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-rw-r--r--include/libelfu/modelops.h3
-rw-r--r--include/options.h2
-rw-r--r--src/main.c10
-rw-r--r--src/model/insert.c111
-rw-r--r--src/options.c23
5 files changed, 141 insertions, 8 deletions
diff --git a/include/libelfu/modelops.h b/include/libelfu/modelops.h
index 9475eba..c89630f 100644
--- a/include/libelfu/modelops.h
+++ b/include/libelfu/modelops.h
@@ -17,4 +17,7 @@ int elfu_mCheck(ElfuElf *me);
ElfuElf* elfu_mFromElf(Elf *e);
void elfu_mToElf(ElfuElf *me, Elf *e);
+
+GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size);
+
#endif
diff --git a/include/options.h b/include/options.h
index f39f01e..ee9d612 100644
--- a/include/options.h
+++ b/include/options.h
@@ -8,6 +8,8 @@ typedef struct {
int printHeader;
int printSegments;
int printSections;
+ unsigned insertBeforeOffs;
+ unsigned insertBeforeSz;
} CLIOpts;
diff --git a/src/main.c b/src/main.c
index 991fe09..4467a2c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -67,12 +67,16 @@ int main(int argc, char **argv)
if (me) {
printf("Model successfully loaded.\n");
-
elfu_mCheck(me);
- printf("Model checked.\n");
+ printf("Input model checked.\n");
- elfu_mToElf(me, hOut.e);
+ if (opts.insertBeforeSz) {
+ elfu_mInsertBefore(me, opts.insertBeforeOffs, opts.insertBeforeSz);
+ }
+ elfu_mCheck(me);
+ printf("Output model checked.\n");
+ elfu_mToElf(me, hOut.e);
printf("Model converted to ELF, ready to be written.\n");
} else {
printf("Failed to load model.\n");
diff --git a/src/model/insert.c b/src/model/insert.c
new file mode 100644
index 0000000..2086c6e
--- /dev/null
+++ b/src/model/insert.c
@@ -0,0 +1,111 @@
+#include <assert.h>
+#include <sys/types.h>
+#include <gelf.h>
+#include <libelfu/libelfu.h>
+
+
+
+/*
+ * Insert space at a given position in the file by moving everything
+ * after it towards the end of the file, and everything before it
+ * towards lower memory regions where it is mapped.
+ *
+ * off must not be in the middle of any data structure, such as
+ * PHDRs, SHDRs, or sections. Behaviour is undefined if it is.
+ *
+ * PHDRs will be patched such that everything AFTER off is mapped to
+ * the same address in memory, and everything BEFORE it is shifted to
+ * lower addresses, making space for the new data in-between.
+ */
+GElf_Xword elfu_mInsertBefore(ElfuElf *me, GElf_Off off, GElf_Xword size)
+{
+ ElfuScn *ms;
+ ElfuPhdr *mp;
+
+ assert(me);
+
+ // TODO: Take p_align into account
+
+ /* Move SHDRs and PHDRs */
+ if (me->ehdr.e_shoff >= off) {
+ me->ehdr.e_shoff += size;
+ }
+
+ if (me->ehdr.e_phoff >= off) {
+ me->ehdr.e_phoff += size;
+ }
+
+ /* Patch PHDRs to include new data */
+ CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
+ GElf_Off end = mp->phdr.p_offset + mp->phdr.p_filesz;
+
+ if (mp->phdr.p_offset >= off) {
+ /* Insertion before PHDR's content, so it's just shifted */
+ mp->phdr.p_offset += size;
+ } else {
+ /* mp->phdr.p_offset < off */
+
+ if (off < end) {
+ /* Mark this as a modified area */
+
+ /* Insertion in the middle of PHDR, so let it span the new data */
+ mp->phdr.p_filesz += size;
+ mp->phdr.p_memsz += size;
+ mp->phdr.p_vaddr -= size;
+ mp->phdr.p_paddr -= size;
+ } else {
+ /* Insertion after PHDR's content, so it may need to be
+ remapped. This will happen in a second pass.
+ */
+ }
+ }
+ }
+
+ /* For each LOAD header, find clashing headers that need to be
+ remapped to lower memory areas.
