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binutils-gdb/gdb/ft32-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 FT32.
Copyright (C) 2009-2022 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 "frame.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "value.h"
#include "inferior.h"
#include "symfile.h"
#include "objfiles.h"
#include "osabi.h"
#include "language.h"
#include "arch-utils.h"
#include "regcache.h"
#include "trad-frame.h"
#include "dis-asm.h"
#include "record.h"
#include "opcode/ft32.h"
#include "ft32-tdep.h"
#include "gdb/sim-ft32.h"
#include <algorithm>
#define RAM_BIAS 0x800000 /* Bias added to RAM addresses. */
/* Use an invalid address -1 as 'not available' marker. */
enum { REG_UNAVAIL = (CORE_ADDR) (-1) };
struct ft32_frame_cache
{
/* Base address of the frame */
CORE_ADDR base;
/* Function this frame belongs to */
CORE_ADDR pc;
/* Total size of this frame */
LONGEST framesize;
/* Saved registers in this frame */
CORE_ADDR saved_regs[FT32_NUM_REGS];
/* Saved SP in this frame */
CORE_ADDR saved_sp;
/* Has the new frame been LINKed. */
bfd_boolean established;
};
/* Implement the "frame_align" gdbarch method. */
static CORE_ADDR
ft32_frame_align (struct gdbarch *gdbarch, CORE_ADDR sp)
{
/* Align to the size of an instruction (so that they can safely be
pushed onto the stack. */
return sp & ~1;
}
constexpr gdb_byte ft32_break_insn[] = { 0x02, 0x00, 0x34, 0x00 };
typedef BP_MANIPULATION (ft32_break_insn) ft32_breakpoint;
/* FT32 register names. */
static const char *const ft32_register_names[] =
{
"fp", "sp",
"r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
"r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
"r16", "r17", "r18", "r19", "r20", "r21", "r22", "r23",
"r24", "r25", "r26", "r27", "r28", "cc",
"pc"
};
/* Implement the "register_name" gdbarch method. */
static const char *
ft32_register_name (struct gdbarch *gdbarch, int reg_nr)
{
if (reg_nr < 0)
return NULL;
if (reg_nr >= FT32_NUM_REGS)
return NULL;
return ft32_register_names[reg_nr];
}
/* Implement the "register_type" gdbarch method. */
static struct type *
ft32_register_type (struct gdbarch *gdbarch, int reg_nr)
{
if (reg_nr == FT32_PC_REGNUM)
{
ft32_gdbarch_tdep *tdep = gdbarch_tdep<ft32_gdbarch_tdep> (gdbarch);
return tdep->pc_type;
}
else if (reg_nr == FT32_SP_REGNUM || reg_nr == FT32_FP_REGNUM)
return builtin_type (gdbarch)->builtin_data_ptr;
else
return builtin_type (gdbarch)->builtin_int32;
}
/* Write into appropriate registers a function return value
of type TYPE, given in virtual format. */
static void
ft32_store_return_value (struct type *type, struct regcache *regcache,
const gdb_byte *valbuf)
{
struct gdbarch *gdbarch = regcache->arch ();
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR regval;
int len = TYPE_LENGTH (type);
/* Things always get returned in RET1_REGNUM, RET2_REGNUM. */
regval = extract_unsigned_integer (valbuf, len > 4 ? 4 : len, byte_order);
regcache_cooked_write_unsigned (regcache, FT32_R0_REGNUM, regval);
if (len > 4)
{
regval = extract_unsigned_integer (valbuf + 4,
len - 4, byte_order);
regcache_cooked_write_unsigned (regcache, FT32_R1_REGNUM, regval);
}
}
/* Fetch a single 32-bit instruction from address a. If memory contains
a compressed instruction pair, return the expanded instruction. */
static ULONGEST
ft32_fetch_instruction (CORE_ADDR a, int *isize,
enum bfd_endian byte_order)
{
unsigned int sc[2];
ULONGEST inst;
CORE_ADDR a4 = a & ~3;
inst = read_code_unsigned_integer (a4, 4, byte_order);
*isize = ft32_decode_shortcode (a4, inst, sc) ? 2 : 4;
if (*isize == 2)
return sc[1 & (a >> 1)];
else
return inst;
}
/* Decode the instructions within the given address range. Decide
when we must have reached the end of the function prologue. If a
frame_info pointer is provided, fill in its saved_regs etc.
Returns the address of the first instruction after the prologue. */
static CORE_ADDR
ft32_analyze_prologue (CORE_ADDR start_addr, CORE_ADDR end_addr,
struct ft32_frame_cache *cache,
struct gdbarch *gdbarch)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR next_addr;
ULONGEST inst;
int isize = 0;
int regnum, pushreg;
struct bound_minimal_symbol msymbol;
const int first_saved_reg = 13; /* The first saved register. */
/* PROLOGS are addresses of the subroutine prologs, PROLOGS[n]
is the address of __prolog_$rN.
