Revert "Remove text-relocation support for lp32"
This reverts commit cb00add1b382d1e3045876d7e1ccbee2fdce976b.
Bug: 20020312
Bug: 20013628
Change-Id: I8baa3d4b6c7fef50c9e2531257d5b96762099eb3
diff --git a/linker/linker.cpp b/linker/linker.cpp
index 49c10a7..ebf125e 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -2297,8 +2297,13 @@
break;
case DT_TEXTREL:
- DL_ERR("text relocations (DT_TEXTREL) found in the ELF file \"%s\"", name);
+#if defined(__LP64__)
+ DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", name);
return false;
+#else
+ has_text_relocations = true;
+ break;
+#endif
case DT_SYMBOLIC:
has_DT_SYMBOLIC = true;
@@ -2310,8 +2315,12 @@
case DT_FLAGS:
if (d->d_un.d_val & DF_TEXTREL) {
- DL_ERR("text relocations (DF_TEXTREL) found in the ELF file \"%s\"", name);
+#if defined(__LP64__)
+ DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", name);
return false;
+#else
+ has_text_relocations = true;
+#endif
}
if (d->d_un.d_val & DF_SYMBOLIC) {
has_DT_SYMBOLIC = true;
@@ -2420,6 +2429,20 @@
local_group_root_ = this;
}
+#if !defined(__LP64__)
+ if (has_text_relocations) {
+ // Make segments writable to allow text relocations to work properly. We will later call
+ // phdr_table_protect_segments() after all of them are applied and all constructors are run.
+ DL_WARN("%s has text relocations. This is wasting memory and prevents "
+ "security hardening. Please fix.", name);
+ if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
+ DL_ERR("can't unprotect loadable segments for \"%s\": %s",
+ name, strerror(errno));
+ return false;
+ }
+ }
+#endif
+
if (android_relocs_ != nullptr) {
// check signature
if (android_relocs_size_ > 3 &&
@@ -2490,6 +2513,17 @@
DEBUG("[ finished linking %s ]", name);
+#if !defined(__LP64__)
+ if (has_text_relocations) {
+ // All relocations are done, we can protect our segments back to read-only.
+ if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
+ DL_ERR("can't protect segments for \"%s\": %s",
+ name, strerror(errno));
+ return false;
+ }
+ }
+#endif
+
/* We can also turn on GNU RELRO protection */
if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
diff --git a/linker/linker.h b/linker/linker.h
index ed26917..bf3e7bf 100644
--- a/linker/linker.h
+++ b/linker/linker.h
@@ -226,8 +226,8 @@
// value to get the corresponding address in the process' address space.
ElfW(Addr) load_bias;
-#if defined(__arm__)
- bool unused4; // DO NOT USE, maintained for compatibility
+#if !defined(__LP64__)
+ bool has_text_relocations;
#endif
bool has_DT_SYMBOLIC;
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 66b28ae..2c4ca15 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -412,6 +412,70 @@
return true;
}
+/* Used internally. Used to set the protection bits of all loaded segments
+ * with optional extra flags (i.e. really PROT_WRITE). Used by
+ * phdr_table_protect_segments and phdr_table_unprotect_segments.
+ */
+static int _phdr_table_set_load_prot(const ElfW(Phdr)* phdr_table, size_t phdr_count,
+ ElfW(Addr) load_bias, int extra_prot_flags) {
+ const ElfW(Phdr)* phdr = phdr_table;
+ const ElfW(Phdr)* phdr_limit = phdr + phdr_count;
+
+ for (; phdr < phdr_limit; phdr++) {
+ if (phdr->p_type != PT_LOAD || (phdr->p_flags & PF_W) != 0) {
+ continue;
+ }
+
+ ElfW(Addr) seg_page_start = PAGE_START(phdr->p_vaddr) + load_bias;
+ ElfW(Addr) seg_page_end = PAGE_END(phdr->p_vaddr + phdr->p_memsz) + load_bias;
+
+ int ret = mprotect(reinterpret_cast<void*>(seg_page_start),
+ seg_page_end - seg_page_start,
+ PFLAGS_TO_PROT(phdr->p_flags) | extra_prot_flags);
+ if (ret < 0) {
+ return -1;
+ }
+ }
+ return 0;
+}
+
+/* Restore the original protection modes for all loadable segments.
+ * You should only call this after phdr_table_unprotect_segments and
+ * applying all relocations.
+ *
+ * Input:
+ * phdr_table -> program header table
+ * phdr_count -> number of entries in tables
+ * load_bias -> load bias
+ * Return:
+ * 0 on error, -1 on failure (error code in errno).
+ */
+int phdr_table_protect_segments(const ElfW(Phdr)* phdr_table,
+ size_t phdr_count, ElfW(Addr) load_bias) {
+ return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, 0);
+}
+
+/* Change the protection of all loaded segments in memory to writable.
+ * This is useful before performing relocations. Once completed, you
+ * will have to call phdr_table_protect_segments to restore the original
+ * protection flags on all segments.
+ *
+ * Note that some writable segments can also have their content turned
+ * to read-only by calling phdr_table_protect_gnu_relro. This is no
+ * performed here.
+ *
+ * Input:
+ * phdr_table -> program header table
+ * phdr_count -> number of entries in tables
+ * load_bias -> load bias
+ * Return:
+ * 0 on error, -1 on failure (error code in errno).
+ */
+int phdr_table_unprotect_segments(const ElfW(Phdr)* phdr_table,
+ size_t phdr_count, ElfW(Addr) load_bias) {
+ return _phdr_table_set_load_prot(phdr_table, phdr_count, load_bias, PROT_WRITE);
+}
+
/* Used internally by phdr_table_protect_gnu_relro and
* phdr_table_unprotect_gnu_relro.
*/
diff --git a/linker/linker_phdr.h b/linker/linker_phdr.h
index cc3296b..50f2117 100644
--- a/linker/linker_phdr.h
+++ b/linker/linker_phdr.h
@@ -84,6 +84,12 @@
size_t phdr_table_get_load_size(const ElfW(Phdr)* phdr_table, size_t phdr_count,
ElfW(Addr)* min_vaddr = nullptr, ElfW(Addr)* max_vaddr = nullptr);
+int phdr_table_protect_segments(const ElfW(Phdr)* phdr_table,
+ size_t phdr_count, ElfW(Addr) load_bias);
+
+int phdr_table_unprotect_segments(const ElfW(Phdr)* phdr_table, size_t phdr_count,
+ ElfW(Addr) load_bias);
+
int phdr_table_protect_gnu_relro(const ElfW(Phdr)* phdr_table, size_t phdr_count,
ElfW(Addr) load_bias);
