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old-cross-binutils/gdb/solib-irix.c
Pedro Alves f37f681c2b [IRIX] eliminate deprecated_insert_raw_breakpoint uses 
The IRIX support wants to set a breakpoint to be hit when the startup
phase is complete, which is where shared libraries have been mapped
in.  AFAIU, for most IRIX ports, that location is the entry point.

For MIPS IRIX however, GDB needs to set a breakpoint earlier, in
__dbx_link, as explained by:

 #ifdef SYS_syssgi
   /* On mips-irix, we need to stop the inferior early enough during
      the startup phase in order to be able to load the shared library
      symbols and insert the breakpoints that are located in these shared
      libraries.  Stopping at the program entry point is not good enough
      because the -init code is executed before the execution reaches
      that point.

      So what we need to do is to insert a breakpoint in the runtime
      loader (rld), more precisely in __dbx_link().  This procedure is
      called by rld once all shared libraries have been mapped, but before
      the -init code is executed.  Unfortuantely, this is not straightforward,
      as rld is not part of the executable we are running, and thus we need
      the inferior to run until rld itself has been mapped in memory.

      For this, we trace all syssgi() syscall exit events.  Each time
      we detect such an event, we iterate over each text memory maps,
      get its associated fd, and scan the symbol table for __dbx_link().
      When found, we know that rld has been mapped, and that we can insert
      the breakpoint at the symbol address.  Once the dbx_link() breakpoint
      has been inserted, the syssgi() notifications are no longer necessary,
      so they should be canceled.  */
   proc_trace_syscalls_1 (pi, SYS_syssgi, PR_SYSEXIT, FLAG_SET, 0);
 #endif

The loop in irix_solib_create_inferior_hook then runs until whichever
breakpoint is hit first, the one set by solib-irix.c or the one set by
procfs.c.

Note the comment in disable_break talks about __dbx_init, but I think
that's a typo for __dbx_link:

 -  /* Note that it is possible that we have stopped at a location that
 -     is different from the location where we inserted our breakpoint.
 -     On mips-irix, we can actually land in __dbx_init(), so we should
 -     not check the PC against our breakpoint address here.  See procfs.c
 -     for more details.  */

This looks very much like referring to the loop in
irix_solib_create_inferior_hook stopping at __dbx_link instead of at
the entry point.

What this patch does is convert these deprecated raw breakpoints to
standard solib_event breakpoints.  When the first solib-event
breakpoint is hit, we delete all solib-event breakpoints.  We do that
in the so_ops->handle_event hook.

This allows getting rid of the loop in irix_solib_create_inferior_hook
completely, which should allow properly handling signals and other
events in the early startup phase, like in SVR4.

Built on x86_64 Fedora 20 with --enable-targets=all (builds
solib-irix.c).

Joel tested that with an earlier version of this patch "info shared"
after starting a program gave the same list of shared libraries as
before.

gdb/ChangeLog:
2014-09-12  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (remove_solib_event_breakpoints_at_next_stop)
	(create_and_insert_solib_event_breakpoint): New functions.
	* breakpoint.h (create_and_insert_solib_event_breakpoint)
	(remove_solib_event_breakpoints_at_next_stop): New declarations.
	* procfs.c (dbx_link_bpt_addr, dbx_link_bpt): Delete globals.
	(remove_dbx_link_breakpoint): Delete function.
	(insert_dbx_link_bpt_in_file): Use
	create_and_insert_solib_event_breakpoint instead of
	deprecated_insert_raw_breakpoint.
	(procfs_wait): Don't check whether we hit __dbx_link here.
	(procfs_mourn_inferior): Don't delete the __dbx_link breakpoint
	here.
	* solib-irix.c (base_breakpoint): Delete global.
	(disable_break): Delete function.
	(enable_break): Use create_solib_event_breakpoint
	instead of deprecated_insert_raw_breakpoint.
	(irix_solib_handle_event): New function.
	(irix_solib_create_inferior_hook): Don't run the target or disable
	the mapping-complete breakpoint here.
	(_initialize_irix_solib): Install irix_solib_handle_event as
	so_ops->handle_event hook.
2014-09-12 20:02:01 +01:00

