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more ELF shlib when no DT_INIT (especially Android): hook DT_INIT_ARRAY[0]

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https://github.com/upx/upx/issues/191  [partial, not finished]
	modified:   p_lx_elf.cpp
	modified:   p_lx_elf.h
	modified:   stub/src/arm.v4a-linux.shlib-init.S
	modified:   stub/src/arm.v4t-linux.shlib-init.S
This commit is contained in:
John Reiser
2018-03-26 16:30:52 -07:00
parent 9b990c4eae
commit 5e9b6bd69d
8 changed files with 1734 additions and 1757 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/p_lx_elf.cpp
+26 -33
View File
@@ -330,7 +330,7 @@ off_t PackLinuxElf::pack3(OutputFile *fo, Filter &ft) // return length of output
if (xct_off) { // is_shlib
upx_uint64_t const firstpc_va = (jni_onload_va
? jni_onload_va
: elf_unsigned_dynamic(upx_dt_init) );
: user_init_va);
set_te32(&disp, firstpc_va - load_va);
fo->write(&disp, sizeof(disp)); // DT_INIT.d_val
len += sizeof(disp);
@@ -401,11 +401,12 @@ off_t PackLinuxElf32::pack3(OutputFile *fo, Filter &ft)
set_te32(&elfout.phdr[1].p_flags, Elf32_Phdr::PF_W|Elf32_Phdr::PF_R);
}
if (0!=xct_off) { // shared library
unsigned word = (Elf32_Ehdr::EM_ARM==e_machine) + load_va + sz_pack2; // Thumb mode
set_te32(&file_image[user_init_off], word); // set the hook
unsigned off = fo->st_size();
Elf32_Phdr *phdr = (Elf32_Phdr *)lowmem.subref(
"bad e_phoff", e_phoff, e_phnum * sizeof(Elf32_Phdr));
unsigned off = fo->st_size();
unsigned off_init = 0; // where in file
unsigned va_init = sz_pack2; // virtual address
so_slide = 0;
for (unsigned j = 0; j < e_phnum; ++j, ++phdr) {
unsigned const len = get_te32(&phdr->p_filesz);
@@ -435,36 +436,15 @@ off_t PackLinuxElf32::pack3(OutputFile *fo, Filter &ft)
set_te32(&phdr->p_offset, so_slide + ioff);
}
else { // Change length of first PT_LOAD.
va_init += get_te32(&phdr->p_vaddr);
set_te32(&phdr->p_filesz, sz_pack2 + lsize);
set_te32(&phdr->p_memsz, sz_pack2 + lsize);
}
continue; // all done with this PT_LOAD
}
// Compute new offset of &DT_INIT.d_val.
if (Elf32_Phdr::PT_DYNAMIC==type) {
off_init = ioff + ((xct_off < ioff) ? so_slide : 0);
Elf32_Dyn *dyn = (Elf32_Dyn *)(void *)&file_image[ioff];
for (int j2 = len; j2 > 0; ++dyn, j2 -= sizeof(*dyn)) {
if (get_te32(&dyn->d_tag) == upx_dt_init) {
off_init += (unsigned char *)&dyn->d_val
- (unsigned char *)&file_image[ioff];
break;
}
}
// fall through to relocate .p_offset
}
if (xct_off < ioff)
set_te32(&phdr->p_offset, so_slide + ioff);
} // end each Phdr
if (off_init) { // change DT_INIT.d_val
fo->seek(off_init, SEEK_SET);
va_init |= (Elf32_Ehdr::EM_ARM==e_machine); // THUMB mode
unsigned word; set_te32(&word, va_init);
fo->rewrite(&word, sizeof(word));
flen = fo->seek(0, SEEK_END);
}
if (opt->o_unix.android_shlib) {
// Update {DYNAMIC}.sh_offset by so_slide.
Elf32_Shdr *shdr = (Elf32_Shdr *)lowmem.subref(
@@ -1892,20 +1872,33 @@ bool PackLinuxElf32::canPack()
xct_va = ~0u;
if (e_shnum) {
for (int j= e_shnum; --j>=0; ++shdr) {
unsigned const sh_type = get_te32(&shdr->sh_type);
if (Elf32_Shdr::SHF_EXECINSTR & get_te32(&shdr->sh_flags)) {
xct_va = umin(xct_va, get_te32(&shdr->sh_addr));
}
// Hook the first slot of DT_PREINIT_ARRAY or DT_INIT_ARRAY.
if (( Elf32_Dyn::DT_PREINIT_ARRAY==upx_dt_init
&& Elf32_Shdr::SHT_PREINIT_ARRAY==sh_type)
|| ( Elf32_Dyn::DT_INIT_ARRAY ==upx_dt_init
&& Elf32_Shdr::SHT_INIT_ARRAY ==sh_type) ) {
user_init_off = get_te32(&shdr->sh_offset);
user_init_va = get_te32(&file_image[user_init_off]);
}
// By default /usr/bin/ld leaves 4 extra DT_NULL to support pre-linking.
// Take one if DT_INIT is not present.
if (Elf32_Shdr::SHT_DYNAMIC == get_te32(&shdr->sh_type)
&& Elf32_Dyn::DT_INIT != upx_dt_init) {
// Take one as a last resort.
if ((Elf32_Dyn::DT_INIT==upx_dt_init || !upx_dt_init)
&& Elf32_Shdr::SHT_DYNAMIC == sh_type) {
unsigned const n = get_te32(&shdr->sh_size) / sizeof(Elf32_Dyn);
Elf32_Dyn *dynp = const_cast<Elf32_Dyn *>(dynseg);
for (; Elf32_Dyn::DT_NULL != dynp->d_tag; ++dynp) /* empty */ ;
Elf32_Dyn *dynp = (Elf32_Dyn *)&file_image[shdr->sh_offset];
for (; Elf32_Dyn::DT_NULL != dynp->d_tag; ++dynp) {
if (upx_dt_init == get_te32(&dynp->d_tag)) {
break; // re-found DT_INIT
}
}
if ((1+ dynp) < (n+ dynseg)) { // not the terminator, so take it
set_te32(&dynp->d_tag, Elf32_Dyn::DT_INIT);
dynp->d_val = 0;
upx_dt_init = Elf32_Dyn::DT_INIT;
user_init_va = get_te32(&dynp->d_val); // 0 if (0==upx_dt_init)
set_te32(&dynp->d_tag, upx_dt_init = Elf32_Dyn::DT_INIT);
user_init_off = (char const *)&dynp->d_val - (char const *)&file_image[0];
}
}
}