NixOS/patchelf
1
0
Fork 0
mirror of https://github.com/NixOS/patchelf.git synced 2025-10-20 13:03:57 +08:00
Code Issues Packages Projects Releases Wiki Activity

* Start of refactoring to support growing the RPATH.

Browse Source
This commit is contained in:
Eelco Dolstra
2005-09-30 18:10:19 +00:00
parent 1587dc98e2
commit ab3d0a012c
1 changed files with 208 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

237
src/patchelf.cc
View File

@@ -1,5 +1,7 @@
#include <string>
#include <vector>
#include <map>
#include <algorithm>
#include <stdlib.h>
#include <stdio.h>
@@ -18,13 +20,10 @@
using namespace std;
const unsigned int pageSize = 4096;
static string fileName;
static string newInterpreter;
static bool doShrinkRPath = false;
static bool printRPath = false;
static bool printInterpreter = false;
static off_t fileSize, maxSize;
static unsigned char * contents = 0;
@@ -37,6 +36,13 @@ static unsigned int firstPage;
static bool changed = false;
static bool rewriteHeaders = false;
typedef string SectionName;
typedef map<SectionName, string> ReplacedSections;
static ReplacedSections replacedSections;
static string sectionNames; /* content of the .shstrtab section */
static void error(string msg)
{
@@ -99,26 +105,26 @@ static unsigned int roundUp(unsigned int n, unsigned int m)
}
static void shiftFile(void)
static void shiftFile(unsigned int extraPages)
{
/* Move the entire contents of the file one page further. */
unsigned int oldSize = fileSize;
growFile(fileSize + 4096);
memmove(contents + 4096, contents, oldSize);
memset(contents + sizeof(Elf32_Ehdr), 0, 4096 - sizeof(Elf32_Ehdr));
growFile(fileSize + extraPages * pageSize);
memmove(contents + extraPages * pageSize, contents, oldSize);
memset(contents + sizeof(Elf32_Ehdr), 0, extraPages * pageSize - sizeof(Elf32_Ehdr));
/* Update the ELF header. */
hdr->e_shoff += 4096;
hdr->e_shoff += extraPages * pageSize;
/* Update the offsets in the section headers. */
int i;
for (i = 0; i < hdr->e_shnum; ++i) {
shdrs[i].sh_offset += 4096;
shdrs[i].sh_offset += extraPages * pageSize;
}
/* Update the offsets in the program headers. */
for (i = 0; i < hdr->e_phnum; ++i) {
phdrs[i].p_offset += 4096;
phdrs[i].p_offset += extraPages * pageSize;
}
/* Add a segment that maps the new program/section headers and
@@ -132,8 +138,9 @@ static void shiftFile(void)
Elf32_Phdr & phdr = phdrs[1];
phdr.p_type = PT_LOAD;
phdr.p_offset = 0;
firstPage = 0x08047000; /* !!! */
phdr.p_vaddr = phdr.p_paddr = firstPage;
phdr.p_filesz = phdr.p_memsz = 4096;
phdr.p_filesz = phdr.p_memsz = extraPages * pageSize;
phdr.p_flags = PF_R;
phdr.p_align = 4096;
@@ -143,7 +150,143 @@ static void shiftFile(void)
}
static void setInterpreter(void)
static void checkPointer(void * p, unsigned int size)
{
unsigned char * q = (unsigned char *) p;
assert(q >= contents && q + size <= contents + fileSize);
}
static string getSectionName(const Elf32_Shdr & shdr)
{
return string(sectionNames.c_str() + shdr.sh_name);
}
static Elf32_Shdr & findSection(const SectionName & sectionName)
{
for (unsigned int i = 1; i < hdr->e_shnum; ++i)
if (getSectionName(shdrs[i]) == sectionName) return shdrs[i];
error("cannot find section");
}
static string & replaceSection(const SectionName & sectionName,
unsigned int size)
{
ReplacedSections::iterator i = replacedSections.find(sectionName);
string s;
if (i != replacedSections.end()) {
s = string(i->second);
} else {
Elf32_Shdr & shdr = findSection(sectionName);
s = string((char *) contents + shdr.sh_offset, shdr.sh_size);
}
s.resize(size);
replacedSections[sectionName] = s;
return replacedSections[sectionName];
}
static void rewriteSections()
{
if (replacedSections.empty()) return;
for (ReplacedSections::iterator i = replacedSections.begin();
i != replacedSections.end(); ++i)
fprintf(stderr, "replacing section `%s' with size `%d', content `%s'\n",
i->first.c_str(), i->second.size(), i->second.c_str());
/* What is the index of the last replaced section? */
unsigned int lastReplaced = 0;
for (unsigned int i = 1; i < hdr->e_shnum; ++i) {
string sectionName = getSectionName(shdrs[i]);
if (replacedSections.find(sectionName) != replacedSections.end()) {
printf("using replaced section `%s'\n", sectionName.c_str());
lastReplaced = i;
}
}
assert(lastReplaced != 0);
fprintf(stderr, "last replaced is %d\n", lastReplaced);
/* Try to replace all section before that, as far as possible.
Stop when we reach an irreplacable section (such as one of type
SHT_PROGBITS). These cannot be moved in virtual address space