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/* Shared library support for IRIX.
Copyright (C) 1993-2014 Free Software Foundation, Inc.
This file was created using portions of irix5-nat.c originally
contributed to GDB by Ian Lance Taylor.
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 3 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, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "symtab.h"
#include "bfd.h"
/* FIXME: ezannoni/2004-02-13 Verify that the include below is
really needed. */
#include "symfile.h"
#include "objfiles.h"
#include "gdbcore.h"
#include "target.h"
#include "inferior.h"
#include "infrun.h"
#include "gdbthread.h"
#include "solist.h"
#include "solib.h"
#include "solib-irix.h"
/* Link map info to include in an allocate so_list entry. Unlike some
of the other solib backends, this (Irix) backend chooses to decode
the link map info obtained from the target and store it as (mostly)
CORE_ADDRs which need no further decoding. This is more convenient
because there are three different link map formats to worry about.
We use a single routine (fetch_lm_info) to read (and decode) the target
specific link map data. */
struct lm_info
{
CORE_ADDR addr; /* address of obj_info or obj_list
struct on target (from which the
following information is obtained). */
CORE_ADDR next; /* address of next item in list. */
CORE_ADDR reloc_offset; /* amount to relocate by */
CORE_ADDR pathname_addr; /* address of pathname */
int pathname_len; /* length of pathname */
};
/* It's not desirable to use the system header files to obtain the
structure of the obj_list or obj_info structs. Therefore, we use a
platform neutral representation which has been derived from the IRIX
header files. */
typedef struct
{
gdb_byte b[4];
}
gdb_int32_bytes;
typedef struct
{
gdb_byte b[8];
}
gdb_int64_bytes;
/* The "old" obj_list struct. This is used with old (o32) binaries.
The ``data'' member points at a much larger and more complicated
struct which we will only refer to by offsets. See
fetch_lm_info(). */
struct irix_obj_list
{
gdb_int32_bytes data;
gdb_int32_bytes next;
gdb_int32_bytes prev;
};
/* The ELF32 and ELF64 versions of the above struct. The oi_magic value
corresponds to the ``data'' value in the "old" struct. When this value
is 0xffffffff, the data will be in one of the following formats. The
``oi_size'' field is used to decide which one we actually have. */
struct irix_elf32_obj_info
{
gdb_int32_bytes oi_magic;
gdb_int32_bytes oi_size;
gdb_int32_bytes oi_next;
gdb_int32_bytes oi_prev;
gdb_int32_bytes oi_ehdr;
gdb_int32_bytes oi_orig_ehdr;
gdb_int32_bytes oi_pathname;
gdb_int32_bytes oi_pathname_len;
};
struct irix_elf64_obj_info
{
gdb_int32_bytes oi_magic;
gdb_int32_bytes oi_size;
gdb_int64_bytes oi_next;
gdb_int64_bytes oi_prev;
gdb_int64_bytes oi_ehdr;
gdb_int64_bytes oi_orig_ehdr;
gdb_int64_bytes oi_pathname;
gdb_int32_bytes oi_pathname_len;
gdb_int32_bytes padding;
};
/* Union of all of the above (plus a split out magic field). */
union irix_obj_info
{
gdb_int32_bytes magic;
struct irix_obj_list ol32;
struct irix_elf32_obj_info oi32;
struct irix_elf64_obj_info oi64;
};
/* MIPS sign extends its 32 bit addresses. We could conceivably use
extract_typed_address here, but to do so, we'd have to construct an
appropriate type. Calling extract_signed_integer seems simpler. */
static CORE_ADDR
extract_mips_address (void *addr, int len, enum bfd_endian byte_order)
{
return extract_signed_integer (addr, len, byte_order);
}
/* Fetch and return the link map data associated with ADDR. Note that
this routine automatically determines which (of three) link map
formats is in use by the target. */
static struct lm_info
fetch_lm_info (CORE_ADDR addr)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
struct lm_info li;
union irix_obj_info buf;
li.addr = addr;
/* The smallest region that we'll need is for buf.ol32. We'll read
that first. We'll read more of the buffer later if we have to deal
with one of the other cases. (We don't want to incur a memory error
if we were to read a larger region that generates an error due to
being at the end of a page or the like.) */
read_memory (addr, (gdb_byte *) &buf, sizeof (buf.ol32));
if (extract_unsigned_integer (buf.magic.b, sizeof (buf.magic), byte_order)
!= 0xffffffff)
{
/* Use buf.ol32... */
gdb_byte obj_buf[432];
CORE_ADDR obj_addr = extract_mips_address (&buf.ol32.data,
sizeof (buf.ol32.data),
byte_order);
li.next = extract_mips_address (&buf.ol32.next,
sizeof (buf.ol32.next), byte_order);
read_memory (obj_addr, obj_buf, sizeof (obj_buf));
li.pathname_addr = extract_mips_address (&obj_buf[236], 4, byte_order);
