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Diffstat (limited to 'gdb/solib-svr4.c')
| -rw-r--r-- | gdb/solib-svr4.c | 1356 |
1 files changed, 0 insertions, 1356 deletions
diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c deleted file mode 100644 index 3f98a1e..0000000 --- a/gdb/solib-svr4.c +++ /dev/null @@ -1,1356 +0,0 @@ -/* Handle SVR4 shared libraries for GDB, the GNU Debugger. - Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, - 2001 - Free Software Foundation, Inc. - - This file is part of GDB. - - This program is free software; you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation; either version 2 of the License, or - (at your option) any later version. - - This program 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 General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program; if not, write to the Free Software - Foundation, Inc., 59 Temple Place - Suite 330, - Boston, MA 02111-1307, USA. */ - -#include "defs.h" - -#include "elf/external.h" -#include "elf/common.h" -#include "elf/mips.h" - -#include "symtab.h" -#include "bfd.h" -#include "symfile.h" -#include "objfiles.h" -#include "gdbcore.h" -#include "target.h" -#include "inferior.h" - -#include "solist.h" -#include "solib-svr4.h" - -#ifndef SVR4_FETCH_LINK_MAP_OFFSETS -#define SVR4_FETCH_LINK_MAP_OFFSETS() svr4_fetch_link_map_offsets () -#endif - -static struct link_map_offsets *svr4_fetch_link_map_offsets (void); -static struct link_map_offsets *legacy_fetch_link_map_offsets (void); - -/* fetch_link_map_offsets_gdbarch_data is a handle used to obtain the - architecture specific link map offsets fetching function. */ - -static struct gdbarch_data *fetch_link_map_offsets_gdbarch_data; - -/* legacy_svr4_fetch_link_map_offsets_hook is a pointer to a function - which is used to fetch link map offsets. It will only be set - by solib-legacy.c, if at all. */ - -struct link_map_offsets *(*legacy_svr4_fetch_link_map_offsets_hook)(void) = 0; - -/* Link map info to include in an allocated so_list entry */ - -struct lm_info - { - /* Pointer to copy of link map from inferior. The type is char * - rather than void *, so that we may use byte offsets to find the - various fields without the need for a cast. */ - char *lm; - }; - -/* On SVR4 systems, a list of symbols in the dynamic linker where - GDB can try to place a breakpoint to monitor shared library - events. - - If none of these symbols are found, or other errors occur, then - SVR4 systems will fall back to using a symbol as the "startup - mapping complete" breakpoint address. */ - -static char *solib_break_names[] = -{ - "r_debug_state", - "_r_debug_state", - "_dl_debug_state", - "rtld_db_dlactivity", - "_rtld_debug_state", - NULL -}; - -#define BKPT_AT_SYMBOL 1 - -#if defined (BKPT_AT_SYMBOL) -static char *bkpt_names[] = -{ -#ifdef SOLIB_BKPT_NAME - SOLIB_BKPT_NAME, /* Prefer configured name if it exists. */ -#endif - "_start", - "__start", - "main", - NULL -}; -#endif - -static char *main_name_list[] = -{ - "main_$main", - NULL -}; - -/* Macro to extract an address from a solib structure. - When GDB is configured for some 32-bit targets (e.g. Solaris 2.7 - sparc), BFD is configured to handle 64-bit targets, so CORE_ADDR is - 64 bits. We have to extract only the significant bits of addresses - to get the right address when accessing the core file BFD. */ - -#define SOLIB_EXTRACT_ADDRESS(MEMBER) \ - extract_address (&(MEMBER), sizeof (MEMBER)) - -/* local data declarations */ - -/* link map access functions */ - -static CORE_ADDR -LM_ADDR (struct so_list *so) -{ - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - - return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lmo->l_addr_offset, - lmo->l_addr_size); -} - -static CORE_ADDR -LM_NEXT (struct so_list *so) -{ - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - - return extract_address (so->lm_info->lm + lmo->l_next_offset, lmo->l_next_size); -} - -static CORE_ADDR -LM_NAME (struct so_list *so) -{ - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - - return extract_address (so->lm_info->lm + lmo->l_name_offset, lmo->l_name_size); -} - -static int -IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so) -{ - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - - return extract_address (so->lm_info->lm + lmo->l_prev_offset, - lmo->l_prev_size) == 0; -} - -static CORE_ADDR debug_base; /* Base of dynamic linker structures */ -static CORE_ADDR breakpoint_addr; /* Address where end bkpt is set */ - -/* Local function prototypes */ - -static int match_main (char *); - -static CORE_ADDR bfd_lookup_symbol (bfd *, char *); - -/* - - LOCAL FUNCTION - - bfd_lookup_symbol -- lookup the value for a specific symbol - - SYNOPSIS - - CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname) - - DESCRIPTION - - An expensive way to lookup the value of a single symbol for - bfd's that are only temporary anyway. This is used by the - shared library support to find the address of the debugger - interface structures in the shared library. - - Note that 0 is specifically allowed as an error return (no - such symbol). - */ - -static CORE_ADDR -bfd_lookup_symbol (bfd *abfd, char *symname) -{ - long storage_needed; - asymbol *sym; - asymbol **symbol_table; - unsigned int number_of_symbols; - unsigned int i; - struct cleanup *back_to; - CORE_ADDR symaddr = 0; - - storage_needed = bfd_get_symtab_upper_bound (abfd); - - if (storage_needed > 0) - { - symbol_table = (asymbol **) xmalloc (storage_needed); - back_to = make_cleanup (xfree, (PTR) symbol_table); - number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table); - - for (i = 0; i < number_of_symbols; i++) - { - sym = *symbol_table++; - if (STREQ (sym->name, symname)) - { - /* Bfd symbols are section relative. */ - symaddr = sym->value + sym->section->vma; - break; - } - } - do_cleanups (back_to); - } - - if (symaddr) - return symaddr; - - /* On FreeBSD, the dynamic linker is stripped by default. So we'll - have to check the dynamic string table too. */ - - storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd); - - if (storage_needed > 0) - { - symbol_table = (asymbol **) xmalloc (storage_needed); - back_to = make_cleanup (xfree, (PTR) symbol_table); - number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table); - - for (i = 0; i < number_of_symbols; i++) - { - sym = *symbol_table++; - if (STREQ (sym->name, symname)) - { - /* Bfd symbols are section relative. */ - symaddr = sym->value + sym->section->vma; - break; - } - } - do_cleanups (back_to); - } - - return symaddr; -} - -#ifdef HANDLE_SVR4_EXEC_EMULATORS - -/* - Solaris BCP (the part of Solaris which allows it to run SunOS4 - a.out files) throws in another wrinkle. Solaris does not fill - in the usual a.out link map structures when running BCP programs, - the only way to get at them is via groping around in the dynamic - linker. - The dynamic linker and it's structures are located in the shared - C library, which gets run as the executable's "interpreter" by - the kernel. - - Note that we can assume nothing about the process state at the time - we need to find these structures. We may be stopped on the first - instruction of the interpreter (C shared library), the first - instruction of the executable itself, or somewhere else entirely - (if we attached to the process for example). - */ - -static char *debug_base_symbols[] = -{ - "r_debug", /* Solaris 2.3 */ - "_r_debug", /* Solaris 2.1, 2.2 */ - NULL -}; - -static int look_for_base (int, CORE_ADDR); - -/* - - LOCAL FUNCTION - - look_for_base -- examine file for each mapped address segment - - SYNOPSYS - - static int look_for_base (int fd, CORE_ADDR baseaddr) - - DESCRIPTION - - This function is passed to proc_iterate_over_mappings, which - causes it to get called once for each mapped address space, with - an open file descriptor for the file mapped to that space, and the - base address of that mapped space. - - Our job is to find the debug base symbol in the file that this - fd is open on, if it exists, and if so, initialize the dynamic - linker structure base address debug_base. - - Note that this is a computationally expensive proposition, since - we basically have to open a bfd on every call, so we specifically - avoid opening the exec file. - */ - -static int -look_for_base (int fd, CORE_ADDR baseaddr) -{ - bfd *interp_bfd; - CORE_ADDR address = 0; - char **symbolp; - - /* If the fd is -1, then there is no file that corresponds to this - mapped memory segment, so skip it. Also, if the fd corresponds - to the exec file, skip it as well. */ - - if (fd == -1 - || (exec_bfd != NULL - && fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd))) - { - return (0); - } - - /* Try to open whatever random file this fd corresponds to. Note that - we have no way currently to find the filename. Don't gripe about - any problems we might have, just fail. */ - - if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL) - { - return (0); - } - if (!bfd_check_format (interp_bfd, bfd_object)) - { - /* FIXME-leak: on failure, might not free all memory associated with - interp_bfd. */ - bfd_close (interp_bfd); - return (0); - } - - /* Now try to find our debug base symbol in this file, which we at - least know to be a valid ELF executable or shared library. */ - - for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++) - { - address = bfd_lookup_symbol (interp_bfd, *symbolp); - if (address != 0) - { - break; - } - } - if (address == 0) - { - /* FIXME-leak: on failure, might not free all memory associated with - interp_bfd. */ - bfd_close (interp_bfd); - return (0); - } - - /* Eureka! We found the symbol. But now we may need to relocate it - by the base address. If the symbol's value is less than the base - address of the shared library, then it hasn't yet been relocated - by the dynamic linker, and we have to do it ourself. FIXME: Note - that we make the assumption that the first segment that corresponds - to the shared library has the base address to which the library - was relocated. */ - - if (address < baseaddr) - { - address += baseaddr; - } - debug_base = address; - /* FIXME-leak: on failure, might not free all memory associated with - interp_bfd. */ - bfd_close (interp_bfd); - return (1); -} -#endif /* HANDLE_SVR4_EXEC_EMULATORS */ - -/* - - LOCAL FUNCTION - - elf_locate_base -- locate the base address of dynamic linker structs - for SVR4 elf targets. - - SYNOPSIS - - CORE_ADDR elf_locate_base (void) - - DESCRIPTION - - For SVR4 elf targets the address of the dynamic linker's runtime - structure is contained within the dynamic info section in the - executable file. The dynamic section is also mapped into the - inferior address space. Because the runtime loader fills in the - real address before starting the inferior, we have to read in the - dynamic info section from the inferior address space. - If there are any errors while trying to find the address, we - silently return 0, otherwise the found address is returned. - - */ - -static CORE_ADDR -elf_locate_base (void) -{ - sec_ptr dyninfo_sect; - int dyninfo_sect_size; - CORE_ADDR dyninfo_addr; - char *buf; - char *bufend; - int arch_size; - - /* Find the start address of the .dynamic section. */ - dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic"); - if (dyninfo_sect == NULL) - return 0; - dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect); - - /* Read in .dynamic section, silently ignore errors. */ - dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect); - buf = alloca (dyninfo_sect_size); - if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size)) - return 0; - - /* Find the DT_DEBUG entry in the the .dynamic section. - For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has - no DT_DEBUG entries. */ - - arch_size = bfd_get_arch_size (exec_bfd); - if (arch_size == -1) /* failure */ - return 0; - - if (arch_size == 32) - { /* 32-bit elf */ - for (bufend = buf + dyninfo_sect_size; - buf < bufend; - buf += sizeof (Elf32_External_Dyn)) - { - Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf; - long dyn_tag; - CORE_ADDR dyn_ptr; - - dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag); - if (dyn_tag == DT_NULL) - break; - else if (dyn_tag == DT_DEBUG) - { - dyn_ptr = bfd_h_get_32 (exec_bfd, - (bfd_byte *) x_dynp->d_un.d_ptr); - return dyn_ptr; - } - else if (dyn_tag == DT_MIPS_RLD_MAP) - { - char *pbuf; - - pbuf = alloca (TARGET_PTR_BIT / HOST_CHAR_BIT); - /* DT_MIPS_RLD_MAP contains a pointer to the address - of the dynamic link structure. */ - dyn_ptr = bfd_h_get_32 (exec_bfd, - (bfd_byte *) x_dynp->d_un.d_ptr); - if (target_read_memory (dyn_ptr, pbuf, sizeof (pbuf))) - return 0; - return extract_unsigned_integer (pbuf, sizeof (pbuf)); - } - } - } - else /* 64-bit elf */ - { - for (bufend = buf + dyninfo_sect_size; - buf < bufend; - buf += sizeof (Elf64_External_Dyn)) - { - Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf; - long dyn_tag; - CORE_ADDR dyn_ptr; - - dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag); - if (dyn_tag == DT_NULL) - break; - else if (dyn_tag == DT_DEBUG) - { - dyn_ptr = bfd_h_get_64 (exec_bfd, - (bfd_byte *) x_dynp->d_un.d_ptr); - return dyn_ptr; - } - } - } - - /* DT_DEBUG entry not found. */ - return 0; -} - -/* - - LOCAL FUNCTION - - locate_base -- locate the base address of dynamic linker structs - - SYNOPSIS - - CORE_ADDR locate_base (void) - - DESCRIPTION - - For both the SunOS and SVR4 shared library implementations, if the - inferior executable has been linked dynamically, there is a single - address somewhere in the inferior's data space which is the key to - locating all of the dynamic linker's runtime structures. This - address is the value of the debug base symbol. The job of this - function is to find and return that address, or to return 0 if there - is no such address (the executable is statically linked for example). - - For SunOS, the job is almost trivial, since the dynamic linker and - all of it's structures are statically linked to the executable at - link time. Thus the symbol for the address we are looking for has - already been added to the minimal symbol table for the executable's - objfile at the time the symbol file's symbols were read, and all we - have to do is look it up there. Note that we explicitly do NOT want - to find the copies in the shared library. - - The SVR4 version is a bit more complicated because the address - is contained somewhere in the dynamic info section. We have to go - to a lot more work to discover the address of the debug base symbol. - Because of this complexity, we cache the value we find and return that - value on subsequent invocations. Note there is no copy in the - executable symbol tables. - - */ - -static CORE_ADDR -locate_base (void) -{ - /* Check to see if we have a currently valid address, and if so, avoid - doing all this work again and just return the cached address. If - we have no cached address, try to locate it in the dynamic info - section for ELF executables. */ - - if (debug_base == 0) - { - if (exec_bfd != NULL - && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour) - debug_base = elf_locate_base (); -#ifdef HANDLE_SVR4_EXEC_EMULATORS - /* Try it the hard way for emulated executables. */ - else if (!ptid_equal (inferior_ptid, null_ptid) && target_has_execution) - proc_iterate_over_mappings (look_for_base); -#endif - } - return (debug_base); -} - -/* - - LOCAL