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-rw-r--r--elf/dl-minimal.c97
1 files changed, 84 insertions, 13 deletions
diff --git a/elf/dl-minimal.c b/elf/dl-minimal.c
index 42192f8..c79ce23 100644
--- a/elf/dl-minimal.c
+++ b/elf/dl-minimal.c
@@ -26,11 +26,87 @@
#include <sys/param.h>
#include <sys/types.h>
#include <ldsodefs.h>
+#include <dl-irel.h>
+#include <dl-hash.h>
+#include <dl-sym-post.h>
#include <_itoa.h>
#include <malloc/malloc-internal.h>
#include <assert.h>
+/* The rtld startup code calls __rtld_malloc_init_stubs after the
+ first self-relocation to adjust the pointers to the minimal
+ implementation below. Before the final relocation,
+ __rtld_malloc_init_real is called to replace the pointers with the
+ real implementation. */
+__typeof (calloc) *__rtld_calloc;
+__typeof (free) *__rtld_free;
+__typeof (malloc) *__rtld_malloc;
+__typeof (realloc) *__rtld_realloc;
+
+/* Defined below. */
+static __typeof (calloc) rtld_calloc attribute_relro;
+static __typeof (free) rtld_free attribute_relro;
+static __typeof (malloc) rtld_malloc attribute_relro;
+static __typeof (realloc) rtld_realloc attribute_relro;
+
+void
+__rtld_malloc_init_stubs (void)
+{
+ __rtld_calloc = &rtld_calloc;
+ __rtld_free = &rtld_free;
+ __rtld_malloc = &rtld_malloc;
+ __rtld_realloc = &rtld_realloc;
+}
+
+/* Lookup NAME at VERSION in the scope of MATCH. */
+static void *
+lookup_malloc_symbol (struct link_map *main_map, const char *name,
+ struct r_found_version *version)
+{
+
+ const ElfW(Sym) *ref = NULL;
+ lookup_t result = _dl_lookup_symbol_x (name, main_map, &ref,
+ main_map->l_scope,
+ version, 0, 0, NULL);
+
+ assert (ELFW(ST_TYPE) (ref->st_info) != STT_TLS);
+ void *value = DL_SYMBOL_ADDRESS (result, ref);
+
+ return _dl_sym_post (result, ref, value, 0, main_map);
+}
+
+void
+__rtld_malloc_init_real (struct link_map *main_map)
+{
+ /* We cannot use relocations and initializers for this because the
+ changes made by __rtld_malloc_init_stubs break REL-style
+ (non-RELA) relocations that depend on the previous pointer
+ contents. Also avoid direct relocation depedencies for the
+ malloc symbols so this function can be called before the final
+ rtld relocation (which enables RELRO, after which the pointer
+ variables cannot be written to). */
+
+ struct r_found_version version;
+ version.name = symbol_version_string (libc, GLIBC_2_0);
+ version.hidden = 0;
+ version.hash = _dl_elf_hash (version.name);
+ version.filename = NULL;
+
+ void *new_calloc = lookup_malloc_symbol (main_map, "calloc", &version);
+ void *new_free = lookup_malloc_symbol (main_map, "free", &version);
+ void *new_malloc = lookup_malloc_symbol (main_map, "malloc", &version);
+ void *new_realloc = lookup_malloc_symbol (main_map, "realloc", &version);
+
+ /* Update the pointers in one go, so that any internal allocations
+ performed by lookup_malloc_symbol see a consistent
+ implementation. */
+ __rtld_calloc = new_calloc;
+ __rtld_free = new_free;
+ __rtld_malloc = new_malloc;
+ __rtld_realloc = new_realloc;
+}
+
/* Minimal malloc allocator for used during initial link. After the
initial link, a full malloc implementation is interposed, either
the one in libc, or a different one supplied by the user through
@@ -38,14 +114,9 @@
static void *alloc_ptr, *alloc_end, *alloc_last_block;
-/* Declarations of global functions. */
-extern void weak_function free (void *ptr);
-extern void * weak_function realloc (void *ptr, size_t n);
-
-
/* Allocate an aligned memory block. */
-void * weak_function
-malloc (size_t n)
+static void *
+rtld_malloc (size_t n)
{
if (alloc_end == 0)
{
@@ -87,8 +158,8 @@ malloc (size_t n)
/* We use this function occasionally since the real implementation may
be optimized when it can assume the memory it returns already is
set to NUL. */
-void * weak_function
-calloc (size_t nmemb, size_t size)
+static void *
+rtld_calloc (size_t nmemb, size_t size)
{
/* New memory from the trivial malloc above is always already cleared.
(We make sure that's true in the rare occasion it might not be,
@@ -104,8 +175,8 @@ calloc (size_t nmemb, size_t size)
}
/* This will rarely be called. */
-void weak_function
-free (void *ptr)
+void
+rtld_free (void *ptr)
{
/* We can free only the last block allocated. */
if (ptr == alloc_last_block)
@@ -118,8 +189,8 @@ free (void *ptr)
}
/* This is only called with the most recent block returned by malloc. */
-void * weak_function
-realloc (void *ptr, size_t n)
+void *
+rtld_realloc (void *ptr, size_t n)
{
if (ptr == NULL)
return malloc (n);