li.pathname_len = 0; /* unknown */
li.reloc_offset = extract_mips_address (&obj_buf[196], 4, byte_order)
- extract_mips_address (&obj_buf[248], 4, byte_order);
}
else if (extract_unsigned_integer (buf.oi32.oi_size.b,
sizeof (buf.oi32.oi_size), byte_order)
== sizeof (buf.oi32))
{
/* Use buf.oi32... */
/* Read rest of buffer. */
read_memory (addr + sizeof (buf.ol32),
((gdb_byte *) &buf) + sizeof (buf.ol32),
sizeof (buf.oi32) - sizeof (buf.ol32));
/* Fill in fields using buffer contents. */
li.next = extract_mips_address (&buf.oi32.oi_next,
sizeof (buf.oi32.oi_next), byte_order);
li.reloc_offset = extract_mips_address (&buf.oi32.oi_ehdr,
sizeof (buf.oi32.oi_ehdr),
byte_order)
- extract_mips_address (&buf.oi32.oi_orig_ehdr,
sizeof (buf.oi32.oi_orig_ehdr), byte_order);
li.pathname_addr = extract_mips_address (&buf.oi32.oi_pathname,
sizeof (buf.oi32.oi_pathname),
byte_order);
li.pathname_len = extract_unsigned_integer (buf.oi32.oi_pathname_len.b,
sizeof (buf.oi32.
oi_pathname_len),
byte_order);
}
else if (extract_unsigned_integer (buf.oi64.oi_size.b,
sizeof (buf.oi64.oi_size), byte_order)
== sizeof (buf.oi64))
{
/* Use buf.oi64... */
/* Read rest of buffer. */
read_memory (addr + sizeof (buf.ol32),
((gdb_byte *) &buf) + sizeof (buf.ol32),
sizeof (buf.oi64) - sizeof (buf.ol32));
/* Fill in fields using buffer contents. */
li.next = extract_mips_address (&buf.oi64.oi_next,
sizeof (buf.oi64.oi_next), byte_order);
li.reloc_offset = extract_mips_address (&buf.oi64.oi_ehdr,
sizeof (buf.oi64.oi_ehdr),
byte_order)
- extract_mips_address (&buf.oi64.oi_orig_ehdr,
sizeof (buf.oi64.oi_orig_ehdr), byte_order);
li.pathname_addr = extract_mips_address (&buf.oi64.oi_pathname,
sizeof (buf.oi64.oi_pathname),
byte_order);
li.pathname_len = extract_unsigned_integer (buf.oi64.oi_pathname_len.b,
sizeof (buf.oi64.
oi_pathname_len),
byte_order);
}
else
{
error (_("Unable to fetch shared library obj_info or obj_list info."));
}
return li;
}
/* The symbol which starts off the list of shared libraries. */
#define DEBUG_BASE "__rld_obj_head"
static CORE_ADDR debug_base; /* Base of dynamic linker structures. */
/* Locate the base address of dynamic linker structs.
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 symbol defined by the macro DEBUG_BASE.
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 much more complicated because 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. We have to go
to a lot more work to discover the address of DEBUG_BASE. 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.
Irix 5 is basically like SunOS.
Note that we can assume nothing about the process state at the time
we need to find this address. We may be stopped on the first instruc-
tion 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 CORE_ADDR
locate_base (void)
{
struct bound_minimal_symbol msymbol;
CORE_ADDR address = 0;
msymbol = lookup_minimal_symbol (DEBUG_BASE, NULL, symfile_objfile);
if ((msymbol.minsym != NULL) && (BMSYMBOL_VALUE_ADDRESS (msymbol) != 0))
{
address = BMSYMBOL_VALUE_ADDRESS (msymbol);
}
return (address);
}
/* Arrange for dynamic linker to hit breakpoint.
This functions inserts a breakpoint at the entry point of the
main executable, where all shared libraries are mapped in. */
static int
enable_break (void)
{
if (symfile_objfile != NULL && has_stack_frames ())
{
CORE_ADDR entry_point;
if (entry_point_address_query (&entry_point))
{
create_solib_event_breakpoint (target_gdbarch (), entry_point);
return 1;
}
}
return 0;
}
/* Implement the "handle_event" target_solib_ops method. */
static void
irix_solib_handle_event (void)
{
/* We are now at the "mapping complete" breakpoint, we no longer
need it. Note that it is possible that we have stopped at a
location that is different from the location where we inserted
our breakpoint: On mips-irix, we can actually land in
__dbx_link(), so we should not check the PC against our
breakpoint address here. See procfs.c for more details. Note
we're being called by the bpstat handling code, and so can't
delete the breakpoint immediately. Mark it for later deletion,
which has the same effect (it'll be removed before we next resume
or if we're stopping). */
remove_solib_event_breakpoints_at_next_stop ();
/* The caller calls solib_add, which will add any shared libraries
that were mapped in. */
}
/* Implement the "create_inferior_hook" target_solib_ops method.
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
irix_solib_create_inferior_hook (int from_tty)
{
struct inferior *inf;
struct thread_info *tp;
inf = current_inferior ();
/* If we are attaching to the inferior, the shared libraries