__prolog_$rN pushes registers from 13 through n inclusive.
So for example CALL __prolog_$r15 is equivalent to:
PUSH $r13
PUSH $r14
PUSH $r15
Note that PROLOGS[0] through PROLOGS[12] are unused. */
CORE_ADDR prologs[32];
cache->saved_regs[FT32_PC_REGNUM] = 0;
cache->framesize = 0;
for (regnum = first_saved_reg; regnum < 32; regnum++)
{
char prolog_symbol[32];
snprintf (prolog_symbol, sizeof (prolog_symbol), "__prolog_$r%02d",
regnum);
msymbol = lookup_minimal_symbol (prolog_symbol, NULL, NULL);
if (msymbol.minsym)
prologs[regnum] = msymbol.value_address ();
else
prologs[regnum] = 0;
}
if (start_addr >= end_addr)
return end_addr;
cache->established = 0;
for (next_addr = start_addr; next_addr < end_addr; next_addr += isize)
{
inst = ft32_fetch_instruction (next_addr, &isize, byte_order);
if (FT32_IS_PUSH (inst))
{
pushreg = FT32_PUSH_REG (inst);
cache->framesize += 4;
cache->saved_regs[FT32_R0_REGNUM + pushreg] = cache->framesize;
}
else if (FT32_IS_CALL (inst))
{
for (regnum = first_saved_reg; regnum < 32; regnum++)
{
if ((4 * (inst & 0x3ffff)) == prologs[regnum])
{
for (pushreg = first_saved_reg; pushreg <= regnum;
pushreg++)
{
cache->framesize += 4;
cache->saved_regs[FT32_R0_REGNUM + pushreg] =
cache->framesize;
}
}
}
break;
}
else
break;
}
for (regnum = FT32_R0_REGNUM; regnum < FT32_PC_REGNUM; regnum++)
{
if (cache->saved_regs[regnum] != REG_UNAVAIL)
cache->saved_regs[regnum] =
cache->framesize - cache->saved_regs[regnum];
}
cache->saved_regs[FT32_PC_REGNUM] = cache->framesize;
/* It is a LINK? */
if (next_addr < end_addr)
{
inst = ft32_fetch_instruction (next_addr, &isize, byte_order);
if (FT32_IS_LINK (inst))
{
cache->established = 1;
for (regnum = FT32_R0_REGNUM; regnum < FT32_PC_REGNUM; regnum++)
{
if (cache->saved_regs[regnum] != REG_UNAVAIL)
cache->saved_regs[regnum] += 4;
}
cache->saved_regs[FT32_PC_REGNUM] = cache->framesize + 4;
cache->saved_regs[FT32_FP_REGNUM] = 0;
cache->framesize += FT32_LINK_SIZE (inst);
next_addr += isize;
}
}
return next_addr;
}
/* Find the end of function prologue. */
static CORE_ADDR
ft32_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
CORE_ADDR func_addr = 0, func_end = 0;
const char *func_name;
/* See if we can determine the end of the prologue via the symbol table.
If so, then return either PC, or the PC after the prologue, whichever
is greater. */
if (find_pc_partial_function (pc, &func_name, &func_addr, &func_end))
{
CORE_ADDR post_prologue_pc
= skip_prologue_using_sal (gdbarch, func_addr);
if (post_prologue_pc != 0)
return std::max (pc, post_prologue_pc);
else
{
/* Can't determine prologue from the symbol table, need to examine
instructions. */
struct symtab_and_line sal;
struct symbol *sym;
struct ft32_frame_cache cache;
CORE_ADDR plg_end;
memset (&cache, 0, sizeof cache);
plg_end = ft32_analyze_prologue (func_addr,
func_end, &cache, gdbarch);
/* Found a function. */
sym = lookup_symbol (func_name, NULL, VAR_DOMAIN, NULL).symbol;
/* Don't use line number debug info for assembly source files. */
if ((sym != NULL) && sym->language () != language_asm)
{
sal = find_pc_line (func_addr, 0);
if (sal.end && sal.end < func_end)
{
/* Found a line number, use it as end of prologue. */
return sal.end;
}
}
/* No useable line symbol. Use result of prologue parsing method. */
return plg_end;
}
}
/* No function symbol -- just return the PC. */
return pc;
}
/* Implementation of `pointer_to_address' gdbarch method.
On FT32 address space zero is RAM, address space 1 is flash.
