Stream *stream) {
progs_top = progs + elf.phnum;

// Read linker program
if (stream->read(progs, sizeof(ELF64_PROG) * elf.phnum)
!= sizeof(ELF64_PROG) * elf.phnum)
if (stream->read(progs, sizeof(ELF64_PROG) * elf.phnum) != sizeof(ELF64_PROG) * elf.phnum)
goto err;
off += sizeof(ELF64_PROG) * elf.phnum;

for (prog = progs; prog < progs_top; prog++) {
switch (prog->type) {
case PT_NULL: break;
case PT_PHDR:
if ((prog->offset != elf.phoff) ||
(prog->filesz != sizeof(ELF64_PROG) * elf.phnum))
if ((prog->offset != elf.phoff) || (prog->filesz != sizeof(ELF64_PROG) * elf.phnum))
goto err;
break;
case PT_LOAD:
Expand All @@ -350,11 +403,9 @@ size_t readelf(Process *process, Stream *stream) {
off = prog->offset + offset_load;
}
buf = new char[prog->filesz - offset_load]();
if (stream->read(buf, prog->filesz - offset_load) !=
prog->filesz - offset_load) goto err;
if (stream->read(buf, prog->filesz - offset_load) != prog->filesz - offset_load) goto err;
off += prog->filesz - offset_load;
process->writeData(vaddr + offset_load, buf,
prog->filesz - offset_load);
process->writeData(vaddr + offset_load, buf, prog->filesz - offset_load);
delete[] buf; buf = nullptr;
prog->vaddr = vaddr;
}
Expand All @@ -367,8 +418,7 @@ size_t readelf(Process *process, Stream *stream) {
}
}

process->writeData(vaddr_start + sizeof(ELF_HDR),
progs, sizeof(ELF64_PROG) * elf.phnum);
process->writeData(vaddr_start + sizeof(ELF_HDR), progs, sizeof(ELF64_PROG) * elf.phnum);

goto done;
err:
Expand Down
25 changes: 25 additions & 0 deletions src/readelf/readelf_internal.h
View file
Expand Up @@ -184,6 +184,31 @@ enum ELF64_RELOC_TYPE: uint32_t {
R_X86_64_PC8 // 8 bit sign extended pc relative
};

enum ELF64_SYM_BIND: uint8_t {
STB_LOCAL = 0,
STB_GLOBAL = 1,
STB_WEAK = 2,
STB_LOOS = 10,
STB_HIOS = 12,
STB_LOPROC = 13,
STB_HIPROC = 15,
};

enum ELF64_SYM_TYPE: uint8_t {
STT_NOTYPE = 0,
STT_OBJECT = 1,
STT_FUNC = 2,
STT_SECTION = 3,
STT_FILE = 4,
STT_COMMON = 5,
STT_TLS = 6,
STT_LOOS = 10,
STT_HIOS = 12,
STT_LOPROC = 13,
STT_SPARC_REGISTER = 13,
STT_HIPROC = 15,
};

struct ELF64_DYN {
ELF64_DYN_TAG tag;
uint64_t val;
Expand Down

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