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Linux i386 allow compression of position-independent main executables (gcc -pie).

Browse Source 
p_elf.h p_lx_elf.cpp p_lx_elf.h p_lx_exc.cpp
	stub/fold_elf86.asm stub/fold_elf86.h stub/l_lx_elf.c
	stub/l_lx_elf86.asm stub/l_lx_elf86.h stub/l_lx_elf86.lds
	stub/linux.hh

committer: jreiser <jreiser> 1126886896 +0000
This commit is contained in:
John Reiser
2005-09-16 16:08:16 +00:00
parent eb6c51426a
commit 3f7b642c7d
11 changed files with 761 additions and 515 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/stub/l_lx_elf.c
+41 -30
View File
@@ -83,7 +83,7 @@ xread(struct Extent *x, char *buf, size_t count)
#else //}{ save debugging time
#define ERR_LAB
static void
err_exit(int a)
err_exit(int a) __attribute__ ((__noreturn__));
{
(void)a; // debugging convenience
exit(127);
@@ -156,8 +156,8 @@ ERR_LAB
if (h.sz_cpr < h.sz_unc) { // Decompress block
nrv_uint out_len;
int const j = (*f_decompress)(xi->buf, h.sz_cpr, xo->buf, &out_len,
h.b_method);
int const j = (*f_decompress)((unsigned char *)xi->buf, h.sz_cpr,
(unsigned char *)xo->buf, &out_len, h.b_method );
if (j != 0 || out_len != (nrv_uint)h.sz_unc)
err_exit(7);
// Skip Ehdr+Phdrs: separate 1st block, not filtered
@@ -165,7 +165,7 @@ ERR_LAB
&& ((512 < out_len) // this block is longer than Ehdr+Phdrs
|| (xo->size==(unsigned)h.sz_unc) ) // block is last in Extent
) {
(*f_unf)(xo->buf, out_len, h.b_cto8, h.b_ftid);
(*f_unf)((unsigned char *)xo->buf, out_len, h.b_cto8, h.b_ftid);
}
xi->buf += h.sz_cpr;
xi->size -= h.sz_cpr;
@@ -179,9 +179,9 @@ ERR_LAB
}
// Create (or find) an escape hatch to use when munmapping ourselves the stub.
// Called by do_xmap to create it, and by assembler code to find it.
// Called by do_xmap to create it; remembered in AT_NULL.d_val
static void *
make_hatch(Elf32_Phdr const *const phdr)
make_hatch(Elf32_Phdr const *const phdr, unsigned const reloc)
{
unsigned *hatch = 0;
if (phdr->p_type==PT_LOAD && phdr->p_flags & PF_X) {
@@ -194,11 +194,11 @@ make_hatch(Elf32_Phdr const *const phdr)
// and the action is the same when either test succeeds.
// Try page fragmentation just beyond .text .
if ( ( (hatch = (void *)(phdr->p_memsz + phdr->p_vaddr)),
if ( ( (hatch = (void *)(phdr->p_memsz + phdr->p_vaddr + reloc)),
( phdr->p_memsz==phdr->p_filesz // don't pollute potential .bss
&& 4<=(~PAGE_MASK & -(int)hatch) ) ) // space left on page
// Try Elf32_Ehdr.e_ident[12..15] . warning: 'const' cast away
|| ( (hatch = (void *)(&((Elf32_Ehdr *)phdr->p_vaddr)->e_ident[12])),
|| ( (hatch = (void *)(&((Elf32_Ehdr *)phdr->p_vaddr + reloc)->e_ident[12])),
(phdr->p_offset==0) ) ) {
// Omitting 'const' saves repeated literal in gcc.
unsigned /*const*/ escape = 0xc36180cd; // "int $0x80; popa; ret"
@@ -274,7 +274,8 @@ xfind_pages(unsigned mflags, Elf32_Phdr const *phdr, int phnum,
lo -= ~PAGE_MASK & lo; // round down to page boundary
hi = PAGE_MASK & (hi - lo - PAGE_MASK -1); // page length
szlo = PAGE_MASK & (szlo - PAGE_MASK -1); // page length
addr = do_mmap((void *)lo, hi, PROT_READ|PROT_WRITE|PROT_EXEC, mflags, 0, 0);
addr = do_mmap((void *)lo, hi, PROT_READ|PROT_WRITE|PROT_EXEC,
mflags, 0, 0 );
*p_brk = hi + addr; // the logical value of brk(0)
munmap(szlo + addr, hi - szlo); // desirable if PT_LOAD non-contiguous
return (unsigned long)addr - lo;
@@ -282,13 +283,13 @@ xfind_pages(unsigned mflags, Elf32_Phdr const *phdr, int phnum,
static Elf32_Addr // entry address
do_xmap(int const fdi, Elf32_Ehdr const *const ehdr, struct Extent *const xi,
Elf32_auxv_t *const av)
Elf32_auxv_t *const av, unsigned *p_reloc)
{
Elf32_Phdr const *phdr = (Elf32_Phdr const *) (ehdr->e_phoff +
(char const *)ehdr);
char *v_brk;
unsigned long const reloc = xfind_pages(
((ET_DYN!=ehdr->e_type) ? MAP_FIXED : 0), phdr, ehdr->e_phnum, &v_brk);
unsigned const reloc = xfind_pages(
((ET_EXEC==ehdr->e_type) ? MAP_FIXED : 0), phdr, ehdr->e_phnum, &v_brk);
int j;
for (j=0; j < ehdr->e_phnum; ++phdr, ++j)
if (PT_PHDR==phdr->p_type) {
@@ -298,13 +299,11 @@ do_xmap(int const fdi, Elf32_Ehdr const *const ehdr, struct Extent *const xi,
unsigned const prot = PF_TO_PROT(phdr->p_flags);
struct Extent xo;
size_t mlen = xo.size = phdr->p_filesz;
char *addr = xo.buf = (char *)phdr->p_vaddr;
char *haddr = phdr->p_memsz + addr;
char *addr = xo.buf = (char *)(phdr->p_vaddr + reloc);
char *haddr = phdr->p_memsz + addr;
size_t frag = (int)addr &~ PAGE_MASK;
mlen += frag;
addr -= frag;
addr += reloc;
haddr += reloc;
// Decompressor can overrun the destination by 3 bytes.
