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binutils-gdb/gdb/auxv.c

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/* Auxiliary vector support for GDB, the GNU debugger.
Copyright (C) 2004-2019 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 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 "target.h"
#include "gdbtypes.h"
#include "command.h"
#include "inferior.h"
#include "valprint.h"
#include "gdbcore.h"
#include "observable.h"
#include "gdbsupport/filestuff.h"
#include "objfiles.h"
#include "auxv.h"
#include "elf/common.h"
#include <unistd.h>
#include <fcntl.h>
/* Implement the to_xfer_partial target_ops method. This function
handles access via /proc/PID/auxv, which is a common method for
native targets. */
static enum target_xfer_status
procfs_xfer_auxv (gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset,
ULONGEST len,
ULONGEST *xfered_len)
{
int fd;
ssize_t l;
std::string pathname = string_printf ("/proc/%d/auxv", inferior_ptid.pid ());
fd = gdb_open_cloexec (pathname, writebuf != NULL ? O_WRONLY : O_RDONLY, 0);
if (fd < 0)
return TARGET_XFER_E_IO;
if (offset != (ULONGEST) 0
&& lseek (fd, (off_t) offset, SEEK_SET) != (off_t) offset)
l = -1;
else if (readbuf != NULL)
l = read (fd, readbuf, (size_t) len);
else
l = write (fd, writebuf, (size_t) len);
(void) close (fd);
if (l < 0)
return TARGET_XFER_E_IO;
else if (l == 0)
return TARGET_XFER_EOF;
else
{
*xfered_len = (ULONGEST) l;
return TARGET_XFER_OK;
}
}
/* This function handles access via ld.so's symbol `_dl_auxv'. */
static enum target_xfer_status
ld_so_xfer_auxv (gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset,
ULONGEST len, ULONGEST *xfered_len)
{
struct bound_minimal_symbol msym;
CORE_ADDR data_address, pointer_address;
struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
size_t ptr_size = TYPE_LENGTH (ptr_type);
size_t auxv_pair_size = 2 * ptr_size;
gdb_byte *ptr_buf = (gdb_byte *) alloca (ptr_size);
LONGEST retval;
size_t block;
msym = lookup_minimal_symbol ("_dl_auxv", NULL, NULL);
if (msym.minsym == NULL)
return TARGET_XFER_E_IO;
if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
return TARGET_XFER_E_IO;
/* POINTER_ADDRESS is a location where the `_dl_auxv' variable
resides. DATA_ADDRESS is the inferior value present in
`_dl_auxv', therefore the real inferior AUXV address. */
pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);
/* The location of the _dl_auxv symbol may no longer be correct if
ld.so runs at a different address than the one present in the
file. This is very common case - for unprelinked ld.so or with a
PIE executable. PIE executable forces random address even for
libraries already being prelinked to some address. PIE
executables themselves are never prelinked even on prelinked
systems. Prelinking of a PIE executable would block their
purpose of randomizing load of everything including the
executable.
If the memory read fails, return -1 to fallback on another
mechanism for retrieving the AUXV.
In most cases of a PIE running under valgrind there is no way to
find out the base addresses of any of ld.so, executable or AUXV
as everything is randomized and /proc information is not relevant
for the virtual executable running under valgrind. We think that
we might need a valgrind extension to make it work. This is PR
11440. */
if (target_read_memory (pointer_address, ptr_buf, ptr_size) != 0)
return TARGET_XFER_E_IO;
data_address = extract_typed_address (ptr_buf, ptr_type);
/* Possibly still not initialized such as during an inferior
startup. */
if (data_address == 0)
return TARGET_XFER_E_IO;
data_address += offset;
if (writebuf != NULL)
{
if (target_write_memory (data_address, writebuf, len) == 0)
{
*xfered_len = (ULONGEST) len;
return TARGET_XFER_OK;
}
else
return TARGET_XFER_E_IO;
}
/* Stop if trying to read past the existing AUXV block. The final
AT_NULL was already returned before. */
if (offset >= auxv_pair_size)
{
if (target_read_memory (data_address - auxv_pair_size, ptr_buf,
ptr_size) != 0)
return TARGET_XFER_E_IO;
if (extract_typed_address (ptr_buf, ptr_type) == AT_NULL)
return TARGET_XFER_EOF;
}
retval = 0;
block = 0x400;
gdb_assert (block % auxv_pair_size == 0);
while (len > 0)
{
if (block > len)
block = len;
/* Reading sizes smaller than AUXV_PAIR_SIZE is not supported.
