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Code Issues Releases Wiki Activity

Make ::forward_Shdrs more friendly to Android dlopen()

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https://github.com/upx/upx/issues/220
https://github.com/upx/upx/issues/609
This commit is contained in:
John Reiser 2023-06-22 10:16:25 -07:00 committed by Markus F.X.J. Oberhumer
parent 5d2c74008e
commit b4a793ed26
2 changed files with 102 additions and 71 deletions
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169
src/p_lx_elf.cpp
View File

@ -5536,7 +5536,26 @@ void PackLinuxElf32mipsel::defineSymbols(Filter const *ft)
#include "p_elf_enum.h" #include "p_elf_enum.h"
#undef WANT_SHDR_ENUM #undef WANT_SHDR_ENUM
void PackLinuxElf32::forward_Shdrs(OutputFile *fo) // ::forward_Shdrs adds info for the benefit of gdb and Android dlopen().
// De-compression (runtime and offline) ignores the added information
// because it uses the de-compressed Ehdr etc.
// All the added space is redundant; libbfd should take a hint:
// if no Shdrs, then use PT_DYNAMIC instead.
// (.ARM_attributes (ARM_ATTRIBUTES) is not redundant.)
//
// want_types_mask: SHT_PROGBITS is needed else gdb complains:
// /build/gdb-MVZsgD/gdb-10.1/gdb/symfile.c:878: internal-error: sect_index_text not initialized
// and Continuing is not reasonable.
// However, SHT_PROGBITS with compression gives:
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// warning: Loadable section ".text" outside of ELF segments
// warning: Loadable section ".plt" outside of ELF segments
// because compression gives smaller extents, with no reasonable _Shdr fields.
// At least gdb can continue.
void PackLinuxElf32::forward_Shdrs(OutputFile *fo, Elf32_Ehdr *const eho)
{ {
if (saved_opt_android_shlib) { // Forward select _Shdr if (saved_opt_android_shlib) { // Forward select _Shdr
// Keep _Shdr for rtld data (below xct_off). // Keep _Shdr for rtld data (below xct_off).
@ -5547,12 +5566,13 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
unsigned const want_types_mask = unsigned const want_types_mask =
1u<<SHT_SYMTAB 1u<<SHT_SYMTAB
| 1u<<SHT_RELA | 1u<<SHT_RELA
| 1u<<SHT_PROGBITS // see comment at PackLinuxElf64::forward_Shdrs | 1u<<SHT_PROGBITS // see comment above
| 1u<<SHT_HASH | 1u<<SHT_HASH
| 1u<<SHT_DYNAMIC | 1u<<SHT_DYNAMIC
| 1u<<SHT_NOTE | 1u<<SHT_NOTE
| 1u<<SHT_REL | 1u<<SHT_REL
| 1u<<SHT_DYNSYM | 1u<<SHT_DYNSYM
//| 1u<<SHT_STRTAB // covered by (j == e_shstrndx)
| 1u<<SHT_INIT_ARRAY | 1u<<SHT_INIT_ARRAY
| 1u<<SHT_FINI_ARRAY | 1u<<SHT_FINI_ARRAY
| 1u<<SHT_PREINIT_ARRAY | 1u<<SHT_PREINIT_ARRAY
@ -5560,7 +5580,6 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
| 1u<<(0x1f & SHT_GNU_verneed) | 1u<<(0x1f & SHT_GNU_verneed)
| 1u<<(0x1f & SHT_GNU_verdef) | 1u<<(0x1f & SHT_GNU_verdef)