RAM appears at address RAM_BIAS, flash at address 0. */
static CORE_ADDR
ft32_pointer_to_address (struct gdbarch *gdbarch,
struct type *type, const gdb_byte *buf)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
CORE_ADDR addr
= extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
if (TYPE_ADDRESS_CLASS_1 (type))
return addr;
else
return addr | RAM_BIAS;
}
/* Implementation of `address_class_type_flags' gdbarch method.
This method maps DW_AT_address_class attributes to a
type_instance_flag_value. */
static type_instance_flags
ft32_address_class_type_flags (int byte_size, int dwarf2_addr_class)
{
/* The value 1 of the DW_AT_address_class attribute corresponds to the
__flash__ qualifier, meaning pointer to data in FT32 program memory.
*/
if (dwarf2_addr_class == 1)
return TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1;
return 0;
}
/* Implementation of `address_class_type_flags_to_name' gdbarch method.
Convert a type_instance_flag_value to an address space qualifier. */
static const char*
ft32_address_class_type_flags_to_name (struct gdbarch *gdbarch,
type_instance_flags type_flags)
{
if (type_flags & TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1)
return "flash";
else
return NULL;
}
/* Implementation of `address_class_name_to_type_flags' gdbarch method.
Convert an address space qualifier to a type_instance_flag_value. */
static bool
ft32_address_class_name_to_type_flags (struct gdbarch *gdbarch,
const char* name,
type_instance_flags *type_flags_ptr)
{
if (strcmp (name, "flash") == 0)
{
*type_flags_ptr = TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1;
return true;
}
else
return false;
}
/* Given a return value in `regbuf' with a type `valtype',
extract and copy its value into `valbuf'. */
static void
ft32_extract_return_value (struct type *type, struct regcache *regcache,
gdb_byte *dst)
{
struct gdbarch *gdbarch = regcache->arch ();
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
bfd_byte *valbuf = dst;
int len = TYPE_LENGTH (type);
ULONGEST tmp;
/* By using store_unsigned_integer we avoid having to do
anything special for small big-endian values. */
regcache_cooked_read_unsigned (regcache, FT32_R0_REGNUM, &tmp);
store_unsigned_integer (valbuf, (len > 4 ? len - 4 : len), byte_order, tmp);
/* Ignore return values more than 8 bytes in size because the ft32
returns anything more than 8 bytes in the stack. */
if (len > 4)
{
regcache_cooked_read_unsigned (regcache, FT32_R1_REGNUM, &tmp);
store_unsigned_integer (valbuf + len - 4, 4, byte_order, tmp);
}
}
/* Implement the "return_value" gdbarch method. */
static enum return_value_convention
ft32_return_value (struct gdbarch *gdbarch, struct value *function,
struct type *valtype, struct regcache *regcache,
gdb_byte *readbuf, const gdb_byte *writebuf)
{
if (TYPE_LENGTH (valtype) > 8)
return RETURN_VALUE_STRUCT_CONVENTION;
else
{
if (readbuf != NULL)
ft32_extract_return_value (valtype, regcache, readbuf);
if (writebuf != NULL)
ft32_store_return_value (valtype, regcache, writebuf);
return RETURN_VALUE_REGISTER_CONVENTION;
}
}
/* Allocate and initialize a ft32_frame_cache object. */
static struct ft32_frame_cache *
ft32_alloc_frame_cache (void)
{
struct ft32_frame_cache *cache;
int i;
cache = FRAME_OBSTACK_ZALLOC (struct ft32_frame_cache);
for (i = 0; i < FT32_NUM_REGS; ++i)
cache->saved_regs[i] = REG_UNAVAIL;
return cache;
}
/* Populate a ft32_frame_cache object for this_frame. */
static struct ft32_frame_cache *
ft32_frame_cache (struct frame_info *this_frame, void **this_cache)
{
struct ft32_frame_cache *cache;
CORE_ADDR current_pc;
int i;
if (*this_cache)
return (struct ft32_frame_cache *) *this_cache;
cache = ft32_alloc_frame_cache ();
*this_cache = cache;
cache->base = get_frame_register_unsigned (this_frame, FT32_FP_REGNUM);
if (cache->base == 0)
return cache;
cache->pc = get_frame_func (this_frame);
current_pc = get_frame_pc (this_frame);
if (cache->pc)
{
struct gdbarch *gdbarch = get_frame_arch (this_frame);
ft32_analyze_prologue (cache->pc, current_pc, cache, gdbarch);
if (!cache->established)
cache->base = get_frame_register_unsigned (this_frame, FT32_SP_REGNUM);
}
cache->saved_sp = cache->base - 4;
for (i = 0; i < FT32_NUM_REGS; ++i)
if (cache->saved_regs[i] != REG_UNAVAIL)
