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Code Issues Releases Wiki Activity

WIP: Elf64 shlib cleanup

Browse Source 
modified:   file.cpp
	modified:   file.h
	modified:   p_elf_enum.h
	modified:   p_lx_elf.cpp
	modified:   p_lx_elf.h
This commit is contained in:
John Reiser 2021-07-02 18:33:38 -07:00 committed by Markus F.X.J. Oberhumer
parent d5263a56ce
commit 85f0c5a445
5 changed files with 103 additions and 38 deletions
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5
src/file.cpp
View File

@ -405,6 +405,11 @@ void OutputFile::rewrite(const void *buf, int len)
bytes_written -= len; // restore
}
upx_off_t OutputFile::tell() const
{
return super::tell();
}
upx_off_t OutputFile::seek(upx_off_t off, int whence)
{
mem_size_assert(1, off >= 0 ? off : -off); // sanity check

1
src/file.h
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@ -143,6 +143,7 @@ public:
// FIXME - these won't work when using the '--stdout' option
virtual upx_off_t seek(upx_off_t off, int whence) override;
virtual upx_off_t tell() const;
virtual void rewrite(const void *buf, int len);
// util

1
src/p_elf_enum.h
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@ -86,6 +86,7 @@
#ifdef WANT_PHDR_ENUM
#undef WANT_PHDR_ENUM
enum { // p_type
PT_NULL = 0, /* Ingore: a "comment" */
PT_LOAD = 1, /* Loadable program segment */
PT_DYNAMIC = 2, /* Dynamic linking information */
PT_INTERP = 3, /* Name of program interpreter */

