diff options
| -rw-r--r-- | gdb/ChangeLog | 22 | ||||
| -rw-r--r-- | gdb/elfread.c | 379 | ||||
| -rw-r--r-- | gdb/infcall.c | 29 | ||||
| -rw-r--r-- | gdb/minsyms.c | 33 | ||||
| -rw-r--r-- | gdb/symtab.h | 18 |
5 files changed, 480 insertions, 1 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index fc4fdbe..0895286 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,5 +1,27 @@ 2011-03-28 Jan Kratochvil <jan.kratochvil@redhat.com> + STT_GNU_IFUNC reader implementation. + * elfread.c: Include gdbtypes.h, value.h and infcall.h. + (SYMBOL_GOT_PLT_SUFFIX, elf_rel_plt_read) + (elf_objfile_gnu_ifunc_cache_data, struct elf_gnu_ifunc_cache) + (elf_gnu_ifunc_cache_hash, elf_gnu_ifunc_cache_eq) + (elf_gnu_ifunc_record_cache, elf_gnu_ifunc_resolve_by_cache) + (elf_gnu_ifunc_resolve_by_got, elf_gnu_ifunc_resolve_name) + (elf_gnu_ifunc_resolve_addr): New. + (elf_symfile_read): Call elf_rel_plt_read. + (elf_gnu_ifunc_fns): New. + (_initialize_elfread): Initialize elf_objfile_gnu_ifunc_cache_data. + Install elf_gnu_ifunc_fns. + * infcall.c (find_function_return_type): New function. + (find_function_addr): Resolve TYPE_GNU_IFUNC functions, if possible. + * minsyms.c (stub_gnu_ifunc_resolve_addr) + (stub_gnu_ifunc_resolve_name): New functions. + (stub_gnu_ifunc_fns, gnu_ifunc_fns_p): New variables. + * symtab.h (struct gnu_ifunc_fns, gnu_ifunc_resolve_addr) + (gnu_ifunc_resolve_name, gnu_ifunc_fns_p): New. + +2011-03-28 Jan Kratochvil <jan.kratochvil@redhat.com> + Code cleanup for later STT_GNU_IFUNC support. * infcall.c (find_function_addr): Remove variable code, use explicit dereferences for it. Move VALUE_TYPE initialization later. diff --git a/gdb/elfread.c b/gdb/elfread.c index 200b82f..115251c 100644 --- a/gdb/elfread.c +++ b/gdb/elfread.c @@ -38,6 +38,9 @@ #include "demangle.h" #include "psympriv.h" #include "filenames.h" +#include "gdbtypes.h" +#include "value.h" +#include "infcall.h" extern void _initialize_elfread (void); @@ -58,6 +61,13 @@ struct elfinfo static void free_elfinfo (void *); +/* Minimal symbols located at the GOT entries for .plt - that is the real + pointer where the given entry will jump to. It gets updated by the real + function address during lazy ld.so resolving in the inferior. These + minimal symbols are indexed for <tab>-completion. */ + +#define SYMBOL_GOT_PLT_SUFFIX "@got.plt" + /* Locate the segments in ABFD. */ static struct symfile_segment_data * @@ -582,6 +592,362 @@ elf_symtab_read (struct objfile *objfile, int type, do_cleanups (back_to); } +/* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX) + for later look ups of which function to call when user requests + a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target + library defining `function' we cannot yet know while reading OBJFILE which + of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later + DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */ + +static void +elf_rel_plt_read (struct objfile *objfile, asymbol **dyn_symbol_table) +{ + bfd *obfd = objfile->obfd; + const struct elf_backend_data *bed = get_elf_backend_data (obfd); + asection *plt, *relplt, *got_plt; + unsigned u; + int plt_elf_idx; + bfd_size_type reloc_count, reloc; + char *string_buffer = NULL; + size_t string_buffer_size = 0; + struct cleanup *back_to; + struct gdbarch *gdbarch = objfile->gdbarch; + struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr; + size_t ptr_size = TYPE_LENGTH (ptr_type); + + if (objfile->separate_debug_objfile_backlink) + return; + + plt = bfd_get_section_by_name (obfd, ".plt"); + if (plt == NULL) + return; + plt_elf_idx = elf_section_data (plt)->this_idx; + + got_plt = bfd_get_section_by_name (obfd, ".got.plt"); + if (got_plt == NULL) + return; + + /* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */ + for (relplt = obfd->sections; relplt != NULL; relplt = relplt->next) + if (elf_section_data (relplt)->this_hdr.sh_info == plt_elf_idx + && (elf_section_data (relplt)->this_hdr.sh_type == SHT_REL + || elf_section_data (relplt)->this_hdr.sh_type == SHT_RELA)) + break; + if (relplt == NULL) + return; + + if (! bed->s->slurp_reloc_table (obfd, relplt, dyn_symbol_table, TRUE)) + return; + + back_to = make_cleanup (free_current_contents, &string_buffer); + + reloc_count = relplt->size / elf_section_data (relplt)->this_hdr.sh_entsize; + for (reloc = 0; reloc < reloc_count; reloc++) + { + const char *name, *name_got_plt; + struct minimal_symbol *msym; + CORE_ADDR address; + const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX); + size_t name_len; + + name = bfd_asymbol_name (*relplt->relocation[reloc].sym_ptr_ptr); + name_len = strlen (name); + address = relplt->relocation[reloc].address; + + /* Does the pointer reside in the .got.plt section? */ + if (!(bfd_get_section_vma (obfd, got_plt) <= address + && address < bfd_get_section_vma (obfd, got_plt) + + bfd_get_section_size (got_plt))) + continue; + + /* We cannot check if NAME is a reference to mst_text_gnu_ifunc as in + OBJFILE the symbol is undefined and the objfile having NAME defined + may not yet have been loaded. */ + + if (string_buffer_size < name_len + got_suffix_len) + { + string_buffer_size = 2 * (name_len + got_suffix_len); + string_buffer = xrealloc (string_buffer, string_buffer_size); + } + memcpy (string_buffer, name, name_len); + memcpy (&string_buffer[name_len], SYMBOL_GOT_PLT_SUFFIX, + got_suffix_len); + + msym = record_minimal_symbol (string_buffer, name_len + got_suffix_len, + 1, address, mst_slot_got_plt, got_plt, + objfile); + if (msym) + MSYMBOL_SIZE (msym) = ptr_size; + } + + do_cleanups (back_to); +} + +/* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */ + +static const struct objfile_data *elf_objfile_gnu_ifunc_cache_data; + +/* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */ + +struct elf_gnu_ifunc_cache +{ + /* This is always a function entry address, not a function descriptor. */ + CORE_ADDR addr; + + char name[1]; +}; + +/* htab_hash for elf_objfile_gnu_ifunc_cache_data. */ + +static hashval_t +elf_gnu_ifunc_cache_hash (const void *a_voidp) +{ + const struct elf_gnu_ifunc_cache *a = a_voidp; + + return htab_hash_string (a->name); +} + +/* htab_eq for elf_objfile_gnu_ifunc_cache_data. */ + +static int +elf_gnu_ifunc_cache_eq (const void *a_voidp, const void *b_voidp) +{ + const struct elf_gnu_ifunc_cache *a = a_voidp; + const struct elf_gnu_ifunc_cache *b = b_voidp; + + return strcmp (a->name, b->name) == 0; +} + +/* Record the target function address of a STT_GNU_IFUNC function NAME is the + function entry address ADDR. Return 1 if NAME and ADDR are considered as + valid and therefore they were successfully recorded, return 0 otherwise. + + Function does not expect a duplicate entry. Use + elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already + exists. */ + +static int +elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr) +{ + struct minimal_symbol *msym; + asection *sect; + struct objfile *objfile; + htab_t htab; + struct elf_gnu_ifunc_cache entry_local, *entry_p; + void **slot; + + msym = lookup_minimal_symbol_by_pc (addr); + if (msym == NULL) + return 0; + if (SYMBOL_VALUE_ADDRESS (msym) != addr) + return 0; + /* minimal symbols have always SYMBOL_OBJ_SECTION non-NULL. */ + sect = SYMBOL_OBJ_SECTION (msym)->the_bfd_section; + objfile = SYMBOL_OBJ_SECTION (msym)->objfile; + + /* If .plt jumps back to .plt the symbol is still deferred for later + resolution and it has no use for GDB. Besides ".text" this symbol can + reside also in ".opd" for ppc64 function descriptor. */ + if (strcmp (bfd_get_section_name (objfile->obfd, sect), ".plt") == 0) + return 0; + + htab = objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data); + if (htab == NULL) + { + htab = htab_create_alloc_ex (1, elf_gnu_ifunc_cache_hash, + elf_gnu_ifunc_cache_eq, + NULL, &objfile->objfile_obstack, + hashtab_obstack_allocate, + dummy_obstack_deallocate); + set_objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data, htab); + } + + entry_local.addr = addr; + obstack_grow (&objfile->objfile_obstack, &entry_local, + offsetof (struct elf_gnu_ifunc_cache, name)); + obstack_grow_str0 (&objfile->objfile_obstack, name); + entry_p = obstack_finish (&objfile->objfile_obstack); + + slot = htab_find_slot (htab, entry_p, INSERT); + if (*slot != NULL) + { + struct elf_gnu_ifunc_cache *entry_found_p = *slot; + struct gdbarch *gdbarch = objfile->gdbarch; + + if (entry_found_p->addr != addr) + { + /* This case indicates buggy inferior program, the resolved address + should never change. */ + + warning (_("gnu-indirect-function \"%s\" has changed its resolved " + "function_address from %s to %s"), + name, paddress (gdbarch, entry_found_p->addr), + paddress (gdbarch, addr)); + } + + /* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */ + } + *slot = entry_p; + + return 1; +} + +/* Try to find the target resolved function entry address of a STT_GNU_IFUNC + function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P + is not NULL) and the function returns 1. It returns 0 otherwise. + + Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this + function. */ + +static int +elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p) +{ + struct objfile *objfile; + + ALL_PSPACE_OBJFILES (current_program_space, objfile) + { + htab_t htab; + struct elf_gnu_ifunc_cache *entry_p; + void **slot; + + htab = objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data); + if (htab == NULL) + continue; + + entry_p = alloca (sizeof (*entry_p) + strlen (name)); + strcpy (entry_p->name, name); + + slot = htab_find_slot (htab, entry_p, NO_INSERT); + if (slot == NULL) + continue; + entry_p = *slot; + gdb_assert (entry_p != NULL); + + if (addr_p) + *addr_p = entry_p->addr; + return 1; + } + + return 0; +} + +/* Try to find the target resolved function entry address of a STT_GNU_IFUNC + function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P + is not NULL) and the function returns 1. It returns 0 otherwise. + + Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. + elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to + prevent cache entries duplicates. */ + +static int +elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p) +{ + char *name_got_plt; + struct objfile *objfile; + const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX); + + name_got_plt = alloca (strlen (name) + got_suffix_len + 1); + sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name); + + ALL_PSPACE_OBJFILES (current_program_space, objfile) + { + bfd *obfd = objfile->obfd; + struct gdbarch *gdbarch = objfile->gdbarch; + struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr; + size_t ptr_size = TYPE_LENGTH (ptr_type); + CORE_ADDR pointer_address, addr; + asection *plt; + gdb_byte *buf = alloca (ptr_size); + struct minimal_symbol *msym; + + msym = lookup_minimal_symbol (name_got_plt, NULL, objfile); + if (msym == NULL) + continue; + if (MSYMBOL_TYPE (msym) != mst_slot_got_plt) + continue; + pointer_address = SYMBOL_VALUE_ADDRESS (msym); + + plt = bfd_get_section_by_name (obfd, ".plt"); + if (plt == NULL) + continue; + + if (MSYMBOL_SIZE (msym) != ptr_size) + continue; + if (target_read_memory (pointer_address, buf, ptr_size) != 0) + continue; + addr = extract_typed_address (buf, ptr_type); + addr = gdbarch_convert_from_func_ptr_addr (gdbarch, addr, + ¤t_target); + + if (addr_p) + *addr_p = addr; + if (elf_gnu_ifunc_record_cache (name, addr)) + return 1; + } + + return 0; +} + +/* Try to find the target resolved function entry address of a STT_GNU_IFUNC + function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P + is not NULL) and the function returns 1. It returns 0 otherwise. + + Both the elf_objfile_gnu_ifunc_cache_data hash table and + SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */ + +static int +elf_gnu_ifunc_resolve_name (const char *name, CORE_ADDR *addr_p) +{ + if (elf_gnu_ifunc_resolve_by_cache (name, addr_p)) + return 1; + + if (elf_gnu_ifunc_resolve_by_got (name, addr_p)) + return 1; + + return 0; +} + +/* Call STT_GNU_IFUNC - a function returning addresss of a real function to + call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned + is the entry point of the resolved STT_GNU_IFUNC target function to call. + */ + +static CORE_ADDR +elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) +{ + char *name_at_pc; + CORE_ADDR start_at_pc, address; + struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func; + struct value *function, *address_val; + + /* Try first any non-intrusive methods without an inferior call. */ + + if (find_pc_partial_function (pc, &name_at_pc, &start_at_pc, NULL) + && start_at_pc == pc) + { + if (elf_gnu_ifunc_resolve_name (name_at_pc, &address)) + return address; + } + else + name_at_pc = NULL; + + function = allocate_value (func_func_type); + set_value_address (function, pc); + + /* STT_GNU_IFUNC resolver functions have no parameters. FUNCTION is the + function entry address. ADDRESS may be a function descriptor. */ + + address_val = call_function_by_hand (function, 0, NULL); + address = value_as_address (address_val); + address = gdbarch_convert_from_func_ptr_addr (gdbarch, address, + ¤t_target); + + if (name_at_pc) + elf_gnu_ifunc_record_cache (name_at_pc, address); + + return address; +} + struct build_id { size_t size; @@ -823,6 +1189,8 @@ elf_symfile_read (struct objfile *objfile, int symfile_flags) bfd_errmsg (bfd_get_error ())); elf_symtab_read (objfile, ST_DYNAMIC, dynsymcount, dyn_symbol_table, 0); + + elf_rel_plt_read (objfile, dyn_symbol_table); } /* Add synthetic symbols - for instance, names for any PLT entries. */ @@ -1128,8 +1496,19 @@ static const struct sym_fns elf_sym_fns_gdb_index = &dwarf2_gdb_index_functions }; +/* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */ + +static const struct gnu_ifunc_fns elf_gnu_ifunc_fns = +{ + elf_gnu_ifunc_resolve_addr, + elf_gnu_ifunc_resolve_name, +}; + void _initialize_elfread (void) { add_symtab_fns (&elf_sym_fns); + + elf_objfile_gnu_ifunc_cache_data = register_objfile_data (); + gnu_ifunc_fns_p = &elf_gnu_ifunc_fns; } diff --git a/gdb/infcall.c b/gdb/infcall.c index e07cf00..ca23704 100644 --- a/gdb/infcall.c +++ b/gdb/infcall.c @@ -228,6 +228,21 @@ value_arg_coerce (struct gdbarch *gdbarch, struct value *arg, return value_cast (type, arg); } +/* Return the return type of a function with its first instruction exactly at + the PC address. Return NULL otherwise. */ + +static struct type * +find_function_return_type (CORE_ADDR pc) +{ + struct symbol *sym = find_pc_function (pc); + + if (sym != NULL && BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) == pc + && SYMBOL_TYPE (sym) != NULL) + return TYPE_TARGET_TYPE (SYMBOL_TYPE (sym)); + + return NULL; +} + /* Determine a function's address and its return type from its value. Calls error() if the function is not valid for calling. */ @@ -257,7 +272,19 @@ find_function_addr (struct value *function, struct type **retval_type) } if (TYPE_CODE (ftype) == TYPE_CODE_FUNC || TYPE_CODE (ftype) == TYPE_CODE_METHOD) - value_type = TYPE_TARGET_TYPE (ftype); + { + value_type = TYPE_TARGET_TYPE (ftype); + + if (TYPE_GNU_IFUNC (ftype)) + { + funaddr = gnu_ifunc_resolve_addr (gdbarch, funaddr); + + /* Skip querying the function symbol if no RETVAL_TYPE has been + asked for. */ + if (retval_type) + value_type = find_function_return_type (funaddr); + } + } else if (TYPE_CODE (ftype) == TYPE_CODE_INT) { /* Handle the case of functions lacking debugging info. diff --git a/gdb/minsyms.c b/gdb/minsyms.c index 534a8b2..80f9497 100644 --- a/gdb/minsyms.c +++ b/gdb/minsyms.c @@ -708,6 +708,39 @@ in_gnu_ifunc_stub (CORE_ADDR pc) return msymbol && MSYMBOL_TYPE (msymbol) == mst_text_gnu_ifunc; } +/* See elf_gnu_ifunc_resolve_addr for its real implementation. */ + +static CORE_ADDR +stub_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) +{ + error (_("GDB cannot resolve STT_GNU_IFUNC symbol at address %s without " + "the ELF support compiled in."), + paddress (gdbarch, pc)); +} + +/* See elf_gnu_ifunc_resolve_name for its real implementation. */ + +static int +stub_gnu_ifunc_resolve_name (const char *function_name, + CORE_ADDR *function_address_p) +{ + error (_("GDB cannot resolve STT_GNU_IFUNC symbol \"%s\" without " + "the ELF support compiled in."), + function_name); +} + +/* See elf_gnu_ifunc_fns for its real implementation. */ + +static const struct gnu_ifunc_fns stub_gnu_ifunc_fns = +{ + stub_gnu_ifunc_resolve_addr, + stub_gnu_ifunc_resolve_name, +}; + +/* A placeholder for &elf_gnu_ifunc_fns. */ + +const struct gnu_ifunc_fns *gnu_ifunc_fns_p = &stub_gnu_ifunc_fns; + /* Find the minimal symbol named NAME, and return both the minsym struct and its objfile. This only checks the linkage name. Sets *OBJFILE_P and returns the minimal symbol, if it is found. If it diff --git a/gdb/symtab.h b/gdb/symtab.h index 0645515..bc48d3c 100644 --- a/gdb/symtab.h +++ b/gdb/symtab.h @@ -1044,6 +1044,24 @@ extern struct minimal_symbol *lookup_minimal_symbol_by_pc (CORE_ADDR); extern int in_gnu_ifunc_stub (CORE_ADDR pc); +/* Functions for resolving STT_GNU_IFUNC symbols which are implemented only + for ELF symbol files. */ + +struct gnu_ifunc_fns +{ + /* See elf_gnu_ifunc_resolve_addr for its real implementation. */ + CORE_ADDR (*gnu_ifunc_resolve_addr) (struct gdbarch *gdbarch, CORE_ADDR pc); + + /* See elf_gnu_ifunc_resolve_name for its real implementation. */ + int (*gnu_ifunc_resolve_name) (const char *function_name, + CORE_ADDR *function_address_p); +}; + +#define gnu_ifunc_resolve_addr gnu_ifunc_fns_p->gnu_ifunc_resolve_addr +#define gnu_ifunc_resolve_name gnu_ifunc_fns_p->gnu_ifunc_resolve_name + +extern const struct gnu_ifunc_fns *gnu_ifunc_fns_p; + extern struct minimal_symbol * lookup_minimal_symbol_and_objfile (const char *, struct objfile **); |