FUNCTION - - first_link_map_member -- locate first member in dynamic linker's map - - SYNOPSIS - - static CORE_ADDR first_link_map_member (void) - - DESCRIPTION - - Find the first element in the inferior's dynamic link map, and - return its address in the inferior. This function doesn't copy the - link map entry itself into our address space; current_sos actually - does the reading. */ - -static CORE_ADDR -first_link_map_member (void) -{ - CORE_ADDR lm = 0; - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - char *r_map_buf = xmalloc (lmo->r_map_size); - struct cleanup *cleanups = make_cleanup (xfree, r_map_buf); - - read_memory (debug_base + lmo->r_map_offset, r_map_buf, lmo->r_map_size); - - lm = extract_address (r_map_buf, lmo->r_map_size); - - /* FIXME: Perhaps we should validate the info somehow, perhaps by - checking r_version for a known version number, or r_state for - RT_CONSISTENT. */ - - do_cleanups (cleanups); - - return (lm); -} - -/* - - LOCAL FUNCTION - - open_symbol_file_object - - SYNOPSIS - - void open_symbol_file_object (void *from_tty) - - DESCRIPTION - - If no open symbol file, attempt to locate and open the main symbol - file. On SVR4 systems, this is the first link map entry. If its - name is here, we can open it. Useful when attaching to a process - without first loading its symbol file. - - If FROM_TTYP dereferences to a non-zero integer, allow messages to - be printed. This parameter is a pointer rather than an int because - open_symbol_file_object() is called via catch_errors() and - catch_errors() requires a pointer argument. */ - -static int -open_symbol_file_object (void *from_ttyp) -{ - CORE_ADDR lm, l_name; - char *filename; - int errcode; - int from_tty = *(int *)from_ttyp; - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - char *l_name_buf = xmalloc (lmo->l_name_size); - struct cleanup *cleanups = make_cleanup (xfree, l_name_buf); - - if (symfile_objfile) - if (!query ("Attempt to reload symbols from process? ")) - return 0; - - if ((debug_base = locate_base ()) == 0) - return 0; /* failed somehow... */ - - /* First link map member should be the executable. */ - if ((lm = first_link_map_member ()) == 0) - return 0; /* failed somehow... */ - - /* Read address of name from target memory to GDB. */ - read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size); - - /* Convert the address to host format. */ - l_name = extract_address (l_name_buf, lmo->l_name_size); - - /* Free l_name_buf. */ - do_cleanups (cleanups); - - if (l_name == 0) - return 0; /* No filename. */ - - /* Now fetch the filename from target memory. */ - target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode); - - if (errcode) - { - warning ("failed to read exec filename from attached file: %s", - safe_strerror (errcode)); - return 0; - } - - make_cleanup (xfree, filename); - /* Have a pathname: read the symbol file. */ - symbol_file_add_main (filename, from_tty); - - return 1; -} - -/* LOCAL FUNCTION - - current_sos -- build a list of currently loaded shared objects - - SYNOPSIS - - struct so_list *current_sos () - - DESCRIPTION - - Build a list of `struct so_list' objects describing the shared - objects currently loaded in the inferior. This list does not - include an entry for the main executable file. - - Note that we only gather information directly available from the - inferior --- we don't examine any of the shared library files - themselves. The declaration of `struct so_list' says which fields - we provide values for. */ - -static struct so_list * -svr4_current_sos (void) -{ - CORE_ADDR lm; - struct so_list *head = 0; - struct so_list **link_ptr = &head; - - /* Make sure we've looked up the inferior's dynamic linker's base - structure. */ - if (! debug_base) - { - debug_base = locate_base (); - - /* If we can't find the dynamic linker's base structure, this - must not be a dynamically linked executable. Hmm. */ - if (! debug_base) - return 0; - } - - /* Walk the inferior's link map list, and build our list of - `struct so_list' nodes. */ - lm = first_link_map_member (); - while (lm) - { - struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS (); - struct so_list *new - = (struct so_list *) xmalloc (sizeof (struct so_list)); - struct cleanup *old_chain = make_cleanup (xfree, new); - - memset (new, 0, sizeof (*new)); - - new->lm_info = xmalloc (sizeof (struct lm_info)); - make_cleanup (xfree, new->lm_info); - - new->lm_info->lm = xmalloc (lmo->link_map_size); - make_cleanup (xfree, new->lm_info->lm); - memset (new->lm_info->lm, 0, lmo->link_map_size); - - read_memory (lm, new->lm_info->lm, lmo->link_map_size); - - lm = LM_NEXT (new); - - /* For SVR4 versions, the first entry in the link map is for the - inferior executable, so we must ignore it. For some versions of - SVR4, it has no name. For others (Solaris 2.3 for example), it - does have a name, so we can no longer use a missing name to - decide when to ignore it. */ - if (IGNORE_FIRST_LINK_MAP_ENTRY (new)) - free_so (new); - else - { - int errcode; - char *buffer; - - /* Extract this shared object's name. */ - target_read_string (LM_NAME (new), &buffer, - SO_NAME_MAX_PATH_SIZE - 1, &errcode); - if (errcode != 0) - { - warning ("current_sos: Can't read pathname for load map: %s\n", - safe_strerror (errcode)); - } - else - { - strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1); - new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0'; - xfree (buffer); - strcpy (new->so_original_name, new->so_name); - } - - /* If this entry has no name, or its name matches the name - for the main executable, don't include it in the list. */ - if (! new->so_name[0] - || match_main (new->so_name)) - free_so (new); - else - { - new->next = 0; - *link_ptr = new; - link_ptr = &new->next; - } - } - - discard_cleanups (old_chain); - } - - return head; -} - - -/* On some systems, the only way to recognize the link map entry for - the main executable file is by looking at its name. Return - non-zero iff SONAME matches one of the known main executable names. */ - -static int -match_main (char *soname) -{ - char **mainp; - - for (mainp = main_name_list; *mainp != NULL; mainp++) - { - if (strcmp (soname, *mainp) == 0) - return (1); - } - - return (0); -} - -/* Return 1 if PC lies in the dynamic symbol resolution code of the - SVR4 run time loader. */ -static CORE_ADDR interp_text_sect_low; -static CORE_ADDR interp_text_sect_high; -static CORE_ADDR interp_plt_sect_low; -static CORE_ADDR interp_plt_sect_high; - -static int -svr4_in_dynsym_resolve_code (CORE_ADDR pc) -{ - return ((pc >= interp_text_sect_low && pc < interp_text_sect_high) - || (pc >= interp_plt_sect_low && pc < interp_plt_sect_high) - || in_plt_section (pc, NULL)); -} - - -/* - - LOCAL FUNCTION - - enable_break -- arrange for dynamic linker to hit breakpoint - - SYNOPSIS - - int enable_break (void) - - DESCRIPTION - - Both the SunOS and the SVR4 dynamic linkers have, as part of their - debugger interface, support for arranging for the inferior to hit - a breakpoint after mapping in the shared libraries. This function - enables that breakpoint. - - For SunOS, there is a special flag location (in_debugger) which we - set to 1. When the dynamic linker sees this flag set, it will set - a breakpoint at a location known only to itself, after saving the - original contents of that place and the breakpoint address itself, - in it's own internal structures. When we resume the inferior, it - will eventually take a SIGTRAP when it runs into the breakpoint. - We handle this (in a different place) by restoring the contents of - the breakpointed location (which is only known after it stops), - chasing around to locate the shared libraries that have been - loaded, then resuming. - - For SVR4, the debugger interface structure contains a member (r_brk) - which is statically initialized at the time the shared library is - built, to the offset of a function (_r_debug_state) which is guaran- - teed to be called once before mapping in a library, and again when - the mapping is complete. At the time we are examining this member, - it contains only the unrelocated offset of the function, so we have - to do our own relocation. Later, when the dynamic linker actually - runs, it relocates r_brk to be the actual address of _r_debug_state(). - - The debugger interface structure also contains an enumeration which - is set to either RT_ADD or RT_DELETE prior to changing the mapping, - depending upon whether or not the library is being mapped or unmapped, - and then set to RT_CONSISTENT after the library is mapped/unmapped. - */ - -static int -enable_break (void) -{ - int success = 0; - -#ifdef BKPT_AT_SYMBOL - - struct minimal_symbol *msymbol; - char **bkpt_namep; - asection *interp_sect; - - /* First, remove all the solib event breakpoints. Their addresses - may have changed since the last time we ran the program. */ - remove_solib_event_breakpoints (); - - interp_text_sect_low = interp_text_sect_high = 0; - interp_plt_sect_low = interp_plt_sect_high = 0; - - /* Find the .interp section; if not found, warn the user and drop - into the old breakpoint at symbol code. */ - interp_sect = bfd_get_section_by_name (exec_bfd, ".interp"); - if (interp_sect) - { - unsigned int interp_sect_size; - char *buf; - CORE_ADDR load_addr = 0; - int load_addr_found = 0; - struct so_list *inferior_sos; - bfd *tmp_bfd = NULL; - int tmp_fd = -1; - char *tmp_pathname = NULL; - CORE_ADDR sym_addr = 0; - - /* Read the contents of the .interp section into a local buffer; - the contents specify the dynamic linker this program uses. */ - interp_sect_size = bfd_section_size (exec_bfd, interp_sect); - buf = alloca (interp_sect_size); - bfd_get_section_contents (exec_bfd, interp_sect, - buf, 0, interp_sect_size); - - /* Now we need to figure out where the dynamic linker was - loaded so that we can load its symbols and place a breakpoint - in the dynamic linker itself. - - This address is stored on the stack. However, I've been unable - to find any magic formula to find it for Solaris (appears to - be trivial on GNU/Linux). Therefore, we have to try an alternate - mechanism to find the dynamic linker's base address. */ - - tmp_fd = solib_open (buf, &tmp_pathname); - if (tmp_fd >= 0) - tmp_bfd = bfd_fdopenr (tmp_pathname, gnutarget, tmp_fd); - - if (tmp_bfd == NULL) - goto bkpt_at_symbol; - - /* Make sure the dynamic linker's really a useful object. */ - if (!bfd_check_format (tmp_bfd, bfd_object)) - { - warning ("Unable to grok dynamic linker %s as an object file", buf); - bfd_close (tmp_bfd); - goto bkpt_at_symbol; - } - - /* If the entry in _DYNAMIC for the dynamic linker has already - been filled in, we can read its base address from there. */ - inferior_sos = svr4_current_sos (); - if (inferior_sos) - { - /* Connected to a running target. Update our shared library table. */ - solib_add (NULL, 0, NULL, auto_solib_add); - } - while (inferior_sos) - { - if (strcmp (buf, inferior_sos->so_original_name) == 0) - { - load_addr_found = 1; - load_addr = LM_ADDR (inferior_sos); - break; - } - inferior_sos = inferior_sos->next; - } - - /* Otherwise we find the dynamic linker's base address by examining - the current pc (which should point at the entry point for the - dynamic linker) and subtracting the offset of the entry point. */ - if (!load_addr_found) - load_addr = read_pc () - tmp_bfd->start_address; - - /* Record the relocated start and end address of the dynamic linker - text and plt section for svr4_in_dynsym_resolve_code. */ - interp_sect = bfd_get_section_by_name (tmp_bfd, ".text"); - if (interp_sect) - { - interp_text_sect_low = - bfd_section_vma (tmp_bfd, interp_sect) + load_addr; - interp_text_sect_high = - interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect); - } - interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt"); - if (interp_sect) - { - interp_plt_sect_low = - bfd_section_vma (tmp_bfd, interp_sect) + load_addr; - interp_plt_sect_high = - interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect); - } - - /* Now try to set a breakpoint in the dynamic linker. */ - for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++) - { - sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep); - if (sym_addr != 0) - break; - } - - /* We're done with the temporary bfd. */ - bfd_close (tmp_bfd); - - if (sym_addr != 0) - { - create_solib_event_breakpoint (load_addr + sym_addr); - return 1; - } - - /* For whatever reason we couldn't set a breakpoint in the dynamic - linker. Warn and drop into the old code. */ - bkpt_at_symbol: - warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code."); - } - - /* Scan through the list of symbols, trying to look up the symbol and - set a breakpoint there. Terminate loop when we/if we succeed. */ - - breakpoint_addr = 0; - for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++) - { - msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile); - if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0)) - { - create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol)); - return 1; - } - } - - /* Nothing good happened. */ - success = 0; - -#endif /* BKPT_AT_SYMBOL */ - - return (success); -} - -/* - - LOCAL FUNCTION - - special_symbol_handling -- additional shared library symbol handling - - SYNOPSIS - - void special_symbol_handling () - - DESCRIPTION - - Once the symbols from a shared object have been loaded in the usual - way, we are called to do any system specific symbol handling that - is needed. - - For SunOS4, this consisted of grunging around in the dynamic - linkers structures to find symbol definitions for "common" symbols - and adding them to the minimal symbol table for the runtime common - objfile. - - However, for SVR4, there's nothing to do. - - */ - -static void -svr4_special_symbol_handling (void) -{ -} - -/* Relocate the main executable. This function should be called upon - stopping the inferior process at the entry point to the program. - The entry point from BFD is compared to the PC and if they are - different, the main executable is relocated by the proper amount. - - As written it will only attempt to relocate executables which - lack interpreter sections. It seems likely that only dynamic - linker executables will get relocated, though it should work - properly for a position-independent static executable as well. */ - -static void -svr4_relocate_main_executable (void) -{ - asection *interp_sect; - CORE_ADDR pc = read_pc (); - - /* Decide if the objfile needs to be relocated. As indicated above, - we will only be here when execution is stopped at the beginning - of the program. Relocation is necessary if the address at which - we are presently stopped differs from the start address stored in - the executable AND there's no interpreter section. The condition - regarding the interpreter section is very important because if - there *is* an interpreter section, execution will begin there - instead. When there is an interpreter section, the start address - is (presumably) used by the interpreter at some point to start - execution of the program. - - If there is an interpreter, it is normal for it to be set to an - arbitrary address at the outset. The job of finding it is - handled in enable_break(). - - So, to summarize, relocations are necessary when there is no - interpreter section and the start address obtained from the - executable is different from the address at which