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binutils-gdb/gdb/ia64-linux-tdep.c
Andrew Burgess 08106042d9 gdb: move the type cast into gdbarch_tdep 
I built GDB for all targets on a x86-64/GNU-Linux system, and
then (accidentally) passed GDB a RISC-V binary, and asked GDB to "run"
the binary on the native target.  I got this error:

  (gdb) show architecture
  The target architecture is set to "auto" (currently "i386").
  (gdb) file /tmp/hello.rv32.exe
  Reading symbols from /tmp/hello.rv32.exe...
  (gdb) show architecture
  The target architecture is set to "auto" (currently "riscv:rv32").
  (gdb) run
  Starting program: /tmp/hello.rv32.exe
  ../../src/gdb/i387-tdep.c:596: internal-error: i387_supply_fxsave: Assertion `tdep->st0_regnum >= I386_ST0_REGNUM' failed.

What's going on here is this; initially the architecture is i386, this
is based on the default architecture, which is set based on the native
target.  After loading the RISC-V executable the architecture of the
current inferior is updated based on the architecture of the
executable.

When we "run", GDB does a fork & exec, with the inferior being
controlled through ptrace.  GDB sees an initial stop from the inferior
as soon as the inferior comes to life.  In response to this stop GDB
ends up calling save_stop_reason (linux-nat.c), which ends up trying
to read register from the inferior, to do this we end up calling
target_ops::fetch_registers, which, for the x86-64 native target,
calls amd64_linux_nat_target::fetch_registers.

After this I eventually end up in i387_supply_fxsave, different x86
based targets will end in different functions to fetch registers, but
it doesn't really matter which function we end up in, the problem is
this line, which is repeated in many places:

  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);

The problem here is that the ARCH in this line comes from the current
inferior, which, as we discussed above, will be a RISC-V gdbarch, the
tdep field will actually be of type riscv_gdbarch_tdep, not
i386_gdbarch_tdep.  After this cast we are relying on undefined
behaviour, in my case I happen to trigger an assert, but this might
not always be the case.

The thing I tried that exposed this problem was of course, trying to
start an executable of the wrong architecture on a native target.  I
don't think that the correct solution for this problem is to detect,
at the point of cast, that the gdbarch_tdep object is of the wrong
type, but, I did wonder, is there a way that we could protect
ourselves from incorrectly casting the gdbarch_tdep object?

I think that there is something we can do here, and this commit is the
first step in that direction, though no actual check is added by this
commit.

This commit can be split into two parts:

 (1) In gdbarch.h and arch-utils.c.  In these files I have modified
 gdbarch_tdep (the function) so that it now takes a template argument,
 like this:

    template<typename TDepType>
    static inline TDepType *
    gdbarch_tdep (struct gdbarch *gdbarch)
    {
      struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
      return static_cast<TDepType *> (tdep);
    }

  After this change we are no better protected, but the cast is now
  done within the gdbarch_tdep function rather than at the call sites,
  this leads to the second, much larger change in this commit,

  (2) Everywhere gdbarch_tdep is called, we make changes like this:

    -  i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
    +  i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (arch);

There should be no functional change after this commit.

In the next commit I will build on this change to add an assertion in
gdbarch_tdep that checks we are casting to the correct type.
2022-07-21 15:19:42 +01:00