since that would invalidate absolute references to them. */
assert(lastReplaced + 1 < shdrs.size()); /* !!! I'm lazy. */
off_t startOffset = shdrs[lastReplaced + 1].sh_offset;
for (unsigned int i = 1; i <= lastReplaced; ++i) {
Elf32_Shdr & shdr(shdrs[i]);
string sectionName = getSectionName(shdr);
fprintf(stderr, "looking at section `%s'\n", sectionName.c_str());
if (replacedSections.find(sectionName) != replacedSections.end()) continue;
if (shdr.sh_type == SHT_PROGBITS && sectionName != ".interp") {
startOffset = shdr.sh_addr;
lastReplaced = i - 1;
break;
} else {
fprintf(stderr, "replacing section `%s' which is in the way\n", sectionName.c_str());
replaceSection(sectionName, shdr.sh_size);
}
}
fprintf(stderr, "first reserved offset is %d\n", startOffset);
/* Right now we assume that the section headers are somewhere near
the end, which appears to be the case most of the time.
Therefore its not accidentally overwritten by the replaced
sections. !!! Fix this. */
assert(hdr->e_shoff >= startOffset);
/* Compute the total space needed for the replaced sections, the
ELF header, and the program headers. */
off_t neededSpace = sizeof(Elf32_Ehdr) + phdrs.size() * sizeof(Elf32_Phdr);
for (ReplacedSections::iterator i = replacedSections.begin();
i != replacedSections.end(); ++i)
neededSpace += roundUp(i->second.size(), 4);
fprintf(stderr, "needed space is %d\n", neededSpace);
/* If we need more space at the start of the file, then grow the
file by the minimum number of pages and adjust internal
offsets. */
if (neededSpace > startOffset) {
/* We also need an additional program header, so adjust for that. */
if (neededSpace > startOffset) neededSpace += sizeof(Elf32_Phdr);
fprintf(stderr, "needed space is %d\n", neededSpace);
unsigned int neededPages = roundUp(neededSpace - startOffset, pageSize) / pageSize;
fprintf(stderr, "needed pages is %d\n", neededPages);
shiftFile(neededPages);
}
}
static void setSubstr(string & s, unsigned int pos, const string & t)
{
assert(pos + t.size() <= s.size());
copy(t.begin(), t.end(), s.begin() + pos);
}
static void setInterpreter(const string & newInterpreter)
{
string & section = replaceSection(".interp", newInterpreter.size() + 1);
setSubstr(section, 0, newInterpreter + '\0');
changed = true;
}
#if 0
static void setInterpreter()
{
/* Find the PT_INTERP segment and replace it by a new one that
contains the new interpreter name. */
@@ -183,7 +326,7 @@ static void concatToRPath(string & rpath, const string & path)
}
static void shrinkRPath(void)
static void shrinkRPath()
{
/* Shrink the RPATH. */
if (doShrinkRPath || printRPath) {
@@ -301,17 +444,11 @@ static void shrinkRPath(void)
}
}
}
#endif
static void patchElf(void)
static void parseElf()
{
if (!printInterpreter && !printRPath)
fprintf(stderr, "patching ELF file `%s'\n", fileName.c_str());
mode_t fileMode;
readFile(fileName, &fileMode);
/* Check the ELF header for basic validity. */
if (fileSize < sizeof(Elf32_Ehdr)) error("missing ELF header");
@@ -344,6 +481,52 @@ static void patchElf(void)
for (int i = 0; i < hdr->e_shnum; ++i)
shdrs.push_back(* ((Elf32_Shdr *) (contents + hdr->e_shoff) + i));
/* Get the section header string table section (".shstrtab"). Its
index in the section header table is given by e_shstrndx field
of the ELF header. */
unsigned int shstrtabIndex = hdr->e_shstrndx;
assert(shstrtabIndex < shdrs.size());
unsigned int shstrtabSize = shdrs[shstrtabIndex].sh_size;
char * shstrtab = (char * ) contents + shdrs[shstrtabIndex].sh_offset;
checkPointer(shstrtab, shstrtabSize);
assert(shstrtabSize > 0);
assert(shstrtab[shstrtabSize - 1] == 0);
sectionNames = string(shstrtab, shstrtabSize);
}
static string newInterpreter;
static bool doShrinkRPath = false;
static bool printRPath = false;
static bool printInterpreter = false;
static void patchElf()
{
if (!printInterpreter && !printRPath)
fprintf(stderr, "patching ELF file `%s'\n", fileName.c_str());
mode_t fileMode;
readFile(fileName, &fileMode);
parseElf();
/* Do what we're supposed to do. */
if (newInterpreter != "")
setInterpreter(newInterpreter);
rewriteSections();
if (changed)
writeFile(fileName, fileMode);
else
fprintf(stderr, "nothing changed in `%s'\n", fileName.c_str());
#if 0
/* Find the next free virtual address page so that we can add
segments without messing up other segments. */
int i;
@@ -381,11 +564,7 @@ static void patchElf(void)
if (freeOffset > 4096) error("ran out of space in page 0");
}
if (changed)
writeFile(fileName, fileMode);
else
fprintf(stderr, "nothing changed in `%s'\n", fileName.c_str());
#endif
}