133
src/p_lx_elf.cpp
View File

@ -590,8 +590,8 @@ off_t PackLinuxElf64::pack3(OutputFile *fo, Filter &ft)
}
if (PT_LOAD64 == type) {
if ((xct_off - ioff) < len) { // Change length of compressed PT_LOAD.
set_te64(&phdr->p_filesz, sz_pack2 + lsize - ioff);
set_te64(&phdr->p_memsz, sz_pack2 + lsize - ioff);
set_te64(&phdr->p_filesz, sz_pack2 + lsize);
set_te64(&phdr->p_memsz, sz_pack2 + lsize);
if (user_init_off < xct_off) { // MIPS puts PT_DYNAMIC here
// Allow for DT_INIT in a new [stolen] slot
unsigned off2 = user_init_off - sizeof(word);
@ -4204,8 +4204,8 @@ int PackLinuxElf64::pack2(OutputFile *fo, Filter &ft)
// compress extents
unsigned hdr_u_len = sizeof(Elf64_Ehdr) + sz_phdrs;
total_in = (is_shlib ? 0 : xct_off);
total_out = (is_shlib ? sz_elf_hdrs : xct_off);
total_in = (is_shlib ? 0 : xct_off);
total_out = (is_shlib ? 0 : xct_off);
uip->ui_pass = 0;
ft.addvalue = 0;
@ -4241,6 +4241,23 @@ int PackLinuxElf64::pack2(OutputFile *fo, Filter &ft)
total_out += len;
}
if (len != x.size) {
linfo.l_checksum = 0;
linfo.l_magic = UPX_MAGIC_LE32;
set_le16(&linfo.l_lsize, lsize);
linfo.l_version = (unsigned char)ph.version;
linfo.l_format = (unsigned char)ph.format;
linfo_off = fo->tell();
fo->write(&linfo, sizeof(linfo));
total_out += sizeof(linfo);
overlay_offset = total_out;
p_info hbuf;
set_te32(&hbuf.p_progid, 0);
set_te32(&hbuf.p_filesize, file_size);
set_te32(&hbuf.p_blocksize, blocksize);
fo->write(&hbuf, sizeof(hbuf));
total_out += sizeof(p_info);
x.offset = 0;
x.size = sz_elf_hdrs;
packExtent(x, nullptr, fo, 0, 0, true);
@ -4253,12 +4270,25 @@ int PackLinuxElf64::pack2(OutputFile *fo, Filter &ft)
}
else {
if (!(Elf64_Phdr::PF_W & get_te64(&phdri[k].p_flags))) {
// Read-only PT_LOAD, assume not written by relocationa.
// Also assume not the source for R_*_COPY relocation,
// therefore compress it.
packExtent(x, &ft, fo, 0, 0, true);
// De-compressing will re-create it, but otherwise ignore it.
Elf64_Phdr *phdro = (Elf64_Phdr *)(1+ (Elf64_Ehdr *)&lowmem[0]);
set_te32(&phdro[k].p_type, Elf64_Phdr::PT_NULL);
}
else {
// Read-write PT_LOAD.
// Might be relocated, so cannot be compressed.
// (Could compress if not relocated; complicates run-time.)
// Postpone writing until "slide", but account for its size.
total_in += x.size;
}
// else wait until slide
}
}
else if (hdr_u_len < (u64_t)x.size) {
else // main program, not shared library
if (hdr_u_len < (u64_t)x.size) {
if (0 == nx) { // 1st PT_LOAD64 must cover Ehdr at 0==p_offset
unsigned const delta = hdr_u_len;
if (ft.id < 0x40) {
@ -4420,7 +4450,7 @@ void PackLinuxElf32mipsel::defineSymbols(Filter const *ft)
void PackLinuxElf32::pack4(OutputFile *fo, Filter &ft)
{
overlay_offset = sz_elf_hdrs + sizeof(linfo);
overlay_offset = xct_off ? xct_off : (sz_elf_hdrs + sizeof(linfo));
if (opt->o_unix.preserve_build_id) {
// calc e_shoff here and write shdrout, then o_shstrtab
@ -4481,7 +4511,9 @@ void PackLinuxElf32::pack4(OutputFile *fo, Filter &ft)
void PackLinuxElf64::pack4(OutputFile *fo, Filter &ft)
{
overlay_offset = sz_elf_hdrs + sizeof(linfo);
if (!xct_off) {
overlay_offset = sz_elf_hdrs + sizeof(linfo);
}
if (opt->o_unix.preserve_build_id) {
// calc e_shoff here and write shdrout, then o_shstrtab
@ -4511,8 +4543,10 @@ void PackLinuxElf64::pack4(OutputFile *fo, Filter &ft)
fo->seek(0, SEEK_SET);
if (0!=xct_off) { // shared library
fo->rewrite(&lowmem[0], sizeof(ehdri) + e_phnum * sizeof(Elf64_Phdr));
fo->seek(sz_elf_hdrs, SEEK_SET);
fo->rewrite(&linfo, sizeof(linfo));
//fo->seek(xct_off, SEEK_SET); // FIXME
//fo->rewrite(&linfo, sizeof(linfo));
fo->seek(linfo_off, SEEK_SET);
fo->rewrite(&linfo, sizeof(linfo)); // duplicate?
}
else {
if (PT_NOTE64 == get_te64(&elfout.phdr[C_NOTE].p_type)) {