| 1u<<(0x1f & SHT_GNU_HASH); | 1u<<(0x1f & SHT_GNU_HASH);
Elf32_Ehdr *eho = &elfout.ehdr;
MemBuffer mb_ask_for(e_shnum * sizeof(eho->e_shnum)); MemBuffer mb_ask_for(e_shnum * sizeof(eho->e_shnum));
memset(mb_ask_for, 0, mb_ask_for.getSize()); memset(mb_ask_for, 0, mb_ask_for.getSize());
unsigned short *const ask_for = (unsigned short *)mb_ask_for.getVoidPtr(); unsigned short *const ask_for = (unsigned short *)mb_ask_for.getVoidPtr();
@ -5574,15 +5593,19 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
++sh_in; ++sh_out; unsigned n_sh_out = 1; ++sh_in; ++sh_out; unsigned n_sh_out = 1;
for (unsigned j = 1; j < e_shnum; ++j, ++sh_in) { for (unsigned j = 1; j < e_shnum; ++j, ++sh_in) {
unsigned sh_offset = get_te32(&sh_in->sh_offset);
unsigned sh_flags = get_te32(&sh_in->sh_flags);
unsigned sh_info = get_te32(&sh_in->sh_info);
unsigned sh_type = get_te32(&sh_in->sh_type); unsigned sh_type = get_te32(&sh_in->sh_type);
unsigned sh_flags = get_te32(&sh_in->sh_flags);
unsigned sh_addr = get_te32(&sh_in->sh_addr);
unsigned sh_offset = get_te32(&sh_in->sh_offset);
unsigned sh_size = get_te32(&sh_in->sh_size);
unsigned sh_info = get_te32(&sh_in->sh_info);
if (ask_for[j]) { // Some previous _Shdr requested me if (ask_for[j]) { // Some previous _Shdr requested me
// Tell them my new index // Tell them my new index
set_te32(&sh_out0[ask_for[j]].sh_info, n_sh_out); set_te32(&sh_out0[ask_for[j]].sh_info, n_sh_out); // sh_info vs st_shndx
}
if (sh_info < e_shnum) { // wild sh_info abounds!
ask_for[sh_info] = j; // Enter my request, if any
} }
ask_for[sh_info] = j; // Enter my request, if any
if ( (sh_offset && sh_offset < xct_off) if ( (sh_offset && sh_offset < xct_off)
|| (Elf32_Shdr::SHF_WRITE & sh_flags) || (Elf32_Shdr::SHF_WRITE & sh_flags)
|| (j == e_shstrndx) || (j == e_shstrndx)
@ -5590,25 +5613,36 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
|| (want_types_mask & (1<<(0x1f & sh_type))) || (want_types_mask & (1<<(0x1f & sh_type)))
) { ) {
*sh_out = *sh_in; *sh_out = *sh_in;
if (sec_arm_attr == sh_in) { if (sh_offset > xct_off) { // default: so_slide down
set_te32(&sh_out->sh_offset, total_out); set_te32(&sh_out->sh_offset, so_slide + sh_offset);
fi->seek(get_te32(&sh_in->sh_offset), SEEK_SET);
unsigned len = get_te32(&sh_in->sh_size);
fi->read(ibuf, len);
fo->write(ibuf, len);
total_out += len;
} }
if (j == e_shstrndx) { if (sh_addr > xct_off) { // default: so_slide down
if (!(SHF_WRITE & sh_flags)) {
set_te32(&sh_out->sh_addr, so_slide + sh_addr);
}
// BEWARE: .p_vaddr does not slide
}
if (j == e_shstrndx) { // changes Elf32_Ehdr itself
set_te16(&eho->e_shstrndx, sh_out - (Elf32_Shdr *)mb_shdro.getVoidPtr()); set_te16(&eho->e_shstrndx, sh_out - (Elf32_Shdr *)mb_shdro.getVoidPtr());
set_te32(&sh_out->sh_offset, total_out);
