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Code Issues Releases Wiki Activity

--android-shlib preserves selected Elf64_Shdr

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modified:   p_lx_elf.cpp
	modified:   p_lx_elf.h
This commit is contained in:
John Reiser 2017-03-31 13:24:36 -07:00
parent ce7f1292dc
commit 20bc848bd6
2 changed files with 57 additions and 0 deletions
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56
src/p_lx_elf.cpp
View File

@ -3626,6 +3626,62 @@ void PackLinuxElf64::pack4(OutputFile *fo, Filter &ft)
fo->write(buildid_data,shdrout.shdr[1].sh_size);
}
if (0!=xct_off) { // shared library
if (opt->o_unix.android_shlib && shdri) { // dlopen() checks Elf64_Shdr vs Elf64_Phdr
unsigned load0_hi = ~0;
Elf64_Phdr const *phdr = phdri;
for (unsigned j = 0; j < e_phnum; ++j, ++phdr) {
upx_uint64_t load0_lo = get_te64(&phdr->p_vaddr);
upx_uint64_t load0_sz = get_te64(&phdr->p_memsz);
if (PT_LOAD64==get_te32(&phdr->p_type)
&& (xct_off - load0_lo) < load0_sz) {
load0_hi = load0_lo + load0_sz;
break;
}
}
MemBuffer smap(e_shnum); smap.clear(); // smap[0] = 0; // SHN_UNDEF
MemBuffer snew(e_shnum * sizeof(*shdri));
Elf64_Shdr const *shdr = shdri;
unsigned k = 0;
for (unsigned j = 0; j < e_shnum; ++j, ++shdr) {
// Select some Elf64_Shdr by .sh_type
unsigned const type = get_te32(&shdr->sh_type);
unsigned const flags = get_te32(&shdr->sh_flags);
if (((Elf64_Shdr::SHT_STRTAB == type) && (Elf64_Shdr::SHF_ALLOC & flags))
|| ((Elf64_Shdr::SHT_DYNAMIC == type) && (Elf64_Shdr::SHF_ALLOC & flags))
|| ( ((1+ Elf64_Shdr::SHT_LOOS) <= type) // SHT_ANDROID_REL
&& ((2+ Elf64_Shdr::SHT_LOOS) >= type)) // SHT_ANDROID_RELA
) {
Elf64_Shdr *const sptr = k + (Elf64_Shdr *)(void *)snew;
upx_uint64_t va = get_te64(&shdr->sh_addr);
if (xct_off <= va && va <= load0_hi) {
throwCantPack("Android-required Shdr in packed region");
}
*sptr = *shdr; // copy old Elf64_Shdr
smap[j] = 1+ k++; // for later forwarding
}
}
if (k && fo) {
set_te64(&ehdri.e_shoff, fpad4(fo));
set_te16(&ehdri.e_shentsize, sizeof(*shdri));
set_te16(&ehdri.e_shnum, 1+ k);
Elf64_Shdr shdr_undef; memset(&shdr_undef, 0, sizeof(shdr_undef));
fo->write(&shdr_undef, sizeof(shdr_undef));
for (unsigned j = 0; j < k; ++j) { // forward .sh_link
Elf64_Shdr *const sptr = j + (Elf64_Shdr *)(void *)snew;
upx_uint64_t sh_offset = get_te64(&sptr->sh_offset);
if (xct_off <= sh_offset) {
set_te64(&sptr->sh_offset, so_slide + sh_offset);
}
sptr->sh_name = 0; // we flushed .e_shstrndx
set_te16(&sptr->sh_link, smap[sptr->sh_link]);
set_te16(&sptr->sh_info, smap[sptr->sh_info]); // ?
}
fo->write(snew, k * sizeof(*shdri));
}
}
}
// Cannot pre-round .p_memsz. If .p_filesz < .p_memsz, then kernel
// tries to make .bss, which requires PF_W.
// But strict SELinux (or PaX, grSecurity) disallows PF_W with PF_X.

1
src/p_lx_elf.h
View File

@ -274,6 +274,7 @@ protected:
Elf64_Shdr const *shdri; // from input file
upx_uint64_t e_phoff;
upx_uint64_t e_shoff;
unsigned so_slide;
unsigned char *note_body; // concatenated contents of PT_NOTEs, if any
unsigned note_size; // total size of PT_NOTEs
upx_uint64_t page_mask; // AND clears the offset-within-page