if (addr != do_mmap(addr, mlen + (xi ? 3 : 0), PROT_READ | PROT_WRITE,
@@ -320,7 +319,7 @@ do_xmap(int const fdi, Elf32_Ehdr const *const ehdr, struct Extent *const xi,
frag = (-mlen) &~ PAGE_MASK; // distance to next page boundary
bzero(mlen+addr, frag); // fragment at hi end
if (xi) {
void *const hatch = make_hatch(phdr);
void *const hatch = make_hatch(phdr, reloc);
if (0!=hatch) {
/* always update AT_NULL, especially for compressed PT_INTERP */
auxv_up((Elf32_auxv_t *)(~1 & (int)av), AT_NULL, (unsigned)hatch);
@@ -355,6 +354,9 @@ ERR_LAB
do_brk(v_brk);
}
}
if (0!=p_reloc) {
*p_reloc = reloc;
}
return ehdr->e_entry + reloc;
}
@@ -369,23 +371,29 @@ void *upx_main(
Elf32_auxv_t *const av,
unsigned const sz_compressed,
f_expand *const f_decompress,
Elf32_Ehdr *const ehdr,
int junk, // %esp from 'pusha'
struct Extent xo,
struct Extent xi
struct Extent xi,
unsigned const volatile dynbase
) __asm__("upx_main");
void *upx_main(
Elf32_auxv_t *const av,
unsigned const sz_compressed,
f_expand *const f_decompress,
Elf32_Ehdr *const ehdr, // temp char[MAX_ELF_HDR+OVERHEAD]
int junk, // %esp from 'pusha'
struct Extent xo, // {sz_unc, ehdr} for ELF headers
struct Extent xi // {sz_cpr, &b_info} for ELF headers
struct Extent xi, // {sz_cpr, &b_info} for ELF headers
unsigned const volatile dynbase // value+result: compiler must not change
)
{
Elf32_Ehdr *const ehdr = (Elf32_Ehdr *)xo.buf; // temp char[MAX_ELF_HDR+OVERHEAD]
Elf32_Phdr const *phdr = (Elf32_Phdr const *)(1+ ehdr);
Elf32_Addr reloc;
Elf32_Addr entry;
(void)junk;
// sizeof(Ehdr+Phdrs), compressed; including b_info header
size_t const sz_pckhdrs = xi.size;
@@ -396,19 +404,22 @@ void *upx_main(
xi.buf -= sz_pckhdrs;
xi.size = sz_compressed;
// AT_PHDR.a_un.a_val is set again by do_xmap if PT_PHDR is present.
auxv_up(av, AT_PHDR , (unsigned)(1+(Elf32_Ehdr *)phdr->p_vaddr));
auxv_up(av, AT_PHENT , ehdr->e_phentsize);
auxv_up(av, AT_PHNUM , ehdr->e_phnum);
// Some kernels omit AT_PHNUM,AT_PHENT,AT_PHDR because this stub has no PT_INTERP.
// That is "too much" optimization. Linux 2.6.x seems to give all AT_*.
//auxv_up(av, AT_PAGESZ, PAGE_SIZE); /* ld-linux.so.2 does not need this */
auxv_up(av, AT_ENTRY , (unsigned)ehdr->e_entry);
entry = do_xmap((int)f_decompress, ehdr, &xi, av);
auxv_up(av, AT_PHNUM , ehdr->e_phnum);
auxv_up(av, AT_PHENT , ehdr->e_phentsize);
auxv_up(av, AT_PHDR , dynbase + (unsigned)(1+(Elf32_Ehdr *)phdr->p_vaddr));
// AT_PHDR.a_un.a_val is set again by do_xmap if PT_PHDR is present.
// This is necessary for ET_DYN if|when we override a prelink address.
entry = do_xmap((int)f_decompress, ehdr, &xi, av, &reloc);
auxv_up(av, AT_ENTRY , entry); // might not be necessary?
{ // Map PT_INTERP program interpreter
int j;
for (j=0; j < ehdr->e_phnum; ++phdr, ++j) if (PT_INTERP==phdr->p_type) {
char const *const iname = (char const *)phdr->p_vaddr;
int const fdi = open(iname, O_RDONLY, 0);
int const fdi = open(reloc + (char const *)phdr->p_vaddr, O_RDONLY, 0);
if (0 > fdi) {
err_exit(18);
}
@@ -416,7 +427,7 @@ void *upx_main(
ERR_LAB
err_exit(19);
}
entry = do_xmap(fdi, ehdr, 0, 0);
entry = do_xmap(fdi, ehdr, 0, 0, 0);
break;
}
}