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08106042d9
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.
293 lines
8.2 KiB
C
293 lines
8.2 KiB
C
/* Target-dependent code for NetBSD/alpha.
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Copyright (C) 2002-2022 Free Software Foundation, Inc.
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Contributed by Wasabi Systems, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "defs.h"
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#include "frame.h"
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#include "gdbcore.h"
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#include "osabi.h"
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#include "regcache.h"
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#include "regset.h"
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#include "value.h"
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#include "alpha-tdep.h"
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#include "alpha-bsd-tdep.h"
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#include "netbsd-tdep.h"
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#include "solib-svr4.h"
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#include "target.h"
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/* Core file support. */
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/* Sizeof `struct reg' in <machine/reg.h>. */
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#define ALPHANBSD_SIZEOF_GREGS (32 * 8)
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/* Sizeof `struct fpreg' in <machine/reg.h. */
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#define ALPHANBSD_SIZEOF_FPREGS ((32 * 8) + 8)
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/* Supply register REGNUM from the buffer specified by FPREGS and LEN
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in the floating-point register set REGSET to register cache
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REGCACHE. If REGNUM is -1, do this for all registers in REGSET. */
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static void
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alphanbsd_supply_fpregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *fpregs, size_t len)
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{
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const gdb_byte *regs = (const gdb_byte *) fpregs;
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int i;
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gdb_assert (len >= ALPHANBSD_SIZEOF_FPREGS);
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for (i = ALPHA_FP0_REGNUM; i < ALPHA_FP0_REGNUM + 31; i++)
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{
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if (regnum == i || regnum == -1)
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regcache->raw_supply (i, regs + (i - ALPHA_FP0_REGNUM) * 8);
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}
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if (regnum == ALPHA_FPCR_REGNUM || regnum == -1)
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regcache->raw_supply (ALPHA_FPCR_REGNUM, regs + 32 * 8);
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}
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/* Supply register REGNUM from the buffer specified by GREGS and LEN
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in the general-purpose register set REGSET to register cache
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REGCACHE. If REGNUM is -1, do this for all registers in REGSET. */
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static void
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alphanbsd_aout_supply_gregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *gregs, size_t len)
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{
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const gdb_byte *regs = (const gdb_byte *) gregs;
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int i;
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/* Table to map a GDB register number to a trapframe register index. */
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static const int regmap[] =
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{
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0, 1, 2, 3,
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4, 5, 6, 7,
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8, 9, 10, 11,
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12, 13, 14, 15,
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30, 31, 32, 16,
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17, 18, 19, 20,
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21, 22, 23, 24,
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25, 29, 26
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};
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gdb_assert (len >= ALPHANBSD_SIZEOF_GREGS);
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for (i = 0; i < ARRAY_SIZE(regmap); i++)
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{
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if (regnum == i || regnum == -1)
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regcache->raw_supply (i, regs + regmap[i] * 8);
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}
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if (regnum == ALPHA_PC_REGNUM || regnum == -1)
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regcache->raw_supply (ALPHA_PC_REGNUM, regs + 31 * 8);
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if (len >= ALPHANBSD_SIZEOF_GREGS + ALPHANBSD_SIZEOF_FPREGS)
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{
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regs += ALPHANBSD_SIZEOF_GREGS;
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len -= ALPHANBSD_SIZEOF_GREGS;
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alphanbsd_supply_fpregset (regset, regcache, regnum, regs, len);
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}
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}
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/* Supply register REGNUM from the buffer specified by GREGS and LEN
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in the general-purpose register set REGSET to register cache
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REGCACHE. If REGNUM is -1, do this for all registers in REGSET. */
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static void
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alphanbsd_supply_gregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *gregs, size_t len)
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{
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const gdb_byte *regs = (const gdb_byte *) gregs;
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int i;
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if (len >= ALPHANBSD_SIZEOF_GREGS + ALPHANBSD_SIZEOF_FPREGS)
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{
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alphanbsd_aout_supply_gregset (regset, regcache, regnum, gregs, len);
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return;
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}
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for (i = 0; i < ALPHA_ZERO_REGNUM; i++)
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{
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if (regnum == i || regnum == -1)
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regcache->raw_supply (i, regs + i * 8);
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}
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if (regnum == ALPHA_PC_REGNUM || regnum == -1)
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regcache->raw_supply (ALPHA_PC_REGNUM, regs + 31 * 8);
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}
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/* NetBSD/alpha register sets. */
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static const struct regset alphanbsd_gregset =
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{
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NULL,
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alphanbsd_supply_gregset,
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NULL,
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REGSET_VARIABLE_SIZE
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};
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static const struct regset alphanbsd_fpregset =
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{
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NULL,
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alphanbsd_supply_fpregset
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};
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/* Iterate over supported core file register note sections. */
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void
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alphanbsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
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iterate_over_regset_sections_cb *cb,
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void *cb_data,
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const struct regcache *regcache)
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{
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cb (".reg", ALPHANBSD_SIZEOF_GREGS, ALPHANBSD_SIZEOF_GREGS,
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&alphanbsd_gregset, NULL, cb_data);
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cb (".reg2", ALPHANBSD_SIZEOF_FPREGS, ALPHANBSD_SIZEOF_FPREGS,
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&alphanbsd_fpregset, NULL, cb_data);
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}
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/* Signal trampolines. */
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/* Under NetBSD/alpha, signal handler invocations can be identified by the
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designated code sequence that is used to return from a signal handler.