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/* Target-dependent code for the IA-64 for GDB, the GNU debugger.
Copyright (C) 2000-2022 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 "ia64-tdep.h"
#include "arch-utils.h"
#include "gdbcore.h"
#include "regcache.h"
#include "osabi.h"
#include "solib-svr4.h"
#include "symtab.h"
#include "linux-tdep.h"
#include "regset.h"
#include <ctype.h>
/* The sigtramp code is in a non-readable (executable-only) region
of memory called the ``gate page''. The addresses in question
were determined by examining the system headers. They are
overly generous to allow for different pages sizes. */
#define GATE_AREA_START 0xa000000000000100LL
#define GATE_AREA_END 0xa000000000020000LL
/* Offset to sigcontext structure from frame of handler. */
#define IA64_LINUX_SIGCONTEXT_OFFSET 192
static int
ia64_linux_pc_in_sigtramp (CORE_ADDR pc)
{
return (pc >= (CORE_ADDR) GATE_AREA_START && pc < (CORE_ADDR) GATE_AREA_END);
}
/* IA-64 GNU/Linux specific function which, given a frame address and
a register number, returns the address at which that register may be
found. 0 is returned for registers which aren't stored in the
sigcontext structure. */
static CORE_ADDR
ia64_linux_sigcontext_register_address (struct gdbarch *gdbarch,
CORE_ADDR sp, int regno)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
gdb_byte buf[8];
CORE_ADDR sigcontext_addr = 0;
/* The address of the sigcontext area is found at offset 16 in the
sigframe. */
read_memory (sp + 16, buf, 8);
sigcontext_addr = extract_unsigned_integer (buf, 8, byte_order);
if (IA64_GR0_REGNUM <= regno && regno <= IA64_GR31_REGNUM)
return sigcontext_addr + 200 + 8 * (regno - IA64_GR0_REGNUM);
else if (IA64_BR0_REGNUM <= regno && regno <= IA64_BR7_REGNUM)
return sigcontext_addr + 136 + 8 * (regno - IA64_BR0_REGNUM);
else if (IA64_FR0_REGNUM <= regno && regno <= IA64_FR127_REGNUM)
return sigcontext_addr + 464 + 16 * (regno - IA64_FR0_REGNUM);
else
switch (regno)
{
case IA64_IP_REGNUM :
return sigcontext_addr + 40;
case IA64_CFM_REGNUM :
return sigcontext_addr + 48;
case IA64_PSR_REGNUM :
return sigcontext_addr + 56; /* user mask only */
/* sc_ar_rsc is provided, from which we could compute bspstore, but
I don't think it's worth it. Anyway, if we want it, it's at offset
64. */
case IA64_BSP_REGNUM :
return sigcontext_addr + 72;
case IA64_RNAT_REGNUM :
return sigcontext_addr + 80;
case IA64_CCV_REGNUM :
return sigcontext_addr + 88;
case IA64_UNAT_REGNUM :
return sigcontext_addr + 96;
case IA64_FPSR_REGNUM :
return sigcontext_addr + 104;
case IA64_PFS_REGNUM :
return sigcontext_addr + 112;
case IA64_LC_REGNUM :
return sigcontext_addr + 120;
case IA64_PR_REGNUM :
return sigcontext_addr + 128;
default :
return 0;
}
}
static void
ia64_linux_write_pc (struct regcache *regcache, CORE_ADDR pc)
{
ia64_write_pc (regcache, pc);
/* We must be careful with modifying the instruction-pointer: if we
just interrupt a system call, the kernel would ordinarily try to
restart it when we resume the inferior, which typically results
in SIGSEGV or SIGILL. We prevent this by clearing r10, which
will tell the kernel that r8 does NOT contain a valid error code
and hence it will skip system-call restart.
The clearing of r10 is safe as long as ia64_write_pc() is only
called as part of setting up an inferior call. */
regcache_cooked_write_unsigned (regcache, IA64_GR10_REGNUM, 0);
}
/* Implementation of `gdbarch_stap_is_single_operand', as defined in
gdbarch.h. */
static int
ia64_linux_stap_is_single_operand (struct gdbarch *gdbarch, const char *s)
{
return ((isdigit (*s) && s[1] == '[' && s[2] == 'r') /* Displacement. */
|| *s == 'r' /* Register value. */
|| isdigit (*s)); /* Literal number. */
}
/* Core file support. */
static const struct regcache_map_entry ia64_linux_gregmap[] =
{
{ 32, IA64_GR0_REGNUM, 8 }, /* r0 ... r31 */