Tails unaligned to AUXV_PAIR_SIZE will not be read during a
call (they should be completed during next read with
new/extended buffer). */
block &= -auxv_pair_size;
if (block == 0)
break;
if (target_read_memory (data_address, readbuf, block) != 0)
{
if (block <= auxv_pair_size)
break;
block = auxv_pair_size;
continue;
}
data_address += block;
len -= block;
/* Check terminal AT_NULL. This function is being called
indefinitely being extended its READBUF until it returns EOF
(0). */
while (block >= auxv_pair_size)
{
retval += auxv_pair_size;
if (extract_typed_address (readbuf, ptr_type) == AT_NULL)
{
*xfered_len = (ULONGEST) retval;
return TARGET_XFER_OK;
}
readbuf += auxv_pair_size;
block -= auxv_pair_size;
}
}
*xfered_len = (ULONGEST) retval;
return TARGET_XFER_OK;
}
/* Implement the to_xfer_partial target_ops method for
TARGET_OBJECT_AUXV. It handles access to AUXV. */
enum target_xfer_status
memory_xfer_auxv (struct target_ops *ops,
enum target_object object,
const char *annex,
gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset,
ULONGEST len, ULONGEST *xfered_len)
{
gdb_assert (object == TARGET_OBJECT_AUXV);
gdb_assert (readbuf || writebuf);
/* ld_so_xfer_auxv is the only function safe for virtual
executables being executed by valgrind's memcheck. Using
ld_so_xfer_auxv during inferior startup is problematic, because
ld.so symbol tables have not yet been relocated. So GDB uses
this function only when attaching to a process.
*/
if (current_inferior ()->attach_flag != 0)
{
enum target_xfer_status ret;
ret = ld_so_xfer_auxv (readbuf, writebuf, offset, len, xfered_len);
if (ret != TARGET_XFER_E_IO)
return ret;
}
return procfs_xfer_auxv (readbuf, writebuf, offset, len, xfered_len);
}
/* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
Return 0 if *READPTR is already at the end of the buffer.
Return -1 if there is insufficient buffer for a whole entry.
Return 1 if an entry was read into *TYPEP and *VALP. */
int
default_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
{
const int sizeof_auxv_field = gdbarch_ptr_bit (target_gdbarch ())
/ TARGET_CHAR_BIT;
const enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
gdb_byte *ptr = *readptr;
if (endptr == ptr)
return 0;
if (endptr - ptr < sizeof_auxv_field * 2)
return -1;
*typep = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
ptr += sizeof_auxv_field;
*valp = extract_unsigned_integer (ptr, sizeof_auxv_field, byte_order);
ptr += sizeof_auxv_field;
*readptr = ptr;
return 1;
}
/* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
Return 0 if *READPTR is already at the end of the buffer.
Return -1 if there is insufficient buffer for a whole entry.
Return 1 if an entry was read into *TYPEP and *VALP. */
int
target_auxv_parse (gdb_byte **readptr,
gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
{
struct gdbarch *gdbarch = target_gdbarch();
if (gdbarch_auxv_parse_p (gdbarch))
return gdbarch_auxv_parse (gdbarch, readptr, endptr, typep, valp);
return current_top_target ()->auxv_parse (readptr, endptr, typep, valp);
}
/* Auxiliary Vector information structure. This is used by GDB
for caching purposes for each inferior. This helps reduce the
overhead of transfering data from a remote target to the local host. */
struct auxv_info
{
gdb::optional<gdb::byte_vector> data;
};
/* Per-inferior data key for auxv. */
static const struct inferior_key<auxv_info> auxv_inferior_data;
/* Invalidate INF's auxv cache. */
static void
invalidate_auxv_cache_inf (struct inferior *inf)
{
auxv_inferior_data.clear (inf);
}
/* Invalidate current inferior's auxv cache. */
static void
invalidate_auxv_cache (void)
{
invalidate_auxv_cache_inf (current_inferior ());
}
/* Fetch the auxv object from inferior INF. If auxv is cached already,
return a pointer to the cache. If not, fetch the auxv object from the
target and cache it. This function always returns a valid INFO pointer. */
static struct auxv_info *
get_auxv_inferior_data (struct target_ops *ops)
{
struct auxv_info *info;
struct inferior *inf = current_inferior ();
info = auxv_inferior_data.get (inf);
if (info == NULL)
{
info = auxv_inferior_data.emplace (inf);
info->data = target_read_alloc (ops, TARGET_OBJECT_AUXV, NULL);
}
return info;
}
/* Extract the auxiliary vector entry with a_type matching MATCH.
