diff options
Diffstat (limited to 'elf/dl-ifunc.c')
| -rw-r--r-- | elf/dl-ifunc.c | 192 |
1 files changed, 192 insertions, 0 deletions
diff --git a/elf/dl-ifunc.c b/elf/dl-ifunc.c new file mode 100644 index 0000000..96e4d07 --- /dev/null +++ b/elf/dl-ifunc.c @@ -0,0 +1,192 @@ +/* Delayed IFUNC processing. + Copyright (C) 2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#ifdef HAVE_IFUNC + +# include <dl-ifunc.h> +# include <errno.h> +# include <ldsodefs.h> +# include <sys/mman.h> +# include <unistd.h> + +/* Machine-specific definitions. */ +# include <dl-ifunc-reloc.h> + +/* This struct covers a whole page containing individual struct + dl_ifunc_relocation elements, which are allocated individually by + allocate_relocation below. */ +struct dl_ifunc_relocation_array +{ + struct dl_ifunc_relocation_array *next; + struct dl_ifunc_relocation data[]; +}; + +/* Global list of allocated arrays of struct dl_ifunc_relocation + elements. */ +static struct dl_ifunc_relocation_array *array_list; + +/* Position of the next allocation in the current array used as the + source of struct dl_ifunc_relocation allocations. */ +static struct dl_ifunc_relocation *next_alloc; +static unsigned int remaining_alloc; + +/* Allocate a new struct dl_ifunc_relocation_array object. Return the + first data object therein. Update array_list, next_alloc, + remaining_alloc. This function assumes taht remaining_alloc is + zero. */ +static struct dl_ifunc_relocation * +allocate_array (void) +{ + size_t page_size = GLRO(dl_pagesize); + void *ptr = __mmap (NULL, page_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (ptr == MAP_FAILED) + _dl_signal_error (ENOMEM, NULL, NULL, + "cannot allocate IFUNC resolver information"); + struct dl_ifunc_relocation_array *new_head = ptr; + new_head->next = array_list; + array_list = new_head; + next_alloc = &new_head->data[1]; + /* The function returns the first element of the new array. */ + remaining_alloc + = (page_size - offsetof (struct dl_ifunc_relocation_array, data)) + / sizeof (new_head->data[0]) - 1; + return &new_head->data[0]; +} + +/* Allocate whone struct dl_ifunc_relocation element from the active + array. Updated next_alloc, remaining_alloc, and potentially + array_list. */ +static struct dl_ifunc_relocation * +allocate_ifunc (void) +{ + if (remaining_alloc == 0) + return allocate_array (); + --remaining_alloc; + return next_alloc++; +} + +/* Deallocate the list of array allocations starting at + array_list. */ +static void +free_allocations (void) +{ + size_t page_size = GLRO(dl_pagesize); + struct dl_ifunc_relocation_array *p = array_list; + while (p != NULL) + { + struct dl_ifunc_relocation_array *next = p->next; + munmap (p, page_size); + p = next; + } + /* Restart from scratch if _dl_ifunc_record_reloc is called + again. */ + array_list = NULL; + next_alloc = NULL; + remaining_alloc = 0; +} + +/* Process all delayed IFUNC resolutions for IFUNC_MAP alone. */ +static void +apply_relocations (struct link_map *ifunc_map) +{ + if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS) + && ifunc_map->l_name != NULL) + _dl_debug_printf ("applying delayed IFUNC relocations against %s\n", + ifunc_map->l_name); + + struct dl_ifunc_relocation *p = ifunc_map->l_ifunc_relocations; + unsigned int count = 0; + while (p != NULL) + { + if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS) + && ifunc_map->l_name != NULL) + { + if (p->ifunc_sym == NULL) + _dl_debug_printf ("processing relative IFUNC relocation for %s\n", + ifunc_map->l_name); + else + { + const char *strtab = (const char *) D_PTR (ifunc_map, l_info[DT_STRTAB]); + _dl_debug_printf ("binding IFUNC symbol %s in %s against %s\n", + strtab + p->ifunc_sym->st_name, + p->reloc_map->l_name, ifunc_map->l_name); + } + } + _dl_ifunc_process_relocation (p, ifunc_map); + p = p->next; + ++count; + } + + if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS) + && ifunc_map->l_name != NULL) + _dl_debug_printf ("%u delayed IFUNC relocations performed against %s\n", + count, ifunc_map->l_name); + + /* No deallocation takes place here. All allocated objects are + freed in bulk by a later call to free_allocations. */ + ifunc_map->l_ifunc_relocations = NULL; +} + +void internal_function +_dl_ifunc_record_reloc (struct link_map *reloc_map, + const ElfW(Rela) *reloc, + ElfW(Addr) *reloc_addr, + struct link_map *ifunc_map, + const ElfW(Sym) *ifunc_sym) +{ + /* Add the delayed IFUNC relocation to the list for ifunc_map. */ + struct dl_ifunc_relocation *ifunc = allocate_ifunc (); + *ifunc = (struct dl_ifunc_relocation) + { + .reloc_map = reloc_map, + .reloc = reloc, + .reloc_addr = reloc_addr, + .ifunc_sym = ifunc_sym, + .next = ifunc_map->l_ifunc_relocations, + }; + ifunc_map->l_ifunc_relocations = ifunc; +} + +void internal_function +_dl_ifunc_apply_relocations (struct link_map *new) +{ + /* Traverse the search list in reverse order, in case an IFUNC + resolver calls into one its dependencies, and those dependency + needs IFUNC resolution as well. */ + struct link_map **r_list = new->l_searchlist.r_list; + for (unsigned int i = new->l_searchlist.r_nlist; i-- > 0; ) + { + struct link_map *l = r_list[i]; + if (l->l_ifunc_relocations != NULL) + apply_relocations (l); + } + free_allocations (); +} + +void internal_function +_dl_ifunc_clear_relocations (struct link_map *map) +{ + Lmid_t nsid = map->l_ns; + struct link_namespaces *ns = &GL(dl_ns)[nsid]; + for (struct link_map *l = ns->_ns_loaded; l != NULL; l = l->l_next) + l->l_ifunc_relocations = NULL; + free_allocations (); +} + +#endif /* HAVE_IFUNC */ |