diff options
Diffstat (limited to 'elf/dl-minimal.c')
| -rw-r--r-- | elf/dl-minimal.c | 97 |
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); |