diff options
Diffstat (limited to 'sysdeps/alpha/dl-machine.h')
| -rw-r--r-- | sysdeps/alpha/dl-machine.h | 146 |
1 files changed, 62 insertions, 84 deletions
diff --git a/sysdeps/alpha/dl-machine.h b/sysdeps/alpha/dl-machine.h index 173a4111f8..88c357ea07 100644 --- a/sysdeps/alpha/dl-machine.h +++ b/sysdeps/alpha/dl-machine.h @@ -33,6 +33,9 @@ where the dynamic linker should not map anything. */ #define ELF_MACHINE_USER_ADDRESS_MASK 0x120000000UL +/* Translate a processor specific dynamic tag to the index in l_info array. */ +#define DT_ALPHA(x) (DT_ALPHA_##x - DT_LOPROC + DT_NUM) + /* Return nonzero iff ELF header is compatible with the running host. */ static inline int elf_machine_matches_host (const Elf64_Ehdr *ehdr) @@ -55,105 +58,74 @@ elf_machine_dynamic (void) } /* Return the run-time load address of the shared object. */ + static inline Elf64_Addr elf_machine_load_address (void) { - /* NOTE: While it is generally unfriendly to put data in the text - segment, it is only slightly less so when the "data" is an - instruction. While we don't have to worry about GLD just yet, an - optimizing linker might decide that our "data" is an unreachable - instruction and throw it away -- with the right switches, DEC's - linker will do this. What ought to happen is we should add - something to GAS to allow us access to the new GPREL_HI32/LO32 - relocation types stolen from OSF/1 3.0. */ - /* This code relies on the fact that BRADDR relocations do not - appear in dynamic relocation tables. Not that that would be very - useful anyway -- br/bsr has a 4MB range and the shared libraries - are usually many many terabytes away. */ - - Elf64_Addr dot; - long int zero_disp; - - asm("br %0, 1f\n" - "0:\n\t" - "br $0, 2f\n" - "1:\n\t" - ".section\t.data\n" - "2:\n\t" - ".quad 0b\n\t" - ".previous" - : "=r"(dot)); - - zero_disp = *(int *) dot; - zero_disp = (zero_disp << 43) >> 41; - - return dot - *(Elf64_Addr *) (dot + 4 + zero_disp); + /* This relies on the compiler using gp-relative addresses for static symbols. */ + static void *dot = ˙ + return (void *)&dot - dot; } /* Set up the loaded object described by L so its unrelocated PLT entries will jump to the on-demand fixup code in dl-runtime.c. */ static inline int -elf_machine_runtime_setup (struct link_map *l, int lazy, int profile) +elf_machine_runtime_setup (struct link_map *map, int lazy, int profile) { - Elf64_Addr plt; - extern void _dl_runtime_resolve (void); - extern void _dl_runtime_profile (void); + extern char _dl_runtime_resolve_new[] attribute_hidden; + extern char _dl_runtime_profile_new[] attribute_hidden; + extern char _dl_runtime_resolve_old[] attribute_hidden; + extern char _dl_runtime_profile_old[] attribute_hidden; + + struct pltgot { + char *resolve; + struct link_map *link; + }; + + struct pltgot *pg; + long secureplt; + char *resolve; + + if (map->l_info[DT_JMPREL] == 0 || !lazy) + return lazy; + + /* Check to see if we're using the read-only plt form. */ + secureplt = map->l_info[DT_ALPHA(PLTRO)] != 0; + + /* If the binary uses the read-only secure plt format, PG points to + the .got.plt section, which is the right place for ld.so to place + its hooks. Otherwise, PG is currently pointing at the start of + the plt; the hooks go at offset 16. */ + pg = (struct pltgot *) D_PTR (map, l_info[DT_PLTGOT]); + pg += !secureplt; + + /* This function will be called