GDB is - currently stopped. - - [ The astute reader will note that we also test to make sure that - the executable in question has the DYNAMIC flag set. It is my - opinion that this test is unnecessary (undesirable even). It - was added to avoid inadvertent relocation of an executable - whose e_type member in the ELF header is not ET_DYN. There may - be a time in the future when it is desirable to do relocations - on other types of files as well in which case this condition - should either be removed or modified to accomodate the new file - type. (E.g, an ET_EXEC executable which has been built to be - position-independent could safely be relocated by the OS if - desired. It is true that this violates the ABI, but the ABI - has been known to be bent from time to time.) - Kevin, Nov 2000. ] - */ - - interp_sect = bfd_get_section_by_name (exec_bfd, ".interp"); - if (interp_sect == NULL - && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0 - && bfd_get_start_address (exec_bfd) != pc) - { - struct cleanup *old_chain; - struct section_offsets *new_offsets; - int i, changed; - CORE_ADDR displacement; - - /* It is necessary to relocate the objfile. The amount to - relocate by is simply the address at which we are stopped - minus the starting address from the executable. - - We relocate all of the sections by the same amount. This - behavior is mandated by recent editions of the System V ABI. - According to the System V Application Binary Interface, - Edition 4.1, page 5-5: - - ... Though the system chooses virtual addresses for - individual processes, it maintains the segments' relative - positions. Because position-independent code uses relative - addressesing between segments, the difference between - virtual addresses in memory must match the difference - between virtual addresses in the file. The difference - between the virtual address of any segment in memory and - the corresponding virtual address in the file is thus a - single constant value for any one executable or shared - object in a given process. This difference is the base - address. One use of the base address is to relocate the - memory image of the program during dynamic linking. - - The same language also appears in Edition 4.0 of the System V - ABI and is left unspecified in some of the earlier editions. */ - - displacement = pc - bfd_get_start_address (exec_bfd); - changed = 0; - - new_offsets = xcalloc (symfile_objfile->num_sections, - sizeof (struct section_offsets)); - old_chain = make_cleanup (xfree, new_offsets); - - for (i = 0; i < symfile_objfile->num_sections; i++) - { - if (displacement != ANOFFSET (symfile_objfile->section_offsets, i)) - changed = 1; - new_offsets->offsets[i] = displacement; - } - - if (changed) - objfile_relocate (symfile_objfile, new_offsets); - - do_cleanups (old_chain); - } -} - -/* - - GLOBAL FUNCTION - - svr4_solib_create_inferior_hook -- shared library startup support - - SYNOPSIS - - void svr4_solib_create_inferior_hook() - - DESCRIPTION - - When gdb starts up the inferior, it nurses it along (through the - shell) until it is ready to execute it's first instruction. At this - point, this function gets called via expansion of the macro - SOLIB_CREATE_INFERIOR_HOOK. - - For SunOS executables, this first instruction is typically the - one at "_start", or a similar text label, regardless of whether - the executable is statically or dynamically linked. The runtime - startup code takes care of dynamically linking in any shared - libraries, once gdb allows the inferior to continue. - - For SVR4 executables, this first instruction is either the first - instruction in the dynamic linker (for dynamically linked - executables) or the instruction at "start" for statically linked - executables. For dynamically linked executables, the system - first exec's /lib/libc.so.N, which contains the dynamic linker, - and starts it running. The dynamic linker maps in any needed - shared libraries, maps in the actual user executable, and then - jumps to "start" in the user executable. - - For both SunOS shared libraries, and SVR4 shared libraries, we - can arrange to cooperate with the dynamic linker to discover the - names of shared libraries that are dynamically linked, and the - base addresses to which they are linked. - - This function is responsible for discovering those names and - addresses, and saving sufficient information about them to allow - their symbols to be read at a later time. - - FIXME - - Between enable_break() and disable_break(), this code does not - properly handle hitting breakpoints which the user might have - set in the startup code or in the dynamic linker itself. Proper - handling will probably have to wait until the implementation is - changed to use the "breakpoint handler function" method. - - Also, what if child has exit()ed? Must exit loop somehow. - */ - -static void -svr4_solib_create_inferior_hook (void) -{ - /* Relocate the main executable if necessary. */ - svr4_relocate_main_executable (); - - if (!enable_break ()) - { - warning ("shared library handler failed to enable breakpoint"); - return; - } - -#if defined(_SCO_DS) - /* SCO