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In particular, the return address of a signal handler points to the
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following code sequence:
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ldq a0, 0(sp)
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lda sp, 16(sp)
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lda v0, 295(zero) # __sigreturn14
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call_pal callsys
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Each instruction has a unique encoding, so we simply attempt to match
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the instruction the PC is pointing to with any of the above instructions.
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If there is a hit, we know the offset to the start of the designated
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sequence and can then check whether we really are executing in the
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signal trampoline. If not, -1 is returned, otherwise the offset from the
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start of the return sequence is returned. */
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static const gdb_byte sigtramp_retcode[] =
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{
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0x00, 0x00, 0x1e, 0xa6, /* ldq a0, 0(sp) */
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0x10, 0x00, 0xde, 0x23, /* lda sp, 16(sp) */
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0x27, 0x01, 0x1f, 0x20, /* lda v0, 295(zero) */
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0x83, 0x00, 0x00, 0x00, /* call_pal callsys */
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};
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#define RETCODE_NWORDS 4
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#define RETCODE_SIZE (RETCODE_NWORDS * 4)
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static LONGEST
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alphanbsd_sigtramp_offset (struct gdbarch *gdbarch, CORE_ADDR pc)
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{
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gdb_byte ret[RETCODE_SIZE], w[4];
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LONGEST off;
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int i;
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if (target_read_memory (pc, w, 4) != 0)
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return -1;
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for (i = 0; i < RETCODE_NWORDS; i++)
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{
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if (memcmp (w, sigtramp_retcode + (i * 4), 4) == 0)
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break;
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}
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if (i == RETCODE_NWORDS)
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return (-1);
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off = i * 4;
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pc -= off;
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if (target_read_memory (pc, ret, sizeof (ret)) != 0)
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return -1;
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if (memcmp (ret, sigtramp_retcode, RETCODE_SIZE) == 0)
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return off;
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return -1;
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}
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static int
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alphanbsd_pc_in_sigtramp (struct gdbarch *gdbarch,
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CORE_ADDR pc, const char *func_name)
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{
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return (nbsd_pc_in_sigtramp (pc, func_name)
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|| alphanbsd_sigtramp_offset (gdbarch, pc) >= 0);
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}
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static CORE_ADDR
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alphanbsd_sigcontext_addr (struct frame_info *frame)
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{
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/* FIXME: This is not correct for all versions of NetBSD/alpha.
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We will probably need to disassemble the trampoline to figure
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out which trampoline frame type we have. */
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if (!get_next_frame (frame))
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return 0;
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return get_frame_base (get_next_frame (frame));
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}
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static void
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alphanbsd_init_abi (struct gdbarch_info info,
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struct gdbarch *gdbarch)
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{
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alpha_gdbarch_tdep *tdep = gdbarch_tdep<alpha_gdbarch_tdep> (gdbarch);
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/* Hook into the DWARF CFI frame unwinder. */
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alpha_dwarf2_init_abi (info, gdbarch);
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/* Hook into the MDEBUG frame unwinder. */
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alpha_mdebug_init_abi (info, gdbarch);
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nbsd_init_abi (info, gdbarch);
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/* NetBSD/alpha does not provide single step support via ptrace(2); we
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must use software single-stepping. */
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set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
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/* NetBSD/alpha has SVR4-style shared libraries. */
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set_solib_svr4_fetch_link_map_offsets
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(gdbarch, svr4_lp64_fetch_link_map_offsets);
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tdep->dynamic_sigtramp_offset = alphanbsd_sigtramp_offset;
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tdep->pc_in_sigtramp = alphanbsd_pc_in_sigtramp;
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tdep->sigcontext_addr = alphanbsd_sigcontext_addr;
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tdep->jb_pc = 2;
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tdep->jb_elt_size = 8;
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set_gdbarch_iterate_over_regset_sections
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(gdbarch, alphanbsd_iterate_over_regset_sections);
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}
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void _initialize_alphanbsd_tdep ();
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void
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_initialize_alphanbsd_tdep ()
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{
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/* Even though NetBSD/alpha used ELF since day one, it used the
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traditional a.out-style core dump format before NetBSD 1.6, but
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we don't support those. */
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gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_NETBSD,
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alphanbsd_init_abi);
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}
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