{ 1, REGCACHE_MAP_SKIP, 8 }, /* FIXME: NAT collection bits? */
{ 1, IA64_PR_REGNUM, 8 },
{ 8, IA64_BR0_REGNUM, 8 }, /* b0 ... b7 */
{ 1, IA64_IP_REGNUM, 8 },
{ 1, IA64_CFM_REGNUM, 8 },
{ 1, IA64_PSR_REGNUM, 8 },
{ 1, IA64_RSC_REGNUM, 8 },
{ 1, IA64_BSP_REGNUM, 8 },
{ 1, IA64_BSPSTORE_REGNUM, 8 },
{ 1, IA64_RNAT_REGNUM, 8 },
{ 1, IA64_CCV_REGNUM, 8 },
{ 1, IA64_UNAT_REGNUM, 8 },
{ 1, IA64_FPSR_REGNUM, 8 },
{ 1, IA64_PFS_REGNUM, 8 },
{ 1, IA64_LC_REGNUM, 8 },
{ 1, IA64_EC_REGNUM, 8 },
{ 0 }
};
/* Size of 'gregset_t', as defined by the Linux kernel. Note that
this is more than actually mapped in the regmap above. */
#define IA64_LINUX_GREGS_SIZE (128 * 8)
static const struct regcache_map_entry ia64_linux_fpregmap[] =
{
{ 128, IA64_FR0_REGNUM, 16 }, /* f0 ... f127 */
{ 0 }
};
#define IA64_LINUX_FPREGS_SIZE (128 * 16)
static void
ia64_linux_supply_fpregset (const struct regset *regset,
struct regcache *regcache,
int regnum, const void *regs, size_t len)
{
const gdb_byte f_zero[16] = { 0 };
const gdb_byte f_one[16] =
{ 0, 0, 0, 0, 0, 0, 0, 0x80, 0xff, 0xff, 0, 0, 0, 0, 0, 0 };
regcache_supply_regset (regset, regcache, regnum, regs, len);
/* Kernel generated cores have fr1==0 instead of 1.0. Older GDBs
did the same. So ignore whatever might be recorded in fpregset_t
for fr0/fr1 and always supply their expected values. */
if (regnum == -1 || regnum == IA64_FR0_REGNUM)
regcache->raw_supply (IA64_FR0_REGNUM, f_zero);
if (regnum == -1 || regnum == IA64_FR1_REGNUM)
regcache->raw_supply (IA64_FR1_REGNUM, f_one);
}
static const struct regset ia64_linux_gregset =
{
ia64_linux_gregmap,
regcache_supply_regset, regcache_collect_regset
};
static const struct regset ia64_linux_fpregset =
{
ia64_linux_fpregmap,
ia64_linux_supply_fpregset, regcache_collect_regset
};
static void
ia64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
iterate_over_regset_sections_cb *cb,
void *cb_data,
const struct regcache *regcache)
{
cb (".reg", IA64_LINUX_GREGS_SIZE, IA64_LINUX_GREGS_SIZE, &ia64_linux_gregset,
NULL, cb_data);
cb (".reg2", IA64_LINUX_FPREGS_SIZE, IA64_LINUX_FPREGS_SIZE,
&ia64_linux_fpregset, NULL, cb_data);
}
static void
ia64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
ia64_gdbarch_tdep *tdep = gdbarch_tdep<ia64_gdbarch_tdep> (gdbarch);
static const char *const stap_register_prefixes[] = { "r", NULL };
static const char *const stap_register_indirection_prefixes[] = { "[",
NULL };
static const char *const stap_register_indirection_suffixes[] = { "]",
NULL };
linux_init_abi (info, gdbarch, 0);
/* Set the method of obtaining the sigcontext addresses at which
registers are saved. */
tdep->sigcontext_register_address = ia64_linux_sigcontext_register_address;
/* Set the pc_in_sigtramp method. */
tdep->pc_in_sigtramp = ia64_linux_pc_in_sigtramp;
set_gdbarch_write_pc (gdbarch, ia64_linux_write_pc);
set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
set_solib_svr4_fetch_link_map_offsets
(gdbarch, linux_lp64_fetch_link_map_offsets);
/* Enable TLS support. */
set_gdbarch_fetch_tls_load_module_address (gdbarch,
svr4_fetch_objfile_link_map);
/* Core file support. */
set_gdbarch_iterate_over_regset_sections
(gdbarch, ia64_linux_iterate_over_regset_sections);
/* SystemTap related. */
set_gdbarch_stap_register_prefixes (gdbarch, stap_register_prefixes);
set_gdbarch_stap_register_indirection_prefixes (gdbarch,
stap_register_indirection_prefixes);
set_gdbarch_stap_register_indirection_suffixes (gdbarch,
stap_register_indirection_suffixes);
set_gdbarch_stap_gdb_register_prefix (gdbarch, "r");
set_gdbarch_stap_is_single_operand (gdbarch,
ia64_linux_stap_is_single_operand);
}
void _initialize_ia64_linux_tdep ();
void
_initialize_ia64_linux_tdep ()
{
gdbarch_register_osabi (bfd_arch_ia64, 0, GDB_OSABI_LINUX,
ia64_linux_init_abi);
}
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