Return zero if no such entry was found, or -1 if there was
an error getting the information. On success, return 1 after
storing the entry's value field in *VALP. */
int
target_auxv_search (struct target_ops *ops, CORE_ADDR match, CORE_ADDR *valp)
{
CORE_ADDR type, val;
auxv_info *info = get_auxv_inferior_data (ops);
if (!info->data)
return -1;
gdb_byte *data = info->data->data ();
gdb_byte *ptr = data;
size_t len = info->data->size ();
while (1)
switch (target_auxv_parse (&ptr, data + len, &type, &val))
{
case 1: /* Here's an entry, check it. */
if (type == match)
{
*valp = val;
return 1;
}
break;
case 0: /* End of the vector. */
return 0;
default: /* Bogosity. */
return -1;
}
/*NOTREACHED*/
}
/* Print the description of a single AUXV entry on the specified file. */
void
fprint_auxv_entry (struct ui_file *file, const char *name,
const char *description, enum auxv_format format,
CORE_ADDR type, CORE_ADDR val)
{
fprintf_filtered (file, ("%-4s %-20s %-30s "),
plongest (type), name, description);
switch (format)
{
case AUXV_FORMAT_DEC:
fprintf_filtered (file, ("%s\n"), plongest (val));
break;
case AUXV_FORMAT_HEX:
fprintf_filtered (file, ("%s\n"), paddress (target_gdbarch (), val));
break;
case AUXV_FORMAT_STR:
{
struct value_print_options opts;
get_user_print_options (&opts);
if (opts.addressprint)
fprintf_filtered (file, ("%s "), paddress (target_gdbarch (), val));
val_print_string (builtin_type (target_gdbarch ())->builtin_char,
NULL, val, -1, file, &opts);
fprintf_filtered (file, ("\n"));
}
break;
}
}
/* The default implementation of gdbarch_print_auxv_entry. */
void
default_print_auxv_entry (struct gdbarch *gdbarch, struct ui_file *file,
CORE_ADDR type, CORE_ADDR val)
{
const char *name = "???";
const char *description = "";
enum auxv_format format = AUXV_FORMAT_HEX;
switch (type)
{
#define TAG(tag, text, kind) \
case tag: name = #tag; description = text; format = kind; break
TAG (AT_NULL, _("End of vector"), AUXV_FORMAT_HEX);
TAG (AT_IGNORE, _("Entry should be ignored"), AUXV_FORMAT_HEX);
TAG (AT_EXECFD, _("File descriptor of program"), AUXV_FORMAT_DEC);
TAG (AT_PHDR, _("Program headers for program"), AUXV_FORMAT_HEX);
TAG (AT_PHENT, _("Size of program header entry"), AUXV_FORMAT_DEC);
TAG (AT_PHNUM, _("Number of program headers"), AUXV_FORMAT_DEC);
TAG (AT_PAGESZ, _("System page size"), AUXV_FORMAT_DEC);
TAG (AT_BASE, _("Base address of interpreter"), AUXV_FORMAT_HEX);
TAG (AT_FLAGS, _("Flags"), AUXV_FORMAT_HEX);
TAG (AT_ENTRY, _("Entry point of program"), AUXV_FORMAT_HEX);
TAG (AT_NOTELF, _("Program is not ELF"), AUXV_FORMAT_DEC);
TAG (AT_UID, _("Real user ID"), AUXV_FORMAT_DEC);
TAG (AT_EUID, _("Effective user ID"), AUXV_FORMAT_DEC);
TAG (AT_GID, _("Real group ID"), AUXV_FORMAT_DEC);
TAG (AT_EGID, _("Effective group ID"), AUXV_FORMAT_DEC);
TAG (AT_CLKTCK, _("Frequency of times()"), AUXV_FORMAT_DEC);
TAG (AT_PLATFORM, _("String identifying platform"), AUXV_FORMAT_STR);
TAG (AT_HWCAP, _("Machine-dependent CPU capability hints"),
AUXV_FORMAT_HEX);
TAG (AT_FPUCW, _("Used FPU control word"), AUXV_FORMAT_DEC);
TAG (AT_DCACHEBSIZE, _("Data cache block size"), AUXV_FORMAT_DEC);
TAG (AT_ICACHEBSIZE, _("Instruction cache block size"), AUXV_FORMAT_DEC);
TAG (AT_UCACHEBSIZE, _("Unified cache block size"), AUXV_FORMAT_DEC);
TAG (AT_IGNOREPPC, _("Entry should be ignored"), AUXV_FORMAT_DEC);
TAG (AT_BASE_PLATFORM, _("String identifying base platform"),
AUXV_FORMAT_STR);
TAG (AT_RANDOM, _("Address of 16 random bytes"), AUXV_FORMAT_HEX);
TAG (AT_HWCAP2, _("Extension of AT_HWCAP"), AUXV_FORMAT_HEX);
TAG (AT_EXECFN, _("File name of executable"), AUXV_FORMAT_STR);
TAG (AT_SECURE, _("Boolean, was exec setuid-like?"), AUXV_FORMAT_DEC);
TAG (AT_SYSINFO, _("Special system info/entry points"), AUXV_FORMAT_HEX);
