diff options
Diffstat (limited to 'elf/dl-fptr.c')
| -rw-r--r-- | elf/dl-fptr.c | 323 |
1 files changed, 323 insertions, 0 deletions
diff --git a/elf/dl-fptr.c b/elf/dl-fptr.c new file mode 100644 index 0000000000..78beecfdcb --- /dev/null +++ b/elf/dl-fptr.c @@ -0,0 +1,323 @@ +/* Manage function descriptors. Generic version. + Copyright (C) 1999,2000,2001,2002,2003,2004 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <libintl.h> +#include <unistd.h> +#include <string.h> +#include <sys/param.h> +#include <sys/mman.h> +#include <link.h> +#include <ldsodefs.h> +#include <elf/dynamic-link.h> +#include <dl-fptr.h> +#include <atomic.h> + +#ifndef ELF_MACHINE_BOOT_FPTR_TABLE_LEN +/* ELF_MACHINE_BOOT_FPTR_TABLE_LEN should be greater than the number of + dynamic symbols in ld.so. */ +# define ELF_MACHINE_BOOT_FPTR_TABLE_LEN 256 +#endif + +#ifndef ELF_MACHINE_LOAD_ADDRESS +# error "ELF_MACHINE_LOAD_ADDRESS is not defined." +#endif + +#ifndef COMPARE_AND_SWAP +# define COMPARE_AND_SWAP(ptr, old, new) \ + (atomic_compare_and_exchange_bool_acq (ptr, new, old) == 0) +#endif + +ElfW(Addr) _dl_boot_fptr_table [ELF_MACHINE_BOOT_FPTR_TABLE_LEN]; + +static struct local + { + struct fdesc_table *root; + struct fdesc *free_list; + unsigned int npages; /* # of pages to allocate */ + /* the next to members MUST be consecutive! */ + struct fdesc_table boot_table; + struct fdesc boot_fdescs[1024]; + } +local = + { + .root = &local.boot_table, + .npages = 2, + .boot_table = + { + .len = sizeof (local.boot_fdescs) / sizeof (local.boot_fdescs[0]), + .first_unused = 0 + } + }; + +/* Create a new fdesc table and return a pointer to the first fdesc + entry. The fdesc lock must have been acquired already. */ + +static struct fdesc_table * +new_fdesc_table (struct local *l, size_t *size) +{ + size_t old_npages = l->npages; + size_t new_npages = old_npages + old_npages; + struct fdesc_table *new_table; + + /* If someone has just created a new table, we return NULL to tell + the caller to use the new table. */ + if (! COMPARE_AND_SWAP (&l->npages, old_npages, new_npages)) + return (struct fdesc_table *) NULL; + + *size = old_npages * GLRO(dl_pagesize); + new_table = __mmap (NULL, *size, + PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); + if (new_table == MAP_FAILED) + _dl_signal_error (errno, NULL, NULL, + N_("cannot map pages for fdesc table")); + + new_table->len + = (*size - sizeof (*new_table)) / sizeof (struct fdesc); + new_table->first_unused = 1; + return new_table; +} + + +static ElfW(Addr) +make_fdesc (ElfW(Addr) ip, ElfW(Addr) gp) +{ + struct fdesc *fdesc = NULL; + struct fdesc_table *root; + unsigned int old; + struct local *l; + + ELF_MACHINE_LOAD_ADDRESS (l, local); + + retry: + root = l->root; + while (1) + { + old = root->first_unused; + if (old >= root->len) + break; + else if (COMPARE_AND_SWAP (&root->first_unused, old, old + 1)) + { + fdesc = &root->fdesc[old]; + goto install; + } + } + + if (l->free_list) + { + /* Get it from free-list. */ + do + { + fdesc = l->free_list; + if (fdesc == NULL) + goto retry; + } + while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list, + (ElfW(Addr)) fdesc, fdesc->ip)); + } + else + { + /* Create a new fdesc table. */ + size_t size; + struct fdesc_table *new_table = new_fdesc_table (l, &size); + + if (new_table == NULL) + goto retry; + + new_table->next = root; + if (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->root, + (ElfW(Addr)) root, + (ElfW(Addr)) new_table)) + { + /* Someone has just installed a new table. Return NULL to + tell the caller to use the new table. */ + __munmap (new_table, size); + goto retry; + } + + /* Note that the first entry was reserved while allocating the + memory for the new page. */ + fdesc = &new_table->fdesc[0]; + } + + install: + fdesc->ip = ip; + fdesc->gp = gp; + + return (ElfW(Addr)) fdesc; +} + + +static inline ElfW(Addr) * __attribute__ ((always_inline)) +make_fptr_table (struct link_map *map) +{ + const ElfW(Sym) *symtab + = (const void *) D_PTR (map, l_info[DT_SYMTAB]); + const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]); + ElfW(Addr) *fptr_table; + size_t size; + size_t len; + + /* XXX Apparently the only way to find out the size of the dynamic + symbol section is to assume that the string table follows right + afterwards... */ + len = ((strtab - (char *) symtab) + / map->l_info[DT_SYMENT]->d_un.d_val); + size = ((len * sizeof (fptr_table[0]) + GLRO(dl_pagesize) - 1) + & -GLRO(dl_pagesize)); + /* XXX We don't support here in the moment systems without MAP_ANON. + There probably are none for IA-64. In case this is proven wrong + we will have to open /dev/null here and use the file descriptor + instead of the hard-coded -1. */ + fptr_table = __mmap (NULL, size, + PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, + -1, 0); + if (fptr_table == MAP_FAILED) + _dl_signal_error (errno, NULL, NULL, + N_("cannot map pages for fptr table")); + + if (COMPARE_AND_SWAP ((ElfW(Addr) *) &map->l_mach.fptr_table, + (ElfW(Addr)) NULL, (ElfW(Addr)) fptr_table)) + map->l_mach.fptr_table_len = len; + else + __munmap (fptr_table, len * sizeof (fptr_table[0])); + + return map->l_mach.fptr_table; +} + + +ElfW(Addr) +_dl_make_fptr (struct link_map *map, const ElfW(Sym) *sym, + ElfW(Addr) ip) +{ + ElfW(Addr) *ftab = map->l_mach.fptr_table; + const ElfW(Sym) *symtab; + Elf_Symndx symidx; + struct local *l; + + if (__builtin_expect (ftab == NULL, 0)) + ftab = make_fptr_table (map); + + symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]); + symidx = sym - symtab; + + if (symidx >= map->l_mach.fptr_table_len) + _dl_signal_error (0, NULL, NULL, + N_("internal error: symidx out of range of fptr table")); + + while (ftab[symidx] == 0) + { + /* GOT has already been relocated in elf_get_dynamic_info - + don't try to relocate it again. */ + ElfW(Addr) fdesc + = make_fdesc (ip, map->l_info[DT_PLTGOT]->d_un.d_ptr); + + if (__builtin_expect (COMPARE_AND_SWAP (&ftab[symidx], (ElfW(Addr)) NULL, + fdesc), 1)) + { + /* Noone has updated the entry and the new function + descriptor has been installed. */ +#if 0 + const char *strtab + = (const void *) D_PTR (map, l_info[DT_STRTAB]); + + ELF_MACHINE_LOAD_ADDRESS (l, local); + if (l->root != &l->boot_table + || l->boot_table.first_unused > 20) + _dl_debug_printf ("created fdesc symbol `%s' at %lx\n", + strtab + sym->st_name, ftab[symidx]); +#endif + break; + } + else + { + /* We created a duplicated function descriptor. We put it on + free-list. */ + struct fdesc *f = (struct fdesc *) fdesc; + + ELF_MACHINE_LOAD_ADDRESS (l, local); + + do + f->ip = (ElfW(Addr)) l->free_list; + while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &l->free_list, + f->ip, fdesc)); + } + } + + return ftab[symidx]; +} + + +void +_dl_unmap (struct link_map *map) +{ + ElfW(Addr) *ftab = map->l_mach.fptr_table; + struct fdesc *head = NULL, *tail = NULL; + size_t i; + + __munmap ((void *) map->l_map_start, + map->l_map_end - map->l_map_start); + + if (ftab == NULL) + return; + + /* String together the fdesc structures that are being freed. */ + for (i = 0; i < map->l_mach.fptr_table_len; ++i) + { + if (ftab[i]) + { + *(struct fdesc **) ftab[i] = head; + head = (struct fdesc *) ftab[i]; + if (tail == NULL) + tail = head; + } + } + + /* Prepend the new list to the free_list: */ + if (tail) + do + tail->ip = (ElfW(Addr)) local.free_list; + while (! COMPARE_AND_SWAP ((ElfW(Addr) *) &local.free_list, + tail->ip, (ElfW(Addr)) head)); + + __munmap (ftab, (map->l_mach.fptr_table_len + * sizeof (map->l_mach.fptr_table[0]))); + + map->l_mach.fptr_table = NULL; +} + + +ElfW(Addr) +_dl_lookup_address (const void *address) +{ + ElfW(Addr) addr = (ElfW(Addr)) address; + struct fdesc_table *t; + unsigned long int i; + + for (t = local.root; t != NULL; t = t->next) + { + i = (struct fdesc *) addr - &t->fdesc[0]; + if (i < t->first_unused && addr == (ElfW(Addr)) &t->fdesc[i]) + { + addr = t->fdesc[i].ip; + break; + } + } + + return addr; +} |