to perform the relocation. They're + not declared as functions to convince the compiler to use gp + relative relocations for them. */ + if (secureplt) + resolve = _dl_runtime_resolve_new; + else + resolve = _dl_runtime_resolve_old; - if (l->l_info[DT_JMPREL] && lazy) + if (__builtin_expect (profile, 0)) { - /* The GOT entries for the functions in the PLT have not been - filled in yet. Their initial contents are directed to the - PLT which arranges for the dynamic linker to be called. */ - plt = D_PTR (l, l_info[DT_PLTGOT]); - - /* This function will be called to perform the relocation. */ - if (__builtin_expect (profile, 0)) - { - *(Elf64_Addr *)(plt + 16) = (Elf64_Addr) &_dl_runtime_profile; - - if (GLRO(dl_profile) != NULL - && _dl_name_match_p (GLRO(dl_profile), l)) - { - /* This is the object we are looking for. Say that we really - want profiling and the timers are started. */ - GL(dl_profile_map) = l; - } - } + if (secureplt) + resolve = _dl_runtime_profile_new; else - *(Elf64_Addr *)(plt + 16) = (Elf64_Addr) &_dl_runtime_resolve; - - /* Identify this shared object */ - *(Elf64_Addr *)(plt + 24) = (Elf64_Addr) l; + resolve = _dl_runtime_profile_old; - /* If the first instruction of the plt entry is not - "br $28, plt0", we have to reinitialize .plt for lazy relocation. */ - if (*(unsigned int *)(plt + 32) != 0xc39ffff7) + if (GLRO(dl_profile) && _dl_name_match_p (GLRO(dl_profile), map)) { - unsigned int val = 0xc39ffff7; - unsigned int *slot, *end; - const Elf64_Rela *rela = (const Elf64_Rela *) - D_PTR (l, l_info[DT_JMPREL]); - Elf64_Addr l_addr = l->l_addr; - - /* br t12,.+4; ldq t12,12(t12); nop; jmp t12,(t12),.+4 */ - *(unsigned long *)plt = 0xa77b000cc3600000; - *(unsigned long *)(plt + 8) = 0x6b7b000047ff041f; - slot = (unsigned int *)(plt + 32); - end = (unsigned int *)(plt + 32 - + l->l_info[DT_PLTRELSZ]->d_un.d_val / 2); - while (slot < end) - { - /* br at,.plt+0 */ - *slot = val; - *(Elf64_Addr *) rela->r_offset = (Elf64_Addr) slot - l_addr; - val -= 3; - slot += 3; - ++rela; - } + /* This is the object we are looking for. Say that we really + want profiling and the timers are started. */ + GL(dl_profile_map) = map; } } + pg->resolve = resolve; + pg->link = map; + return lazy; } @@ -280,7 +252,7 @@ $fixup_stack: \n\ /* Fix up the instructions of a PLT entry to invoke the function rather than the dynamic linker. */ static inline Elf64_Addr -elf_machine_fixup_plt (struct link_map *l, lookup_t t, +elf_machine_fixup_plt (struct link_map *map, lookup_t t, const Elf64_Rela *reloc, Elf64_Addr *got_addr, Elf64_Addr value) { @@ -291,10 +263,16 @@ elf_machine_fixup_plt (struct link_map *l, lookup_t t, /* Store the value we are going to load. */ *got_addr = value; + /* If this binary uses the read-only secure plt format, we're done. */ + if (map->l_info[DT_ALPHA(PLTRO)]) + return value; + + /* Otherwise we have to modify the plt entry in place to do the branch. */ + /* Recover the PLT entry address by calculating reloc's index into the .rela.plt, and finding that entry in the .plt. */ - rela_plt = (void *) D_PTR (l, l_info[DT_JMPREL]); - plte = (void *) (D_PTR (l, l_info[DT_PLTGOT]) + 32); + rela_plt = (const Elf64_Rela *) D_PTR (map, l_info[DT_JMPREL]); + plte = (Elf64_Word *) (D_PTR (map, l_info[DT_PLTGOT]) + 32); plte += 3 * (reloc - rela_plt); /* Find the displacement from the plt entry to the function. */ |