@ -4626,6 +4660,25 @@ PackLinuxElf64::unRela64(
fo->rewrite(rela0, relasz);
}
// File layout of compressed .so shared library:
// 1. new Elf headers: Ehdr, PT_LOAD (r-x), PT_LOAD (rw-, if any), non-PT_LOAD Phdrs
// 2. Space for (original - 2) PT_LOAD Phdr
// 3. Remaining original contents of file below xct_off
// xct_off: (&lowest eXecutable Shdr section)
// 4. l_info (12 bytes)
// overlay_offset:
// 5. p_info (12 bytes)
// 6. compressed original Elf headers
// 7. compressed remainder of PT_LOAD above xct_off
// 8. compressed read-only PT_LOAD above xct_off (if any)
// 9. uncompressed Read-Write PT_LOAD (slide down N pages)
// 10. int[6] tables for de-compressor
// DT_INIT:
// 11. de-compressing loader
// 12. compressed gaps between PT_LOADs (and EOF) above xct_off
// 13. 32-byte pack header
// 14. 4-byte overlay offset
void PackLinuxElf64::un_shlib_1(
OutputFile *const fo,
MemBuffer &o_elfhdrs,
@ -4707,46 +4760,50 @@ void PackLinuxElf64::un_shlib_1(
u_fi.readx((void *)o_elfhdrs,o_elfhdrs.getSize());
u_fi.close();
// New style: up to xct_off
// New style: not compressed, up to xct_off
if (ph.u_len < xct_off) {
if (fo) {
fo->write(&ibuf[ph.u_len], xct_off - ph.u_len);
}
}
// Tail of PT_LOAD beginning at xct_off
fi->readx(&hdr.b, sizeof(hdr.b));
fi->seek(-(off_t)sizeof(struct b_info), SEEK_CUR);
ph.c_len = get_te32(&hdr.b.sz_cpr);
ph.u_len = get_te32(&hdr.b.sz_unc);
unpackExtent(ph.u_len, fo, c_adler, u_adler, false, szb_info);
funpad4(fi);
unsigned const l_offset = fi->tell();
// Copy (slide) the remaining PT_LOAD; they are not compressed
// because relocation processing by rtld might alter their memory image
// Now handle compressed PT_LOADs
Elf64_Phdr const *i_phdr = phdri;
Elf64_Phdr const *o_phdr = (Elf64_Phdr const *)(1+ (Elf64_Ehdr const *)(void const *)o_elfhdrs);
int once = 0;
for (unsigned k = 0; k < e_phnum; ++k, ++i_phdr, ++o_phdr) {
unsigned type = get_te32(&i_phdr->p_type);
unsigned vaddr = get_te64(&i_phdr->p_vaddr);
unsigned offset = get_te64(&i_phdr->p_offset);
unsigned filesz = get_te64(&i_phdr->p_filesz);
if (xct_off <= vaddr) {
if (PT_LOAD64==type) {
fi->seek(offset, SEEK_SET);
fi->readx(ibuf, filesz);
total_in += filesz;
unsigned o_offset = get_te64(&o_phdr->p_offset);
fo->seek(o_offset, SEEK_SET);
fo->write(ibuf, filesz);
total_out = filesz + o_offset; // high-water mark
unsigned type = get_te32(&o_phdr->p_type); // output side avoids PT_NULL
unsigned flags = get_te32(&o_phdr->p_flags);
unsigned vaddr = get_te64(&o_phdr->p_vaddr);
unsigned filesz = get_te64(&o_phdr->p_filesz);
unsigned o_offset = get_te64(&o_phdr->p_offset);
unsigned i_offset = get_te64(&i_phdr->p_offset);
if (xct_off <= vaddr) { // beyond rtld control info
if (PT_LOAD64==type
&& xct_off < (filesz + vaddr)) {
if (!(Elf64_Phdr::PF_W & flags)) { // Read-only, so was compressed
fi->readx(&hdr.b, sizeof(hdr.b));
fi->seek(-(off_t)sizeof(struct b_info), SEEK_CUR);
ph.c_len = get_te32(&hdr.b.sz_cpr);
ph.u_len = get_te32(&hdr.b.sz_unc);
unpackExtent(ph.u_len, fo, c_adler, u_adler, false, szb_info);
}
else { // Writeable, so might be relocataed, so not compressed
if (!once++) {
funpad4(fi);
}
fi->seek(i_offset, SEEK_SET);
fi->readx(ibuf, filesz);
total_in += filesz;
fo->seek(o_offset, SEEK_SET);
fo->write(ibuf, filesz);
total_out = filesz + o_offset; // high-water mark
}
}
}
}
// loader offset
fi->seek(l_offset, SEEK_SET);
// position fi at loader offset
fi->seek(overlay_offset, SEEK_SET); // FIXME?
}
void PackLinuxElf64::un_DT_INIT(

1
src/p_lx_elf.h
View File

@ -91,6 +91,7 @@ protected:
upx_uint64_t jni_onload_va; // runtime &JNI_OnLoad
upx_uint64_t user_init_va;
unsigned user_init_off; // within file_image
unsigned linfo_off;
upx_uint16_t e_machine;
unsigned char ei_class;