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Create new soname entry if shlib is missing one, merge modifySoname()…
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… and getSoname()

Basically this is just a modified copy of the rpath code
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@darealshinji
darealshinji committed Jul 13, 2015
1 parent f6886c2 commit 764dacc
Showing 1 changed file with 69 additions and 58 deletions.
127 changes: 69 additions & 58 deletions src/patchelf.cc
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Expand Up @@ -154,9 +154,9 @@ class ElfFile

string getInterpreter();

string getSoname();
typedef enum { printSoname, replaceSoname } sonameMode;

void setSoname(const string & newSoname);
void modifySoname(sonameMode op, const string & newSoname);

void setInterpreter(const string & newInterpreter);

Expand Down Expand Up @@ -899,8 +899,13 @@ string ElfFile<ElfFileParamNames>::getInterpreter()
}

template<ElfFileParams>
string ElfFile<ElfFileParamNames>::getSoname()
void ElfFile<ElfFileParamNames>::modifySoname(sonameMode op, const string & newSoname)
{
if (rdi(hdr->e_type) != ET_DYN) {
debug("this is not a dynamic library\n");
return;
}

Elf_Shdr & shdrDynamic = findSection(".dynamic");
Elf_Shdr & shdrDynStr = findSection(".dynstr");
char * strTab = (char *) contents + rdi(shdrDynStr.sh_offset);
Expand All @@ -909,76 +914,82 @@ string ElfFile<ElfFileParamNames>::getSoname()
Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
Elf_Addr strTabAddr = 0;
for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++)
if (rdi(dyn->d_tag) == DT_STRTAB) strTabAddr = rdi(dyn->d_un.d_ptr);
if (rdi(dyn->d_tag) == DT_STRTAB)
strTabAddr = rdi(dyn->d_un.d_ptr);
if (!strTabAddr) error("strange: no string table");

/* We assume that the virtual address in the DT_STRTAB entry
of the dynamic section corresponds to the .dynstr section. */
assert(strTabAddr == rdi(shdrDynStr.sh_addr));

Elf_Dyn * dynSoname = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
/* Walk through the dynamic section, look for the DT_SONAME entry. */
static vector<string> neededLibs;
dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
Elf_Dyn * dynSoname = 0;
char * soname = 0;
for ( ; rdi(dynSoname->d_tag) != DT_NULL; dynSoname++) {
if (rdi(dynSoname->d_tag) == DT_SONAME) {
soname = strTab + rdi(dynSoname->d_un.d_val);
break;
for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++) {
if (rdi(dyn->d_tag) == DT_SONAME) {
dynSoname = dyn;
soname = strTab + rdi(dyn->d_un.d_val);
} else if (rdi(dyn->d_tag) == DT_INIT)
neededLibs.push_back(string(strTab + rdi(dyn->d_un.d_val)));
}

if (op == printSoname) {
if (soname) {
if (string(soname ? soname : "") == "")
debug("DT_SONAME is empty\n");
else
printf("%s\n", soname);
} else {
debug("no DT_SONAME found\n");
}
return;
}

if (rdi(dynSoname->d_tag) == DT_NULL)
error("Specified ELF file does not contain any DT_SONAME entry in .dynamic section!");
if (string(soname ? soname : "") == newSoname) {
debug("current and proposed new SONAMEs are equal keeping DT_SONAME entry\n");
return;
}

return soname;
}
/* Zero out the previous SONAME */
unsigned int sonameSize = 0;
if (soname) {
sonameSize = strlen(soname);
memset(soname, 'X', sonameSize);
}

template<ElfFileParams>
void ElfFile<ElfFileParamNames>::setSoname(const string & newSoname)
{
Elf_Shdr & shdrDynamic = findSection(".dynamic");
Elf_Shdr & shdrDynStr = findSection(".dynstr");
char * strTab = (char *) contents + rdi(shdrDynStr.sh_offset);
debug("new SONAME is `%s'\n", newSoname.c_str());