fi->seek(get_te32(&sh_in->sh_offset), SEEK_SET);
unsigned len = get_te32(&sh_in->sh_size);
fi->read(ibuf, len);
fo->write(ibuf, len);
total_out += len;
} }
if (Elf32_Shdr::SHF_WRITE & sh_flags || SHT_NOTE == sh_type) { if (j == e_shstrndx
if (sh_offset > xct_off) { || sec_arm_attr == sh_in
|| (SHT_NOTE == sh_type && xct_off < sh_offset)
) { // append a copy
set_te32(&sh_out->sh_offset, total_out);
fi->seek((upx_off_t)sh_offset, SEEK_SET);
fi->read(ibuf, sh_size);
fo->write(ibuf, sh_size);
total_out += sh_size;
} else
if (SHT_PROGBITS == sh_type) {
if (sh_offset <= xct_off
&& 0 == strcmp(".text", shstrtab + get_te32(&sh_in->sh_name)) ) {
// .text was compressed (but perhaps omitting some leading
// portion, if less than 4 PT_LOAD)
set_te32(&sh_out->sh_size, so_slide + sh_size);
} else
if (0 == sh_in->sh_addr) { // .gnu_debuglink etc
set_te32(&sh_out->sh_offset, so_slide + sh_offset); set_te32(&sh_out->sh_offset, so_slide + sh_offset);
} }
} }
@ -5650,7 +5684,6 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
fo->write(&file_image[get_te32(&sec_arm_attr->sh_offset)], attr_len); fo->write(&file_image[get_te32(&sec_arm_attr->sh_offset)], attr_len);
total_out = fpad4(fo, total_out += attr_len); total_out = fpad4(fo, total_out += attr_len);
Elf32_Ehdr *eho = &elfout.ehdr;
set_te16(&eho->e_shnum, 3); set_te16(&eho->e_shnum, 3);
set_te16(&eho->e_shentsize, sizeof(Elf32_Shdr)); set_te16(&eho->e_shentsize, sizeof(Elf32_Shdr));
set_te32(&eho->e_shoff, total_out); set_te32(&eho->e_shoff, total_out);
@ -5664,7 +5697,7 @@ void PackLinuxElf32::forward_Shdrs(OutputFile *fo)
} }
} }
void PackLinuxElf64::forward_Shdrs(OutputFile *fo) void PackLinuxElf64::forward_Shdrs(OutputFile *fo, Elf64_Ehdr *const eho)
{ {
if (saved_opt_android_shlib) { // Forward select _Shdr if (saved_opt_android_shlib) { // Forward select _Shdr
// Keep _Shdr for rtld data (below xct_off). // Keep _Shdr for rtld data (below xct_off).
@ -5675,26 +5708,13 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
unsigned const want_types_mask = unsigned const want_types_mask =
1u<<SHT_SYMTAB 1u<<SHT_SYMTAB
| 1u<<SHT_RELA | 1u<<SHT_RELA
| 1u<<SHT_PROGBITS // see comment above
| 1u<<SHT_PROGBITS
// SHT_PROGBITS is needed else gdb complains:
// /build/gdb-MVZsgD/gdb-10.1/gdb/symfile.c:878: internal-error: sect_index_text not initialized
// and Continuing is not reasonable.
// However, SHT_PROGBITS with compression gives:
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// BFD: warning: ./libmain.so.upx has a section extending past end of file
// warning: Loadable section ".text" outside of ELF segments
// warning: Loadable section ".plt" outside of ELF segments
// because compression gives smaller extents, with no reasonable _Shdr fields.
// At least gdb can continue.
