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workaround linux bug which demands writeable PT_LOAD for .bss

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This commit is contained in:
John Reiser
2006-06-29 19:07:02 -07:00
parent 6135d61e3d
commit ec9d6c4fd2
6 changed files with 106 additions and 96 deletions
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src/p_lx_exc.cpp
+34 -27
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@@ -84,6 +84,27 @@ const int *PackLinuxI386::getFilters() const
return filters;
}
static void
set_stub_brk(Elf_LE32_Phdr *const phdr1, unsigned brka)
{
#define PAGE_MASK (~0ul<<12)
// linux-2.6.14 binfmt_elf.c: SIGKILL if (0==.p_memsz) on a page boundary
unsigned const brkb = brka | ((0==(~PAGE_MASK & brka)) ? 0x20 : 0);
phdr1->p_type = PT_LOAD; // be sure
phdr1->p_offset = ~PAGE_MASK & brkb;
phdr1->p_vaddr = brkb;
phdr1->p_paddr = brkb;
phdr1->p_filesz = 0;
phdr1->p_memsz = 0;
if (0==phdr1->p_flags) {
phdr1->p_flags = Elf32_Phdr::PF_R|Elf32_Phdr::PF_W;
}
if (0==phdr1->p_align) {
phdr1->p_align = 0x1000;
}
#undef PAGE_MASK
}
void
PackLinuxI386::generateElfHdr(
OutputFile *fo,
@@ -91,7 +112,6 @@ PackLinuxI386::generateElfHdr(
unsigned const brka
)
{
cprElfHdr1 *const h1 = (cprElfHdr1 *)&elfout;
cprElfHdr2 *const h2 = (cprElfHdr2 *)&elfout;
cprElfHdr3 *const h3 = (cprElfHdr3 *)&elfout;
memcpy(h3, proto, sizeof(*h3)); // reads beyond, but OK
@@ -111,32 +131,17 @@ PackLinuxI386::generateElfHdr(
// Info for OS kernel to set the brk()
if (brka) {
#define PAGE_MASK (~0ul<<12)
// linux-2.6.14 binfmt_elf.c: SIGKILL if (0==.p_memsz) on a page boundary
unsigned const brkb = brka | ((0==(~PAGE_MASK & brka)) ? 0x20 : 0);
h2->phdr[1].p_type = PT_LOAD; // be sure
h2->phdr[1].p_offset = ~PAGE_MASK & brkb;
h2->phdr[1].p_vaddr = brkb;
h2->phdr[1].p_paddr = brkb;
h2->phdr[1].p_filesz = 0;
h2->phdr[1].p_memsz = 0;
if (0==h2->phdr[1].p_flags) {
h2->phdr[1].p_flags = Elf32_Phdr::PF_R|Elf32_Phdr::PF_W;
}
if (0==h2->phdr[1].p_align) {
h2->phdr[1].p_align = 0x1000;
}
#undef PAGE_MASK
set_stub_brk(&h2->phdr[1], brka);
}
if (ph.format==UPX_F_LINUX_i386 ) {
assert(h1->ehdr.e_phnum==1);
memset(&h1->linfo, 0, sizeof(h1->linfo));
fo->write(h1, sizeof(*h1));
}
else if (ph.format==UPX_F_LINUX_SH_i386) {
assert(h2->ehdr.e_phnum==1);
h2->ehdr.e_phnum = 1;
if (ph.format==UPX_F_LINUX_i386
|| ph.format==UPX_F_LINUX_SH_i386 ) {
// SELinux, PAx, grSecurity demand no PF_W if PF_X.
// kernel-2.6.12-2.3.legacy_FC3 has a bug which demands
// a PT_LOAD with PF_W, else SIGSEGV when clearing page fragment
// on low page of ".bss", which is the high page of .text.
// So the minimum number of PT_LOAD is 2.
assert(h2->ehdr.e_phnum==2);
memset(&h2->linfo, 0, sizeof(h2->linfo));
fo->write(h2, sizeof(*h2));
}
@@ -166,9 +171,11 @@ PackLinuxI386::pack4(OutputFile *fo, Filter &ft)
(elfout.ehdr.e_phentsize * elfout.ehdr.e_phnum) +
sizeof(l_info) +
((elfout.ehdr.e_phnum==3) ? (unsigned) elfout.phdr[2].p_memsz : 0) ;
elfout.phdr[0].p_filesz = fo->getBytesWritten();
unsigned nw = fo->getBytesWritten();
elfout.phdr[0].p_filesz = nw;
nw = -(-elfout.phdr[0].p_align & -nw); // ALIGN_UP
super::pack4(fo, ft); // write PackHeader and overlay_offset
set_stub_brk(&elfout.phdr[1], nw + elfout.phdr[0].p_vaddr);
#if 0 // {
// /usr/bin/strip from RedHat 8.0 (binutils-2.13.90.0.2-2)