1 files changed, 111 insertions, 0 deletions
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;
+}