+ */
+ CIRCLEQ_FOREACH(mp, &me->phdrList, elem) {
+ if (mp->phdr.p_type == PT_LOAD) {
+ ElfuPhdr *mp2;
+
+ CIRCLEQ_FOREACH(mp2, &me->phdrList, elem) {
+ if (mp2->phdr.p_type != PT_LOAD
+ && mp2->phdr.p_offset + mp2->phdr.p_filesz <= off) {
+ /* The PHDR ends in the file before the injection site */
+ GElf_Off vend1 = mp->phdr.p_vaddr + mp->phdr.p_memsz;
+ GElf_Off pend1 = mp->phdr.p_paddr + mp->phdr.p_memsz;
+ GElf_Off vend2 = mp2->phdr.p_vaddr + mp2->phdr.p_memsz;
+ GElf_Off pend2 = mp2->phdr.p_paddr + mp2->phdr.p_memsz;
+
+ /* If mp and mp2 now overlap in memory */
+ if ((mp2->phdr.p_vaddr < vend1 && vend2 > mp->phdr.p_vaddr)
+ || (mp2->phdr.p_paddr < pend1 && pend2 > mp->phdr.p_paddr)) {
+ /* Move mp2 down in memory, as mp has been resized.
+ Maintaining the relative offset between them is the best
+ guess at maintaining consistency.
+ */
+ mp2->phdr.p_vaddr -= size;
+ mp2->phdr.p_paddr -= size;
+ }
+ }
+ }
+ }
+ }
+
+ /* Move the sections themselves */
+ CIRCLEQ_FOREACH(ms, &me->scnList, elem) {
+ if (ms->shdr.sh_offset >= off) {
+ ms->shdr.sh_offset += size;
+ } else {
+ /* sh_offset < off */
+
+ /* If this was in a LOAD segment, it has been adjusted there
+ and this synchronises it.
+ If not, it doesn't matter anyway.
+ */
+ ms->shdr.sh_addr -= size;
+ }
+ }
+
+ return size;
+}
diff --git a/src/options.c b/src/options.c
index 1b258fe..55a91c5 100644
--- a/src/options.c
+++ b/src/options.c
@@ -11,13 +11,14 @@ static void printUsage(char *progname)
printf("Usage: %s [OPTIONS] <elf-file>\n", progname);
printf("\n"
"Options:\n"
- " -h, --help Print this help message\n"
- " -o, --output Where to write the modified ELF file to\n"
+ " -h, --help Print this help message\n"
+ " -o, --output Where to write the modified ELF file to\n"
"\n"
- " --print-header Print ELF header\n"
- " --print-segments Print program headers\n"
- " --print-sections Print sections\n"
+ " --print-header Print ELF header\n"
+ " --print-segments Print program headers\n"
+ " --print-sections Print sections\n"
"\n"
+ " --insert-before off,sz Insert spacing at given offset\n"
"\n");
}
@@ -28,6 +29,7 @@ void parseOptions(CLIOpts *opts, int argc, char **argv)
char *progname = argv[0];
int c;
int option_index = 0;
+ char *endptr;
static struct option long_options[] = {
{"help", 0, 0, 'h'},
@@ -35,6 +37,7 @@ void parseOptions(CLIOpts *opts, int argc, char **argv)
{"print-header", 0, 0, 10001},
{"print-segments", 0, 0, 10002},
{"print-sections", 0, 0, 10003},
+ {"insert-before", 1, 0, 10004},
{NULL, 0, NULL, 0}
};
@@ -56,6 +59,16 @@ void parseOptions(CLIOpts *opts, int argc, char **argv)
case 10003:
opts->printSections = 1;
break;
+ case 10004:
+ opts->insertBeforeOffs = strtoul(optarg, &endptr, 0);
+ if (endptr[0] != ',') {
+ goto USAGE;
+ }
+ opts->insertBeforeSz = strtoul(endptr + 1, &endptr, 0);
+ if (endptr[0] != '\0' || opts->insertBeforeSz == 0) {
+ goto USAGE;
+ }
+ break;
case '?':
default:
goto USAGE;
generated by cgit v1.2.3 (git 2.39.1) at 2024-10-16 14:26:04 +0000