| 1u<<SHT_HASH | 1u<<SHT_HASH
| 1u<<SHT_DYNAMIC | 1u<<SHT_DYNAMIC
| 1u<<SHT_NOTE | 1u<<SHT_NOTE
| 1u<<SHT_REL | 1u<<SHT_REL
| 1u<<SHT_DYNSYM | 1u<<SHT_DYNSYM
| 1u<<SHT_STRTAB //| 1u<<SHT_STRTAB // covered by (j == e_shstrndx)
| 1u<<SHT_INIT_ARRAY | 1u<<SHT_INIT_ARRAY
| 1u<<SHT_FINI_ARRAY | 1u<<SHT_FINI_ARRAY
| 1u<<SHT_PREINIT_ARRAY | 1u<<SHT_PREINIT_ARRAY
@ -5702,7 +5722,6 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
| 1u<<(0x1f & SHT_GNU_verneed) | 1u<<(0x1f & SHT_GNU_verneed)
| 1u<<(0x1f & SHT_GNU_verdef) | 1u<<(0x1f & SHT_GNU_verdef)
| 1u<<(0x1f & SHT_GNU_HASH); | 1u<<(0x1f & SHT_GNU_HASH);
Elf64_Ehdr *eho = &elfout.ehdr;
MemBuffer mb_ask_for(e_shnum * sizeof(eho->e_shnum)); MemBuffer mb_ask_for(e_shnum * sizeof(eho->e_shnum));
memset(mb_ask_for, 0, mb_ask_for.getSize()); memset(mb_ask_for, 0, mb_ask_for.getSize());
unsigned short *const ask_for = (unsigned short *)mb_ask_for.getVoidPtr(); unsigned short *const ask_for = (unsigned short *)mb_ask_for.getVoidPtr();
@ -5716,10 +5735,12 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
++sh_in; ++sh_out; unsigned n_sh_out = 1; ++sh_in; ++sh_out; unsigned n_sh_out = 1;
for (unsigned j = 1; j < e_shnum; ++j, ++sh_in) { for (unsigned j = 1; j < e_shnum; ++j, ++sh_in) {
u64_t sh_offset = get_te64(&sh_in->sh_offset); unsigned sh_type = get_te32(&sh_in->sh_type);
u64_t sh_flags = get_te64(&sh_in->sh_flags); unsigned sh_info = get_te32(&sh_in->sh_info);
unsigned sh_info = get_te32(&sh_in->sh_info); u64_t sh_flags = get_te64(&sh_in->sh_flags);
unsigned sh_type = get_te32(&sh_in->sh_type); u64_t sh_addr = get_te64(&sh_in->sh_addr);
u64_t sh_offset = get_te64(&sh_in->sh_offset);
u64_t sh_size = get_te64(&sh_in->sh_size);
if (ask_for[j]) { // Some previous _Shdr requested me if (ask_for[j]) { // Some previous _Shdr requested me
// Tell them my new index // Tell them my new index
set_te32(&sh_out0[ask_for[j]].sh_info, n_sh_out); // sh_info vs st_shndx set_te32(&sh_out0[ask_for[j]].sh_info, n_sh_out); // sh_info vs st_shndx
@ -5734,25 +5755,36 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
|| (want_types_mask & (1<<(0x1f & sh_type))) || (want_types_mask & (1<<(0x1f & sh_type)))
) { ) {
*sh_out = *sh_in; *sh_out = *sh_in;
if (sec_arm_attr == sh_in) { if (sh_offset > xct_off) { // default: so_slide down
set_te64(&sh_out->sh_offset, total_out); set_te64(&sh_out->sh_offset, so_slide + sh_offset);
fi->seek(get_te64(&sh_in->sh_offset), SEEK_SET);
u64_t len = get_te64(&sh_in->sh_size);
fi->read(ibuf, len);
fo->write(ibuf, len);
total_out += len;
} }
if (j == e_shstrndx) { if (sh_addr > xct_off) { // default: so_slide down
if (!(SHF_WRITE & sh_flags)) {
set_te64(&sh_out->sh_addr, so_slide + sh_addr);
}
// BEWARE: .p_vaddr does not slide
}
if (j == e_shstrndx) { // changes Elf64_Ehdr itself
set_te16(&eho->e_shstrndx, sh_out - (Elf64_Shdr *)mb_shdro.getVoidPtr()); set_te16(&eho->e_shstrndx, sh_out - (Elf64_Shdr *)mb_shdro.getVoidPtr());
set_te64(&sh_out->sh_offset, total_out);
fi->seek(get_te64(&sh_in->sh_offset), SEEK_SET);
u64_t len = get_te64(&sh_in->sh_size);
fi->read(ibuf, len);
fo->write(ibuf, len);