have already been mapped, so nothing more to do. */
if (inf->attach_flag)
return;
/* Likewise when debugging from a core file, the shared libraries
have already been mapped, so nothing more to do. */
if (!target_can_run (&current_target))
return;
if (!enable_break ())
{
warning (_("shared library handler failed to enable breakpoint"));
return;
}
/* The target 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. */
}
/* Implement the "current_sos" target_so_ops method. */
static struct so_list *
irix_current_sos (void)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
int addr_size = gdbarch_addr_bit (target_gdbarch ()) / TARGET_CHAR_BIT;
CORE_ADDR lma;
gdb_byte addr_buf[8];
struct so_list *head = 0;
struct so_list **link_ptr = &head;
int is_first = 1;
struct lm_info lm;
/* 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;
}
read_memory (debug_base, addr_buf, addr_size);
lma = extract_mips_address (addr_buf, addr_size, byte_order);
while (lma)
{
lm = fetch_lm_info (lma);
if (!is_first)
{
int errcode;
char *name_buf;
int name_size;
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;
/* Extract this shared object's name. */
name_size = lm.pathname_len;
if (name_size == 0)
name_size = SO_NAME_MAX_PATH_SIZE - 1;
if (name_size >= SO_NAME_MAX_PATH_SIZE)
{
name_size = SO_NAME_MAX_PATH_SIZE - 1;
warning (_("current_sos: truncating name of "
"%d characters to only %d characters"),
lm.pathname_len, name_size);
}
target_read_string (lm.pathname_addr, &name_buf,
name_size, &errcode);
if (errcode != 0)
warning (_("Can't read pathname for load map: %s."),
safe_strerror (errcode));
else
{
strncpy (new->so_name, name_buf, name_size);
new->so_name[name_size] = '\0';
xfree (name_buf);
strcpy (new->so_original_name, new->so_name);
}
new->next = 0;
*link_ptr = new;
link_ptr = &new->next;
discard_cleanups (old_chain);
}
is_first = 0;
lma = lm.next;
}
return head;
}
/* Implement the "open_symbol_file_object" target_so_ops method.
If no open symbol file, attempt to locate and open the main symbol
file. On IRIX, 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. */
static int
irix_open_symbol_file_object (void *from_ttyp)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
int addr_size = gdbarch_addr_bit (target_gdbarch ()) / TARGET_CHAR_BIT;
CORE_ADDR lma;
gdb_byte addr_buf[8];
struct lm_info lm;
struct cleanup *cleanups;
int errcode;
int from_tty = *(int *) from_ttyp;
char *filename;
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. */
read_memory (debug_base, addr_buf, addr_size);
lma = extract_mips_address (addr_buf, addr_size, byte_order);
if (lma == 0)
return 0; /* failed somehow... */
lm = fetch_lm_info (lma);
if (lm.pathname_addr == 0)
return 0; /* No filename. */
/* Now fetch the filename from target memory. */
target_read_string (lm.pathname_addr, &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;
}
cleanups = make_cleanup (xfree, filename);
/* Have a pathname: read the symbol file. */
symbol_file_add_main (filename, from_tty);
do_cleanups (cleanups);
return 1;
}
/* Implement the "special_symbol_handling" target_so_ops method.
For IRIX, there's nothing to do. */
static void
irix_special_symbol_handling (void)
{
}
/* Using the solist entry SO, relocate the addresses in SEC. */
static void
irix_relocate_section_addresses (struct so_list *so,
struct target_section *sec)
{
sec->addr += so->lm_info->reloc_offset;
sec->endaddr += so->lm_info->reloc_offset;
}
/* Free the lm_info struct. */
static void
irix_free_so (struct so_list *so)
{
xfree (so->lm_info);
}
/* Clear backend specific state. */
static void
irix_clear_solib (void)
{
debug_base = 0;
}
/* Return 1 if PC lies in the dynamic symbol resolution code of the
run time loader. */
static int
irix_in_dynsym_resolve_code (CORE_ADDR pc)
{
return 0;
}
struct target_so_ops irix_so_ops;
/* Provide a prototype to silence -Wmissing-prototypes. */
extern initialize_file_ftype _initialize_irix_solib;
void
_initialize_irix_solib (void)
{
irix_so_ops.relocate_section_addresses = irix_relocate_section_addresses;
irix_so_ops.free_so = irix_free_so;
irix_so_ops.clear_solib = irix_clear_solib;
irix_so_ops.solib_create_inferior_hook = irix_solib_create_inferior_hook;
irix_so_ops.special_symbol_handling = irix_special_symbol_handling;
irix_so_ops.current_sos = irix_current_sos;
irix_so_ops.open_symbol_file_object = irix_open_symbol_file_object;
irix_so_ops.in_dynsym_resolve_code = irix_in_dynsym_resolve_code;
irix_so_ops.bfd_open = solib_bfd_open;
irix_so_ops.handle_event = irix_solib_handle_event;
}
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