TAG (AT_SYSINFO_EHDR, _("System-supplied DSO's ELF header"),
AUXV_FORMAT_HEX);
TAG (AT_L1I_CACHESHAPE, _("L1 Instruction cache information"),
AUXV_FORMAT_HEX);
TAG (AT_L1D_CACHESHAPE, _("L1 Data cache information"), AUXV_FORMAT_HEX);
TAG (AT_L2_CACHESHAPE, _("L2 cache information"), AUXV_FORMAT_HEX);
TAG (AT_L3_CACHESHAPE, _("L3 cache information"), AUXV_FORMAT_HEX);
TAG (AT_SUN_UID, _("Effective user ID"), AUXV_FORMAT_DEC);
TAG (AT_SUN_RUID, _("Real user ID"), AUXV_FORMAT_DEC);
TAG (AT_SUN_GID, _("Effective group ID"), AUXV_FORMAT_DEC);
TAG (AT_SUN_RGID, _("Real group ID"), AUXV_FORMAT_DEC);
TAG (AT_SUN_LDELF, _("Dynamic linker's ELF header"), AUXV_FORMAT_HEX);
TAG (AT_SUN_LDSHDR, _("Dynamic linker's section headers"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_LDNAME, _("String giving name of dynamic linker"),
AUXV_FORMAT_STR);
TAG (AT_SUN_LPAGESZ, _("Large pagesize"), AUXV_FORMAT_DEC);
TAG (AT_SUN_PLATFORM, _("Platform name string"), AUXV_FORMAT_STR);
TAG (AT_SUN_CAP_HW1, _("Machine-dependent CPU capability hints"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_IFLUSH, _("Should flush icache?"), AUXV_FORMAT_DEC);
TAG (AT_SUN_CPU, _("CPU name string"), AUXV_FORMAT_STR);
TAG (AT_SUN_EMUL_ENTRY, _("COFF entry point address"), AUXV_FORMAT_HEX);
TAG (AT_SUN_EMUL_EXECFD, _("COFF executable file descriptor"),
AUXV_FORMAT_DEC);
TAG (AT_SUN_EXECNAME,
_("Canonicalized file name given to execve"), AUXV_FORMAT_STR);
TAG (AT_SUN_MMU, _("String for name of MMU module"), AUXV_FORMAT_STR);
TAG (AT_SUN_LDDATA, _("Dynamic linker's data segment address"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_AUXFLAGS,
_("AF_SUN_ flags passed from the kernel"), AUXV_FORMAT_HEX);
TAG (AT_SUN_EMULATOR, _("Name of emulation binary for runtime linker"),
AUXV_FORMAT_STR);
TAG (AT_SUN_BRANDNAME, _("Name of brand library"), AUXV_FORMAT_STR);
TAG (AT_SUN_BRAND_AUX1, _("Aux vector for brand modules 1"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_BRAND_AUX2, _("Aux vector for brand modules 2"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_BRAND_AUX3, _("Aux vector for brand modules 3"),
AUXV_FORMAT_HEX);
TAG (AT_SUN_CAP_HW2, _("Machine-dependent CPU capability hints 2"),
AUXV_FORMAT_HEX);
}
fprint_auxv_entry (file, name, description, format, type, val);
}
/* Print the contents of the target's AUXV on the specified file. */
int
fprint_target_auxv (struct ui_file *file, struct target_ops *ops)
{
struct gdbarch *gdbarch = target_gdbarch ();
CORE_ADDR type, val;
int ents = 0;
auxv_info *info = get_auxv_inferior_data (ops);
if (!info->data)
return -1;
gdb_byte *data = info->data->data ();
gdb_byte *ptr = data;
size_t len = info->data->size ();
while (target_auxv_parse (&ptr, data + len, &type, &val) > 0)
{
gdbarch_print_auxv_entry (gdbarch, file, type, val);
++ents;
if (type == AT_NULL)
break;
}
return ents;
}
static void
info_auxv_command (const char *cmd, int from_tty)
{
if (! target_has_stack)
error (_("The program has no auxiliary information now."));
else
{
int ents = fprint_target_auxv (gdb_stdout, current_top_target ());
if (ents < 0)
error (_("No auxiliary vector found, or failed reading it."));
else if (ents == 0)
error (_("Auxiliary vector is empty."));
}
}
void
_initialize_auxv (void)
{
add_info ("auxv", info_auxv_command,
_("Display the inferior's auxiliary vector.\n\
This is information provided by the operating system at program startup."));
/* Observers used to invalidate the auxv cache when needed. */
gdb::observers::inferior_exit.attach (invalidate_auxv_cache_inf);
gdb::observers::inferior_appeared.attach (invalidate_auxv_cache_inf);
gdb::observers::executable_changed.attach (invalidate_auxv_cache);
}
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