/* Find the DT_STRTAB entry in the dynamic section. */
Elf_Dyn * dyn = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
Elf_Addr strTabAddr = 0;
for ( ; rdi(dyn->d_tag) != DT_NULL; dyn++)
if (rdi(dyn->d_tag) == DT_STRTAB) strTabAddr = rdi(dyn->d_un.d_ptr);
if (!strTabAddr) error("strange: no string table");
/* Grow the .dynstr section to make room for the new SONAME. */
debug("SONAME is too long, resizing...\n");

/* We assume that the virtual address in the DT_STRTAB entry
of the dynamic section corresponds to the .dynstr section. */
assert(strTabAddr == rdi(shdrDynStr.sh_addr));
string & newDynStr = replaceSection(".dynstr", rdi(shdrDynStr.sh_size) + newSoname.size() + 1);
setSubstr(newDynStr, rdi(shdrDynStr.sh_size), newSoname + '\0');

Elf_Dyn * dynSoname = (Elf_Dyn *) (contents + rdi(shdrDynamic.sh_offset));
char * soname = 0;
for ( ; rdi(dynSoname->d_tag) != DT_NULL; dynSoname++) {
if (rdi(dynSoname->d_tag) == DT_SONAME) {
soname = strTab + rdi(dynSoname->d_un.d_val);
break;
}
}
if (rdi(dynSoname->d_tag) == DT_NULL)
error("Specified ELF file does not contain any DT_SONAME entry in .dynamic section!");
/* Update the DT_SONAME entry. */
if (dynSoname) {
dynSoname->d_un.d_val = shdrDynStr.sh_size;
} else {
/* There is no DT_SONAME entry in the .dynamic section, so we
have to grow the .dynamic section. */
string & newDynamic = replaceSection(".dynamic", rdi(shdrDynamic.sh_size) + sizeof(Elf_Dyn));

if (newSoname.size() <= strlen(soname)) {
debug("old soname: `%s', new soname: `%s'\n", soname, newSoname.c_str());
strcpy(soname, newSoname.c_str());
changed = true;
}
else {
/* Grow the .dynstr section to make room for the new DT_SONAME */
debug("new soname is too long, resizing .dynstr section...\n");

string & newDynStr = replaceSection(".dynstr",
rdi(shdrDynStr.sh_size) + newSoname.size() + 1);
setSubstr(newDynStr, rdi(shdrDynStr.sh_size), newSoname + '\0');
/* Update the DT_SONAME entry, if any */
if (dynSoname) {
debug("old soname: `%s', new soname: `%s'\n", soname, newSoname.c_str());
dynSoname->d_un.d_val = shdrDynStr.sh_size;
changed = true;
}
unsigned int idx = 0;
for (; rdi(((Elf_Dyn *) newDynamic.c_str())[idx].d_tag) != DT_NULL; idx++);
debug("DT_NULL index is %d\n", idx);

/* Shift all entries down by one. */
setSubstr(newDynamic, sizeof(Elf_Dyn), string(newDynamic, 0, sizeof(Elf_Dyn) * (idx + 1)));

/* Add the DT_SONAME entry at the top. */
Elf_Dyn newDyn;
wri(newDyn.d_tag, DT_SONAME);
newDyn.d_un.d_val = shdrDynStr.sh_size;
setSubstr(newDynamic, 0, string((char *)&newDyn, sizeof(Elf_Dyn)));
}

changed = true;
}

template<ElfFileParams>
Expand Down Expand Up @@ -1351,10 +1362,10 @@ static void patchElf2(ElfFile & elfFile, mode_t fileMode)
printf("%s\n", elfFile.getInterpreter().c_str());

if (printSoname)
printf("%s\n", elfFile.getSoname().c_str());
elfFile.modifySoname(elfFile.printSoname, "");

if (setSoname)
elfFile.setSoname(newSoname);
elfFile.modifySoname(elfFile.replaceSoname, newSoname);

if (newInterpreter != "")
elfFile.setInterpreter(newInterpreter);
Expand Down

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