total_out += len;
} }
if (Elf64_Shdr::SHF_WRITE & sh_flags || SHT_NOTE == sh_type) { if (j == e_shstrndx
if (sh_offset > xct_off) { || sec_arm_attr == sh_in
|| (SHT_NOTE == sh_type && xct_off < sh_offset)
) { // append a copy
set_te64(&sh_out->sh_offset, total_out);
fi->seek((upx_off_t)sh_offset, SEEK_SET);
fi->read(ibuf, sh_size);
fo->write(ibuf, sh_size);
total_out += sh_size;
} else
if (SHT_PROGBITS == sh_type) {
if (sh_offset <= xct_off
&& 0 == strcmp(".text", shstrtab + get_te32(&sh_in->sh_name)) ) {
// .text was compressed (but perhaps omitting some leading
// portion, if less than 4 PT_LOAD)
set_te64(&sh_out->sh_size, so_slide + sh_size);
} else
if (0 == sh_in->sh_addr) { // .gnu_debuglink etc
set_te64(&sh_out->sh_offset, so_slide + sh_offset); set_te64(&sh_out->sh_offset, so_slide + sh_offset);
} }
} }
@ -5767,7 +5799,7 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
fo->write(mb_shdro, len); fo->write(mb_shdro, len);
total_out += len; total_out += len;
fo->seek(0, SEEK_SET); fo->seek(0, SEEK_SET);
fo->write(eho, sizeof(*eho)); fo->rewrite(eho, sizeof(*eho));
fo->seek(0, SEEK_END); fo->seek(0, SEEK_END);
} }
else if (sec_arm_attr) { else if (sec_arm_attr) {
@ -5794,7 +5826,6 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
fo->write(&file_image[get_te64(&sec_arm_attr->sh_offset)], attr_len); fo->write(&file_image[get_te64(&sec_arm_attr->sh_offset)], attr_len);
total_out = fpad8(fo, total_out += attr_len); total_out = fpad8(fo, total_out += attr_len);
Elf64_Ehdr *eho = &elfout.ehdr;
set_te16(&eho->e_shnum, 3); set_te16(&eho->e_shnum, 3);
set_te16(&eho->e_shentsize, sizeof(Elf64_Shdr)); set_te16(&eho->e_shentsize, sizeof(Elf64_Shdr));
set_te64(&eho->e_shoff, total_out); set_te64(&eho->e_shoff, total_out);
@ -5803,7 +5834,7 @@ void PackLinuxElf64::forward_Shdrs(OutputFile *fo)
total_out += sizeof(shdr_aa); total_out += sizeof(shdr_aa);
fo->seek(0, SEEK_SET); fo->seek(0, SEEK_SET);
fo->write(eho, sizeof(*eho)); fo->rewrite(eho, sizeof(*eho));
fo->seek(0, SEEK_END); fo->seek(0, SEEK_END);
} }
} }
@ -5814,7 +5845,8 @@ void PackLinuxElf32::pack4(OutputFile *fo, Filter &ft)
overlay_offset = sz_elf_hdrs + sizeof(linfo); overlay_offset = sz_elf_hdrs + sizeof(linfo);
} }
forward_Shdrs(fo); Elf32_Ehdr *ehdro = (Elf32_Ehdr *)lowmem.getVoidPtr();
forward_Shdrs(fo, ehdro);
if (opt->o_unix.preserve_build_id) { if (opt->o_unix.preserve_build_id) {
// calc e_shoff here and write shdrout, then o_shstrtab // calc e_shoff here and write shdrout, then o_shstrtab
//NOTE: these are pushed last to ensure nothing is stepped on //NOTE: these are pushed last to ensure nothing is stepped on
@ -5855,7 +5887,6 @@ void PackLinuxElf32::pack4(OutputFile *fo, Filter &ft)
} }
if (!sec_arm_attr && !saved_opt_android_shlib) { if (!sec_arm_attr && !saved_opt_android_shlib) {
// Make it abunantly clear that there are no Elf32_Shdr in this shlib // Make it abunantly clear that there are no Elf32_Shdr in this shlib
Elf32_Ehdr *ehdro = (Elf32_Ehdr *)lowmem.getVoidPtr();
ehdro->e_shoff = 0; ehdro->e_shoff = 0;
