Separate library code, build .a/.so

[centaur.git] / src / libelfu / modelops / detour.c

diff --git a/src/libelfu/modelops/detour.c b/src/libelfu/modelops/detour.c
new file mode 100644 (file)
index 0000000..075d945
--- /dev/null
+++ b/src/libelfu/modelops/detour.c
@@ -0,0 +1,51 @@
+#include <libelfu/libelfu.h>
+#include <string.h>
+
+static void* subFindByAddr(ElfuElf *me, ElfuScn *ms, void *aux1, void *aux2)
+{
+  GElf_Addr a = *(GElf_Addr*)aux1;
+
+  if (OVERLAPPING(ms->shdr.sh_addr, ms->shdr.sh_size, a, 1)) {
+    return ms;
+  }
+
+  /* Continue */
+  return NULL;
+}
+
+
+void elfu_mDetour(ElfuElf *me, GElf_Addr from, GElf_Addr to)
+{
+  ElfuScn *ms;
+  GElf_Word scnoffset;
+  unsigned char detourcode[] = {0xe9, 0xfc, 0xff, 0xff, 0xff};
+
+  ms = elfu_mScnForall(me, subFindByAddr, &from, NULL);
+
+  if (!ms) {
+    ELFU_WARN("mDetour: Cannot find address %x in any section.\n",
+              (unsigned)from);
+    return;
+  }
+
+  if (ms->shdr.sh_type != SHT_PROGBITS) {
+    ELFU_WARN("mDetour: Cannot detour in non-PROGBITS section %s.\n",
+              elfu_mScnName(me, ms));
+    return;
+  }
+
+  scnoffset = from - ms->shdr.sh_addr;
+
+  if (ms->shdr.sh_size - scnoffset < 5) {
+    ELFU_WARN("mDetour: Not enough space to insert a detour.\n");
+    return;
+  }
+
+  ELFU_DEBUG("mDetour: Detouring at address %x in section %s to %x.\n",
+             (unsigned)from,
+             elfu_mScnName(me, ms),
+             (unsigned)to);
+
+  *(Elf32_Word*)(detourcode + 1) = to - from - 5;
+  memcpy((char*)ms->data.d_buf + scnoffset, detourcode, 5);
+}