cache->saved_regs[i] = cache->base + cache->saved_regs[i];
return cache;
}
/* Given a GDB frame, determine the address of the calling function's
frame. This will be used to create a new GDB frame struct. */
static void
ft32_frame_this_id (struct frame_info *this_frame,
void **this_prologue_cache, struct frame_id *this_id)
{
struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
this_prologue_cache);
/* This marks the outermost frame. */
if (cache->base == 0)
return;
*this_id = frame_id_build (cache->saved_sp, cache->pc);
}
/* Get the value of register regnum in the previous stack frame. */
static struct value *
ft32_frame_prev_register (struct frame_info *this_frame,
void **this_prologue_cache, int regnum)
{
struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
this_prologue_cache);
gdb_assert (regnum >= 0);
if (regnum == FT32_SP_REGNUM && cache->saved_sp)
return frame_unwind_got_constant (this_frame, regnum, cache->saved_sp);
if (regnum < FT32_NUM_REGS && cache->saved_regs[regnum] != REG_UNAVAIL)
return frame_unwind_got_memory (this_frame, regnum,
RAM_BIAS | cache->saved_regs[regnum]);
return frame_unwind_got_register (this_frame, regnum, regnum);
}
static const struct frame_unwind ft32_frame_unwind =
{
"ft32 prologue",
NORMAL_FRAME,
default_frame_unwind_stop_reason,
ft32_frame_this_id,
ft32_frame_prev_register,
NULL,
default_frame_sniffer
};
/* Return the base address of this_frame. */
static CORE_ADDR
ft32_frame_base_address (struct frame_info *this_frame, void **this_cache)
{
struct ft32_frame_cache *cache = ft32_frame_cache (this_frame,
this_cache);
return cache->base;
}
static const struct frame_base ft32_frame_base =
{
&ft32_frame_unwind,
ft32_frame_base_address,
ft32_frame_base_address,
ft32_frame_base_address
};
/* Allocate and initialize the ft32 gdbarch object. */
static struct gdbarch *
ft32_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
struct gdbarch *gdbarch;
struct type *void_type;
struct type *func_void_type;
/* If there is already a candidate, use it. */
arches = gdbarch_list_lookup_by_info (arches, &info);
if (arches != NULL)
return arches->gdbarch;
/* Allocate space for the new architecture. */
ft32_gdbarch_tdep *tdep = new ft32_gdbarch_tdep;
gdbarch = gdbarch_alloc (&info, tdep);
/* Create a type for PC. We can't use builtin types here, as they may not
be defined. */
void_type = arch_type (gdbarch, TYPE_CODE_VOID, TARGET_CHAR_BIT, "void");
func_void_type = make_function_type (void_type, NULL);
tdep->pc_type = arch_pointer_type (gdbarch, 4 * TARGET_CHAR_BIT, NULL,
func_void_type);
tdep->pc_type->set_instance_flags (tdep->pc_type->instance_flags ()
| TYPE_INSTANCE_FLAG_ADDRESS_CLASS_1);
set_gdbarch_num_regs (gdbarch, FT32_NUM_REGS);
set_gdbarch_sp_regnum (gdbarch, FT32_SP_REGNUM);
set_gdbarch_pc_regnum (gdbarch, FT32_PC_REGNUM);
set_gdbarch_register_name (gdbarch, ft32_register_name);
set_gdbarch_register_type (gdbarch, ft32_register_type);
set_gdbarch_return_value (gdbarch, ft32_return_value);
set_gdbarch_pointer_to_address (gdbarch, ft32_pointer_to_address);
set_gdbarch_skip_prologue (gdbarch, ft32_skip_prologue);
set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
set_gdbarch_breakpoint_kind_from_pc (gdbarch, ft32_breakpoint::kind_from_pc);
set_gdbarch_sw_breakpoint_from_kind (gdbarch, ft32_breakpoint::bp_from_kind);
set_gdbarch_frame_align (gdbarch, ft32_frame_align);
frame_base_set_default (gdbarch, &ft32_frame_base);
/* Hook in ABI-specific overrides, if they have been registered. */
gdbarch_init_osabi (info, gdbarch);
/* Hook in the default unwinders. */
frame_unwind_append_unwinder (gdbarch, &ft32_frame_unwind);
/* Support simple overlay manager. */
set_gdbarch_overlay_update (gdbarch, simple_overlay_update);
set_gdbarch_address_class_type_flags (gdbarch, ft32_address_class_type_flags);
set_gdbarch_address_class_name_to_type_flags
(gdbarch, ft32_address_class_name_to_type_flags);
set_gdbarch_address_class_type_flags_to_name
(gdbarch, ft32_address_class_type_flags_to_name);
return gdbarch;
}
/* Register this machine's init routine. */
void _initialize_ft32_tdep ();
void
_initialize_ft32_tdep ()
{
register_gdbarch_init (bfd_arch_ft32, ft32_gdbarch_init);
}
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