set_te16(&ehdro->e_shentsize, sizeof(Elf32_Shdr)); // Android bug: cannot use 0 set_te16(&ehdro->e_shentsize, sizeof(Elf32_Shdr)); // Android bug: cannot use 0
ehdro->e_shnum = 0; ehdro->e_shnum = 0;
@ -5897,7 +5928,8 @@ void PackLinuxElf64::pack4(OutputFile *fo, Filter &ft)
overlay_offset = sz_elf_hdrs + sizeof(linfo); overlay_offset = sz_elf_hdrs + sizeof(linfo);
} }
forward_Shdrs(fo); Elf64_Ehdr *ehdro = (Elf64_Ehdr *)lowmem.getVoidPtr();
forward_Shdrs(fo, ehdro);
if (opt->o_unix.preserve_build_id) { if (opt->o_unix.preserve_build_id) {
// calc e_shoff here and write shdrout, then o_shstrtab // calc e_shoff here and write shdrout, then o_shstrtab
//NOTE: these are pushed last to ensure nothing is stepped on //NOTE: these are pushed last to ensure nothing is stepped on
@ -5938,7 +5970,6 @@ void PackLinuxElf64::pack4(OutputFile *fo, Filter &ft)
} }
if (!sec_arm_attr && !saved_opt_android_shlib) { if (!sec_arm_attr && !saved_opt_android_shlib) {
// Make it abunantly clear that there are no Elf64_Shdr in this shlib // Make it abunantly clear that there are no Elf64_Shdr in this shlib
Elf64_Ehdr *ehdro = (Elf64_Ehdr *)lowmem.getVoidPtr();
ehdro->e_shoff = 0; ehdro->e_shoff = 0;
set_te16(&ehdro->e_shentsize, sizeof(Elf64_Shdr)); // Android bug: cannot use 0 set_te16(&ehdro->e_shentsize, sizeof(Elf64_Shdr)); // Android bug: cannot use 0
ehdro->e_shnum = 0; ehdro->e_shnum = 0;

4
src/p_lx_elf.h
View File

@ -155,7 +155,7 @@ protected:
virtual int pack2(OutputFile *, Filter &) override; // append compressed data virtual int pack2(OutputFile *, Filter &) override; // append compressed data
virtual off_t pack3(OutputFile *, Filter &) override; // append loader virtual off_t pack3(OutputFile *, Filter &) override; // append loader
virtual void pack4(OutputFile *, Filter &) override; // append pack header virtual void pack4(OutputFile *, Filter &) override; // append pack header
virtual void forward_Shdrs(OutputFile *fo); virtual void forward_Shdrs(OutputFile *fo, Elf32_Ehdr *ehdro);
virtual void unpack(OutputFile *fo) override; virtual void unpack(OutputFile *fo) override;
virtual void un_asl_dynsym(unsigned orig_file_size, OutputFile *); virtual void un_asl_dynsym(unsigned orig_file_size, OutputFile *);
virtual void un_shlib_1( virtual void un_shlib_1(
@ -313,7 +313,7 @@ protected:
virtual int pack2(OutputFile *, Filter &) override; // append compressed data virtual int pack2(OutputFile *, Filter &) override; // append compressed data
virtual off_t pack3(OutputFile *, Filter &) override; // append loader virtual off_t pack3(OutputFile *, Filter &) override; // append loader
virtual void pack4(OutputFile *, Filter &) override; // append pack header virtual void pack4(OutputFile *, Filter &) override; // append pack header
virtual void forward_Shdrs(OutputFile *fo); virtual void forward_Shdrs(OutputFile *fo, Elf64_Ehdr *ehdro);
virtual void unpack(OutputFile *fo) override; virtual void unpack(OutputFile *fo) override;
virtual void un_asl_dynsym(unsigned orig_file_size, OutputFile *); virtual void un_asl_dynsym(unsigned orig_file_size, OutputFile *);
virtual void un_shlib_1( virtual void un_shlib_1(