needs the loop below, other systems should be using the - special shared library breakpoints and the shared library breakpoint - service routine. - - Now run the target. It will eventually hit the breakpoint, at - which point all of the libraries will have been mapped in and we - can go groveling around in the dynamic linker structures to find - out what we need to know about them. */ - - clear_proceed_status (); - stop_soon_quietly = 1; - stop_signal = TARGET_SIGNAL_0; - do - { - target_resume (pid_to_ptid (-1), 0, stop_signal); - wait_for_inferior (); - } - while (stop_signal != TARGET_SIGNAL_TRAP); - stop_soon_quietly = 0; -#endif /* defined(_SCO_DS) */ -} - -static void -svr4_clear_solib (void) -{ - debug_base = 0; -} - -static void -svr4_free_so (struct so_list *so) -{ - xfree (so->lm_info->lm); - xfree (so->lm_info); -} - - -/* Clear any bits of ADDR that wouldn't fit in a target-format - data pointer. "Data pointer" here refers to whatever sort of - address the dynamic linker uses to manage its sections. At the - moment, we don't support shared libraries on any processors where - code and data pointers are different sizes. - - This isn't really the right solution. What we really need here is - a way to do arithmetic on CORE_ADDR values that respects the - natural pointer/address correspondence. (For example, on the MIPS, - converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to - sign-extend the value. There, simply truncating the bits above - TARGET_PTR_BIT, as we do below, is no good.) This should probably - be a new gdbarch method or something. */ -static CORE_ADDR -svr4_truncate_ptr (CORE_ADDR addr) -{ - if (TARGET_PTR_BIT == sizeof (CORE_ADDR) * 8) - /* We don't need to truncate anything, and the bit twiddling below - will fail due to overflow problems. */ - return addr; - else - return addr & (((CORE_ADDR) 1 << TARGET_PTR_BIT) - 1); -} - - -static void -svr4_relocate_section_addresses (struct so_list *so, - struct section_table *sec) -{ - sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR (so)); - sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so)); -} - - -/* Fetch a link_map_offsets structure for native targets using struct - definitions from link.h. See solib-legacy.c for the function - which does the actual work. - - Note: For non-native targets (i.e. cross-debugging situations), - a target specific fetch_link_map_offsets() function should be - defined and registered via set_solib_svr4_fetch_link_map_offsets(). */ - -static struct link_map_offsets * -legacy_fetch_link_map_offsets (void) -{ - if (legacy_svr4_fetch_link_map_offsets_hook) - return legacy_svr4_fetch_link_map_offsets_hook (); - else - { - internal_error (__FILE__, __LINE__, - "legacy_fetch_link_map_offsets called without legacy " - "link_map support enabled."); - return 0; - } -} - -/* Fetch a link_map_offsets structure using the method registered in the - architecture vector. */ - -static struct link_map_offsets * -svr4_fetch_link_map_offsets (void) -{ - struct link_map_offsets *(*flmo)(void) = - gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data); - - if (flmo == NULL) - { - internal_error (__FILE__, __LINE__, - "svr4_fetch_link_map_offsets: fetch_link_map_offsets " - "method not defined for this architecture."); - return 0; - } - else - return (flmo ()); -} - -/* set_solib_svr4_fetch_link_map_offsets() is intended to be called by - a <arch>_gdbarch_init() function. It is used to establish an - architecture specific link_map_offsets fetcher for the architecture - being defined. */ - -void -set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch, - struct link_map_offsets *(*flmo) (void)) -{ - set_gdbarch_data (gdbarch, fetch_link_map_offsets_gdbarch_data, flmo); -} - -/* Initialize the architecture-specific link_map_offsets fetcher. - This is called after <arch>_gdbarch_init() has set up its `struct - gdbarch' for the new architecture, and is only called if the - link_map_offsets fetcher isn't already initialized (which is - usually done by calling set_solib_svr4_fetch_link_map_offsets() - above in <arch>_gdbarch_init()). Therefore we attempt to provide a - reasonable alternative (for native targets anyway) if the - <arch>_gdbarch_init() fails to call - set_solib_svr4_fetch_link_map_offsets(). */ - -static void * -init_fetch_link_map_offsets (struct gdbarch *gdbarch) -{ - return legacy_fetch_link_map_offsets; -} - -static struct target_so_ops svr4_so_ops; - -void -_initialize_svr4_solib (void) -{ - fetch_link_map_offsets_gdbarch_data = - register_gdbarch_data (init_fetch_link_map_offsets, 0); - - svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses; - svr4_so_ops.free_so = svr4_free_so; - svr4_so_ops.clear_solib = svr4_clear_solib; - svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook; - svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling; - svr4_so_ops.current_sos = svr4_current_sos; - svr4_so_ops.open_symbol_file_object = open_symbol_file_object; - svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code; - - /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */ - current_target_so_ops = &svr4_so_ops; -} |